Lina Holm Ingelsrud¹, Shiraz A. Sabah², Eric Bohm³, Karl Bang Christensen⁴, Anders Troelsen^1,5, Andrew J. Price², Anneke Spekenbrink-Spooren⁶, Anne Lubbeke⁷, Christoph Barea⁷, Jasper Most⁸, Conrad Harrison², J. Mark Wilkinson⁹
1 Department of Orthopaedic Surgery, Copenhagen University Hospital – Hvidovre, Denmark 2 University of Oxford, United Kingdom 3 University of Manitoba, Canada 4 Department of Public Health, University of Copenhagen, Denmark 5 Department of Clinical Medicine, University of Copenhagen, Denmark 6 Dutch Arthroplasty Register (LROI), The Netherlands 7 Geneva University Hospitals, University of Geneva, Switzerland 8 Zuyderland Medical Center, Sittard-Geleen, The Netherlands 9 University of Sheffield, United Kingdom

Background: The cross-cultural validity of the Oxford hip score (OHS) and Oxford knee score (OKS) across different language versions is not known.
Aim: To evaluate the cross-cultural validity of the English, Dutch, Danish and French OHS and OKS in patients undergoing hip and knee replacement.
Materials and Methods: Patients undergoing primary hip or knee replacement for osteoarthritis between 2019 to 2022 answering OHS or OKS preoperatively and at 6 or 12 months postoperatively were included from the United Kingdom National Joint Registry (English), the Dutch Arthroplasty Register (LROI) (Dutch), the Copenhagen University Hospital Hvidovre’s local arthroplasty database (Danish), and the Swiss Geneva Arthroplasty Registry (French). Analyses were performed separately for each registry dataset. Unidimensionality of the constructs was evaluated with confirmatory factor analysis (CFA), with root mean square error of approximation (RMSEA) <0.06, Standardized Root Mean Square Residual (SRMR) =0.08, Comparative Fit Index (CFI) >0.95, and Tucker-Lewis Index (TLI) >0.95. Monotonicity was indicated by Loevinger's H coefficient >0.3 and item local independence with the Yen Q3 residual correlations <0.2.
Results: The mean age ranged from 67 to 71 years, female proportion from 54% to 63%, mean BMI from 27 to 30, and proportions with ASA score =3 from 17% to 29%, across hip and knee cohorts where English (n=21,108 and 28,230), Dutch (n=36,792 and 29,651), Danish (n=815 and 1,015) and French (n=590 and 459) instruments were utilised. Preoperative mean OHS ranged from 18 to 23 and OKS from 19 to 24. For the OHS, RMSEA ranged from 0.072 to 0.092. For OKS, RMSEA ranged from 0.057 to 0.061. For both OHS and OKS, SRMR, CFI and TLI were acceptable in all languages. Monotonicity was indicated for all items besides Night pain in the Dutch and Danish OKS. Item independence was confirmed for all items besides OHS Dressing and Washing in the Dutch and Danish versions and Sudden pain and Night pain in the Danish version.
Interpretation / Conclusion: Structural validity of the English, Dutch, Danish and French versions of the OHS and OKS was acceptable. Further analyses will inspect measurement invariance across languages.

Trine Pedersen Ahlmann ^1,2, Charlotte Jensen Myhre^3,4, Martin Lidberg-Larsen^3,4, Claus Varnum^1,2, Karina Steffensen Dahl^2,5
1 Department of Orthopaedic Surgery, Lillebaelt Hospital, University Hospital of Southern Denmark, Vejle, Denmark 2 Department of Regional Health Research, University of Southern Denmark, Odense, Denmark 3 Orthopaedic Research Unit, Clinical Institute, University of Southern Denmark, Denmark 4 Department of Orthopaedic Surgery, Odense University Hospital, Odense, Denmark. 5 Center for Shared Decision Making, Lillebaelt Hospital, University Hospital of Southern Denmark, Vejle, Denmark

Background: Severe osteoarthritis (OA) affecting the hip or knee commonly results in joint arthroplasty, with notable rates of dissatisfaction post-surgery (7% for total hip arthroplasty and 11-18% for total knee arthroplasty). This points at the importance of well-informed decision-making in treatment decisions, highlighting the necessity for patients to understand various options. While shared decision-making (SDM) and patient decision aids (PtDA) are recognized as beneficial tools in consultations, their use in OA consultations remains limited.
Aim: This study aims to develop and field-test an in- consult PtDA tailored for patients with hip or knee OA.
Materials and Methods: Following the International Patient Decision Aid Standards, we conducted an iterative PtDA development process. This involved a systematic literature search, fifteen field observations, two focus group discussions with patients (n=11) and relatives (n=4), and two discussions with orthopaedic surgeons (n=12). Alpha testing was carried out with orthopaedic surgeons (n=12) and newly recruited patients with hip or knee OA (n=15) to assess acceptability and usability.
Results: Field observations and focus group discussions provided valuable insights into the consultation process and dynamics of shared decision- making. Patients emphasized themes such as weighing treatment options, considering quality of life and the pivotal role of the patient-surgeon relationship. In contrast, surgeons expressed scepticism and apprehensions about PtDAs, focusing on concerns about individual practices, information-sharing and potential imbalances in decision-making responsibilities. Patients and surgeons expressed a preference for joint-specific PtDAs leading to the development of distinct editions tailored for hip and knee OA patients. Both patients and surgeons found the PtDAs acceptable and useful in the decision-making process.
Interpretation / Conclusion: Two in-consult PtDAs tailored for severe OA in the hip or knee were successfully developed and tested. They were found to be useful and acceptable by both patients and surgeons, underscoring their potential to enhance the decision-making process for OA treatment.

Annika Gottholt Hansen¹, Kristina Ifigenia Bunyoz¹, Cecilie Henkel¹, Mette Mikkelsen¹, Kirill Gromov¹, Anders Troelsen¹
1. Clinical Orthopaedic Research Hvidovre, Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre, Denmark.

Background: Medial unicompartmental knee arthroplasty (mUKA) has for many surgeons become the treatment of choice in patients with anteromedial osteoarthritis (AMOA) of the knee. Despite the widespread use of mUKA, data on outcomes during the adoption phase are scarce.
Aim: To investigate the learning curve and the clinical and radiological outcome during the implementation of mUKA by 2 knee arthroplasty surgeons.
Materials and Methods: The first 200 mUKA (uncemeted, mobile bearing, microplasty instrumentation) performed by two arthroplasty surgeons, were evaluated to determine whether there was an association between outcomes and the cumulative number of cases performed. The primary outcome was the learning curve of surgery duration. The secondary outcomes were patient reported outcomes (PROMs), including the Oxford Knee Score (OKS), Forgotten Joint Score (FJS), and Activity & Participation Questionnaire (APQ), evaluated at 3, 12, and 24 months postoperatively, the survival rate and implant positioning. The learning curve was estimated using the cumulative summation analysis (CUSUM).
Results: The mean follow-up was 5.8 ± 1.1 years and the mean age at the time of surgery was 64.9 ± 10.4 years. The CUSUM curve reveals a learning curve in surgery duration, with a turning point at the 55th patient, after which the operation duration decreases. Postoperatively PROMs remained consistently good with minimal fluctuation across the initial 200 cases. The median OKS at 12- and 24-months post-surgery was 41 and 43. The implant survival rate was 97.5% at 5 years, with 6 re- operations (3.0%) and 8 revisions (4.0%). Radiographic assessments in the coronal plan revealed 86.5% of patients had tibial placement within 5 degrees of neutral position. No patient exhibited a tibial overhang > 2 mm.
Interpretation / Conclusion: The implementation of medial UKA appears to be safe and efficient, with no compromise in PROM outcomes. Surgical duration decreased after 55 cases, and surgical precision appeared high already in the early phase of adoption.

Lina Holm Ingelsrud¹, Søren T Skou^2,3, Anne Møller⁴, Thomas Bandholm^1,5,6,7, Henrik M Schrøder^8,9, Simon M Bruhn¹, Jakob Kjellberg¹⁰, Anders Troelsen^1,7
1. Department of Orthopaedic Surgery, Copenhagen University Hospital – Hvidovre, Denmark; 2. Research Unit for Musculoskeletal Function and Physiotherapy, Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark; 3. The Research and Implementation Unit PROgrez, Department of Physiotherapy and Occupational Therapy, Næstved-Slagelse-Ringsted Hospitals, Region Zealand, Denmark; 4. Center for Research and Education in General Practice, Department of Public Health, University of Copenhagen, Copenhagen, Denmark; 5. Physical Medicine & Rehabilitation Research Copenhagen (PMR-C), Department of Physical and Occupational Therapy, Copenhagen University Hospital - Hvidovre, Denmark, 6. Department of Clinical Research, Copenhagen University Hospital - Hvidovre, Denmark; 7. Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark; 8. Department of Regional Health Research, University of Southern Denmark, Odense, Denmark; 9. Department of Orthopaedic Surgery, Næstved-Slagelse-Ringsted Hospitals, Region Zealand, Denmark; 10. The Danish Center for Social Science Research (VIVE), Copenhagen, Denmark

Background: Patients encounter diverse treatments for knee osteoarthritis (OA) before undergoing knee arthroplasty.
Aim: To describe 1) the proportions of patients with knee OA who undergo knee arthroplasty within the first two years after consulting an orthopaedic surgeon and 2) which factors are associated with surgery.
Materials and Methods: Patients with primary referral to orthopaedic surgeons for knee OA were included at two high- volume Danish outpatient orthopaedic departments from October 2018 to December 2020. Patients answered questionnaires about prior treatment of knee OA at inclusion and after 6 months and 2 years. Information about knee arthroplasty was extracted from the Danish Knee Arthroplasty Register. Patient characteristics were compared descriptively among those undergoing arthroplasty or not within 6 months and 2 years. Trial ID: NCT03746184.
Results: We included 3,507 of 5,251 eligible patients (67%). Within 6 months, 28% had a knee arthroplasty, with an additional 16% within 2 years. Those operated at 6 months and 2 years were on average 5 and 3 years older and had 3- and 5-points lower Oxford knee scores than non- operated patients. Proportions with Kellgren Lawrence Score 3-4 were 58% in the non- operated, 72% in those operated at 6 months and 78% at 2-years. Knee problems lasting <1 year were reported by 39% of non-operated patients, compared to 15% and 19% in patients operated at 6 months or 2 years. Amongst those who had surgery within 6 months and 2 years, 88% and 82%, responded preferring surgery before the initial consultation, while 47% of non- operated patients preferred surgery. Among respondents at both 6-month and 2-year follow- up (68%, n = 2385), 38% (n = 290) of those operated within 6 months had both performed exercise and received education before surgery, increasing to 60% (n = 249) in those operated at 2 years, compared to 26% in non-operated patients.
Interpretation / Conclusion: Whether undergoing knee arthroplasty or not, within two years after the initial consultation with an orthopedic surgeon, is associated with subtle distinctions in patient characteristics and prior knee OA treatments. Patients’ initial preference for surgery may weigh more when deciding on having surgery.

Christian Bredgaard Jensen^1,4, Oddrún Danielsen^1,2, Claus Varnum^1,3, Thomas Jakobsen^1,5, Mikkel Rathsach Andersen^1,6, Manuel Josef Bieder^1,7, Søren Overgaard^1,8, Christoffer Calov Jørgensen^1,9, Henrik Kehlet ^1,10, Martin Lindberg-Larsen^1,2, Kirill Gromov^1,4
1. Center for Fast-track Hip and Knee Replacement, Denmark; 2. Dept. of Orthopaedic Surgery and traumatology, Odense University Hospital and Svendborg; 3. Dept. of Orthopaedic Surgery, Lillebaelt Hospital – Vejle; 4. Dept. of Orthopaedic Surgery, Hvidovre University Hospital; 5. Dept. of Orthopaedic Surgery, Aalborg University Hospital; 6. Dept. of Orthopaedic Surgery, Copenhagen University Hospital, Herlev- Gentofte; 7. Dept. of Orthopaedic surgery, Næstved, Slagelse and Ringsted Hospitals; 8. Dept. of Orthopaedic Surgery and Traumatology, Copenhagen University Hospital, Bispebjerg; 9. Dept. of Anaesthesia, Hospital of Northern Zeeland, Hillerød; 10. Section of Surgical Pathophysiology, Copenhagen University Hospital, Rigshospitalet;

Background: Hip and knee arthroplasties as day-case procedures can reduce bed occupancy and enhance cost-effectiveness, which is needed to accommodate the future demands for arthroplasty surgeries.
Aim: We aimed to investigate the association between different arthroplasty center setups and the rate of day-of-surgery (DOS) discharge before and after implementation of a day-case setup.
Materials and Methods: We included unilateral primary hip and knee arthroplasty patients from 7 fast-track arthroplasty centers with identical day-case eligibility and discharge criteria initiated in September 2022 under the Center for Fast-track Hip and Knee Replacement. The centers were categorized into three types: Satellite arthroplasty center (SAC): only primary arthroplasties, separate logistics. Elective arthroplasty center (EAC): complex primaries, revisions, separate logistics. Arthroplasty unit orthopedic department (AUO): primary and revision procedures, integrated into general orthopedic department. DOS discharge rate in the study period (September 2022-September 2023) was compared to a control period (July 2019-December 2019) before implementation. The likelihood of DOS discharge for day-case surgery eligible patients was compared between center types using a logistic regression model.
Results: We included 6718 hip and knee arthroplasty patients (1357 from SACs, 4309 from EACs, 1052 from AUOs), and 3974 patients in the control period. The overall DOS discharge rates increased in all three center types after implementation of the day-case surgery setup (SACs; control=3.9%, study=30%. EAC; control=5.5%, study=23%. AUO; control=7.4%, study=14%). Successful DOS discharge was more likely in day-case eligible SAC patients (54%, [OR: 2.3 (CI 1.7-3.1)]) and EAC patients (60%, [OR: 3.1 (CI 2.4-4.1)]), compared to AUO patients (36%).
Interpretation / Conclusion: After implementation of a day-case setup, the overall DOS discharge rates were higher in satellite arthroplasty centers and elective arthroplasty centers, compared to arthroplasty units at orthopedic departments. DOS discharge was also more likely for day-case eligible patients operated in satellite arthroplasty centers and elective arthroplasty centers.

Oddrún Danielsen¹, Jens Lauritsen¹, Martin Lindberg-Larsen¹
1. Dept. of Orthopaedic Surgery and traumatology, Odense University Hospital and Svendborg

Background: Following surgery, patients are eager to return to their regular activities, with the timing of resuming driving being a significant concern. Being fully capable of operating a vehicle involves various factors, including anesthesia, opioids, and immobilized joints. While doctors can offer advice, the legal requirements are imprecise. Currently, there is only limited data on the post-operative driving timeline for hip and knee arthroplasty patients.
Aim: The aim was to estimate variation in time to resume car driving after hip and knee arthroplasty, including the influence of patients’ and surgical factors on resumption.
Materials and Methods: This prospective single-centre study, includes patients undergoing primary total hip arthroplasty (THA), total knee arthroplasty (TKA) and unicompartmental knee arthroplasty (UKA) in a day- case setup at Odense University hospital Svendborg, Denmark from September 2022 to August 2023. Eligible patients received an electronic survey 3 to 12 months after being discharged, with the question “How many weeks after the surgery did you drive a car again?”
Results: A total of 427 day-case eligible patients received the survey and 373 patients (87%) responded to the survey. The proportion who resumed driving at two weeks was 13% (CI: 7-18%) for THA, 11 % (6-19%) for TKA and 24% (16-35%) for UKA. At six weeks 76 (68-83%) for THA, 65% (55-74%) for TKA and 75% (65-84%) for UKA. Female patients had increased risk of delayed car driving resumption compared to males (OR 2.8, CI: 1.6 – 4.8). TKA surgery, psychiatric disorder medication, and clinical frailty scale (CFS) =4 where found to have increased risk of delayed car driving, but were not significant.
Interpretation / Conclusion: More than twice as many UKA patients resumed driving during the first two weeks compared to THA and TKA. Overall, 65%-76% of patients resumed driving within 6 weeks. Female gender was a significant predictor of delay in resuming car driving six weeks post-surgery.

