Poster Walk

16. November
17:00 - 18:00

Poster Walk 1: Lower extremity
Chair: Louise Lau Simonsen / Kristian Behrndtz

149. Optimization of MRI Measurements of Calf Muscle Atrophy Following Acute Achilles Tendon Rupture
Ibrahim El Haddouchi, MS¹, Anders Brøgger Overgård, MD¹, Per Hölmich MD, Professor, DMSc¹, Kristoffer Weisskirchner Barfod, MD, PhD¹
1. Sports Orthopedic Research Center – Copenhagen (SORC-C), Department of Orthopedic Surgery, Copenhagen University Hospital Amager-Hvidovre, Denmark.

Background: Calf muscle atrophy is a major concern following acute Achilles tendon rupture (ATR). Muscle compartment size can be evaluated with magnetic resonance imaging (MRI) either by cross section area (CSA) or volumetric measurement. Volumetric measurement yields the actual size of the muscle compartment but is time consuming.
Aim: The aim of the study was to investigate if CSA measurement could be used as a surrogate for volumetric measurement in evaluation of muscle atrophy of the calf muscles after ATR. Five different models for CSA measurement were proposed. We hypothesized that atrophy estimated with CSA measurement had an R-square value above 0.7 when compared to volumetric measurements.
Materials and Methods: This was a cross-sectional study of patients one year after ATR. MRI of both calves was performed one year after ATR using a Simens 1.5T MRI system with a 3D gradient echo sequence. Evaluated muscles were: Soleus, medial gastrocnemius, lateral gastrocnemius, and the deep flexors (flexor hallucis longus, flexor digitorum longus and tibialis posterior) as one conjoined muscle group. For each muscle, the CSA was measured manually on axial slides for every 2 cm. The muscle volume was calculated as cones with irregular bottoms. Atrophy was estimated using the limb symmetry index (LSI) (injured / uninjured x 100%). Comparison between the 5 proposed models for CSA measurement and volumetric measurement was performed fitting a linear regression model and calculating the R-squared value.
Results: Fifty-four patients were included in the study. The best correlation between CSA and volumetric measurement was obtained when measuring CSA of triceps surae (R2=0.782), soleus (R2=0.642), medial gastrocnemius (R2=0.603), and lateral gastrocnemius (R2=0.559) 26 cm above talus, and the deep flexors 14 cm above talus (R2=0.493).
Interpretation / Conclusion: CSA measurement on MRI can be used as a surrogate for volumetric measurements when investigating atrophy of m. triceps surae. Investigation of atrophy of the individual muscles of the calf by use of CSA measurements should be done with caution.

151. Development and initial validation of the descriptive numeric rating scale for postoperative pain
Karen Bjørnholdt, Carina Andersen
Department of Orthopaedic Surgery, Horsens Regional Hospital

Background: For clinical trials of surgery, the intensity and resolution of pain is an important outcome just as disability. In daily clinical practice, individual change over time and pain treatment is handled well by the numeric rating scale (NRS) 0-10 or visual analogue scale (VAS) and in conversation with patients. However, these scales reach ”worst possible pain” or ”pain as bad as you can imagine”, leaving ample room for subjective interpretation of the scale, which impairs the comparisons necessary in trials.
Aim: We aimed to develop a scale measuring sensory pain intensity for clinical trial use, which minimized the influence of individual imagination, previous experience, and coping skills, to facilitate web-based data collection and comparison of surgical groups.
Materials and Methods: A literature review and qualitative interviews of 10 patients and 10 clinicians as well as a questionnaire regarding placement of wording on the 0-10 scale were the basis of the wording chosen. The scale was pilot tested using RedCap in two rounds (10 patients each), with interviews concerning content validity in orthopaedic day surgery patients. Initial validation with assessment of test-retest reliability, sensitivity to change, known-groups comparison, comparison to NRS and VAS, differential item functioning, and MCID is underway.
Results: Categories (and examples) for description of pain intensity collected from literature and interviews were: Intensity (mild, strong), affective (distressing, terrible), evaluative (acceptable, unbearable), cognitive impact (distracting, demands full attention), sleep impact, activity impact, treatment (need morphine), discriminative (shooting, throbbing), physical signs (sweating, pale), and examples (like bumping your head). Content validity pilot testing improved the questions and scale to be understandable and relevant as well as comprehensive. Results of the remaining initial validation are pending.
Interpretation / Conclusion: The descriptive scale specifies “what is meant by 5” etc., improving precision and validity for this hard to measure but very important outcome. Further studies will establish whether this scale improves pain trajectory modelling and comparison of surgical pain outcomes.

162. Non-removable vs. removable offloading in patients with plantar diabetic foot ulcers. A National Clinical Guideline
Tue Smith Jørgensen,
Department of Orthopedics, Amager and Hvidovre University Hospital

Background: In Denmark, different types of offloading devices are used to treat diabetic foot ulcers, depending on patient and clinician preference, wound location and etiology. It is not clear whether removable or non-removable offloading has a greater effect on wound healing or increases harmful effects. The great variation in clinical practice in Denmark may lead to a regional difference in wound healing success. The 2015 NICE guideline and IWGDF guideline from 2019 recommended a non-removable bandage as offloading for plantar diabetic foot ulcers (except for ischemic and infected wounds).
Aim: To investigate the effect of non-removable or removable offloading devices in plantar diabetic foot ulcers
Materials and Methods: The study is a systematic review and metaanalysis and the systematic litterature search was performed the 31. Of january 2020. The evidens consists of 12 randomised clinical trials. Patients had an average age between 52-73 years and the average duration of diabetes was 8-17 years. The wound size was between 1.3-13.1 cm2 and the intervention period lastet 4, 12 and 16 weeks or until total wound closure.
Results: Among the patients who received treatment with a removable offloading, 144 out of 264 patients achieved wound healing compared with 188 out of 236 in the patients who received a non-removable offloading. The meta-analysis showed that, non- removable offloading is likely to increase wound healing (total wound closure) significantly compared to removable offloading. The relative risk was 0.72 (95% CI: 0.61, 0.85). Two out of 85 patients who received removable offloading underwent an amputation compared to two out of 93 patients who received non removable offloading. The meta- analysis showed no clinically relevant differences, as the relative risk was 0.99 (95% CI: 0.17, 5.87).
Interpretation / Conclusion: Clinicians should consider non-removable offloading rather than removable offloading in patients with plantar diabetic foot ulcers.

208. Experimental treatment of insufficiency fractures in RA patients – a new treatment algorithm in the making?
Mette Sørensen Studstrup¹, Peter Larsen¹ ², Søren Kold¹, Rasmus Elsøe¹
Department of Orthopaedic Surgery, Aalborg University Hospital, Aalborg, Denmark¹; Department of Occupational Therapy and Physiotherapy, Aalborg University Hospital, Aalborg, Denmark²

Background: Patients diagnosed with rheumatoid arthritis (RA) often have substantial pain and disability related to the affected joints. Increased RA activity may result in articular or periarticular pain. Such pain may also be related to juxta- articular insufficiency fractures which initially are seldom detected by conventional x-ray but only visualized by MRI often causing a delay in diagnosis. Conservative treatment of these fractures may be prolonged as especially pain, but also intraosseous edema and fracture healing assessed by MRI resolves exceedingly slow resulting in an extended immobilization period. Cerament V (CV) is a hydroxyapatite and calcium sulfate-based bone void filler with vancomycin used in trauma- and reconstructive surgery.
Aim: We report a small case series including the first 4 patients diagnosed with RA and insufficiency fractures treated experimentally with inforation and injection of CV.
Materials and Methods: This study includes patients in the North Region of Denmark diagnosed with RA insufficiency fractures that did not respond satisfactorily to conservative treatment. All patients are referred with either increased periarticular pain or MRI verified insufficiency fractures in the lower limb. So far 4 patients have received experimental surgical treatment and 2 awaits surgery. Surgery is performed minimally invasive. A small incision is made, depending of the site treated. A large- gauged cannula is used to inforate and inject CV. Postoperative patients are allowed full weight bearing without restrictions.
Results: 4 patients were treated surgically. Follow-up time was 1 – 5 months. 3 patients became pain- free, 1 patient had residual pain, 1 patient experienced leakage of CV, but no sign of infection.
Interpretation / Conclusion: This case series presents a method that may alleviate pain related to insufficiency fractures in patients with RA where conservative treatment has not been sufficient. Inforation and injection of CV may be an option to treat these patients. This procedure is minimal invasive with no immobilization requirements and may be performed in an out-patient setting. Further studies are warranted before this treatment algorithm can be implemented as a standard care for this patient group.