Mette Garval⁽¹⁾, Lone Ramer Mikkelsen⁽¹⁾, Søren Thorgaard Skou^(2,3), Jeppe Lange^(4,5), David Høyrup Christiansen^(1,5)
1. University Clinic for Orthopaedic Pathways (UCOP), Elective Surgery Centre, Regional Hospital Silkeborg 2. The Research and Implementation Unit PROgrez, Næstved-Slagelse-Ringsted Hospitals 3. Research Unit for Musculoskeletal Function and Physiotherapy, University of Southern Denmark 4. Department of Orthopaedics, Regional Hospital Horsens 5. Department of Clinical Medicine, Aarhus University

Background: Until recently, Danish-language validated patient- reported outcome measures (PROMs) to assess early postoperative recovery following hip or knee arthroplasty have been absent. The Oxford Arthroplasty Early Recovery Scale (OARS) and the Oxford Arthroplasty Early Chance Scale (OACS) are PROMs designed to assess joint-related and systemic symptoms and health status during weeks 0-6 following a knee or a hip arthroplasty in a UK population.
Aim: To translate and cross-culturally adapt the OARS and OACS into Danish.
Materials and Methods: The OARS and OACS comprise 14 items measuring patient health status and changes in the patient's health and symptoms during the first 6 post-operative weeks. The scores can be used simultaneously but are independently interpreted. In collaboration with Oxford University, the OARS and OACS were translated and cross-culturally adapted into Danish using a forward-backward translation method in accordance with international guidelines. The translated versions were pilot tested through qualitative interviews with 6 participants conducted 2-3 weeks post-surgery at Regional Hospital Silkeborg. Verbatim transcriptions of the interviews were analysed to evaluate the understanding, relevance and comprehensiveness of the instructions, items and response options (cognitive debriefing).
Results: All 6 participants (3 undergoing hip arthroplasty and 3 knee arthroplasty) found the OARS and OACS to be easy to understand, and quick to complete (the average time to complete both measures was 5 minutes and 22 seconds). All items were considered relevant, and no important topics were reported as missed. There were no suggestions for alternative wording. Overall feedback on the OARS and OACS was positive, supporting the face and content validity of the measures.
Interpretation / Conclusion: The translated versions of OARS and OACS seem suitable for measuring recovery in Danish patients undergoing hip or knee arthroplasty. However, further evaluation of measurement properties is necessary to determine utility when evaluating or comparing the efficacy of perioperative interventions.

Saber M. Saber^1,2,3, Robin Christensen^2,4, Marius Henriksen^2,3, Henning Bliddal^2,3, Troelsen Anders^3,5, Boesen Mikael ^3,6, Asbjørn Seenithamby Poulsen^2,3, Camilla Toft Nielsen^2,3,6, Kristine Ifigenia Bunyoz^2,3,5, Søren Overgaard^1,3
1. Department of Orthopedic Surgery and Traumatology, Copenhagen University Hospital - Bispebjerg & Frederiksberg, Copenhagen, Denmark; 2. The Parker Institute, Copenhagen University Hospital - Bispebjerg & Frederiksberg, Frederiksberg, Denmark; 3. Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen Denmark; 4. Research Unit of Rheumatology, Department of Clinical Research, University of Southern Denmark, Odense University Hospital, Odense, Denmark; 5. Department of Orthopedic Surgery, Copenhagen University Hospital – Hvidovre & Amager, Hivdovre, Denmark; 6. Department of Radiology, Copenhagen University Hospital - Bispebjerg & Frederiksberg, Copenhagen, Denmark .

Background: The Intensive Diet vs Knee Arthroplasty (INKA) trial is a randomized trial assessing weight loss as an alternative to knee arthroplasty (KA) in obese patients with severe knee osteoarthritis awaiting KA (NCT05172843). The external validity of the INKA trial may be hampered if the patients who participate differ from those who decline participation.
Aim: To compare baseline characteristics between patients who enroll in the INKA trial and those who decline participation (i.e., the non-INKA group, abbreviated as nINKA)
Materials and Methods: We applied a cross-sectional study design, collecting and comparing baseline characteristics among all patients eligible for enrolment in the INKA trial from 2 clinics in Copenhagen. Imbalance between accepting (INKA) and declining (nINKA) groups was assessed using standardized differences (StdD). We prespecified that StdD values <0.20 would indicate a clinically insignificant imbalance between groups, whereas values >0.80 indicate incomparability.
Results: Of 913 patients scheduled for KA, 888 were screened for INKA trial eligibility. Of the 217 eligible patients, 92 (42%) were enrolled in the INKA trial, while 37 (17%) participated in the nINKA cross-sectional sample only. Patients enrolled in INKA had on average a less severe Oxford Knee Score of 22.0 (SD: 6.7) compared to declining participants in nINKA with 18.6 (7.2), corresponding to an StdD of 0.50, and an absolute difference of 3.45 (95% Confidence interval 0.64 to 6.26, p=0.017). A consistent similar pattern was noted across all secondary patient-reported outcomes applied in the INKA trial.
Interpretation / Conclusion: We observed discrepancies in patient-reported outcomes, with those who declined enrollment reporting more severe symptoms.

Ahmed Kurmasha¹, Torben Hansen^1,2, Jens Hansen³
1. Department of Orthopaedics, University Clinic for Hand, Hip and Knee Surgery, Gødstrup Hospital, Herning 2. Department of Clinical Medicine, Aarhus University 3. The Faculty of Social Sciences, Department of Sociology, Environmental and Business Economics, University of Southern Denmark

Background: Our Cross-Sectional Study follows the completion of osteoarthritis treatment, utilizing through either unicompartamental or total knee prostheses. In the period from May 2020 to December 2021, 235 patients underwent knee arthroplasty followed by either supervised municipal rehabilitation, or home-based rehabilitation based on individual assessment of the patients by the physiotherapist.
Aim: To investigate the impact of comorbidity, anxiety, and depression on postsurgical referral to supervised municipal rehabilitation of knee arthroplasty patients.
Materials and Methods: 109 (mean 71Y), (64F/45M), received supervised municipal rehabilitation, while 126 (mean 70Y), (59F/67M), underwent home-based rehabilitation. Data were gathered through telephone interviews conducted 12-24 months post-operation, with an 83% response rate. The binary outcome variable indicates whether patients were referred to supervised municipal rehabilitation or home-based rehabilitation. Exposure variables include comorbidity, measured by Charlson Comorbidity Index (CCI) and anxiety and depression levels, categorized as either "no problems" or "not without problems."
Results: The study shows a significant association between comorbidities and referral to supervised municipal rehabilitation, with a risk ratio of 1.35 (CI 1.18-1.54) in the multivariate model, controlling for various factors. Anxiety and depression levels also influence referral, with a higher prevalence (24%) in the supervised municipal rehabilitation group compared to the home- based group (9.5%). The risk ratio for referral with reported anxiety and depression issues is 1.43 (CI 1.05-1.94) in the multivariate model.
Interpretation / Conclusion: The study suggests that patients are often referred based on factors unrelated to knee conditions but rather on general and mental well-being. The implications underscore the potential need for standardized criteria for referral to supervised municipal rehabilitation, recognizing the multifaceted influences on patient outcomes.

Kristine Bunyoz¹, Joseph Dixon², Jason Patel³, Anders Troelsen¹, Abtin Alvand², Will Jackson², Andrew Price², Nickolas Bottomly²
1Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre, Kettegård Alle 30, 2650 Hvidovre, Copenhagen, Denmark 2Nuffield Orthopaedic Centre, Windmill Rd, Oxford, OX3 7LD, UK 3Bart’s Bone and Joint Health, Royal London Hospital, Whitechapel Rd, London E1 1FR, UK

Background: The clinical use of MRI scans for assessing knee osteoarthritis and aiding preoperative planning before a unicompartmental knee arthroplasty (UKA) is increasing. Therefore, an MRI-based depiction of AMOA holds value for both the research community and orthopaedic surgeons. Such a description will enhance understanding of the disease pattern, patient selection, and preoperative planning.
Aim: Describe the MRI findings in patients with AMOA, who meet current indications for medial UKA.
Materials and Methods: We analysed MRI scans from 100 knees evaluated for UKA between 2006-2013. Inclusion criteria comprised full-thickness medial compartment loss and intact lateral compartment joint space on preoperative radiographs. The assessment included cartilage lesions, osteophytes, meniscal damage, and anterior-cruciate ligament (ACL) status. Final decision to proceed with UKA relied on intraoperative findings, independent of MRI.
Results: Complete anteromedial tibial and femoral cartilage loss preserved posterior cartilage rims was evident in all cases. Cartilage thinning occurred in the lateral compartment in 34% of cases. While 62% displayed lateral osteophytes, only 6 exhibited small areas of full-thickness cartilage loss. ACL abnormalities varied: 27% normal, 3% ruptured, and 70% had intrasubstance high signal. Larger osteophytes in the medial (p = 0.012) and lateral (p = 0.002) intercondylar notch correlated significantly with ACL damage. All underwent medial UKA, with no evidence of full lateral compartment cartilage loss intraoperatively.
Interpretation / Conclusion: Isolated ACL high signal does not consistently indicate significant dysfunction. The presence of lateral osteophytes or small areas of cartilage loss shouldn't preclude UKA if full cartilage loss in the weight-bearing area isn't evident intraoperatively. The findings record the range of MRI scan findings in patients who meet current indications for medial UKA, aiding preoperative assessment, if an MRI scan is requested to evaluate the state of the ACL.

Anne Louise Elkjær Christensen¹, Christian Bredgaard Jensen¹, Cecilie Henkel¹, Lina Holm Ingelsrud¹, Kirill Gromow¹, Andrew J Price², Anders Troelsen¹
1.Clinical Orthopedic Research Hvidovre, Department of Orthopeadic Surgery, Copenhagen University Hospital Hvidovre, Denmark 2.Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Science, Nuffield Orthopaedic Centre, Oxford, UK.

Background: Whether medial unicompartmental knee arthroplasty (mUKA) or total knee arthroplasty (TKA) is more suitable for patients with end stage antero-medial osteoarthritis is an ongoing debate. Quality of life, pain relief and functional restoration are important outcomes for these patients.
Aim: We aimed to compare the development over time in patient reported outcome measures (PROMs) between patients receiving medial unicompartmental knee arthroplasty (mUKA) and total knee arthroplasty (TKA).
Materials and Methods: We included patients receiving either TKA or mUKA between March 2018, and February 2020. Included TKAs were performed by surgeons using mUKA in less than 1% of their knee arthroplasties in the study period. PROMs (Oxford Knee Score (OKS), Forgotten Joint Score (FJS), and the Activity and Participation Questionnaire (APQ)) were completed preoperatively, 3, 6, and 12-months postoperatively. Missing values, were handled with multiple imputation, using predictive mean matching. The patients were propensity score matched in a variable 1:2 ratio using BMI, sex, age, and preoperative PROM-scores. We calculated the area under the curve (AUC) using the trapezium rule to quantify the change from the preoperative PROM scores to scores at 3, 6 and 12 months postoperatively. Between-group differences in AUC were analyzed using linear regression adjusted for pre-operative scores.
Results: A total of 536 patients (236 mUKAs and 300 TKAs) were included. AUC was significantly lower for TKA patients compared to mUKA patients for all three PROM scores; (OKS: ?AUC of -21%, CI: [-31%; -11%], FJS: ?AUC of -24% , CI: [-35 % ; -14 %], APQ-27%, CI: [-38 % ; -15 %]). The median PROM scores at 3 months were 35 and 30 for OKS, 50 and 41.67 for FJS, 43.75 and 28.13 for APQ, for the mUKA and TKA groups, respectively. At 6 months median PROM scores increased to 39 and 35 for OKS, 60.21 and 48.96 for FJS and 50 and 37.5 for APQ.
Interpretation / Conclusion: AUC for PROMS during the first year was 21-27% lower for TKA compared with mUKA. This contrast in development trajectories is present especially in the early recovery 3-6 months after surgery and may be relevant for surgeons to consider, when discussing surgical treatment options with patients.

Saber M. Saber^1,2,3, Jens Laigaard^1,3, Martin Lindberg-Larsen⁴, Søren Overgaard^1,3
1. Department of Orthopedic Surgery and Traumatology, Copenhagen University Hospital - Bispebjerg & Frederiksberg, Copenhagen, Denmark; 2. The Parker Institute, Copenhagen University Hospital - Bispebjerg & Frederiksberg, Frederiksberg, Denmark; 3. Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen Denmark; 4. Department of Orthopaedic Surgery and Traumatology, Odense Hospital, Odense, Denmark

Background: Few studies investigated changes in body weight following total hip, total knee and unicondylar knee arthroplasty (THA, TKA and UKA) for osteoarthritis. As many surgeons may recommend weight loss after arthroplasty, we found it important to invistigate it's potential effect.
Aim: To investigate whether an increase or decrease of 5% or more in BMI is associated with a concurrent increase or decrease in persistent postoperative pain (PPP), defined as numeric rating scale (NRS) [0-10]) =4 following arthroplasty, across non-obese and obese patients (BMI=30)
Materials and Methods: Nationwide, register-based cohort survey study. We obtained data on BMI prior to surgery from the Danish Hip and Knee Arthroplasty Registers and sent surveys to patients 15-18 months following arthroplasty, which included patient- reported weight, height, NRS, frequency of pain, use of analgesics, satisfaction [1-5] and pain interference of daily activities (PIDA)
Results: Mean response rate was 71.4%. There was 10- 12% weight-gainers and 18%-20% weight losers following all types of arthroplasties. BMI prior to arthroplasty was 30-32 for weight-losers, 27-29 for weight-gainers, and 27-30 for the rest. For obese weight-losers following THA, 20% had PPP compared to 13% for those without weight change, this gave an Odd Ratio (OR) [95% Confidence Interval] for having PPP of 1.7 [1.0;2.8], being satisfied 0.5 [0.7;0.9], experience frequent pain 1.7 [1.0;2.7], PIDA 2.6 [1.5;4.6], use of analgesics 2.3 [1.00;5.4]. No such association was found for TKA and UKA.
Interpretation / Conclusion: Weight loss was associated with increased incidence of PPP in obese patients following THA. Nevertheless, it is crucial to interpret this association with caution.

Kristine Bunyoz¹, Kirill Gromov¹, Anders Troelsen¹, Andrew Price²
1: Department of orthopaedic surgery, Copenhagen University Hospital Hvidovre 2: Nuffield Orthopaedic Centre

Background: While evidence-based indications are established for medial UKA, the optimal indications for lateral UKA have not received as much attention. Significant differences exist between medial and lateral UKA. The indications for the two procedures may therefore not be identical.
Aim: This review aims to access the indications and contraindications in published cohort studies on lateral UKA, to assess if consensus exists.
Materials and Methods: In July 2023, a systematic review was carried out following the Preferred Reporting Item for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We included cohort studies on lateral UKA with a clear report of indications. Data on indications and contraindications were extracted systematically to evaluate consensus. Further, outcomes specifically related to expanding or testing indications for lateral UKA were also obtained.
Results: 38 studies were included. Lateral UKA was most frequently performed for primary lateral osteoarthritis. The most reported indications were moderate to severe lateral osteoarthritis, with full- thickness cartilage in the medial compartment, intact ligaments, a correctable valgus deformity, and a flexion contracture less than 10-15 degrees. The most reported contraindications were inflammatory arthritis and severe patellofemoral involvement.
Interpretation / Conclusion: While the literature suggests that some agreement does exist regarding indications for lateral UKA, a strong consensus was not found, indicating that well-defined and consensus-based indications for lateral UKA do not yet exist.