206. The Isolated Posterior Malleolus fracture
Thomas Colding-Rasmussen¹ , Benjamin Presman¹ , Ilija Ban¹
¹Dep. of orthopedic surgery, Hvidovre Hospital, Denmark

Background: The surgical treatment of fractures in the posterior malleolus as part of bi- or tri-malleolar fractures are investigated extensively, and studies show that involvement of the posterior malleolus often indicate severe trauma and increase the risk of prolonged pain and arthrosis. However, very few studies investigate the rare isolated posterior malleolus fracture (IPMF).
Aim: To describe the fracture mechanism, diagnosis and treatment of the IPMF through a case report and a literature review
Materials and Methods: A 26-year-old healthy female twisted her ankle on a skateboard and presented herself in the emergency room with discrete diffuse swelling of the ankle and unable to bear weight. 3 plane x-ray showed a non- displaced IPMF. On CT-scan the diagnosis was confirmed, and concomitant fracture/displacement excluded. The patient was treated with a weight bearing orthosis and subsequent weight bearing x-rays 10 days later showed no displacement. The patient was discharged with no further follow-up. A literature review identified one review of 75 cases from 2017
Results: IPMF account for 0.5-4% of all ankle fractures and occur most frequently in adults (31.6 ± 5,7 years). The trauma mechanism is either a twisting motion or an axial loading where talus is pushed against the posterior malleolus. The mechanism is important in the evaluation of potential soft-tissue damage. In up to 75% of the cases, the diagnosis was initially overlooked due to diffuse symptomology and difficult visualization on plain x-rays. Delayed diagnosis can increase the risk of persistent pain and arthrosis. The choice of treatment depends on the size of the fragment and displacement but the indication for surgery is still under debate. 85% of the cases were treated conservatively, and 15% operatively; all successfully with no significant sequelae.
Interpretation / Conclusion: However rare, the IPMF fracture may indicate a complex ankle injury and therefore warrant extra attention when diagnosed. The diagnosis is difficult due to diffuse symptoms and limited visualization on plain x-rays. A CT scan should be performed to determine the fracture pattern and potential concomitant injury. When diagnosed in time and treated properly the risk of sequelae is low.

200. Percutaneous intramedullary screw or rush pin fixation of unstable ankle fractures in fragile people – retrospective study of 80 cases.
Simon Oksbjerre Mortensen¹, Per Hviid Gundtoft², Jeppe Barchmann²
Department of Orthopaedics, Aarhus University Hospital² Department of Orthopaedics, Regionshospitalet Randers¹

Background: Patients with unstable ankle fractures and fragile soft tissues have often been treated with an intramedullary screw or rush pin.
Aim: To evaluate the re-operation rates of patients with unstable ankle fractures treated with fixation of the distal fibula with an intramedullary screw or rush pin.
Materials and Methods: This was a retrospective cohort study. We identified all patients above 18 years of age, who were surgically treated for an ankle fracture at Aarhus University Hospital, Denmark between January 1st, 2012 to December 31th, 2018. All postoperative x- rays of the cohort were assessed and all patients treated with either a 3.5 screw or rush pin were included. From the patients’ medical record we retrieved information on: re-operation, comorbidity, and complications. Major complications were defined as re-operation within 3 month. All x-ray obtained at the outpatient clinic at 6 weeks’ follow-up were retrospectively evaluated for loss of reduction and whether the medial clear space (MCS) were larger than 4 mm or were 1 mm larger than the superior clear space above talus (SCS).
Results: A total of 80 patients were included of which 55 were treated with a screw and 25 with a rush pin. The majority was females (59 patients) and the average age was 75-years (24-100 years). A total of 20 suffered from osteoporosis and 65 had one or more comorbidities. Three patients were re-operated within 3 months due to either fracture displacement (2) or hardware cutout (1). Additionally, one more patient was described in the medical record with fracture displacement, but was treated conservatively due to comorbidity. Early complications were found as superficial wound infection (4) and delayed wound closure (6). In addition to the 3 patients, where fracture displacement was described in the medical record, we identified 9 patients that had loss of reduction at follow-up. A MCS larger than 4 mm was seen in 15 patients and 11 had a MCS that was more than 1 mm larger than the SCS.
Interpretation / Conclusion: Intramedullary fixation of distal fibula fractures, with either a screw or rush pin, has low re-operation rates. However, there is a worrying high proportion with radiological loss of reduction.

196. Complication classification grading in intramedullary bone lengthening nails. A reliability study with an inter-and intra-rater assessment.
Markus Winther Frost¹ ², Ole Rahbek¹ ², Marie Fridberg¹ ², Mindaugas Mikužis¹, Søren Kold¹ ²
1. Department of Orthopedic Surgery Aalborg University Hospital Hobrovej 18-22 9000 Aalborg Denmark: 2. Department of Clinical Medicine Faculty of Medicine Aalborg University Sdr. Skovvej 15 9000 Aalborg

Background: Lower limb lengthening with intramedullary bone lengthening nails has been reported with varying complication rates. The absence of consensus on how to report complications might influence the variability seen in complication rates. Four different severity classification systems have to our knowledge, been used. Since bone lengthening affects different tissue types individually, both the complication severities and tissue origin are essential. However, no known complication severity classifications account for the complication origin or have been tested for reliability.
Aim: The study aims to evaluate a severity and origin complications classification system in bone lengthening nail for inter-and intra-rater agreement.
Materials and Methods: Complication severity was classified according to Black et al. 2015. (I, II, IIIA, IIIB). Complication origins were classified into eight main groups (soft tissue, joint, vascular, bone, neurological, infection, device-related, others) and 33 sub-groups. Four orthopedic surgeons assessed the 48 complications retrieved from patient charts, and 49 reported complications from published literature. The cases were evaluated in a blinded independent set up with at least six weeks apart. Inter-and intra-rater agreement was estimated with Cohen/Congers kappa. Svanholm et al. were used to interpret the kappa values. CI: 95 % confidence intervals.
Results: For the cohort cases, the kappa value of severity and origin was .68 CI(.56-.79) and .63 CI(.53-.73) respectively, giving good inter-rater agreement. A good inter-rater agreement were also observed with a kappa value on the severity of .64 CI(.53-.75) and origin of .74 CI(.65-.83) in the literature retracted cases. A poor to excellent intra-rater agreement was observed for the cohort and literature cases.
Interpretation / Conclusion: This first reliability-tested complication classification system that incorporates severity and origin grading for bone lengthening nails has shown good inter- rater agreement for literature and cohort cases. Differences among intra-rater agreement indicated that the classification system might improve with better reviewer rules and guidance.

163. Concentrations of co-administered vancomycin and meropenem in the internal dead space of a cannulated screw and in cancellous bone adjacent to the screw – evaluated by microdialysis in a porcine model
Sofus Vittrup, Maiken Stilling, Pelle Hanberg, Sara Kousgaard Tøstesen, Martin Bruun Knudsen, Josephine Olsen Kipp, Mats Bue
Aarhus Denmark Microdialysis Research (ADMIRE), Orthopaedic Research Laboratory, Aarhus University Hospital; Department of Clinical Medicine, Aarhus University; Department of Orthopaedic Surgery, Aarhus University Hospital

Background: Cannulated screws are often used in the management of open lower extremity fractures. These fractures exhibit broad contamination profiles, necessitating empirical antibiotic Gram- positive and Gram-negative coverage. To ensure full antibiotic protection, target tissue antibiotic concentrations should, as a minimum, reach and remain above relevant epidemiological cut-off minimal inhibitory concentrations (T>MIC) for a sufficient amount of time.
Aim: To evaluate vancomycin and meropenem target site T>MIC values for bacteria most frequently found in infections following open lower extremity fractures
Materials and Methods: 8 pigs received single doses of vancomycin (1000 mg) and meropenem (1000 mg) simultaneously. Microdialysis catheters were placed in the internal dead space of the cannulated screw, in tibial cancellous bone adjacent to the screw, and in cancellous bone on the contralateral leg for sampling of vancomycin and meropenem concentrations over 8 h. MIC targets ranged from 1-4 µg/mL for vancomycin and 0.125-2 µg/mL for meropenem.
Results: For both drugs, and for all MIC targets investigated (except for the high vancomycin target: 4 µg/mL), the internal dead space of the cannulated screw had the shortest T>MIC. For the high MIC targets, T>MIC ranged between 3- 446 min for vancomycin (4 µg/mL) and 17-181 min for meropenem (2 µg/mL). Vancomycin displayed longer T>MIC (2 and 4 µg/mL), higher area under the concentration time curve (AUC0- last) and peak drug concentration in the proximal tibial cancellous bone without a screw nearby. For meropenem, only the cancellous bone AUC0-last was significantly higher on the side with no screw.
Interpretation / Conclusion: We found short T>MIC, particularly for the high MIC targets for vancomycin and meropenem, both inside the cannulated screw and in cancellous bone adjacent to the screw. The presence of a cannulated screw impaired the penetration of especially vancomycin into cancellous bone adjacent to the screw. More aggressive or different vancomycin and meropenem approaches may be considered to encompass contaminating differences and to ensure a theoretically more sufficient antibiotic protection of cannulated screws when used in the management of open lower extremity fractures.

Poster Walk 2: Hip arthroplasty
Chair: Ann Ganestam / Christian Skovgaard Nielsen

155. Perioperative preventive use of antibiotics, how much is necessary? Effect of single versus multiple prophylactic antibiotic doses on prosthetic joint infections following primary total hip arthroplasty (THA). Protocol for the Pro Hip Quality Trial
Armita Armina Abedi, Claus Varnum, Alma Becic Pedersen, Kirill Gromov, Jesper Hallas, Pernille Iversen, Thomas Jakobsen, Espen Jimenez-Solem, Kristian Kidholm, Anne Kjerulf, Jeppe Lange, Anders Odgaard, Nanna Kæstel Petersen, Flemming Schønning Rosenvinge, Søren Solgaard, Kim Sperling, Andrea Søe-Larsen, Robin Christensen, Søren Overgaard
Department of Orthopedic Surgery and Traumatology, Copenhagen University Hospital, Bispebjerg, Denmark & Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; Department of Orthopedics, Lillebaelt Hospital, Vejle, Denmark; Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark & Department of Clinical Medicine, Aarhus University, Aarhus, Denmark; Department of Orthopedic Surgery, Copenhagen University Hospital Hvidovre, Copenhagen, Denmark; Clinical Pharmacology, Department of Public Health, University of Southern Denmark, Odense, Denmark; The Danish Clinical Quality Program– National Clinical Registries (RKKP); Department of Orthopedics, Aalborg University Hospital, Farsø, Denmark & Department of Clinical Medicine, Aalborg University Hospital, Denmark; Department of Clinical Pharmacology, Bispebjerg and Frederiksberg Hospital, Copenhagen, Denmark; CIMT-Centre for Innovative Medical Technology, Odense University Hospital and University of Southern Denmark, Odense, Denmark; Infectious Disease Epidemiology & Prevention, Statens Serum Institut, Copenhagen, Denmark; Department of Orthopedic Surgery, Horsens Regional Hospital, Denmark; Department of Orthopaedic Surgery, Centre of Head and Orthopedics and University of Copenhagen, Rigshospitalet, Copenhagen, Denmark; Patient Representative; Department of Clinical Microbiology, Odense University Hospital, 5000 Odense C, Denmark; Department of Hip and Knee Surgery, Herlev-Gentofte University Hospital, Hellerup, Denmark; Department of Orthopedic Surgery, Næstved Hospital, Denmark; Patient Representative; Section for Biostatistics and Evidence-Based Research, the Parker Institute, Bispebjerg and Frederiksberg Hospital, Copenhagen, Denmark & Research Unit of Rheumatology, Department of Clinical Research, University of Southern Denmark, Odense University Hospital, Denmark; Department of Orthopedic Surgery and Traumatology, Copenhagen University Hospital, Bispebjerg, Denmark & Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.

Background: A feared complication after THA is periprosthetic joint infection (PJI), associated with high morbidity including prolonged hospitalization, reduced quality of life, increased health-care costs and high mortality. Using antibiotics is one of the main modifiable factors for prevention of PJIs. There is no consensus on the dosages, and current recommendations are based on low- level evidence. No randomized controlled trial (RCT) has compared one preoperative dose with additional doses of antibiotic prophylaxis.
Aim: To compare the effect of a single versus multiple prophylactic antibiotic doses administered within 24 hours on PJI.
Materials and Methods: The study is designed as a cross-over, cluster randomized, non-inferiority trial. All clinical centers use both regimes (one year of each intervention), but the order in which they use the regimes is randomized. In principle all Danish orthopedic surgery departments will be involved. Over two years, app. 18,000 primary THAs conducted at app. 45 public and private hospitals will be included, corresponding to a statistical power of >99.9%. Inclusion criteria: age =18 years, all indications for THA except bone tumor and metastasis. The primary outcome is PJI within 90 days after primary THA. Secondary outcomes include (i) serious adverse events, (ii) potential PJI, (iii) length of stay, (iv) thromboembolic complications, (v) hospital-treated infections, (vi) community-based antibiotic use, (vii) redeemed prescriptions for opioids, (viii) acetaminophen and NSAIDS. The primary analyses will be based on the Intention to Treat (ITT) population. Non- inferiority will be met if the upper limit of two- sided 95% confidence interval around the absolute difference in risk is less than 2.0 percentage points. Outcome measures will be extracted from national databases: The Civil Registration System, The Danish Hip Arthroplasty Register, The Danish National Patient Registry, The Hospital Acquired Infections Database and The Danish National Prescription Database.
Results: Expected in ultimo 2024.
Interpretation / Conclusion: We believe, that results of this RCT will deliver necessary evidence to change clinical practice on antibiotic prophylaxis dosages in the future.

156. Early periprosthetic fracture in cementless total hip arthroplasty - A long term follow-up of 129 cases
Tobias Bak Skov, Mikkel Rathsach Andersen, Peter Frederik Horstmann, Christian Benned Fagernæs, Anne Grete Kjersgaard, Søren Solgaard
Department of Orthopaedic Surgery, Gentofte Hospital

Background: Periprosthetic fracture (PPF) following total hip arthroplasty (THA) puts the patient at risk for an outcome with pain and lower functional level. In the literature uncemented operative technique is associated with a higher risk of PPF.
Aim: To analyze the incidence of perioperative and early PPFs at Gentofte Hospital, and evaluate functional outcome. The incidence of PPFs is compared to data from the Danish Hip Arthroplasty Register (DHR).
Materials and Methods: In the period 2013 to 2019, a total of 6101 patients were treated with THAs at Gentofte Hospital, and uncemented technique was used almost exclusively. Patients with perioperative fractures, or early fractures within 3 months of primary surgery with an uncemented THA, were eligible for inclusion. Data were obtained by lookup in the patients’ medical records. Fractures were classified by the Vancouver classification. Functional outcome was evaluated after a mean of 5.1 years follow-up (2-9 years) using the Oxford Hip Score (OHS) and the Forgotten Joint Score-12 (FJS-12).
Results: The incidence of perioperative and early PPF was 2.1%. Perioperative fractures occurred in 0.9% (n=54) and early fractures in 1.2% (n=75). During the period, the incidence of perioperative and early fractures decreased from 1.3% and 1.6% to 0.4% and 0.9%, respectively. Revision surgery within 3 months due to PPF was performed in 0.7% (n=45). Six patients were revised two or more times. From 2013 to 2018, the DHR reported a mean incidence of perioperative PPF of 1.1%. The mean OHS was 39.1 (15-48). Subclassified in pain and function scale, patients reported a mean of 80.1 (20.8- 100) in pain subscale and 82.9 (33.3-100) in function subscale. The mean of FJS-12 was 64.9 (0-100). Overall, patients undergoing revision surgery reported a lower score of OHS and FJS- 12 compared to non-revised fractures.
Interpretation / Conclusion: Our findings indicate a lower incidence of perioperative PPF compared to the data by DHR, despite the use of uncemented technique. However, the DHR data are not subdivided into fixation technique. Patients tended to report a lower FJS-12, though the relatively high OHS indicates that it is possible to achieve a well-functioning THA after a PPF.