Simon Comtesse¹, Alexander Crotta ¹, Thomas Zumbrunn ², Stephen Ferguson ¹, Arvind von Keudell^(2,3,4)
1. Institute for Biomechanics, ETH Zurich, Switzerland; 2. CustomSurg AG, Switzerland; 3. Brigham and Women’s Hospital, Harvard Medical School, Boston, USA; 4. Bispebjerg Hospital, Copenhagen, Denmark;

Background: The surgical treatment of tibial plateau fractures is complex and subjective, resulting in complication rates up to 28% . Hence, an objective method for the optimization of tibial plateau fractures by means of Finite Element Modelling (FEM) has been introduced. However, while simulation parameters are chosen based on best practice, they introduce uncertainties to the model.
Aim: Therefore, a sensitivity analysis was performed where the modelling parameters were varied to quantify the influence thereof on the simulation results.
Materials and Methods: The CT scan of a cadaveric tibial plateau fracture was segmented, and the bone fragments were aligned to achieve the fracture reduction and further fixed with a medial plate and several locking screws. Hounsfield Units (HU) derived bone material properties based on a phantom-less calibration method as well as joint and muscle forces from subject-specific musculoskeletal gait models were integrated. Modelling parameters were changed systematically and the results were compared relative to the standard simulation in terms of maximum displacement of fracture fragments and von Mises screw stresses.
Results: The following parameters had no or minimal influence on the results (< 5 %): Linear instead of non-linear geometry Linear instead of quadratic elements Frictional coefficient of plate-bone interface Frictional coefficient of bone-bone interface The results for the parameters determining the material properties (hardware and bone) are shown in figure 1.
Interpretation / Conclusion: Although the contact in-between bone fragments and the bone and the plate seems to be an important modelling parameter, their actual frictional coefficient is irrelevant. A much larger impact on the result arises from the parameters directly determining the material properties of the hardware or the bone. However, according to the manufacturers indications, the Young’s Modulus of the plate can be checked precisely. Moreover, the magnitude of applied joint reaction forces has a direct influence on the results in that the maximum fragment displacement and von Mises stresses in the screws increase proportionally to the applied load.

Jacob Juul Pedersen¹, Anders Bo Nielsen², Amandus Gustafsson³, Bjarke Viberg²
1. University of southern Denmark, Odense, Denmark 2. Odense University Hospital, Odense, Denmark 3. University of Copenhagen, Copenhagen, Denmark

Background: Basic orthopaedic surgery skills (BOSS) in drilling and handling instruments have previously been assessed as one of the most prioritized areas in a simulation-based residency curriculum. Still, simulation training in BOSS has yet to be developed and is usually very costly.
Aim: To develop a low-cost simulation-based test to assess BOSS, gather validity evidence for the tests, establish credible pass/fail scores, and explore the consequences of the pass/fail score.
Materials and Methods: Five practical skill stations were developed from a previous published work using pilot testing and interviews: S1) Depth of plunging S2) 2-dimensional drilling S3) Drilling through the center of a long bone by feel S4) Fracture reduction with clamps S5) Fluoroscopy The stations were made of standard items from hardware- and electronic stores. Messick's framework was used to gather validity evidence for the test. A novice group of doctors with no surgical experience (n=11), an expert group of specialized traumatologists (n=9), and a novice group for training to pass (n=7) were included. All scores were measured in millimeters, and each station's test was repeated until a plateau score, defined as no improvement in three subsequent repetitions. Levene’s test and students' t-test compared performances. The pass/fail score was established using the contrasting groups method (CGM).
Results: The simulation setup estimated costs were less than 8.300 DKK. There was moderate to high internal consistency reliability using the interclass correlation coefficient for the 5 stations (0.40 to 0.95). The mean plateau scores when comparing the novice and expert groups for each station were all statistically significantly different (p scores 0.002-0.022). This led to pass/fail scores using CGM for S1: 12mm, S2: 8mm, S3: 4mm, S4: 2mm, and S5: 8mm. The average time and no. of attempts to pass the tests were S1: 5.1 minutes, 8 attempts, S2: 17.6 minutes, 24 attempts, S3: 3.8 minutes, 6 attempts, S4: 6.5 minutes, 5 attempts, S5: 32 minutes, 11 attempts.
Interpretation / Conclusion: We developed a low-cost, simulation-based practical test to assess BOSS with solid validity evidence. This enables a standardized, objective, evidence-based approach to assessing BOSS.

Oliver Lyndrup¹, Charlotte Juhl Lorentsen¹, Ane Simony¹
1. Department of Orthopedic Surgery and Traumatology. Lillebaelt Hospital, University Hospital of Southern Denmark, Kolding

Background: Medical healthcare complaints are a frequent encounter at departments of orthopedic surgery. Consequently, the heads of departments spend a valuable amount of time handling the complaints through dialogue with all parties involved. Being in risk of receiving a complaint is stressful to younger doctors, thus supervision from experienced colleagues is crucial to ensure a safe learning environment.
Aim: This study aimed to report the trends in medical healthcare complaints at two different orthopedic departments at Lillebaelt Hospital, both taking care of acute and elective patients
Materials and Methods: This descriptive study included all medical healthcare complaints at two orthopedic departments at Lillebaelt Hospital, Region of Southern Denmark, during 2023. Outcomes were number of complaints for each medical staff group, in elective/acute setting, for each ground and distribution between the two hospitals.
Results: 58 complaints were registered during the study period, and 16 of these involved more than 1 staff group. In total, 39 (67%) complaints involved a consultant and 16 (28%) involved a resident in training. 28 (48%) complaints was in an elective setting, 19 (32%) was in an acute setting, and 11 (20%) had missing data. In terms of grounds of complaint, 42 (72%) patients complained of treatment, 5 (9%) of behavior, 1 (2%) of the examination, 6 (10%) of a combination of these and 4 (7%) for other reasons. The complaints were distributed between 22 (38%) from the department in Vejle and 36 (62%) from the department in Kolding.
Interpretation / Conclusion: Few complaints involved residents and most of these were aimed at more than 1 group of staff, indicating that fear of complaints amongst young doctors should be low. The department in Vejle had fewer complaints than Kolding, most likely caused by the higher proportion of residents with great responsibilities in clinical practice.

Lili Worre Høpfner Jensen¹, Arash Ghaffari¹, Ole Rahbek¹, Birthe Dinesen², Søren Kold¹
1. Interdisciplinary Orthopaedics, Orthopaedic Surgery Department, Aalborg University Hospital 2. Laboratory for Welfare Technologies – Digital Health & Rehabilitation, ExerciseTech, Department of Health Science and Technology, Aalborg University

Background: Digital communication between patients and healthcare professionals is increasingly used in healthcare. Defined as e-mail, secure messaging, or text messaging, studies describe it as one of the most used features in digital patient portals and eHealth interventions. Enabling asynchronous interaction offers flexibility to both patients and healthcare professionals. Nevertheless, there remains a paucity of literature detailing its utilization in the post-discharge period and the factors motivating or hindering implementation.
Aim: This scoping review aimed to identify and map how digital two-way communication is used between patients and healthcare professionals after hospital discharge, as well as identify facilitators and barriers to implementation.
Materials and Methods: Following the JBI guidance for scoping reviews, we searched seven databases on August 29,2022. Rayyan was employed for screening the articles, and data were extracted using a predefined and iteratively modified data extraction tool. Facilitators and barriers were charted according to the domains and constructs of the Consolidated Framework for Implementation Science (CFIR).
Results: Forty articles were included, primarily published between 2012 and 2022 and from the USA. Digital two-way communication was used across patient populations with similar and overlapping reasons. Facilitators and barriers were identified in 24 of 40 articles and encountered equally yet sparsely across CFIR domains and constructs.
Interpretation / Conclusion: There is a gap in the literature between studies that describe the use of digital two-way communication exhaustively and reports on facilitators and barriers to implementation. This scoping review serves as an overview of the current use of digital two-way communication after hospital discharge and sheds light on facilitators and barriers relevant to managers and clinicians when implementing digital communication.

Markus Mogensen¹, Charlotte Abrahamsen^1,2, Inge Hansen Bruun^2,3, Ane simony^1,2
1. Department of Orthopedics, Kolding, Hospital Lillebelt 2. Institute for Regional Health Services, University of Southern Denmark 3. Department for physical therapy and occupational therapy, Kolding, Hospital Lillebelt

Background: Major lower limb amputation are performed in patients suffering from arteriosclerosis, diabetes and infections. Amputations are a procedure making permanent change in a patients’ physical capability and has an impact on mental wellbeing. A prosthesis can be a useful tool to regain mobility and increase quality of life.
Aim: In this study we examined the change of prosthetic suitability assessment given at time of admission with the prosthetic suitability given at time of discharge comparing the findings with impactful risk factors.
Materials and Methods: Data from amputees was extracted from the KOKO database from Orthopedic Department Kolding, Hospital Lillebelt. Patient demographics and variables were examined, according to assessment of prosthetic suitability. Data was analysed using STATA.
Results: A total of 249 patients underwent a LEA in this study period, of which 107 did not meet the inclusion criteria; 107 patients was excluded due to age < 50 years, missing data, transferred to other hospitals and mortality. A total of 142 (57%) patients were eligible to further analysis, mean age 72 y (60-79), 62 % males. 54 % was active or previous smokers, 43 % had diabetes and 66% arteriosclerosis. 31 was found suitable for prosthesis at the time of admission for surgery, 81 patients was considered maybe and 30 was not candidates for prosthesis. 46 patients changed prosthesis evaluation during the admission period, 3 patients improved and 3 patients declined.
Interpretation / Conclusion: This study highlights there is a difference in prosthetic compatibility from time of admission to time of discharge. 61% of the patients assessed maybe prosthetic suitable at time of admission are equally distributed between prosthetic suitable and not prosthetic suitable at time of discharge. 90% of prosthetic suitable and not prosthetic suitable remains unchanged from admission to discharge. Age, civil status, new mobility score, mobility aids, previous amputation, and accommodation at time of admission were of significance comparing the suitable and the not suitable patients. While BAMS and amputation level were of significance between the maybe prosthetic suitable patients.

Christine Krogsgaard Schrøder^{1, 2}, Vibeke Nørholm², Ingrid Poulsen^{2, 3}, Pia Søe Jensen^{1, 2, 3}
1. The Research Unit of Orthopaedic Nursing, Department of Orthopaedic Surgery, Copenhagen University Hospital, Hvidovre, Denmark; 2. Department of Clinical Research, Copenhagen University Hospital, Hvidovre, Denmark; 3. Department of People and Technology, Health Promotion Research Center, Roskilde University, Denmark.

Background: Integrating nutritional dialogue and education into leg ulcer treatment in the outpatient clinic may enhance wound healing and prevent leg ulcer progression to amputation.
Aim: This study examines the feasibility, acceptability, and fidelity of a nurse-led nutritional intervention including a dialogue tool, patient information, and protein supplement.
Materials and Methods: An observational cohort study, at Hvidovre Hospital's wound clinic using mixed-methods. The intervention comprises 1) a dialogue tool, presenting the correlation between nutritional status, the immune system, and wound healing; 2) an information brochure detailing wound healing, treatment recommendations, and supportive behaviours; and 3) an introduction to protein drinks along with the distribution of a "green" prescription. Eligible participants are patients with first-time referrals for assessment of ulcers or amputation wounds in the lower extremities. Specialized wound nurses will administer the intervention. Following inclusion, patients will receive two follow-up calls after their subsequent clinic visits. The first follow-up will collect patient characteristics, wound information using the Wound-QoL, and closed-ended questionnaire responses assessing the feasibility of the intervention's three components. The second follow-up will involve interviews evaluating the acceptability of the intervention. Feasibility will be determined by predefined criteria for each intervention component, with compliance thresholds set at 80% for feasible and below 30% for non-feasible. The overall feasibility will be assessed through the synthesis of these criteria and thematic analysis of the interviews. Additionally, focus group interviews with nurses will be conducted. The study is registered at Clinical Trials (NCT06255288). Patients will be recruited between 01.02.2024 and 31.05.2024.
Results: The feasibility, acceptability, and fidelity will be reported for each component of the intervention.
Interpretation / Conclusion: This is the first project to provide a three-part nutritional intervention engaging both patients, their relatives, and the nurses regarding lower extremity wound care. The study will be used to inform the development of a subsequent RCT study.

Mads K. D. Mikkelsen^1,2, Andrea R. Jørgensen^1,2, Victor N. Dahl³, Christian M. Wejse³, Mats Bue^1,2, Maiken Stilling^1,2
1. Orthopedic Research Laboratory, Aarhus University Hospital; 2. Department of Orthopedics, Aarhus University Hospital; 3. Department of Infectious Diseases, Aarhus Unioversity Hospital

Background: Extrapulmonary nontuberculous mycobacteria (NTM) infections are notoriously hard to treat, which may partly be due to inadequate tissue concentrations of antimicrobials
Aim: We aimed to evaluate local tissue concentrations of azithromycin in a patient treated for Mycobacterium heraklionense tenosynovitis of the flexor tendons of the index finger.
Materials and Methods: Using microdialysis, we evaluated the local tissue concentrations of azithromycin during three tendon and pulley reconstructive surgeries of the right index finger in a patient treated with an all-oral azithromycin- ethambutol-rifabutin regimen for 11 months. We sampled from the brachioradial muscle, subcutis, and flexor tendon sheaths of the palm and forearm. To increase infection control, we installed local antibiotics in the surgical field of the index finger and distal forearm during surgery 2 in the form of STIMULAN® calcium sulfate beads prepared with azithromycin.
Results: At submission, analysis is complete for the first and second surgery. Plasma concentrations ranged from 0.1-1.1 µg/mL throughout all surgeries and resembled the tissue concentrations, ranging from 0.5-1.8 µg/mL during surgery 1 and 0.3-1.7 µg/mL during surgery 2. Plasma concentrations reached Cmax targets of >0.2 ug/mL from previous studies of pulmonary NTM. During surgery 2, the azithromycin concentrations in the compartments in direct contact with the beads ranged from 56-151 µg/mL during a sampling period of 5 hours. The beads had to be surgically removed after 10 days due to continuous drainage and wound infection with Enterococcus faecalis. One month after the final reconstructive surgery the patient has not shown signs of relapse and is in good recovery.
Interpretation / Conclusion: Azithromycin concentrations in the targeted hand tissues resembled the steady-state concentrations found in plasma following long-term oral azithromycin treatment. When applying azithromycin locally mixed in calcium sulphate beads, high target site concentrations can be achieved. However, calcium sulfate beads should be used with caution under thin skin flaps due to risk of drainage and delayed wound healing. More evidence is needed to challenge current recommended treatment regimens of NTM infections.

Susanne Friis-Søndergaard^1,2, Ane Simony^3,4, Johanne Christensen ⁵, Marie Dahl^2,6
1. Lovisenberg, University of Applied Science. Norway; 2. Vascular Research Unit, Department of Vascular Surery, Hospital Viborg; 3. Department of Orthopedic Surgery, Hospital Lillebelt; 4. Institute for Regional Health Services, University of Southern Denmark; 5. Department of Culture and Language, University of Southern Denmark; 6. Cardiac thoracic and vascular Research Unit, University of Southern Denmark.

Background: Chronic limb-threatening ischemia (CLTI) is accompanied by high utilization of healthcare services, with multidisciplinary professionals providing care in primary and secondary settings. CLTI is a progressive disease that induces physical, emotional, and social burden on the patients, but also requires high patient adherence to avoid severe complications. To our knowledge, no previous studies has focused on the patient perspectives related to this topic.
Aim: The objective of this review was to systematically identify, examine, and conceptually map the existing literature on patients who have CLTI in the context of living with the condition, and explore their experiences of living with CLTI and their treatment and care within a cross-sectoral setting.
Materials and Methods: A systematic search was conducted and completed on September 18th, 2023, without methodological or format restrictions. We identified Population, Concept, and Context to pinpoint the focus of this review process. The JBI methodology for scoping reviews and the PRISMA-ScR checklist were followed.
Results: Based on our search, we found ten relevant scientific qualitative and/or quantitative and one non-scientific sources. We identified four main maps: 1) Dependency on others is my new life condition; 2) I’m more than the sum of my conditions, 3) I’m lost in chaos, be alert to all of me, and 4) Give me more time, my body and mind are under attack.
Interpretation / Conclusion: This scoping review describes how patients’ life is affected by the CLTI and their perception of both shared decision-making alongside treatment and care, emphasizing the need for more person-centered care. To nuance person- centred care further, it is necessary to consider the impact of patients’ cultural values and preferences, about which there is a notable gap in research.