157. Biomechanics of a collum-fixated short stem in total hip arthroplasty.
Anders Tjønneland, Poul Torben Nielsen, Thomas Jakobsen
Department of Orthopedics, Aalborg University Hospital.

Background: Total hip arthroplasty with a short femoral stem component have been developed and used intermittently dating back to late 1930’ies. However, short stem designs have never been widely accepted. A potential benefit of a short stem include more physiologic loading of the proximal part of the femur, resulting in preservation of bone stock in the calcar region. Biomechanical reconstruction of the hip has a significant impact on the clinical outcome and survival of implants. To our knowledge little is known about the ability of a neck stabilized prosthesis to restore the biomechanics of the hip.
Aim: The overall aim of the present study was to evaluate a collum fixated stem, PrimorisTM, effect on hip biomechanics. We hypothised that the biomechanics of the hip can be restored, especially the hip parameters global offset and leg length difference within an acceptable range. The primary outcomes were measurable hip parameters on x-rays after THA using the PrimorisTM stem.
Materials and Methods: Between July 2011 and June 2015, 1294 patients were treated with THA at the Farsoe Clinic and 152 of them had a total hip replacement, with a collum fixated stem, PrimorisTM. 25 patients were excluded (13 contralateral hip prosthesis, 2 peroperative and 5 revision change to metaphyseal / diaphyseal stabilized stem, 5 x-ray not suitable for measurements). The epidemiological data for the remaining 127 patients: mean age of 52 (SD 8.7) and female/male ratio of 16/111. Biomechanical parameters were measured post- operatively at the arthroplasty side, as well as for the native contralateral side on the same x-ray, taken 1 year after surgery: 1. Global offset (GO) 2. Leg length discrepancy (LLD) 3. Neck shaft angle (NSA)
Results: Our findings were a mean GO of -3.4 mm (SD 7.2). A mean LLD of +3.8 mm (SD 6.4). The NSA had a mean increase of 14 degrees (SD 7.4)
Interpretation / Conclusion: In THA a neck stabilized stem, enables restoration of hip anatomy within a beneficial range, in terms of the global offset and the leg length discrepancy where the mean difference is within ±5mm. However the Primoris stem had a tendency being implanted in valgus.

158. Preclinical custom made 3D-CT interpositional intraarticular HipCap implant for patients with osteoarthritis
Jes B Lauritzen, Engin Y Kurt, Sune Lund Sporring, H Martin Kjer
Department of Orthopaedic Surgery and Radiology, Bispebjerg Hospital, University of Copenhagen Department of Applied Mathematics and Computer Science, Technical University of Denmark

Background: An intraarticular hip joint spacer (1,2) has been developed to reduce pain and improve motion in hip joints in patients with osteoarthritis. The implant has a smooth metallic surface with low friction and thereby reduces transferred peak force across the joint from bone to bone, where cartilage has been lost.
Aim: To verify and document the process from 3D-CT imaging to construct a custom made implant that fits properly into the diseased joint in femoral head specimens from patients undergoing operation with insertion of a total hip arthroplasty.
Materials and Methods: 3D-CT scans of patients with arthritis and osteoarthritic femoral specimens were performed to develop the implant size. A 3-dimensional circle measuring was done in 4 steps. Shape evaluation. Alignment. Circle measuring. Extracting the dimensions and creation of a 3D implant model. Six tests were involved in a laboratory study to determine implant fit of the femoral osteoarthritic head, including assessment of circumference, thickness of implant and aperture of the cap to obtain snapping of the implant over the femoral head, so the cap does not dislocate. Test caps were printed in plastic by KAPACITET A/S (Nikolaj S Stauning & Thomas O Christensen). The metal cup implant was constructed of 316LMV steel by ELOS MEDTECH A/S (Ole Z Andersen).
Results: Joint space in arthritic joints was determined to be around 0.75 mm to 1.00 for the desired implant design. The accuracy of the implant size goes down to 0.03 mm. The inner diameter was 46.70 and the aperture cut was 44,50 mm, and the . The method allows for assessing proper thickness of implant to resist deformation. The 3D-CT gives precise information of patients who will not be able to benefit from the implant in cases where the roundness of the femoral head is disturbed.
Interpretation / Conclusion: The 3D-CT based assessment for implant sizing was able to achieve a precise fit. The results from the preclinical studies will be followed by a clinical test study in patients with diseased hip joints. References 1. Lauritzen JB, Sporring SL. Medical implant for reducing pain in diseased joints. WO 2014094785A3. 2. Lauritzen JB. Custom made hip implant WO 2019/025546 A 1.

159. Body mass index related disparities of hip fracture care in Denmark – a population-based cohort study.
Nanna Sofie Astrup Pedersen¹, Inger Mechlenburg¹ ², Pia Kjær Kristensen¹ ²
Department of Orthopaedics, Aarhus University Hospital¹; Department of Clinical Medicine, Aarhus University²

Background: Hip fracture is the leading cause of fall-related mortality in older people. Adherence to the guideline recommended treatment are in Denmark continuously monitored through process performance measures (PPM). Unwarranted variation in fulfillment of the PPM, reflecting guideline recommended hip fracture treatment exist. Patients with either high or low body mass index (BMI) may require extra resources in care e.g. mobilization of an overweight patient often takes more staff, assistive devices, time, and space.
Aim: The aim of this study was to examine the association between patients’ BMI and quality of in- hospital care among patients with hip fracture.
Materials and Methods: A nationwide, population-based cohort study using prospectively collected data from the Danish Multidisciplinary Hip Fracture Registry. The study population consisted of 39,835 patients =65 years admitted with a hip fracture and discharged between 1st of January 2012 and 29th of November 2017. Binomial regression was used to estimate the relative risk for fulfillment of the individual measures with 95% confidence interval (95% CI). Multiple imputation method was applied to handle missing BMI values.
Results: The overall fulfillment of the PPM ranged from 43% for pre¬operative optimization to 95% for receiving a post-discharge rehabilitation program. Patients with missing data on BMI (17%) had the lowest fulfillment of the process performance measures. The obese patients had a lower fulfillment of operation within 36 hours compared to patients with normal weight (82% vs. 85%) corresponding to a RR of 0.85 (95% CI 0.72-0.998). No differences in quality of care were found among patients with underweight or overweight compared to patients with normal weight.
Interpretation / Conclusion: Patients with hip fracture who are underweight or overweight receives the same quality of in-hospital care during admission as patients with normal weight. The obese patients had a slightly higher risk of waiting for surgery than patients with normal weight. The overall fulfillment of PPM was lower than the standards recommended in the national guidelines and future improvements of the quality of in-hospital care should benefit all patients with hip fracture regardless BMI level.

161. Preclinical assessment study of a custom made 3D-CT HipCap implant for dogs with osteoarthritis
James E Miles, Parisa Mazdarani, Berendt Berendt, Sune L Sporring, Jes Bruun Lauritzen
University Hospital for Companion Animals, University of Copenhagen. Department of Orthopaedic Surgery, Bispebjerg Hospital, University of Copenhagen.

Background: An intraarticular hip joint spacer (1,2) was developed to reduce pain and improve motion in hip joints in dogs and human patients with hip joint disease. The implant has a smooth metallic surface with low friction and thereby reduces transferred peak force across the joint from bone to bone, where cartilage has been lost. The first dog has been operated with a fixed sized HipCap implant that needed reaming of the femoral head and acetabulum. The effect of the operation has been successful.
Aim: To verify and document the process from 3D-CT imaging to construct a custom-made implant that fits properly into the diseased joint in cadaver dogs, so reaming can be avoided.
Materials and Methods: Canine cadaver studies were performed to develop the implant size, instrumentation for insertion, and the surgical technique. 3- dimensional circle measuring was done in 4 steps: Shape evaluation; Alignment; Circle measuring; Extracting the dimensions and creation of a 3D implant model. Four tests were involved in a cadaver study to determine joint space in the diseased joint, including assessment of circumference, thickness of implant and aperture of the cap to obtain snapping of the implant over the femoral head, so the cap does not dislocate. Test caps were printed in plastic by KAPACITET A/S (Nikolaj S Stauning & Thomas O Christensen). The metal cup implant was constructed of 316LMV steel by ELOS MEDTECH A/S (Ole Z Andersen).
Results: Joint space in arthritic joints was determined to be around 0.20 to 0.75 mm for dogs for the desired implant design. The accuracy of the implant size goes down to 0.03 mm. Aperture cut was 0.952 of the inner radius of the implant.
Interpretation / Conclusion: The 3D-CT based assessment for implant sizing was able to achieve a precise fit. The results from the preclinical studies in dogs will lead to a clinical test study in dogs with diseased hip joints. The implant can be used independently of the size of the dog. References 1. Lauritzen JB, Sporring SL. Medical implant for reducing pain in diseased joints. WO 2014094785A3. 2. Lauritzen JB. Custom made hip implant WO 2019/025546 A 1.

Poster Walk 3: Hip trauma and infection
Bjarke Viberg / Mats Bue

183. Physical activity in adult patients with hip fracture under 60 years of age is associated with health-related quality of life and strength; Results from the HFU-60 multicenter study
Anna Gaki Lindestrand¹, Sebastian Strøm Rönnquist ² , Bjarke Viberg³ , Søren Overgaard¹ 4, Henrik Palm¹, Cecilia Rogmark ² , Morten Tange Kristensen5 6
Department of Orthopaedic Surgery and Traumatology, Univeristy Hospital Bispebjerg¹ ; Department of Orthopaedics Lund University, Skåne University Hospital Malmö Sweden ² ; Department of Orthopaedic Surgery and Traumatology, Lillebælt Kolding Hospital³; Department of Clinical Medicine, Faculty of Health and Medical Sciences University of Copenhagen4; Departments of Physiotherapy and Orthopedic Surgery, Copenhagen University Hospital – Amager and Hvidovre, Hvidovre, Denmark5; Department of Physical and Occupational Therapy, Copenhagen University Hospital – Bispebjerg and Frederiksberg & Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark6 .

Background: Younger hip fracture patients are often assumed less active than the general population, but knowledge on physical activity (PA), health-related quality of life (HRQOL) and muscle strength in these patients is limited. The World Health Organization (WHO) recommends a minimum of 150 min of moderate intensity aerobic physical activity (PA) per week or 75 min of vigorous-intensity PA weekly for adults older than 18 years.
Aim: We investigated 1) the variation in pre-fracture PA for adult patients with hip fracture under the age of 60; and 2) quantified the association between PA, and patient characteristics, HRQOL and handgrip strength.
Materials and Methods: A prospective multicenter study (4 hospitals) of 207 adult hip fracture patients (85 women and 122 men, median (IQR) age of 53 (48-57) years) admitted 2015-2018. Data was collected through medical records, questionnaires, physical tests, and interviews. PA level was assessed using a validated questionnaire from the Swedish National Board of Health and Welfare, providing a total score from 3 to 19. A score =11 corresponds to fulfillment of the WHO recommendation for weekly PA. Handgrip strength was measured in kilograms using a handheld dynamometer following a standardized protocol. Recall pre-fracture HRQOL was assessed using the EQ-5D-3L questionnaire.
Results: 59% had a PA score below 11, of whom 46% had an ASA grade of 3 or 4, 38% had a BMI over 25 and 81% had a low energy fracture. A PA score <11 points was for both sexes associated with a significantly lower HRQOL versus those with a PA score>11. Correspondingly, a PA score <11 points was associated with weaker hand grip strength and a worse health status (higher ASA-grade, p<0.001).
Interpretation / Conclusion: We found that close to two-thirds of patients had a pre-fracture PA level below WHO recommendations. Being more active was associated with better health status, handgrip strength and HRQOL. Our findings indicate that individuals under 60 years who sustain a hip fracture form a heterogeneous group, some severely comorbid and others highly active and healthy. This suggests a more nuanced understanding of this patient group when it comes to rehabilitation and physical demands.

197. Exploratory study of the OR team's perception of barriers and facilitators in connection with procedure shifts: uncemented hemi-arthroplasty to cemented in patients with acute hip fractures - a case study
Marlene Dyrløv Madsen1, Doris Østergaard1, Klaus Nymark Andersen1, Torben Beck1, Ann-Vibeke Bækgaard Christensen1, Thomas Giver Jensen1, Troels H. Lunn3,4,5, Henrik Palm2,3,5, Kenneth Szkopek2,3, Lene Viholt3,4, Søren Overgaard2,3,5
Copenhagen Academy for Medical Education and Simulation (CAMES Herlev), Capital Region Copenhagen1; Department of Orthopaedic Surgery and Traumatology2; Copenhagen University Hospital - Bispebjerg and Frederiksberg, Copenhagen3; Department of Anesthesia and Intensive Care4; Dept of Clinical Medicine, University of Copenhagen, Copenhagen5, Denmark

Background: DOS has in a Short Clinical Guideline recommended to change from uncemented hemiarthroplasty (HA) to cemented in the treatment of patient with femoral neck fracture. The overall aim was to develop a safe and successful introduction of the new procedure by uncovering all team members' perspectives on the challenges of changing procedure. This is in accordance with implementation science, demonstrating the necessity to prepare all stakeholders prior to procedure change.
Aim: The aim of this study was to explore all operation room (OR) team members´ (surgeons, surgical nurses, anesthesiologists, and anesthesia nurses) perspectives of barriers and facilitators in introducing a change in procedure.
Materials and Methods: Four semi-structured group interviews were conducted with the team. Interviews were transcribed, and anonymized. Data analysis was performed in accordance with Braun and Clarkes approach to reflexive thematic analyses using thematic maps to define themes and sub-themes.
Results: The team contributed with barriers and important needs for training, and supervision. We found several themes regarding barriers and potential fear related to procedural related factors and organizational challenges. Subthemes were lack of time to do the procedure before cementation and uncertainty regarding maintenance of the competencies. Moreover, the team expressed their needs for a “safety package” including both training and a psychological safe learning space. We also found overall themes of more cultural and relational nature, which transcends the other themes, and works as both barriers and facilitators: "myths", “time”, “culture”, giving voice to the importance of the atmosphere in the OR. The concept of "time" and the maintenance of “myths” about difficulties handling cement have a huge impact on the team leading potential fear for the procedure. The team agreed on most, although some points differed specific to professions.
Interpretation / Conclusion: The team’s need for evidence-based training in psychological safe space was evident and should be secured. Time and myths as contributing factors in driving fear needs special notice. All factors should be considered when implementing the new procedure in a training protocol.