Nawfal Khalid-Rasheed Al-Attar¹, Mykola Horodyskyy¹, Jacob Fyhring Mortensen¹, Kenneth Chukwuemeka Obionu², Søren Overgaard²,
1. Department of Orthopaedics, Sjællands Universitets Hospital - Nykøbing Falster 2. Department of Orthopaedics, Bispebjerg Hospital

Background: Ingrown nails present a common and debilitating issue, and while partial matrixectomy is deemed an effective approach for treating ingrown nails, recurrence rates have been observed ranging from 10-50% in the literature. While it can manifest at any age, the most typical age range is 15 to 40 years old, with a male-to- female ratio of 3:1 (1), and factors contributing to recurrence are many. Our study identifies a significant association between complications, including panaricium, abscess, and claw formation, in the postoperative periode and the recurrence of ingrown toenails.
Aim: The aim of this study is to examine the incidence of reoccurrence and risk factors following partial matrixectomy of ingrown nails.
Materials and Methods: This was a retrospective cohort study, including patients aged 18 years and above. The electronic health records from Copenhagen university Hospital, Bispebjerg , department of orthopaedic surgery and traumatologywere reviewed between 2017-2020. Data was analysed using descriptive statistics, while chi-square analysis was performed to analyze the determinants of recurrence.
Results: Of 159 participants, 52% (n=83) were female, and 48% (n=76) were males. The age distribution was: 18-28 years (43.4%), 29-40 years (22%), 41-60 years (15,7%), 61-90 years (18,2%). Among all participants, 72.7% (n=115) were active smokers. Age [OR 1.02, 61-90 (0%); 18-28 (29%); 51-60(38%); 41-50 (60%); 29- 40(64%)], and muscoskeletal disorders (OR 1.06) manifested slightly high recurrence, however with a non-significant association (Age, p=0.07, MSD, p=0.402). Although there was a significant association of recurrences with Smoking (OR 0.24, 95% CI, p=0.000) and gender (OR 0.34, 95% CI, p=0.016), both smokers and males demonstrated lower odds. Furthermore, the incidence of complications was remarkably higher (OR 4.35, 95% CI, p<0.000) among patients with recurrence.
Interpretation / Conclusion: The study identified elevated complication rates among relapsed patients, and highlighted other factors that could lead to recurrence of ingrown toenails.

Adriano Axel Ceccotti¹, Tøttrup Mikkel ², Morch Anica¹, Husum Hans-Chresten¹, Jensen Steen Lund¹
1. Department Orthopaedics, Aalborg University Hospital 2. Department Orthopaedics, Aarhus University Hospital

Background: Anatomic total shoulder arthroplasty (aTSA) is the recommended surgical treatment for severe glenohumeral osteoarthritis providing good pain relief and function. Aseptic loosening of the glenoid component, however, is a major cause for revision. Hybrid components have been introduced combining cemented fixation with bone ingrowth to improve fixation.
Aim: The purpose of this study was to report our mid- term to long-term experience using such a component including clinical outcomes and implant survival.
Materials and Methods: We reviewed all patients who were operated for primary osteoarthritis during the period 2011-19 leaving a minimum of 2 years follow-up. Clinical outcomes included WOOS index. Postoperative radiographs were analyzed for radiolucent lines. Patient records were studied for complications including revisions. Kaplan-Meier estimates for implant survival were calculated.
Results: A total of 256 arthroplasties in 224 patients were included (mean age: 69 years ± 9 years, 149 females). Mean follow-up time was 49 months (range 24 - 127). The response rate for patient reported outcomes was 91%. The median WOOS index was 94% (81%-99%), the median EQ-5D-5L was 0.87 (0.69-0.95), and the mean CMS was 75 (SD 17.7). 13 cases (6%) had a WOOS index below 50%. 8.2% had complications related to surgery. A radiolucent line had developed around the central post in six cases, and at the bone-cement interface in three cases at follow-up. Six cases had been revised (2.3%); three due to aseptic loosening of the glenoid. The 10-year survival estimate was 95.6 % (95% CI: 87.9% - 98.5%).
Interpretation / Conclusion: Anatomic total shoulder arthroplasty with hybrid glenoid fixation provides excellent clinical outcome with a low complication rate in patients with primary glenohumeral osteoarthritis. The 10-year survival rate is high and comparable to that reported for the best performing all-polyethylene components. Longer observation is needed to see if hybrid fixation will outperform standard all-cemented components.

Gustav Kalle Mølbak Vangsgaard¹, Michael Rindom Krogsgaard¹, Christian Fugl Hansen¹
1. Section for Sports Traumatology, M51, Bispebjerg and Frederiksberg Copenhagen University Hospital

Background: Patient reported outcome measures (PROMs) are essential to express the patient’s subjective perspective in clinical studies. Like any measurement instrument PROMs should be valid, reliable, and responsive. Inadequate PROMs induce a high risk of type-II errors. There is no thorough analysis of the PROMs that have been used in the clinical research regarding adhesive capsulitis (AC).
Aim: The aim was to evaluate the quality of these PROMs and identify which are the most useful for future studies on AC.
Materials and Methods: Relevant PROMs used to evaluate patients with AC were identified through PubMed searches and a catalogue of PROMs, and subsequently, validity studies were identified for selected PROMs. Quality assessment involved evaluating development and validation processes, utilizing a rating system. Development quality was assessed based on guidelines emphasizing content validity. Validation studies were rated based on modern test theory models and the psychometric assessments undertaken. Aggregated scores considered both content and construct validity, with the “lowest score counts” principle.
Results: 16 different musculoskeletal PROMs that had been used 160 times in total (range 1- 43) were identified. None of the PROMs were developed specifically for patients with AC. Four PROMs had some degree of patient involvement in the developmental process, but the patients represented broader conditions or other diseases than AC. 39 articles on measurement properties were identified through PubMed, analyzed, and assessed together with 40 articles from the catalogue. Five PROMs have had their psychometric properties validated with an MTT model. However, all five possessed inadequate content validity as none of them had patients involved in the development process. Hence, this study was not able to identify any PROM with adequate content and construct validity for patients with AC.
Interpretation / Conclusion: A new and condition-specific PROM for AC is urgently needed. The current PROMs should be used with significant reservations and results obtained by them should be interpreted with caution.

Kirstine Lyngsøe Hvidberg¹, Cecilie Rud Budtz², Grethe Aalkjær¹, Søren Riis Villumsen³, Brian Elmengaard³, David Høyrup Christiansen², Helle Kvistgaard Østergaard¹
1. Department of Orthopaedics, Viborg Regional Hospital 2. University Clinic for Orthopaedic Pathways (UCOP) Elective Surgery Centre , Silkeborg Regional Hospital 3. Department of Elective Surgery Centre, Silkeborg Regional Hospital

Background: Scapula alata (SA) is a condition characterized by medial winging and decreased upward rotation of the scapula during elevation of the arm, often causing impairment of the shoulder function. There is currently no evidence regarding the most optimal treatment for this condition.
Aim: This study aimed to assess the current treatment approaches used for SA in public hospitals in Denmark.
Materials and Methods: A cross-sectional survey was undertaken using a self-administered questionnaire to healthcare professionals across departments in all public hospitals in Denmark. The survey investigated local treatment guidelines, as well as diagnostic practices with referral to electroneurography(ENG), the use of International Classification of Diseases 10th Revision (ICD10) coding, and the annual number of patients.
Results: In total, 20 hospital departments completed the questionnaire. Treatment approaches included exercise therapy in various contexts, brace treatment, surgery, and, in some cases, a waiting approach. Only four hospitals reported the use of written local guidelines for SA treatment and diagnostics practices. Five hospitals use ENG as part of their diagnostic practice, while five others do so selectively based on specific indications. Seven different ICD-10 codes were reported for SA. The annual patient number ranged from none to 20, with four hospitals accounting for most of the patients. Doctors and physiotherapists are the primary healthcare providers involved in the diagnostic and treatment process.
Interpretation / Conclusion: This survey revealed large national variations in the treatment of SA in Denmark. This emphasizes the need for further research and standardized guidelines for the treatment and diagnostics of patients with SA.

Carl Christian Holkgaard Burvil^{1, 3}, Emil Toft Petersen^{1, 2, 3}, Janni Kjærgaard Thillemann^{1, 2, 3}, Jan Duedal Rölfing^{2, 3} , Maiken Stilling^{1, 2, 3}
1 AutoRSA Research Group, Orthopaedic Research Unit, Aarhus University Hospital, Aarhus N, Denmark 2 Department of Orthopaedic Surgery, Aarhus University Hospital, Aarhus N, Denmark 3 Department of Clinical Medicine, Aarhus University, Aarhus, Denmark

Background: Radius malunion is a common complication of diaphyseal and distal radius fractures and frequently leads to reduced forearm rotation and ulnar wrist pain. The underlying deformity is often multiplanar and corrective “free hand” osteotomies are thus difficult.
Aim: To evaluate outcomes of patient-specific, 3- dimensional (3D) surgical planning for radius malunions.
Materials and Methods: 4 patients with symptomatic radius malunions underwent corrective osteotomies (3 received individually manufactured plates) and 2 cases received a simultaneous triangular fibrocartilage complex (TFCC) reinsertion. Pre- and postoperative data were collected including 1) CT scans of both forearms to plan the osteotomies and to evaluate the achieved correction by bone mirroring of the contralateral forearm, 2) standard AP and LA radiographs (ulna variation, radius angulation and inclination), 3) bilateral dynamic radiostereometry (dRSA) to compare the kinematics of the distal radioulnar joints (DRUJ) at the maximum applied force during a press-test and a rotation-test, 4) physical examination (range of motion (ROM), hand grip strength), and 5) patient reported outcome measures (qDASH, PRWE, and overall satisfaction).
Results: Postoperative bone mirroring and radiographs showed that all 4 radial bones were corrected towards the planned correction. However, the planned ulnar variance was only fully achieved in 1 of 4 cases. Kinematics of the DRUJ improved in 2 patients, were unchanged in 1 patient, and worse in 1 patient during the press-test. The ROM and grip strength changed minimally, except for 1 patient with significant improvement in ROM. The qDASH score improved in 3 of 4 patients (1 was clinically significant) while PRWE improved for all 4 patients (2 were clinically significant). 2 patients reported to be “very satisfied” and 2 reported to be neither satisfied nor dissatisfied with surgery.
Interpretation / Conclusion: Specific 3D-planning using the contralateral healthy arm as a template is of great value when planning radius malunion corrective surgery. Sufficient lengthening of the radius to correct positive ulnar variance is challenging to achieve, but crucial for a good clinical outcome.

Ditte N. Schreiner¹, Gvozdenovic Robert^{2, 3},
1. Medicin, Det Sundhedsvidenskabelige Fakultet, Københavns Universitet 2. Afdelingen for Led- og Knoglekirurgi, Klinik for Skulder-, Albue- og Håndkirurgi, Københavns Universitetshospital - Herlev-Gentofte Hospital 3. Institut for Klinisk Medicin, Det Sundhedsvidenskabelige Fakultet, Københavns Universitet

Background: Wrist arthroscopy is a gold standard in the diagnosis of triangular fibrocartilage complex injuries. Although minimally invasive, this surgical procedure has the disadvantage of being technically advanced, needing high skills, and the interpretation of the findings might be variable among the observers. Even though the ulnocarpal and distal radioulnar joints are not as large as articular spaces of the knee or shoulder, recent studies reveal MR scan could be an alternative diagnostic tool.
Aim: The purpose of this literature review is to investigate the role of Magnetic Resonance Imaging (MRI) in diagnosing triangular fibrocartilage complex (TFCC) injuries in the ulnar wrist. The methodology is interpreted using the STARD standards for diagnostic studies. Additionally, it aims to analyze the clinical utility of the studies.
Materials and Methods: 25 articles were selected through systematic reading of available papers in the databases PubMed, Embase, and Cochrane Library, as well as reference lists from selected articles, using a set of exclusion criteria.
Results: The predictive values of MRI in identifying TFCC lesions vary considerably. However, this study highlights some advantages of using specific sequences, field strengths, post-processing techniques, and specific "pathological markers" alongside MRI. It is also concluded that magnetic resonance arthrography (MRA) shows more promising results than MRI, although the method is more expensive and associated with surgical risks. Additionally, this study addresses the issue of the need for extensive experience in image analysis for both MRI and MRA in diagnosing TFCC lesions.
Interpretation / Conclusion: Although the predictive values of MRI have shown promising results, those are largely based on retrospective studies where the patient groups have been selected among those having ulnar-sided pain, without controls. Therefore, it is concluded that MRI should not be relied upon as an independent diagnostic tool for painful TFCC lesions. There is a need for more well-designed studies to further determine the clinical relevance of this diagnostic modality.

Muhammed Bakhtiyar, Afrim Iljazi, Michael Mørk Petersen, Anders Oddgaard, Christian Wong
Department of Orthopedic Surgery, Rigshospitalet, Copenhagen, Denmark

Background:
Aim: This study aims to assess the incidence of hip displacement and dislocation (denominated as hip migration) among ambulant and non-ambulant Danish children with cerebral palsy (CP) by estimating their cumulative incidence of migrated hips. A secondary objective is to compare the prevalence across different Danish regions.
Materials and Methods: Data were obtained from the Danish Cerebral Palsy Follow-Up Program (CPOP) from the years 2008 to 2021. This population-based cohort study included 1,388 children with CP (58% male, 42% female) as subjects, aged 0-15 years, with an average age of 5.4 years at their last follow-up. The children were categorized according to their Gross Motor Function Classification System level (GMFCS) into ambulators (GMFCS I-III) and non-ambulators (GMFCS IV-V). The Kaplan-Meier estimator was employed to calculate the cumulative incidence of migrated hips from birth until the date of their last radiographic follow-up. Differences between ambulatory and non-ambulatory children and regional differences were assessed with the Log- rank test.
Results: Median radiological follow-up for ambulators was 51 months and 94 months for non-ambulators. The cumulative incidence of hip dislocation was 0.3% (95% CI: 0-0.8 %) and 22.0% (95% CI: 9.2 -34.8 %) for ambulators and non-ambulators, respectively (p<0.0001), whereas the incidence for hip displacement were 21.1% (95% CI: 16.3-25.9 %) and 76.7% (95% CI: 68.6-84.7 %) for ambulators and non-ambulators respectively (p<0.0001). There were no significant regional differences in the incidence of hip dislocation among ambulators, but there were significant differences for non- ambulators. Moreover, significant regional differences were detected in hip displacement for both ambulators and non-ambulators.
Interpretation / Conclusion: The prevalence of hip migration in Danish children with CP is significantly higher among non- ambulators, who are at an increased risk of hip migration compared to their ambulant counterparts. However, the low frequency of radiographic follow- up for ambulators might cause the incidence of hip migration to be underestimated. This study highlights the necessity of continued targeted surveillance and interventions in Danish non- ambulators.