199. Intramedullary nail versus dynamic hip screw with stabilising trochanteric plate in the treatment of unstable intertrochanteric fractures
Christina Frølich Frandsen ¹ ², Maiken Stilling ¹ ² ³, Eva Natalia Glassou ¹ 4, Torben Bæk Hansen ¹ ²
University Clinic for Hand, Hip and Knee Surgery, Department of Orthopaedics, Gødstrup Hospital, Denmark ¹ Department of Clinical Medicine, Aarhus University, Denmark ² Department of Orthopaedics, Aarhus University Hospital, Aarhus, Denmark ³ Department of Quality, Gødstrup Hospital, Denmark 4

Background: Intertrochanteric fractures are typically treated with internal fixation. However, despite extensive research, the best choice of implant for intertrochanteric fractures remains controversial, especially for unstable intertrochanteric fractures. Intramedullary nails (IMNs) have shown better results than dynamic hip screws (DHS), which lead to the development of the trochanteric stabilising plate (TSP). The TSP should stabilise the greater trochanter and lateral femoral wall, however, few have compared it to IMNs.
Aim: The study aimed to compare long IMNs and dynamic hip screw with a trochanteric stabilising plate (DHS-TSP) in the treatment of unstable intertrochanteric fractures with the primary outcome being reoperation within three years.
Materials and Methods: A prospective cohort study included 156 patients treated for an unstable intertrochanteric fracture (AO-type: 31A2.2-3 and 31A3.1-3) with IMN or DHS- TSP. The primary outcome was reoperation within three years. Secondary outcomes were measured during the hospital stay (operation time, total blood loss, blood transfusions, mobilisation and length of stay) and at a one-year postoperative follow-up (pain, patient-reported outcome measures (PROM) and regaining pre-fracture function). Differences between the two groups were analysed using the chi-squared test or Fisher exact test.
Results: The two groups were similar concerning baseline characteristics, expect for IMN being used more frequently in osteosynthesis of AO-type 31A3 fractures (p<0.01). The IMN group had a higher total blood loss (p<0.01) and a lower frequency of mobilisation within 24 hours (p=0.02). However, this was not reflected in the number of blood transfusions (p=0.73) or a decreased walking ability at the one-year follow-up (p=0.09). After one year, the IMN group had less pain (p=0.04) but similar results in terms of all other outcomes, including regaining pre-fracture function (p=0.86), PROM (p=0.35) and reoperation rates (p=0.61).
Interpretation / Conclusion: The findings suggest that both long IMN and DHS- TSP may be used to treat unstable intertrochanteric fractures with similar results regarding regaining function, PROM and reoperation rates.

191. Risk Factors And Influence Of Surgical Skill On Reoperation After Treatment Of Acute Femoral Neck Fracture With Uncemented Hemiarthroplasty
Susanne Faurholt Närhi, Britt Aaen Olesen, Thomas Giver Jensen, Søren Overgaard, Henrik Palm, Michala Skovlund Sørensen
Department of Ortopaedics, Copenhagen University Hospital Bispebjerg

Background: According to national guidelines, it is recommended that a patient with a femoral neck fracture (FNF) eligible for a hemiarthroplasty (HA) should have the stem implanted with cementation, nevertheless the use of uncemented HA is still ongoing.
Aim: Primary aim: Evaluate risk factors of reoperation after treatment of FNF using an uncemented HA. Secondary aim: Evaluate surgeon/supervisor skill level in association with intraoperative complications and risk of conversion to a cemented stem.
Materials and Methods: This is a retrospective study of a consecutive, population-based cohort of patients with FNF treated with HA (BFX stem) in 2010-2016. Variables and preoperative complications were identified from patient files and reoperations were identified from the Danish National Patient Registry. Death was considered a competing event for reoperation in a fitted Cox model. Chi2 test was used to address intraoperative complications and conversion to cemented stem between surgeon skill levels.
Results: 772 stems were implanted as uncemented, 24 were intraoperatively converted to cemented stems (185/550 M/F, mean age 84). There were 37 reoperations occurring (mean) after 37 (0-126) months. The cause specific analyses showed that absence of dementia was a protective factor of reoperation (HR 0.45(CI:0.22-0.90)) and smoking a risk factor (HR 2.30 (CI: 1.11- 4.77). In subdistrubution model dementia failed to be prognostic (HR 0.53 (CI: 0.26- 1.07). Intraoperative complications were seen in 82 stems out of 761, with no significant difference in surgeon skill level. Main reason for complication were fissure treated with a cable. We found that leading surgeon with less than one year of orthopedic training was less likely to convert to cemented stem, compared to those with longer training (p=0.048).
Interpretation / Conclusion: We found that dementia and smoking were the sole predictors for risk of reoperation. Additionally, it was noticeable that if death was not taken into consideration, dementia will not be seen as a risk for reoperation. Less trained leading surgeons had a lower risk of conversion to cemented stem. This may be biased, as more trained personnel are summoned to complications leading to cementation.

203. Computer assisted navigation for cephalomedullary nailing of hip fractures: A prospective usability analysis.
Rasmus A. Hestehave¹, Jan D. Rölfing¹ ², Christian L. Nielsen¹, Ole Brink¹, Per H. Gundtoft¹
Department of Orthopaedics, Aarhus University Hospital¹ ; Corporate HR, MidtSim, Central Denmark Region²

Background: The STRYKER ADAPT computer-assisted navigation system provides intraoperative feedback to the surgeon regarding implant placement of the gamma3 nail. The usability of the ADAPT system has not been evaluated.
Aim: To study the surgeons’ perceived usability of the ADAPT system.
Materials and Methods: This was a descriptive study with prospectively collected data. The ADAPT system was introduced at Aarhus University Hospital in February 2021. Prior to introduction, all surgeons were invited to a general introduction of the system. Furthermore, ADAPT was introduced to the surgical nurses and was on display at the surgical ward at more than one occasion. Following the introduction, it was mandatory to use ADAPT when using the Gamma3 nail to treat intertrochanteric femur fractures. After each procedure, primary and secondary surgeon answered the System Usability Scale (SUS) questionnaire. The SUS is a ten-item questionnaire regarding the perceived usability of a system. SUS scores were translated to adjectives, describing user experience on a 7-point adjective scale (worst imaginable, awful, poor, ok, good, excellent, best imaginable). User acceptability, defined as “not acceptable”, “marginal” or “acceptable”, was used to interpret the SUS scores.
Results: ADAPT was used in 50 procedures by 29 different surgeons, with varying skill-level. 61 of 79 sent questionnaires, were answered. Median SUS-score after first-time use of ADAPT for all 29 surgeons was 43 (range: 5-60), which translated to “poor” and “not acceptable”. For surgeons who performed >=3 ADAPT-assisted procedures, there were no statistically significant difference in their first to latest SUS- score (median difference: 4.3, p=0.5). In free text comments ADAPT was positively described as helpful in placement of K-wire and providing educational opportunities for inexperienced surgeons and negatively as inconsistent, slow, time consuming, and causing excessive fluoroscopy.
Interpretation / Conclusion: Usability of the ADAPT system was ranged as “poor” and “not acceptable” by the majority of operating surgeons. Although the majority found it unnecessary and time-consuming some stated that it might be a useful supplemental tool for inexperienced surgeons.

207. Rehabilitation for life: the effect on physical function of rehabilitation and care in older adults after hip fracture - study protocol for a cluster-randomised stepped-wedge trial
Jonas Ammundsen Ipsen ¹ ², Lars Tobiesen Pedersen¹ ² ³ , Bjarke Viberg4, Birgitte Nørgaard5 , Charlotte Suetta6 7 , Inge Hansen Bruun¹ ²
Department of Physical Therapy and Occupational Therapy, Lillebaelt Hospital, University Hospital of Southern Denmark¹; Department of Regional Health Research, University of Southern Denmark²; Department of Health Education, University College South Denmark³; Department of Orthopaedic Surgery and Traumatology, Lillebaelt Hospital, University Hospital of Southern Denmark4; Department of Public Health, University of Southern Denmark, Denmark5; Department of Geriatric and Palliative Medicine, Bispebjerg and Frederiksberg Hospitals, University of Copenhagen, Denmark6; Department of Medicine, Herlev and Gentofte Hospitals, University of Copenhagen, Denmark7

Background: Hip fractures are the most frequently surgically treated trauma and it has serious consequences for older adults. About 50% do not regain usual physical function and mortalityplus readmissions rates are high. The gap in healthcare delivery might be a cause of inferior rehabilitation and care.
Aim: ‘Rehabilitation for Life’ trial has been developed to challenge this gap and assess the effect of continuous and progressive rehabilitation and care across sectors for older adults after hip fracture.
Materials and Methods: ‘Rehabilitation for Life’ is designed as a stepped wedge cluster randomised trial. The study populations are non-institutionalised, cognitively able, and older patients and health care professionals in both sectors. One regional hospital and all municipalities within the catchment area participate. Patients receive a trolley containing rehabilitation regime, exercise equipment, and a guide, targeted patient and next-of-kin to a digital healthcare app. Health professionals are taught how to facilitate empowerment. The rehabilitation intervention consists of 12 weeks of resistance exercises initiated 1-2 days after discharge. Videoconferences involving, hospital and municipal physiotherapists and patients to enable knowledge transfer. The care intervention consists of a medical assessment including measurement of vital signs conducted by municipal nurses in patients’ own home. A medical hotline enables direct confer with hospital nurses and doctors. Data collection at discharge and follow-up 8, 12, 26 weeks post-surgery include physical measurements. The primary outcome is Timed Up and Go test 8 weeks post-surgery. Among secondary outcomes are 30 day and 1 year mortality rates, readmissions and cost- effectiveness.
Results: So far, 702 patients has been screened, 476 excluded (189 institutionalised, 75 young, 58 non inhabitants of catchment area, 30 fast discharge, 52 other reasons, 72 reclined to participate) and 182 has been included.
Interpretation / Conclusion: The interventions delivered are evidence-based, simple and reproducible. Thus if effective, it can impact usual rehabilitation and care after hip fractures nationwide, especially if it is cost- saving.