Maria Lund Gjættermann^1,2, Jan Duedal Rölfing^1,2, Jannie Dahl Hald^3,4, Bjarne Møller-Madsen^1,2
1. Danish Paediatric Orthopaedic Research, www.dpor.dk, Aarhus University Hospital, AUH, Denmark; 2. Department of Children's Orthopaedics and Reconstruction, Aarhus University Hospital, AUH, Denmark; 3. Department of Endocrinology and Internal Medicine, Aarhus University Hospital, AUH, Denmark; 4. Center for Rare Disorders, Department of Paediatrics, Aarhus University Hospital, AUH, Denmark

Background: Osteogenesis Imperfecta (OI) is a rare genetic connective tissue disorder characterised by increased bone fragility, bone deformities, and increased risk of fractures. One among other radiographic findings in OI patients is Protrusio Acetabuli (AP), in which the acetabulum and femoral head migrate into the pelvic cavity.
Aim: This study aims to investigate the incidence and severity of AP in children with OI, as well as the OI types in which it occurs. Additionally, we aim to investigate the clinical consequences to AP and elucidate potential risk and protective factors.
Materials and Methods: Medical records and pelvic radiographs of 16 children (7 F, 9 M), aged 2-18 years (mean age: 10,5 years), with OI, followed at Department of Children’s Orthopaedics at Aarhus University Hospital between 2018 and 2023, were retrospectively evaluated. Demographic and anthropometric information, along with Sillence and Glorieux classification were registered. The severity and presence of AP were determined utilising the following radiographic criteria: the appearance of the teardrop configuration, the center-edge angle of Wiberg, and the acetabulum’s location relative to the Kohler and iliopectineal line.
Results: 4 of the 16 OI patients had AP. One third of the cases had type III or IV. None of the patients had severe AP with the acetabulum progressing medial to the iliopectineal line. The median age of the AP patients was 13,5 years. 3/4 were female. 3/4 had anisomelia, and 2/4 had scoliosis. 2/4 were dependent on mobility devices. 2/4 experienced pain in the same hip where AP was present, and 1/4 experienced knee pain. Patients over 12 years of age (OR: 2, 95%-CI: 0,2-19,9), with a BMI exceeding 25 (OR: 33, 95%-CI: 1,6-698, p < 0,05), of female gender (OR: 6, 95%-CI: 0,5-77,8), and suffering from scoliosis/anisomelia (OR: 3, 95%-CI: 0,3- 31,6; OR: 3, 95%-CI: 0,24-37,7) had higher odds of developing AP. None of potential protective factors were identified.
Interpretation / Conclusion: OI patients often present with AP. Hence, it may be beneficial to investigate the incidence of AP in adults and its clinical consequences to offer improved management, if not to provide advice on how to prevent AP.

Prajahi Ketheeswaran ^1,2, Line Kjeldgaard Pedersen^1,2, Polina Martinkevich^1,2 , Bjarne Møller-Madsen^{1, 2}
1. Department of Children's Orthopedics, Aarhus Universitet; 2. dpor.dk, Aarhus, Denmark, Denmark

Background: Cerebral Palsy (CP) is a motor function disorder due to damage in the immature brain. One motor function difficulty seen amongst patients with CP is a spastic varus foot deformity caused by an overactivation of the tibialis posterior muscle (TP) or a weakening of the peroneus muscle group. This contributes to several problems in the daily life of these patients. The dynamic characteristic of the disease makes it difficult to treat. One treatment option is tibialis posterior tendon transfer (TPT).
Aim: This study aims to investigate the life quality of patients with CP treated with TPT for spastic varus foot.
Materials and Methods: In this retrospective single-centre follow-up study 24 patients were included of which 19 patients with a total of 26 operated feet answered the patient reported outcome measure (PROM). The mean follow-up time was 2.6 years ± 2.14. PROMs were collected using the validated Danish translation of the Oxford Ankle and Foot Questionnaire (OxAFQ-C). OxAFQ-C investigates four main domains; Physical activity, School and Play, Emotional outcome, and Footwear and Clothing. Answers given by the patient, or a proxy were collected using REDCap or through phone calls.
Results: OxAFQ showed that patients were most satisfied regarding School and Play. As seen in (Fig 1) the majority answered ‘Never’ in three out of four questions asked in this domain, which implies that they were not troubled regarding these events. Patients were least satisfied concerning some aspects of physical activity (Fig 1). In this domain patients answered that they were “Often” or “Always” hindered when running or standing for a longer period.
Interpretation / Conclusion: Results indicate that TPT is valuable to patients with CP and spastic varus foot. The study suggests that patients who underwent TPT experience satisfaction especially concerning School and Play. However, patients were generally satisfied in all four invastigated domains. Information on patient satisfaction of TPT for patients with CP is still scarce. This study invites to consider TPT as a simple soft tissue procedure in spastic varus foot with weakening of the peroneus muscle group or overactivation of TP.

Christian Kveller¹, Thomas Baad-Hansen¹
1. Department of Orthopaedic, Aarhus University Hospital

Background: Sarcomas are rare and aggressive tumors, affecting all age groups, accounting for approximately 1% of all adult malignancies and over 10% of pediatric malignancies. A majority of these tumors are treated with a combination of surgery, chemotherapy, and radiation therapy. Radiation near growth zones can result in abnormal or stunted development, as well as the risk of induction of malignancy secondary to the radiation. Brachytherapy allows delivery of high doses of radiation to the tumor or tumor-bed, while sparing surrounding tissue and treatment duration is shortened compared to external beam radiotherapy, while avoiding radiation- related side effects.
Aim: To assess the functional outcome and long-term effects on extremity function following brachytherapy treatment in all pediatric patients having received brachytherapy at our institution.
Materials and Methods: Pediatric patients having received brachytherapy were identified through internal hospital records and patients were recruited during regular follow-up appointments, during which they were interviewed and completed PROMs.
Results: 3 patients were recruited. None had experienced recurrence during follow-up. Time since treatment ranged from 5-9 years. 66% were treated at or near a physis and 100% of these experienced limb-length discrepancy, while only the patient with lower extremity length discrepancy was symptomatic. 66% had experienced progressive functional deterioration inversely correlated with growth due to unyielding cicatricial tissue, more pronounced in patient with lower extremity affection. 66% had undergone pronounced muscle excision during treatment and experienced decreased endurance in the affected limb. None reported neural deficits despite having received surgery and radiation adjacent to significant peripheral nerves.
Interpretation / Conclusion: Brachytherapy is a viable treatment modality for pediatric sarcomas with good functional results. However, the dynamic growth of the patient poses challenges in securing the best possible functional outcomes. Closer cooperation with oncological late effects clinics and pediatric orthopedic surgeons may be beneficial as the brachytherapy patient’s post-operative conditions mimic growth abnormalities.

Ebrahim Rahdi¹, Catarina Anna Evelina Malmberg¹, Tue Smith Jørgensen², Rafal Yahya¹, Adam Witten¹, Lars Blønd², Per Hölmich¹, Kristoffer Weisskirchner Barfod^1,3
1 Sports Orthopedic Research Center – Copenhagen (SORC-C), Department of Orthopedic Surgery, Copenhagen University Hospital Amager-Hvidovre, Denmark 2 The Zealand University Hospital of Koege 3 Unit of Sports Traumatology, Department of Orthopedic Surgery, Copenhagen University Hospital, Bispebjerg-Frederiksberg

Background: Treatment of patellar dislocation is based on the absence or presence of osseous risk factors.
Aim: To map the literature regarding the use of osseous risk factors, patient reported outcome measures (PROM’s), and treatment methods in studies investigating treatment of patellar dislocation.
Materials and Methods: This was a scoping review following the PRISMA guidelines extension for scoping reviews (PRISMA-ScR). Studies published between January 1, 2013, and April 3, 2023, were eligible for inclusion if investigating the treatment of patellar dislocation and mentioning an osseous risk factor. Case series with fewer than 10 patients, reviews, and meta-analyses were excluded.
Results: A total of 8,923 records were identified, 1,007 were full text-screened, and 300 articles were included. A two-fold increase of articles investigating the treatment of patellar dislocation was observed from 2013 to 2022. Across the included articles, 160 osseous risk factors and 56 PROM’s were identified. 131 (44%) of the included articles used osseous risk factors as in- or exclusion criteria. 26 (9%) articles used a PROM developed for evaluation of patellar instability (the Banff Patellar Instability Instrument or the Norwich Patellar Instability score) to evaluate the treatment effect. The most frequently investigated treatment was medial patellofemoral ligament reconstruction (231 articles, 77%) followed by tibial tubercle osteotomies (87 articles, 29%). A threefold increase of articles investigating these methods was observed from 2013 to 2022, and the same was observed for trochleoplasties.
Interpretation / Conclusion: Since 2013, a two-fold increase in studies investigating treatment outcome after patellar dislocation and mentioning osseous risk factors was seen, but less than half of the studies defined the study population based on the absence or presence of osseous risk factors. Only one out of ten studies used a PROM developed for evaluation of patellar instability to evaluate the treatment effect. The most frequently investigated treatment was medial patellofemoral ligament reconstruction.

Torsten Grønbech Nielsen^1,2, Martin Lind¹, Simon Damgaard Petersen³, Pia Kjær Kristensen²
1. Department of Orthopaedic Surgery, Aarhus University Hospital, Aarhus, Denmark; 2. Department of Clinical Medicine, Aarhus University, Aarhus, Denmark; 3. Department of Orthopedic Surgery and Traumatology, Lillebaelt Hospital, Kolding, Denmark.

Background: The Banff Patellar Instability Instrument 2.0 (BPII 2.0) is a patient reported outcome measure designed specifically for measuring patellofemoral instability. As only few questionnaires evaluating patellar instability has been developed, the BPII 2.0 might be the best option to evaluate patients with patellar instability. The questionnaire has shown good psychometric properties in major countries. A cross-cultural translated Danish version of the BPII 2.0 was done in 2019, but the psychometric properties have not been evaluated.
Aim: This present study aimed to assess the BPII 2.0 psychometric properties in a Danish population of patients with patellar instability. Secondly to present the cross-culturally translated and adapted Danish version of the BPII 2.0.
Materials and Methods: The BPII 2.0 was cross-culturally adapted according to international guidelines. The BPII 2.0-DK was tested for concurrent validity (Spearman Rho), internal consistency (Cronbach alpha), and test-rest reliability (intraclass correlation-ICC) in a cohort of patients with patellar instability. The Tegner activity score, the Victorian Institute of Sport Assessment-Patella (VISA-P), the Anterior knee pain scale (Kujala-DK), and the International Knee Documentation Committee (IKDC) were used to assess convergent validity. The test-retest reliability of the Danish version of the BPII 2.0 was evaluated in 50 patients with patellar instability. The patients completed the score, 2 times with a 7-day interval between assessments.
Results: Very strong concurrent validity was found with a value of 0.80 for VISA-P, 0.79 for Kujala-DK and 0.87 for IKDC. Strong convergent validity was found with the Tegner activity score (0.67). A calculated Cronbach alpha sum score of 0.97 indicating excellent internal consistency among items within the BPII 2.0. Test-retest reliability shows excellent and consistent results between the 2 assessments 7 days apart with ICC sum score of 0.94 and individual sum scores from 0.36 to 0.96.
Interpretation / Conclusion: The BPII 2.0-DK is a valid and reliable tool for patients with patellar disorders, showing excellent internal consistency and excellent test-retest reliability and is comparable to other translated versions of the BPII 2.0.

Christian Dippmann¹, Anette Kourakis¹, Simone Rechter¹, Volkert Siersma², Peter Lavard¹
1 Section for Sports Traumatology M51, Department of orthopedic surgery, Copenhagen University Hospital Bispebjerg and Frederiksberg, Copenhagen, Denmark. A part of IOC Research Center Copenhagen. 2 The Research Unit for General Practice and Section of General Practice, Department of Public Health, University of Copenhagen, Denmark

Background: Recurrent patellar dislocation (chronic patellar instability) is often caused by predisposing factors, with trochlear dysplasia (TD) as the most prominent. Untreated patellar instability leads to impaired function and an increased risk of patellofemoral osteoarthritis. TD can be treated by trochleoplasty (TP) and section of sports traumatology at Bispebjerg Frederiksberg Hospital has performed 78% of the TPs in Denmark between 2011 -21, following a standardized treatment algorithm including Bereiter TP by which all predisposing factors are corrected.
Aim: To analyse a cohort of consecutive patients treated 2011-2021 with Bereiter TP for severe TD, including their concomitant predisposing factors, for two-year clinical and patient reported outcome measures.
Materials and Methods: Prospectively collected information covering 2011 to 2021 was analyzed for all patients undergoing patella stabilizing surgery with TP +/- concomitant procedures to correct predisposing pathology (MPFL reconstruction, medialization/distalization of the tibial tuberosity, de-rotating osteotomy, among others). Data preoperatively and at follow-up after one and two years included clinical examination and scores from patient reported outcome measures (Kujala, KOOS and Lysholm).
Results: From 2011 to September 2021 374 Bereiter TPs were performed on 335 patients (102 males, 233 females, 39 bilateral surgeries). There were 92 cases (25%) who had previous patella stabilising surgery. The mean age at surgery was 22 years (range 12-47). All patients had TP and MPFL- reconstruction. 94 knees (25%) also had medialization of the tibial tuberosity, while 98 (26%) had other additional procedures. 102 knees (27%) had subsequent surgery (in 49 (12.1%) arthroscopically assisted brisement force). Four knees (1.1%) experienced a re- dislocation. There were significant improvements in all PROM-scores (p<.0001), e.g. mean Kujala (range 0-100) had improved 18.7 points (95%CI 16.5-20.9), and mean KOOS QoL 31.0 points (95%CI 28.0-34.0) two years after surgery.
Interpretation / Conclusion: Following our algorithm there was a very low re- dislocation rate and significant improvement of the subjective condition one and two years after Bereiter trochleaplasty.

Kamilla Arp^1,2, Thomas Frydendal^3,4, Troels Kjeldsen^3,4, Ulrik Dalgas⁵, Signe Timm¹, Bjarke Viberg^6,7, Claus Ingwersen^1,8, Claus Varnum^1,2
1. Department of Orthopedic Surgery, Lillebaelt Hospital - University Hospital of Southern Denmark, Beriderbakken 4, 7100 Vejle, Denmark 2. Department of Regional Health Research, University of Southern Denmark, Campusvej 555230 Odense M, Denmark 3. Department of Orthopedic Surgery, Aarhus University Hospital, Palle Juul- Jensens Boulevard 99, 8200 Aarhus N, Denmark 4. Department of Clinical Medicine, Aarhus University, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark 5. Exercise Biology, Department of Public Health, Aarhus University, Dalgas Avenue 4, 8000 Aarhus C, Denmark 6. Orthopaedic Surgery and Traumatology, Odense University Hospital, J. B. Winsløws Vej 4, 5000 Odense C, Denmark 7. Traumatology, Hospital Lillebaelt - University Hospital of Southern Denmark, Sygehusvej 24, 6000 Kolding, Denmark 8. Department of Physio- and Occupational therapy, Lillebaelt Hospital - University Hospital of Southern Denmark, Beriderbakken 4, 7100 Vejle, Denmark

Background: Restoring maximal muscle strength of knee extension and knee flexion following anterior cruciate ligament (ACL) injury and reconstruction is of great importance. It is therefore essential for clinicians and healthcare providers to have dynamometers that are easy-to-use, valid and reliable. The ForceFrame is a novel dynamometer that may be a reliable option in comparison to the gold-standard isokinetic dynamometer.
Aim: To assess the reproducibility of the ForceFrame dynamometer and compare to an isokinetic dynamometer in maximum voluntary isometric contraction (MVIC) during knee extension and flexion.
Materials and Methods: Twenty-seven participants with ACL injury or reconstruction participated in this reproducibility study. ForceFrame MVIC were tested on two separate days: Day one including gold-standard isokinetic dynamometer,day two assessment by a new assessors. Main outcomes were concurrent validity and agreement (ForceFrame vs. isokinetic dynamometer), day-to-day test- retest reliability and agreement and inter-tester reliability of ForceFrame.
Results: ForceFrame showed a fair concurrent validity compared to the isokinetic dynamometer for extension (r=0.56), poor concurrent validity for flexion (r=0.24), Bland-Altman plots between ForceFrame and the isokinetic dynamometer showed a mean difference of -0.51 Nm/kg for extension and -0.32Nm/kg for flexion. There was a good day-to-day test-retest reliability for MVIC of extension (ICC=0.77, CI95: 0.48-0.90) and flexion (ICC=0.83, CI95: 0.61-0.92), while there were excellent inter-tester reliability for MVIC of extension (ICC=0.97, CI95: 0.94-0.98) and flexion (ICC=0.93, 95CI: 0.85- 0.97). Standard error of measurement was 8% and 9% while the smallest detectable change was 22% and 27% for extension and flexion, respectively.
Interpretation / Conclusion: ForceFrame can be used to obtain valid and reliable results to assess MVIC of knee extension and flexion but absolute results may be considered an underestimation of actual MVIC. The test position to assess knee flexion in ForceFrame does not appear to be optimal, and different test-positions may be considered.

Niclas Højgaard Eysturoy^1,5, Hans-Christen Husum², Lina H. Ingelsrud³, Lars Blønd⁴, Elinborg Mortensen¹, Per Holmich⁵, Kristoffer Barfod⁵
1. Department of Orthopedic Surgery, National Hospital of the Faroe Islands, Torshavn, Faroe Island 2. Interdisciplinary Orthopedics, Aalborg University Hospital, Denmark. 3. Clinical Orthopedic Research Hvidovre, Copenhagen University Hospital Amager- Hvidovre, Copenhagen, Denmark 4. Zealand University Hospital, Køge and Aleris Hospital, Copenhagen, Denmark. 5. Sports Orthopedic Research Center – Copenhagen (SORC-C), Department of Orthopedic Surgery, Copenhagen University Hospital Amager-Hvidovre, Copenhagen, Denmark

Background: .
Aim: To investigate patient-reported outcome measurement (PROM) reference data on a national cohort of patients between 15-19 years with prior patella dislocation and trochlear dysplasia.
Materials and Methods: All inhabitants in the Faroe Islands between 15 to 19 years were invited to answer an online survey. The survey included questions concerning prior patellar dislocation and the PROMs: Banff Patella Instability Instrument (BPII), Kujala score, Marx score and the EQ-5D- 5L. Three cohorts were established: 1) The background cohort consisting of the participants with no prior patellar dislocation, 2) The patellar dislocation cohort consisting of all participants with prior patellar dislocation, 3) The trochlear dysplasia cohort consisting of participants with prior patellar dislocation who had trochlear dysplasia.
Results: 3749 persons were contacted, and 1119 (30%) completed the demographic survey and at least one PROM. 43 persons had prior surgery to the knee and were excluded. 102 reported prior patellar dislocation, of whom 57 were found to have trochlear dysplasia. All PROMs except the Marx score reflected worse quality of life and function after patellar dislocation than the background population, most pronounced in the BPII. The percentage of people experiencing problems in the EQ-5D-5L dimensions was increased for the patellar dislocation cohort and the trochlear dysplasia cohort in all EQ-5D-5L domains, except for anxiety/depression.
Interpretation / Conclusion: Young people (age 15-19) with prior patellar dislocation report seriously affected quality of life and function measured with the BPII, the Kujala, the EQ-5D-5L index values, and all EQ-5D-5L domains except anxiety/depression.

Randi Rasmussen¹, Lone Frandsen², Torsten Grønbech Nielsen², Martin Lind ²
1. Department of Physiotherapy and Occupational Therapy 2. Department of Orthopaedics, Aarhus University Hospital

Background: Today, both operative and non-operative treatment of Anterior Cruciate Ligament (ACL) injuries are considered viable treatment options depending on the individual patient's preference. The Danish Knee Ligament Reconstruction Registry (DKRR) monitor the outcomes of surgeries for ACL-injury. However, no registry data exist for ACL injury patients who are managed non-operatively
Aim: To investigate how many patients remained non- operatively treated five years after physiotherapy-led non-operative treatment. Furthermore, we aimed to describe and compare the demographics and epidemiology characteristics of patients who managed with non-operative treatment and patients who failed non-operative treatment and were converted to ACLR
Materials and Methods: A retrospective analysis was performed to identify patients with ACL injuries referred to non-operative treatment at The Orthopaedic Rehabilitation Center in Aarhus between 2014 and 2018. Demographic and epidemiology data were extracted from medical records. Furthermore, patients were encouraged to complete a questionnaire. Finally, data from the Danish Knee Ligament Registry was extracted to identify the patients who underwent ACLR
Results: A total of 289 patients (290 knees), with 63.5% females and a mean age of 37.4 years (range 18-64) were identified in medical records. Mean time from physiotherapy-led non-operative treatment to ACLR was nine months. Seventy-four percent (216 patients) managed with non-operative treatment five years after physiotherapy-led non-operative treatment. 76% of these were females with a mean age was 39.2 years. 161 patients had an isolated ACL injury while 52 had ACL and medial collateral ligament (MCL) injury. Of the 72 patients that converted to ACL reconstruction were 66% females with a mean age of 32.7 years. Fourty-eight patients had an isolated ACLR and three patients had ACLR and MCL reconstruction while 21 patients had ACLR and meniscal surgery
Interpretation / Conclusion: 74% of patients with ACL injury treated with physiotherapy-led non-operative treatment managed without conversation to ACLR five years after treatment. More females than males were referred to non-operative treatment. Patients converted to ACLR within the first year after treatment

Kamilla Arp^1,2, Jacob Nedermark¹, Kim Ingwersen^2,3, Eva Ageberg⁴, Claus Varnum^1,2, Bjarke Viberg⁵,
1.Department of Orthopedic Surgery, Lillebaelt Hospital – Vejle, University Hospital of Southern Denmark, Denmark 2. Department of Regional Health Research, University of Southern Denmark, Odense, Denmark 3. Department of Physiotherapy, Lillebaelt Hospital – Vejle, University Hospital of Southern Denmark, Vejle, Denmark 4. Department of Health Sciences, Faculty of Medicine, Lund University, Lund, Sweden 5. Orthopaedic Surgery and Traumatology, Odense University Hospital, Odense, Denmark

Background: Some patients with anterior cruciate ligament (ACL) injury initially treated with rehabilitation need ACL reconstruction (ACLR), yet it is unclear what characterizes these patients.
Aim: This review aimed to describe predictors for ACLR in patients initially treated with rehabilitation.
Materials and Methods: A systematic literature search was performed in the Cochrane, Embase, Medline, SportsDiscus and Web of Science databases from inception to 21st of February 2023. Articles describing characteristics in adult patients with ACL injury undergoing ACLR after minimum of 5 weeks rehabilitation were included. It was a priori chosen that characteristics described in at least three articles were considered more certain and could be defined as a predictor for ACLR. Characteristics described in less than three articles were considered less certain and therefore defined as possible predictors. Articles were screened by two independent reviewers. The study was originally intended as a systematic review with meta-analysis but in case of limited data we would convert to a scoping review, as was the case for this review.
Results: There were 22,836 studies identified and 181 full texts were screened of which 10 papers were finally included. Only lower age and higher preinjury activity level were identified as predictors for ACLR. Another 12 possible predictors were identified in single studies. Through an iterative process, potential predictors were categorized into 4 groups: patient demographics, knee function, patient-reported outcome measures and anatomical structures.
Interpretation / Conclusion: Lower age and higher preinjury activity level were the only predictors for ACLR after initial treatment with rehabilitation. The evidence regarding which patients need delayed ACL reconstruction is very limited. While younger and highly active patients show a higher need for ACLR more studies focusing on predictors and reasons for delayed ACLR are warranted.

Johanna Dalsgaard¹, Signe Petri¹, Henrik Sjølander¹, Jens Christian Pörneki², Knud Gade Freund³, Niels Maagaard¹, Bjarke Viberg¹
1. Department of Orthopaedic Surgery and Traumatology, Odense University Hospital; 2. Department of Orthopaedic Surgery and Traumatology, Hospital Lillebaelt – University Hospital of Southern Denmark; 3. Department of Orthopaedic Surgery and Traumatology, Hospital of South West Jutland.

Background: Most hospitals in the Region of Southern Denmark uses a lesser demanding technique for the reconstruction of the medial patellofemoral ligament (MPFL) but it has not been assessed for complications. Instead of anchoring the MPFL graft in the bone, the graft is sutured into the top of the medial collateral ligament (MCL) using it as a pulley providing a functional non-anatomical reconstruction. This procedure offers several advantages: a simpler technical procedure without the use of fluoroscopy, the fixation is dynamic and not static as with an interference screw in the femur, and the procedure can be used for children with open physis as well.
Aim: To assess the outcome of an operative method for non-anatomic medial patellofemoral ligament (MPFL) reconstruction using the medial collateral ligament (MCL) as a pulley in adults above 16 years old
Materials and Methods: Patients were retrieved using procedural codes for MPFL reconstruction at hospitals the region of Southern Denmark from 1st of January 2016 to 31st of December 2020. Health care records were reviewed for data concerning surgical information with one- and two-year follow-up. All patients with a primary MPFL reconstruction (no previous surgery) were included. Major complications were defined as re-dislocations, infections, and reoperations with intervention of the graft. Minor complications were defined as arthroscopy of the knee without graft intervention.
Results: There were 420 knees (342 patients) with non-anatomic MPFL reconstruction included in the study. The median age was 22 (16-78) years and 68.5% were female. The gracilis tendon was used as the graft in 92.4% of the cases and there were 76 (18.2%) patients who had additional minor surgery to the primary intervention such as synovectomy, lateral release, and cartilage debridements or reinsertions. There were an overall of 14 (3.3%) complications within 1 year and 26 (6.2%) within 2 years. Within the first year, 10 (2.4%) were major complications, and four (1%) were minor. Within 2 years, 18 (4.8%) were major complications and eight (1.9%) were minor.
Interpretation / Conclusion: Using the MCL as a pulley demonstrates low rates of major complications and can safely be used in the reconstruction of the MPFL.

Andreas Bentzen^1,2, Per Gundtoft¹, Karin Silbernagel³, Stian Jørgensen^1,4,5, Inger Mechlenburg^1,2,6
1. Department of Orthopaedic Surgery, Aarhus University Hospital 2. Department of Clinical Medicine, Aarhus University 3. Department of Physical Therapy, University of Delaware, USA. 4. Department of Occupational and Physical Therapy, Horsens Regional Hospital 5. H-HIP, Department of Orthopedic Surgery, Regional Horsens Regional Hospital 6. Department of Public Health, Aarhus University

Background: Blood flow restriction exercise (BFRE) has been proposed as a viable method for preserving muscle mass and function after an injury, particularly during periods of load restrictions, such as after an acute Achilles tendon rupture. However, its effectiveness and safety in patients with an Achilles tendon rupture have yet to be evaluated in a randomized trial.
Aim: The objective of this trial is twofold: firstly, to investigate the effectiveness of early initiated BFRE in patients with non-surgically treated acute Achilles tendon rupture; secondly, to evaluate whether there is a difference in outcome when applying BFRE in the beginning (1-12 weeks) versus later in the rehabilitation period (13-24 weeks).
Materials and Methods: This is an assessor-blinded, randomized, controlled multicenter trial with patients assigned in a 1:1 ratio to two parallel groups, that either receive BFRE in weeks 1-12 followed by usual care in weeks 13-24, or receive usual care in weeks 1-12 followed by BFRE in weeks 13-24. The BFRE program is performed three times weekly on the injured leg at 80% of the pressure required to restrict the arterial blood flow fully. Post-intervention tests are conducted in week 13, comparing early BFRE with usual care, and in week 25, comparing early BFRE with late BFRE. At the 13-week evaluation, the primary outcome is the Single-Leg Heel-Rise test which assesses the patient’s ability to raise the heel of the injured leg a minimum of 2 cm. At the 25- week evaluation, the primary outcome is the Achilles tendon Total Rupture Score which assesses the patient’s self-reported symptoms and physical ability.
Results: Results are expected in early 2027.
Interpretation / Conclusion: BFRE may enable patients with Achilles tendon rupture to return to normal function far earlier than with current rehabilitation practices. We expect that positive results regarding the effectiveness of BFRE in patients with an Achilles tendon rupture may profoundly impact the physiotherapeutic practice within this patient group, both locally at participating hospitals and possibly on a national and international scale.

Rasmus Elsoe¹, Rikke Thorninger², Rasmus Severinsen², Jens-Christian Beuke³, Rikke Serritslev³, Steffen Skov Jensen⁴, Morten Kjerri Rasmussen⁴, Peter Szephalmi⁵, Juozas Petruskevicius⁶, Jeppe Barckman⁶, Nils Henrik Bruun⁷, Peter Larsen^1,8
1 Department of Orthopedic Surgery, Aalborg University Hospital, Denmark 2 Department of Orthopedic Surgery, Randers, Denmark 3 Department of Orthopedic Surgery Kolding, Denmark 4 Department of Orthopedic Surgery Viborg, Denmark 5 Department of Orthopedic Surgery, Hjoerring Hospital, Denmark 6 Department of Orthopedic Surgery, Aarhus University Hospital Denmark 7 Research Data and Biostatistics, Aalborg University Hospital, Aalborg Denmark 8 Department of Occupational Therapy and Physiotherapy, Aalborg University Hospital, Aalborg, Denmark

Background: Following surgical management of patella fractures, patients commonly report pain, difficulties with weight-bearing tasks such as walking, running, and climbing stairs and restrictions in quality of life. Recently a locking plat system for surgical management of patella fractures have been introduced. To date, no studies have tested standard treatment with tension band wiring against locking plate fixation in a randomized study design.
Aim: We aim to compare the 1-year patient- reported Knee Injury and Osteoarthritis Outcome subscale Scores (KOOS5- subscales) after standard care tension band fixation with locking plate fixation for patients with patella fractures.
Materials and Methods: This study is a multicenter randomized and prospective clinical trial. A total of 122 patients will be included in the study, and the primary outcome will be the KOOS at 12 months following surgery.
Results: This is a study protocol - no results will be available
Interpretation / Conclusion: Findings from the present study is expected to advance the understanding of outcome following surgical treatment of patella fractures.

Jens Trærup^1,2
1 Department of Orthopaedic Surgery, Aalborg University Hospital, Aalborg, Denmark 2 Department of Occupational Therapy and Physiotherapy, Aalborg University Hospital, Aalborg, Denmark.

Background: Evidence is lacking in psychometric properties such as validity, reliability, responsiveness, and minimal clinically important difference for PROMs to patients with lateral tibial plateau fractures
Aim: This study aimed to establish validity, reliability, and responsiveness and to estimate the minimal clinically important difference (MICD) of the Knee Injury Osteoarthritis outcome score (KOOS) for patients with lateral tibial plateau fractures.
Materials and Methods: Adult patients with surgically treated lateral tibial plateau fractures (AO 41B) were included. The primary outcome measure was the KOOS subscales: Pain, Symptoms, Activity of Daily Living (ADL), Sport and Recreational Activities (Sport/rec), and Quality of Life (QOL). The KOOS was repeated at 14 and 15 days, six weeks, and 6 and 12 months. Content validity was evaluated by patients ranking the relevance of all the items in the KOOS, test-retest reliability by an interclass correlation coefficient, and responsiveness by effect size end estimation of minimal clinically important difference (MCID) by the anchor-base method.
Results: Forty-one patients with a mean age of 54.8 years (ranging from 21 to 81 years) were included. The results showed an acceptable content validity of all the KOOS subscales. The test-retest reliability was moderate to high for all five subscales, with an interclass-correlation coefficient ranging from 0.6- 0.9. At the 6- and 12-month follow-ups, the responsiveness showed large effect sizes for all the KOOS subscales, ranging from 0.9 to 2.1. The MCIDs for the KOOS subscales were: Pain 5.6, Symptoms 7.9, ADL 5.3, Sport/Rec 6.1, and QOL 6.1.
Interpretation / Conclusion: The KOOS appear to be a valid and useful patient- reported outcome measure to capture patients’ perceived outcomes within one year following a lateral tibial plateau fracture.

Rasmus Stokholm¹, Peter Larsen^1,2, Jan Duedal Rölfing³, Marie Arildsen¹, Christian Rasmussen¹, Firaz Mahdi⁴, Rasmus Elsoe¹
1.Department of Orthopedic Surgery, Aalborg University Hospital, Aalborg, Denmark 2. Department of Occupational Therapy and Physiotherapy, Aalborg University Hospital, Aalborg, Denmark. 3. Department of Orthopedics, Aarhus University Hospital, Aarhus, Denmark. 4. Department of Radiology, Aalborg University Hospital, Aalborg, Denmark

Background: Available literature lacks information regarding the accuracy and reliability of the AO/OTA classification for tibial shaft fractures.
Aim: This study aimed to assess the inter- and intra-observer agreement and accuracy of the AO/OTA 42 classification (4-signs) for adult patients with tibial shaft fractures.
Materials and Methods: The study design is an accuracy, inter- and intra-observer agreement study. Anterior and posterior (AP) and side X-rays of the fracture were used in the examination. The raters comprised two junior doctors and two orthopedic trauma consultants. A committee including two consultant orthopedic trauma surgeons, one consultant orthopedic radiologist, and one associate professor was established to represent the “golden standard.” Each patient was scored twice, including a washout period between the first and second examinations of minimum 18 days.
Results: A total of 101 patients were included. X-rays were available for all 101 patients. Based on the golden standard classification, AO/OTA 42-A1 (56%) was the most common fracture type, followed by AO/OTA 42-A3 (14%). The agreement, when comparing the four raters and the golden standard classification was between 75% and 86% (Choen’s kappa 0.53 to 0.79). Choen’s kappa coefficient for intra-and inter-observer agreement was between 0.57 and 0.74 and 0.47 and 0.59, respectively.
Interpretation / Conclusion: This study showed substantial to moderate accuracy of the AO/OTA 42- classification for tibial shaft fractures. Inter- and intra- observation agreements showed substantial to moderate agreement. Results indicated that using the AO/OTA 42- classification for tibial shaft fractures may be valuable in clinical practice.