188. Comorbidity burden and the risk of infection among hip fracture patients: a Danish population-based cohort study
Nadia R. Gadgaard¹, Claus Varnum² ³, Rob Nelissen4, Christina Vandenbroucke-Grauls¹ 5, Henrik T. Sørensen¹, Alma B. Pedersen¹
Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus University, Denmark¹; Department of Orthopedic Surgery, Lillebaelt Hospital – Vejle, Denmark²; Department of Regional Health Research, University of Southern Denmark, Denmark³; Department of Orthopedics, Leiden University Medical Center, The Netherlands4; Department of Medical Microbiology and Infection Control, Amsterdam University Medical Centers, Amsterdam, The Netherlands5

Background: Although both the risk of postoperative infection and comorbidity burden have increased among Danish hip fracture patients during the last decade, the impact of comorbidity on infection risk is unknown.
Aim: We aimed to examine the magnitude of the association between comorbidity burden and any infection after surgery for hip fracture.
Materials and Methods: Utilizing Danish population-based medical registries, we identified patients undergoing hip fracture surgery between 2004-2018 (n=92,600). Comorbidity was categorized using the Charlson comorbidity index (CCI) as low (CCI score = 0), moderate (CCI score = 1-2), or severe (CCI score =>3). Outcome was any hospital treated infection within 30 days and 1 year of surgery. We estimated cumulative incidences considering death a competing risk and, by Cox regression, hazard ratios (HR) with 95% confidence interval (CI) adjusting for age, sex, and surgery year.
Results: Cumulative incidence of any infection increased with increasing comorbidity burden, from 12.6% (CI: 12.2-12.9%) to 19.5% (CI: 18.9-20.1%) and 22.2% (CI: 21.7-22.6%) to 36.6% (CI: 35.9- 37.3%) among patients with low to severe comorbidity within 30 days and 1 year after surgery. Compared to patients with low comorbidity, those with moderate and severe comorbidity had adjusted HRs of 1.3 (CI: 1.3-1.4) and 1.6 (CI: 1.5-1.7) for any infection within 30 days, and 1.4 (CI: 1.4-1.5) and 1.9 (CI: 1.9-2.0) within 1-year of surgery.
Interpretation / Conclusion: Among hip fracture patients, a higher comorbidity burden was associated with increased hazards for hospital treated infection. Focus on in-hospital care of most comorbid hip fracture patients, screening, and more aggressive prevention of infection could potentially reduce infection risk.

Poster Walk 4: Knee
Chair: Julie R. Brandt / Mikkel R. Andersen

165. Validation of the indication ”pain without loosening” for revision of knee arthroplasties in the Danish Knee Arthroplasty Register.
Kristine B. Arndt¹, Henrik M. Schrøder², Anders Troelsen³, Mikkel R. Andersen4, Lasse E. Rasmussen5, Martin Lindberg-Larsen¹
Department of Orthopaedic Surgery and Traumatology, Odense University Hospital¹, Denmark; Department of Orthopaedic Surgery. Naestved Hospital², Denmark; Department of Orthopaedic Surgery, Copenhagen University Hospital, Hvidovre³, Denmark; Department of Orthopedics, Herlev Gentofte Hospital4, Copenhagen , Denmark; Department of Orthopaedic Surgery, Lillebaelt Hospital - Vejle5, Denmark

Background: 13% of revisions of knee arthroplasties registered in the Danish Knee Arthroplasty Register (DKR) are for the indication “pain without loosening. However, the indication is not validated and might cover other hidden indications as well.
Aim: The aim of this study was to investigate the indication “pain without loosening” in the DKR, and screen for other possible indications hidden in this category.
Materials and Methods: We included patients undergoing first-time revision knee arthroplasty for the indication “pain without loosening” as the only registered indication in the DKR. Revisions performed in the time period January 1, 2016 to December 31, 2018 at five Danish centers were included in the study. Medical records and radiographs were reviewed for all patients and CT scans for those available (29 patients).
Results: 86 patients were included in the study. The distribution of Kellgren-Lawrence arthrosis grade up to the primary knee arthroplasty were grade 1 (1%), grade 2 (18%), grade 3 (41%) and grade 4 (20%). The primary knee arthroplasties were TKA (56 patients), unicompartmental knee arthroplasty (27 patients) and patellofemoral prosthesis (3 patients). All were revised to a total knee arthroplasty (TKA). We did not find any hidden indication in 60% of the cases assessed from medical records, radiographs and CT scans. We found hidden indications in 40% of cases; stiffness, malposition of components, instability, progression of arthrosis, liner dislocation and aseptic loosening. The hidden indications were existing in the DKR in 9% of the cases. Radiographic deviations were present in 50% of cases revised for pain without other hidden indications and in 79% of cases where another indication was present.
Interpretation / Conclusion: We did not find other hidden indication for 60% of cases other than the registered indication “pain without loosening”. Stiffness and malposition of components were hidden indications and may lack in the DKR.

166. Usage of guideline-adherent core treatments and different treatment pathways among patients with knee osteoarthritis: a prospective cohort study
Simon Majormoen Bruhn¹, Lina Holm Ingelsrud¹, Søren T. Skou² ³, Thomas Bandholm4 5 6, Anne Møller7, Henrik Morville Schrøder8 ?, Anders Troelsen¹
Clinical Orthopaedic Research Hvidovre (CORH), Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre, Denmark¹; Research Unit for Musculoskeletal Function and Physiotherapy, Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark²; The Research Unit PROgrez, Department of Physiotherapy and Occupational Therapy, Næstved-Slagelse-Ringsted Hospitals, Region Zealand, Denmark³; Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre, Denmark4; Physical Medicine & Rehabilitation Research Copenhagen (PMR- C), Department of Physical and Occupational Therapy, Copenhagen University Hospital Hvidovre, Denmark5; Department of Clinical Research, Copenhagen University Hospital Hvidovre, Denmark6; Center for Research and Education in General Practice, Department of Public Health, University of Copenhagen, Denmark7; Department of Regional Health Research, University of Southern Denmark, Odense, Denmark8; Department of Orthopaedic Surgery, Næstved-Slagelse-Ringsted Hospitals, Region Zealand, Denmark?