Camilla Cronstad Jørgensen¹, Kamilla Jægerum Nielsen ², Michael Lundeman³, Jacob Fyhring Mortensen⁴
1: Anaestisiology department, Nykøbing Falster hospital. 2: Orthopaedics, Slagelse hospital. 3: Radiobotics ApS. 4: orthopaedic department, Nykøbing Falster Hospital.

Background: Fast diagnosis and treatment are pivotal in the management of hip fractures and have been shown to reduce the 1-year mortality rate and number of complications following surgery.
Aim: The aim of this study was to investigate how the use of an artificial intelligence (AI) decision support tool may affect the diagnostic accuracy of clinicians working with the diagnostic workup of hip and pelvic fractures in an accident and emergency (A&E) department.
Materials and Methods: Radiographic exams from 214 adult patients referred with suspicion of hip fractures were consecutively collected using stratified sampling to ensure a 50% fracture prevalence. Two radiographers, two medical interns and two consultants evaluated fracture status on all exams without and with support from the AI tool. The reference standard was defined from the radiological reports, taking additional information from computed tomography into consideration when relevant. The change in sensitivity and specificity was recorded.
Results: The patient age was 78.0 (standard deviation: 11.9) and 149 were females. The sensitivity and specificity across all clinicians changed from 0.93 (CI: 0.91;0.95) and 0.87(CI: 0.85; 0.90) to 0.96 (CI: 0.95; 0.98) and 0.86 (CI: 0.83; 0.89), respectively. The change was equivalent to a 43% reduction in missed fractures and 8% increase in overcalls. The improvement in sensitivity was consistent for all six readers. The specificity, on the other hand, decreased for the radiographers and the seniors, but not for the interns. Furthermore, with the help from the AI tool, radiographers and interns found as many fractures as the senior orthopedists, but not as many as the AI.
Interpretation / Conclusion: The sensitivity for hip and pelvic fracture detection among and clinicians increased significantly when supported by the AI tool. The change in specificity was not statistically significant. The improvement in diagnostic performance may lead to improvements in patient care through better initial diagnosis and shorter time to surgery, however, this warrants further research in a prospective study.

Jan Duedal Rölfing^1,2, Rikke Thorninger^1,2, Ole Brink^1,2, Rehne Lessmann Hansen^1,2, Ahmed Abood^1,2, Per Hviid Gundtoft^1,2,
1. Department of Orthopaedics, Aarhus University Hospital 2. International RESTORE collaborators

Background: Hip fractures occur predominently in as fragility fractures in postmenopausal women. The 1-year cumulative incidence of secondary hip fractures has been estimated to be 2-10%, increasing up to 20% by 5 years. Preventing a contralateral secondary hip fractures may thus be an important treatment goal after sustaining a hip fracture.
Aim: RESTORE (NCT04796350) will evaluate the safety and efficacy of AGN1 LOEP in reducing the incidence of secondary hip fractures in subjects presenting with an index hip fracture and undergoing hip fracture repair surgery.
Materials and Methods: Up to 2,400 women =65 years of age will be randomized (1:1) to receive AGN1 LOEP on the contralateral, non-fractured hip in a single- blinded, multi-national study. AGN1, a proprietary calcium-based implant material is delivered using a minimally invasive procedure to strengthen the proximal femur. The cumulative incidence of secondary fractures and adverse events (primary outcomes) will be compared to a non-treated, control arm over a 5-year study period. As an event driven study, efficacy and safety analysis will be performed once 56 secondary hip fractures occur across both study arms. An interim analysis at the 28- event mark may result in an “early-win” termination of recruitment, subject to a statistically significant effect. Areal bone mineral density (aBMD) will be compared at 12, 24 and 60-months using interval DXA scans, as secondary outcome measure.
Results: To date, 224 patients have been enrolled across 51 sites in Austria, Denmark, France, Germany, Italy, the Netherlands, Spain, the UK and Japan. Aiming at a total of up to 100 RESTORE sites globally, additional sites in Canada and Europe are currently in activation.
Interpretation / Conclusion: The first Danish site, Aarhus University Hospital, was activated in February 2024. Other Danish and Scandinavian sites may follow. Hopefully, minimally invasive AGN1 LOEP will prove as safe as well as effective in preventing secondary fractures in at risk treated hips.

Marie Arildsen¹, Jan Duedal Rölfing^{1, 2}, Mats Bue^{1, 2}, Juozas Petruskevicius¹
1. Department of Orthopaedics, Aarhus University Hospital, Denmark 2. Department of Clinical Medicine, Aarhus University, Denmark

Background: Tibial non-unions are notoriously difficult to treat due to the high risk of infection and the need for multiple surgical procedures. Non-union occurs after approx. 2% of all fractures and up to 17% of tibial fractures. The treatment is costly, often demanding long recovery with the risk of chronic pain, reduced functional outcomes and amputation.
Aim: To report healing, infection rates and clinically relevant non-union scores in surgically treated tibial shaft non-union patients.
Materials and Methods: A single-centre retrospective follow-up study of a consecutive cohort of 53 patients (18 F, median age 56 (IQR 24-64), and 35 M, median age 50 (IQR 34- 62)) treated at Aarhus University Hospital from Dec 2018 until Dec 2023. Pathological fractures, as well as non-union after osteotomies, were excluded. Infection status was evaluated based on the diagnostic criteria for fracture-related infections. NUSS was used as clinical non-union score and RUST to evaluate radiographic healing.
Results: During a mean follow-up of 2.8.y, 49 patients (92%) obtained healing, 2 were amputated, and 2 were lost to follow-up. 21 patients were confirmed infected: 17 monomicrobial, 3 polymicrobial and 1 with negative growth but a confirmatory clinical sign. 8 patients were identified as likely infected based on biochemical markers, presence of a persistent wound and a single bacteria identified by culture. 24 patients were ruled unlikely of infection. For data analysis infected and likely infected were pooled and tested against non-infected. The mean number of surgical revisions for the infected group was 2.5 (range 1-8) and for non- infected group, 1.8 (range 1-4). Neither the median RUST score 13.6 (IQR 13- 15) vs. 14.3 (IQR 13-15) or the median NUSS score 34 (IQR 26-38) vs. 27 (IQR (20-38) were significantly different between the infected and non-infected groups. External fixation for definitive surgical management was more often used in the infected group (p=0.01).
Interpretation / Conclusion: Results indicate that future standardized prospective data collection is needed in patients with tibial non-union to optimize the diagnostic approach and improve treatment. Treatment of these patients is complex and should be performed in a multidisciplinary team.

Ulrik Kähler Olesen¹
Department of Orthopedics, Rigshospitalet, Copenhagen.

Background: Current focus on reducing health care cost by increasing flow in all aspects of surgical treatment, demands efficient solutions.
Aim: To evaluate the preliminary results of 22 cases of fast track surgeries in reconstructive orthopedic. Based on a new protocol aiming at discharge on the day or the day-after surgery: Avoiding epidurals and other motor blocks, minimizing blood loss (blodlessness, vasoconstrictors, compression), promoting fast mobilisation, involving all caregivers (surgeons, anesthesiologist, nurses, physiotherapists).
Materials and Methods: 20 patients booked for 22 elective procedures: Intramedullary lengthenings (6), osteotomies around the knee (7), bone transport (1) and hardware removals (8) were evaluated for LOS (length of stay), complications, and general satisfaction with the setup.
Results: 7 of 10 patients planned for same-day discharge achieved the goal. 3 patients had one extra night in hospital. 6 of 11 patients planned for discharge on the day after surgery achieved the goal. 5 patients had 2-4 additional nights in the hospital. Of these, 4 were osteotomies around the knee and one external ring fixator. Reasons for delay were pain (5), logistics (missing relative at home, late start (3), bleeding (1) and/or anticoagulant treatment issues (1).
Interpretation / Conclusion: Our protocol was relatively succesfull in achieving the time-saving goals, given the heterogenecity of the population. Reconstructive nailing seems less troublesome than osteotomies. Most patients were more than happy to recover in their home and expressed overall satisfaction with the setup. However, meticulous planning of all details in the flow, backup in case of delays, flexibility and close follow up, involvement of all allied health care givers, including relatives - is mandated to ensure compliance with the protocol.

Charlotte Mosbak Festersen ¹, Sakshi Andersen¹, Rikke Holmgaard¹
1. Department of Plastic Surgery and Burns Treatment, Rigshospitalet

Background: High voltage current can cause serious damage to the skin, but also to underlying tissue. Current passes through tissue with the lowest resistance (e.g. nerves, vessels, muscles) where it will generate heat, cause tissue necrosis and subsequently edema. Muscle breakdown (rhabdomyolysis) and edema in the muscle compartments may lead to compartment syndrome (CS), and if so, fasciotomy needs to be performed.
Aim: The purpose of this case report is to describe how the body is affected by high voltage current and to highlight possible complications.
Materials and Methods: Case report of a patient with severe injuries due to high voltage current.
Results: A 17-year-old male was admitted to the hospital in Greenland following a high voltage accident by a transmission tower. Examination revealed bilateral circumferential 3rd degree burns on the lower extremities and 2nd degree burns on some of the body and face. Due to the severe burns, the patient was intubated, but prior to this expressed severe pain from both feet. At initial assessment, there was no pulse or capillary refill (CR), but CS was not suspected. The patient had dark red urine - a sign of myoglobinuria. Transfer to Denmark was delayed 32 hours, and upon arrival, both feet appeared vital with bleeding from the dermis and with no obvious signs of CS. The patient underwent necrectomy of the 3rd degree burns 47 hours after the trauma, and during this, bilateral CS of the lower extremities was suspected. Bilateral fasciotomy was performed to regain sufficient blood supply distally however, the muscles were only partially vital. Bilateral transtibial amputation was performed 15 days after the trauma.
Interpretation / Conclusion: CS is a well-described complication to high voltage injuries typically characterized by pain as the predominant clinical symptom. In cases where electrical current passes through the body it is important to consider internal injuries especially in intubated patients who are unable to express pain. Key indicators such as the absence of distal pulses, delayed CR and the presence of myoglobinuria are indicators of potential internal damage. Therefore, fasciotomies must be performed with a low threshold if there is any anamnestic or clinical suspicion of CS.

Papa Kwadwo Morgan-Asiedu^1,2, Easton Ryan^1,3, Bram Verhofste^1,3, Devon Brameier¹, Nishant Suneja¹, Derek Stenquist¹, Michael Weaver¹, Arvind G. Von Keudell¹
1. Harvard Medical School Orthopedic Trauma Initiative, Brigham and Women's Hospital 2. Perelman School of Medicine, University of Pennsylvania 3. Harvard Combined Orthopedics Residency Program

Background: There is scarce evidence comparing infection rates in complex bicondylar tibial plateau fractures treated with single versus dual plated Open Reduction Internal Fixation (ORIF)
Aim: To identify the rate of surgical site infection (SSI) in OTA/AO 41C tibial plateau fractures treated with single versus dual plating
Materials and Methods: Setting: Retrospective cohort study of patients presenting to two level 1 trauma centers with OTA/AO 41C tibial plateau closed fractures who received ORIF Intervention: Single vs dual plated ORIF Primary outcome: SSIs after index operation Covariates: Age, sex, BMI, tobacco use, alcohol use, compartment syndrome Chi square comparisons: Overall SSI rates, superficial SSIs, deep infections requiring reoperation stratified by AO fracture subclass to account for asymmetric distribution of higher energy fractures
Results: We included 223 patients with mean age 53.4 years, 49.3% (n=110) males, mean BMI 28.3. 148 had single plated ORIF and 75 had dual plated ORIF. Cohorts were similar in terms of age, number of males, mean BMI, tobacco use, alcohol use & compartment syndrome. The overall rate of SSIs was 24.2% (n=54); single plating had a lower infection rate (19.6%, n=29, p=0.02) than dual plating (33.3%, n=25). Single plating had lower rates of superficial SSIs (4.7%, n=7, p=0.02) than dual plating (13.3%, n=10). The rates of deep infection requiring reoperation were similar for single plating (16.9%, n=25, p=0.09) and dual plating (26.7%, n=20). Among 41C1 fractures, single plating had lower infection rates (3.0%, n=1, p<0.01) than dual plating (44.4%, n=4). Among 41C2 fractures, single plating had lower infection rates (8.6%, n=3, p<0.01) than dual plating (37.5%). However, 41C3 fracture infection rates were similar between single plating (34.3%, n=23, p=0.58) and dual plating (29.3%, n=12). Finally, among dual plated patients with infections requiring reoperation, 60% (n=12) involved the medial component, 20% (n=4) involved the lateral, and 15% (n=3) involved both components.
Interpretation / Conclusion: Per this study, single plating in fixation of OTA/AO 41C tibial plateau closed fractures is associated with a lower rate of SSIs as compared to dual plating, especially for 41C1 and 41C2 fractures.

Alec Friswold, Devon Brameier, Faith Selzer, Liqin Wang, Li Zhou, Michael Weaver, Arvind von Keudell
Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115, USA.

Background: Geriatric hip fractures utilize substantial hospital resources. The Center for Medicare & Medicaid Services (CMS) reimburses hospitals by a fixed amount as determined by patients’ Medicare Severity Diagnosis Related Group (MS-DRG), which assign payment weights based on the average resources required to manage that condition.
Aim: In this study, we evaluate whether current CMS estimates of resource utilization for the MS-DRG, “Hip and Femur Procedures Except Major Joint”, the most commonly allocated MS-DRG for geriatric femur fractures, is consistent with resource utilization of these patients at a large academic medical center.
Materials and Methods: Analysis included 198 patients over 65 years old who underwent surgical repair of a hip fracture between 2018-2020 at a Level 1 Trauma Center and were reimbursed under one of three MS-DRGs: “Hip and femur procedures except major joint without complication or comorbidity (CC)”, “…with CC”, and “…with major CC (MCC)”. Financial data was obtained for each episode. Primary outcome was a percentage difference in total cost of care compared to the “without CC” group. Secondary outcomes include difference in length of stay (LOS) between the study site and CMS, profitability, and frailty within each MS- DRG.
Results: Compared to patients without CC, treating patients with MCC on average cost 60% more (p<0.05). The average profit per episode was negative for all three MS- DRGs. Moreover, patients coded with MCC were 64% less profitable than patients coded without CC. The average LOS at the study site was 1.9 days longer than the LOS CMS cites for this condition. Moreover, severely frail patients made up 38% of patients with a MCC compared to 7% of patients without a CC.
Interpretation / Conclusion: Negative profits across all versions of the “Hip and Femur Procedures Except Major Joint” MS-DRG suggest current payment weights are not sufficiently meeting the cost to treat. This may be due to CMS underestimating the average LOS, and thus resource utilization, of these patients. Caring for patients with major complications was associated with more negative profit, suggesting the current payment model may disincentivize treating patients who are more likely to have complications.

Müjgan Yilmaz¹, Linda Fernandes², Michael Mørk Petersen³
1. Department of Orthopaedics, North Zealand Hospital, Denmark 2. University College Copenhagen, Copenhagen, Denmark 3. Department of Orthopaedics, Rigshospitalet, Denmark

Background: In patients with malignant bone tumors, metastases, or benign tumors causing significant bone loss, limb-salvage surgery is the recommended surgical intervention.
Aim: We evaluated the effects (surgical and functional outcomes) of using pelvic reconstruction using personalized, 3D- printed pelvic implants in bone tumor surgery.
Materials and Methods: A single-center cohort study including 12 patients (M/F=8/4, mean age 51, range:15- 76 years) reconstructed with custom-made 3D-printed pelvic prosthesis. Pathology: Chondrosarcoma (n=4), Ewing sarcoma (n=1), Giant cell tumor (n=1), B- cell lymphoma (n=1), Renal cell carcinoma (n=2), Ductal carcinoma (n=1), Planocellular carcinoma (n=1) and Aneurismal bone cyst (n=1). Ten patients were available for follow-up (not alive=1, sick=1) and were assessed with active/passive ROM, isometric muscle strength, MSTS, TESS, EQ-5D-5L, EORTC QLQ-C30, 6-minute walk test, and 30- second chair-stand test on average 4 years postoperatively.
Results: The probability of avoiding revision due to implant failure calculated by Kaplan-Meier survival analysis was 85.7% (95%CI: 63.3%-100%) at 5 years. We found that active-ROM for the surgical limb was decreased compared to the healthy contralateral site in hip abduction (p=0.007), adduction (p=0.007), internal rotation (p=0.007), and external rotation (p=0.007). Hip flexion was decreased in passive ROM (p=0.007). In the surgical limbs, we found decreased hip muscle strength in flexion (p=0.008), abduction (p=0.008), knee extension (p=0.008), and flexion (p=0.008). EQ-5D-5L (preoperative: 0.9 (range:0.87- 0.97) and 0.9 (postoperative range:0.84- 0.92)), TESS (mean: 68.3, range:55-90), MSTS (mean: 66.1, range:55-85), and EORTC QLQ-C30 (mean: 63.3, range:55-80) 6- minute walk test (mean: 413.6 m, range:320-501.5) and 30-second chair- stand test (mean: 11.2, range:7-18) was assessed at follow-up.
Interpretation / Conclusion: Reconstruction with custom-made 3D- printed pelvic prosthesis has overall expected lower isometric muscle strength and ROM compared with the healthy site.

Kasper Vestergaard Rydberg¹, Flemming Secher Kromann Nielsen², Anna Bertoli Borgognoni³, Michael Melchior Bendtsen⁴, Thomas Baad-Hansen⁵
1. Department of Orthopaedics, Aarhus University Hospital; 2. Department of Radiology, Aarhus University Hospital; 3. Department of Orthopaedics, Aarhus University Hospital; 4. Department of Orthopaedics, Aarhus University Hospital; 5.Department of Orthopaedics, Aarhus University Hospital.

Background: Misdiagnosis of soft tissue sarcomas as hematomas can lead to treatment delays, larger tumors, metastasis, difficult surgical removal, and poor prognosis.
Aim: We present three cases where patients initially diagnosed with hematoma-like soft tissue masses were later found to have sarcomas. The aim of the study is to identify and highlight diagnostic characteristics of a suspected hematoma that should arise suspicion of a soft tissue sarcoma.
Materials and Methods: The study is a retrospect case study. In the three patients' journals we found information about patient history, clinical examinations, imaging diagnostics, and biopsies.
Results: The extended duration from the initial appearance of a thigh swelling to diagnosis delays surgical intervention, allowing tumor growth and metastasis, reducing the chance of successful treatment. Larger tumors are harder to remove surgically, increasing the risk of incomplete removal and potential cancer spillage, heightening the risk of relapse. Additionally, tumor expansion within soft tissue and muscle necessitates more extensive limb removal during surgery, leading to reduced postoperative limb function. The patients presented with a lump accompanied by swelling and pain. Intriguingly, none of the patients manifested subcutaneous ecchymosis. Consequently, the absence of ecchymosis coupled with the presence of a lump, swelling, and pain in an extremity signals potential suspicion of soft tissue sarcoma, particularly in the absence of direct trauma. The study suggests that delayed MRI extends the interval between clinical appearance of a tumor and final surgical treatment, ultimately worsening prognosis and increasing the risk of unplanned excisions. MRI should therefore be performed without further delay. Core needle biopsy or open biopsy yielded conclusive diagnoses in all three cases presented, suggesting these methods should be prioritized for obtaining correct diagnosis.
Interpretation / Conclusion: A soft tissue sarcoma should be suspected when a patient presents with a lump, swelling, and pain in the absence of a direct trauma. MRI scans and core needle biopsies are vital in soft tissue sarcoma diagnostics and should be performed without unnecessary delay.

Niklas Tøndevold¹¹, Lærke Ragborg ¹, Martin Heegaard¹, Martin Gehrchen¹, Benny Dahl¹
1. Ortopaedic department U, Copenhagen University Hospital Rigshospitalet

Background: Surgical treatment for adolescent idiopathic scoliosis (AIS) is typically performed before the patients embark on their work life. A few multicenter studies have shown a decline in patient-reported outcome when patients are followed beyond the traditional two years after surgery. However, most of these large studies are characterized by a low follow-up rate and the inherent heterogeneity of multi-center studies.
Aim: Determine health-related quality of life in patients surgically treated for scoliosis with a minimum of 5- year follow up.
Materials and Methods: All patients surgically treated for AIS from marts 2011 to marts 2018 were included. All patients had multi-segmental all-pedicle screw constructs. Patient-reported outcome; SRS-22, NRS 1-10 and EQ-5D-3L were collected pre-operatively and at 1- year, 2-year and final follow-up. Radiological and clinical follow included use of daily pain medication, work status including weekly work hours and physical activity level.
Results: One hundred and sixty-four of 178 (92%) patients surgically treated for AIS during the inclusion period were available for follow-up. Mean age at surgery was 15.6 years. Mean follow-up was 6.8(SD±1.4) years with a mean age of 22.3(SD±2.4). Sixteen patients (10%) had revision surgery, most commonly due to infection (26%). We found no change in main curve correction between 2 and 5 year follow-up (29° vs 30°, p=0.78) and no significant difference in SRS-22 (Table 1). At 5-year follow-up, 132 (80%) patients used over-the-counter painkillers once a week or less and only 2 patients (1.2%) used morphine daily. Thirteen patients (8%) where unemployed and the rest was in either full- time employed or studying.
Interpretation / Conclusion: In this single-center study, we found no decline in patient reported outcomes at minimum 5-year follow-up. With a 92% follow-up rate and use of all- pedicle screw constructs, it is illustrative of the advances made in surgical treatment of AIS over the last decade.

Niklas Tøndevold¹, Gehrchen Martin¹, Benny Dahl¹,
1. Orthopeadic department U, Copenhagen University Hospital, Rigshospitalet

Background: Late surgical site infection (>90 days) is seen in 1.7 to 6.9% of patients undergoing surgery for AIS. Cutibacterium acnes (C. acnes) is reported to be the most common finding in these patients. However, the same pattern is not seen ASD patients. C. acnes is known to act as an opportunistic pathogen through biofilm. Particularly shoulder arthroplasties but also breast implants and cardiovascular device-related infections are known to have high infection rates with that pathogen. However, whether inoculation is hematogenic or the result of bacterial contamination at the initial surgery is not known.
Aim: Exmine the presence of skin bacteria, especially Cutibacterium acnes, is more prevalent in the surgical field of patients treated for adolescent idiopathic scoliosis (AIS) than that of patients treated for adult spinal deformity (ASD).
Materials and Methods: We included patients at least two years after their last spine surgery (ASD group) or no prior spine surgery (AIS group) undergoing surgery at our institution from January 1 through December 31, 2020. The patients were surgically prepared according to the consensus guidelines. Three muscle tissue samples were obtained before wound closure, and two positive cultures were considered a positive test result. Furthermore, the unused rod tip was sent for sonication. All cultures were observed for 14 days.
Results: We included 161 AIS patients and 23 ASD patients. There were no statistically significant differences between the 2 groups regarding surgical time or blood loss. Cultures were positive in 112 AIS patients (68%) and in 2 ASD patients (8.6%). Of the 112 positive AIS cultures 100 had C. acnes as the only pathogen. The remaining were other skin bacteria. Bacteria were found on 92 of the rod tips (81%) all were C. acnes. WGS showed no sign of a single contaminate source.
Interpretation / Conclusion: C. acnes is present in the muscle tissue of most patients surgically treated for AIS. In the majority of cases the same bacteria were found on the unused sterile implant only handled by the surgeons, possibly by contamination from the surgical gloves. Surgeons treating these patients should therefore make sure of targeting this pathogen in their prophylactic strategy.

Lærke Ragborg^1,2, Amy McIntosh², David Thornberg², Jamie Gross², Søren Ohrt-Nissen¹, Martin Gehrchen¹, Benny Dahl¹, Daniel Sucato², Megan Johnson²
1. Spine Unit, Dept. of Orthopedic Surgery, Rigshospitalet, København, Denmark 2. Scottish Rite for Children, Dallas, United States of America

Background: Modern brace design aims to correct spinal deformity in the coronal, sagittal, and axial planes through personalized brace construction. However, limited data is available confirming if axial changes actually occur when patients are treated with a thoracolumbar sacral orthosis (TLSO).
Aim: To assess if axial changes occur in-brace.
Materials and Methods: A consecutive cohort of patients diagnosed with AIS who underwent bi-planar, low-dose x-rays with subsequent 3D reconstructions at both pre- brace and inbrace was assessed retrospectively for inclusion. All patients were prescribed a full- time, 3D CAD/CAM, de-rotational TLSO. Axial rotation magnitude and direction were compared at each vertebral level between pre-brace and in- brace images to detect where changes occurred according to major curve location (Thoracic (T1- T11) and Lumbar (T12-L5)). Magnitude was calculated as the absolute value of the difference between in-brace and pre-brace. Direction of axial rotation was termed “amplification” or "de- rotation" defined as an increase in magnitude toward the initial direction or a change in the opposite direction regardless of magnitude, respectively.
Results: We included 126 consecutive patients, 91 (72%) were females and 93 (74%) had main thoracic curves. Pre-brace major Cobb angle was 32±8° and in-brace Cobb angles reduced to 23±8°. Overall and within groups, there was a greater proportion of de- rotation compared to amplification at every level. For thoracic curves, the highest frequency of de- rotation occurred at T8-T9 with the largest changes in magnitude occurring at T1-T4 (Figure 1). For lumbar curves, the highest frequency of de-rotation occurred at T7-T8, T11 and L1, with the highest magnitude of de-rotation occurring at T12 .
Interpretation / Conclusion: A TLSO does influence axial rotation in patients with adolescent idiopathic scoliosis while in-brace. Although de-rotation primarily occurs around the apical regions, changes can be observed throughout the length of the spine regardless of curve type.

Christian Wong^1,2, Benny Dahl^1,2
Department of Orthopedic Surgery, Rigshospitalet, 2100 Osterbroo, Denmark Department of Orthopedic Surgery, Copenhagen University Hospital, Hvidovre, Denmark

Background: The role of the spinal muscles in scoliogenesis is not fully substantiated. Do they act scoliogenic (inducing scoliosis) or counteract scoliosis in adolescent idiopathic scoliosis (AIS)?
Aim: In this study, we will examine this by using selectively placed Transcutaneous Electric Stimulation (TES) combined with a cinematic radiographic technique and by performing electromyographic (EMG) evaluations during various motor tasks
Materials and Methods: This is a cross-sectional study of subjects with small-curve AIS. Using cinematic radiography, they were evaluated dynamically either under electrical stimulation or when performing motor tasks of left and right lateral bending and rotation while measuring the muscle activity by EMG.
Results: Five subjects volunteered for TES and six subjects performed the motor tasks with EMG.When analyzing the spatial positions when calibrated, we found that the spinal muscles exert a compressive ‘response’ with a minor change in the Cobb angle (CA) in small-curve AIS (CA = 10–20°). In larger curves (CA > 20°), TES induced a relative four-fold change in the CA compared to small-curve AIS with a ratio of 0.6. When adding the absolute EMG ratios for all four motor tasks, the subject with progression had almost 10-fold fewer summed EMG ratios, and the subject with regression had more than 3-fold higher summed EMG ratios.
Interpretation / Conclusion: Based on these findings, we suggest that the spinal muscles in small-curve AIS have a stabilizing function, maintaining a straight spine and keeping it in the midline. When deformities are larger (CA > 20°), the spine muscle curve exerts a 'scoliogenic response’. This suggests that the role of the muscles converts from counteracting AIS and stabilizing the spine to being scoliogenic for a CA of more than 20°. Moreover, we interpret higher EMG ratios as heightened asymmetric spinal muscle activity when the spinal muscles try to balance the spine to maintain or correct the deformity. When progression occurs, this is preceded or accompanied by decreased EMG ratios. These findings must be substantiated by larger studies.

Martin Heegaard¹, Kristín Ingadóttir¹, Lærke Ragborg¹, Benny Dahl¹, Lars V. Hansen¹, Søren Ohrt-Nissen¹, Martin Gehrchen¹
1. Spine unit, Rigshospitalet, Copenhagen University Hospital, Denmark

Background: Low bone mineral density (BMD) is a known risk factor for revision surgery in patients with adult spinal deformity (ASD). Hounsfield units (HUs) on CT scans have been suggested as a proxy for assessing BMD.
Aim: This study aimed to assess HUs in the lumbar region, including the upper instrumented vertebra (UIV) as well as UIV+1, and the association with mechanical failure in patients undergoing ASD surgery.
Materials and Methods: We retrospectively included ASD patients undergoing surgery from 2010-2020 with a minimum of two-year follow-up. We excluded patients without a preoperative CT scan, or a CT scan made more than one year before surgery. Mechanical failure was defined as proximal junctional failure, pseudarthrosis, or implant failure requiring revision surgery. On preoperative CT scans, HUs were measured on three axial slices on each vertebra from L1 to L5 and, if available, at UIV and UIV+1. A logistic regression model was used to assess the association between HUs and mechanical failure.
Results: We included 170 patients with a mean age of 63 (±12) years, 108 (64%) were females, and the median instrumentation was 13 [IQR 10-16] levels. Mechanical failure occurred in 27% (n=46) of patients at two-year follow-up. Mean lumbar HUs were 146 ±51 in the mechanical failure group and 135 (±52) in the no-revision group (p=0.232). The area under the curve was 0.58 (95% CI 0.48-0.68) corresponding to no to low discriminatory power in predicting mechanical failure using lumbar HUs. Univariate logistic regression analysis showed no statistically significant difference between mechanical failure and HUs in the lumbar region (OR= 1.00, 95%CI 1.00-1.01, p=0.239) or at UIV/UIV+1 (OR= 1.00, 95%CI 0.99-1.01, p=0.286).
Interpretation / Conclusion: We found no association between mechanical failure and HUs on preoperative CT scans in ASD patients. Thus, we cannot recommend using HUs to predict mechanical failure in these patients.

Katerina Znacko, Anders Kruse, Dennis Winge Hallager


Background: Cervical disc replacement (CDR) offers motion preservation compared to fusion for degenerative disc disease. Potential harms should be weighed against the possible advantages when patients are counselled on the treatment choice.
Aim: To present a rare case of posterior core migration in an unconstrained CDR device, highlighting the risk of devastating complications and discus failure mechanism.
Materials and Methods: A 29-year-old woman underwent arthroplasty at C5/6 with an unconstrained device in 2016 for a disc herniation, when conservative treatment failed. In 2024, she presented with recurrent neck and right sided arm pain, and difficulty in neck flexion. Imaging revealed posterior migration of the device core, which occupied the right side of the spinal canal. Revision surgery unveiled a loose upper metal endplate with soft tissue metallosis and severe wear of the migrated core. The device was removed, and after debridement, anterior fusion surgery was performed. Soft tissue and device sonication cultures were obtained.
Results: Postoperatively, the symptoms had resolved, and cultures revealed Cutibacterium acnes infection. Antibiotic treatment was initiated, and the patient is currently planned for follow-up at three months in our outpatient clinic.
Interpretation / Conclusion: Discussion: This case underscores CDR surgery complexities, urging research into device failure mechanisms. Loosening of the upper endplate may exacerbate core wear, facilitating core migration. Conclusion: Posterior core migration in unconstrained CDR devices poses a severe risk, which surgeons and patients should consider when choosing this surgical option.