Background: A large variety of treatments for knee osteoarthritis (OA) exists and patients often undergo treatments not in accordance with clinical guidelines.
Aim: To present 1) the proportion of patients receiving guideline-adherent core treatments and 2) the most common treatment pathways that patients with primary referral to an orthopaedic surgeon due to knee OA pursue before and after consulting an orthopaedic surgeon.
Materials and Methods: This cohort study consecutively invited patients with primary referral to an orthopaedic surgeon due to knee OA from October 2018 to December 2020. At inclusion, patients selected which treatments they had received for knee OA from a pre-defined list of 18 treatments before consulting the orthopaedic surgeon. After six months, patients selected from the same list, which treatments they received since the consultation or until surgery. The proportion of patients receiving the recommended combination of guideline-adherent core treatments (education and exercise) was described. Additionally, we investigated which three treatment pathways that were the most common.
Results: Out of 5,251 eligible patients, 3,507 were included and 2,574 had complete six months data. Responders’ (58% female) mean (SD) age was 66.1 (10.1) years and mean (SD) BMI 29.5 (5.7) kg/m². The proportion of patients receiving guideline- adherent core treatments was 35% (899). 10% (245) received no treatment. Out of 797 patients undergoing knee arthroplasty, 37% (297) received guideline-adherent core treatments, and 7% (59) received no treatments before surgery. The most common treatment pathways were: 1) No treatment 7% (n=186), 2) no treatment initially followed by exercise after consultation 3% (n=88), 3) pharmacological treatment initially, followed by no treatment after consultation 2% (n=65). The number of unique pathways was 1,289.
Interpretation / Conclusion: In only one third of the patients with knee OA, treatment pathways adhered to clinical guidelines. In addition, the proportion of patients receiving no treatments and the large number of different treatment pathways suggests a need for a more structured effort to increase the use of guideline- adherent core treatments. Registration: NCT03746184, protocol: PMCID: PMC8264876

164. The 10-year evolution of day case hip and knee arthroplasty
Christian Bredgaard Jensen¹, Anders Troelsen¹, Christian Skovgaard Nielsen¹, Martin Lindberg-Larsen², Kirill Gromov¹
Dept. of Orthopaedic Surgery, Clinical Orthopaedic Surgery Hvidovre (CORH), Copenhagen University Hospital Hvidovre¹; Dept. of Orthopaedic Surgery, Orthopaedic Research Unit (ORU), Odense University Hospital²

Background: Investigations have reported decreasing length of stay following hip and knee arthroplasty in multiple nations, without increased risk of readmission. Studies have also found day case arthroplasty surgery to be safe and feasible in selected patients. However, no previous study has reported the trend in use of day case arthroplasty surgery on a national scale.
Aim: The aim of this study was to investigate the use of day case surgery in total hip (THA), total knee (TKA), and unicompartmental knee (UKA) arthroplasty from 2010 to 2020.
Materials and Methods: Primary unilateral THAs, TKAs, and UKAs performed as treatment for osteoarthritis were identified in the Danish National Patient Register using procedure and diagnoses codes. Day case surgery was defined as discharge on the day of surgery. Systematic utilization of day case surgery was defined as >5% day case surgery. Any unplanned overnight admissions within 90 days of surgery was registered as readmissions.
Results: From 2010-2020 Danish hospitals performed 86,070 THAs, 70,323 TKAs and 10,440 UKAs. From 2010-2014, less than 0.5% of THAs and TKAs were day case procedures. This increased to 5.4% of THAs and 2.8% of TKAs in 2019. From 2010-2014, 11% of UKAs were day case procedures, but this increased to 20% in 2019. 0% of public hospital performed day case THA and TKA from 2010-2014. This increased to 33% and 13% of hospitals performing THA and TKA, respectively in 2019. 14% of public hospitals performed day case UKA in 2010 - this increased to 63% in 2019. The overall 90-day readmission rate decreased from 10.3% in 2010 to 8.9% in 2019. In 2010 10%, 11%, and 6.7% of THAs, TKAs and UKAs, respectively, were readmitted. This decreased to 9.1% and 9.2% of THAs and TKAs in 2019. Readmission rates after UKA fluctuated between 5-7%, with 6.6% being readmitted in 2019.
Interpretation / Conclusion: From 2010-2020 the usage of day case surgery in THA, TKA and UKA increased. The number of hospitals performing day case surgery increased. Despite the increasingly elderly and comorbid arthroplasty population, increased use of day case surgery does not appear to increase readmission rates on a national level.

167. Concurrent validity of linear accelerations measured by low sampling frequency accelerometers during overground walking in elderly patients with knee osteoarthritis
Arash Ghaffari¹, Ole Rahbek¹, Rikke Emilie Kildahl Lauritsen¹, Andreas Kappel¹, John Rasmussen², Søren Kold¹
Interdisciplinary Orthopaedics, Aalborg University Hospital¹; Dept. of Materials and Production, Aalborg University²

Background: The tendency towards using sensors for remote monitoring of the patients at home is increasing. One of the most important characteristics of the sensors is their sampling rate. Higher sampling rate results in higher quality data and lower noise. However, higher sampling frequency comes with a cost regarding handling the data.
Aim: To determine the validity of measurements performed by low sampling frequency (12.5 Hz) accelerometers (SENS) in patients with knee osteoarthritis compared to a previously validated system (Xsens). We also determined the test-retest reliability of SENS.
Materials and Methods: Participants were patients with unilateral knee osteoarthritis referred to Aalborg University Hospital, Farsø. Gait analysis was performed simultaneously by using Xsens and SENS in two repetitions of over-ground walking at a self-selected speed. After processing, the signals from SENS and VirtualSENS were compared in different coordinate axes in time and frequency domains. ICC for SENS data from first and second trials were calculated to assess the repeatability of the measurements.
Results: We included 32 patients (18 females) with median age 70.1[48.1 – 85.4]. Mean height and weight of the patients were 173.2 ± 9.6 cm and 84.2 ± 14.7 kg respectively. The correlation between accelerations in time domain measured by SENS and VirtualSENS in different axes was r = 0.94 in y-axis (anteroposterior), r = 0.91 in x-axis (vertical), r = 0.83 in z-axis (mediolateral), and r = 0.89 for the magnitude vector. In frequency domain, the value and the power of fundamental frequencies (F0) of SENS and VirtualSENS signals demonstrated strong correlation (r = 0.98 and r = 0.99 respectively). The result of test-retest evaluation showed excellent repeatability for acceleration measurement by SENS sensors. ICC was between 0.89 to 0.94 for different coordinate axes.
Interpretation / Conclusion: Low sampling frequency accelerometers can provide valid and reliable measurements especially for home monitoring of the patients, in which handling big data and sensors cost and battery lifetime are among important issues.

168. Is postoperative urinary retention a new problem after surgery or an unknown chronic disorder in men undergoing elective hip, knee or shoulder arthroplasty; a pilot study
Inger Markussen Gryet, Helle Kjær Hvidtfeldt, Kirsten Herold, Merete Frydenlund Pedersen
Elective Surgery Center, Silkeborg Regional Hospital

Background: Postoperative urinary retention (POUR) is a common complication in total joint arthroplasty surgery. A routine procedure for pre-operative bladder scan of patients undergoing total hip arthroplasty (THA), total knee arthroplasty (TKA), uni-compartmental knee arthroplasty (UKA) or total shoulder arthroplasty (TSA) is not established in many departments. Consequently, when POUR is found, it is unclear whether it is a new problem or an unknown chronic urinary retention (CUR). CUR can be an unknown medical disorder, and the risk of CUR increases with age. The risk of POUR is associated with CUR and spinal anesthesia.
Aim: To determine if residual urine (> 150ml pre- and postoperatively) is a problem in elective orthopedic surgery in men >65 years undergoing THA, TSA, TKA or UKA.
Materials and Methods: A pilot test, performing bladder scans on all men aged >65 years undergoing THA, TKA, UKA or TSA surgery during a four-week period in 2021. Bladder scans were performed before surgery and after recent voiding, and repeated postoperatively after voiding if residual urine was =150ml preoperatively. The limit for post void residual urine is defined as =150ml and CUR as =300ml. Data was collected retrospectively from the medical records.
Results: 72 men aged >65 years underwent surgery during the four-week period of testing. 5 men were excluded because of known urinary disorder treated with catheterization. 12 men eligible for inclusion were not scanned. 55 were scanned preoperatively: 5 (9%) had residual urine, 2 (4%) had CUR. 2 of the patients with residual urine described symptoms of residual urine in the outpatient clinic. 11 (20%) of the 55 men were re-scanned postoperatively: 6 of those had >150ml residual urine, additionally 1 had >300ml. 1 of the patients with CUR preoperatively was treated and discharged with an indwelling urinary catheter.
Interpretation / Conclusion: 9% (5/55) in this pilot test had residual urine and 4% (2/55) patients had CUR preoperatively. 11 of 55 patients were bladder scanned postoperatively, 6 had >150ml and 1 >300ml. A collaboration with urologists has been established to form a local guideline for men with residual urine to improve the quality of treatment.

169. Reliability of Teitges test
RIkke Dyhr Hansen, Jørgen Haraszuk, Per Hölmich, Kristoffer Weisskirchner Barfod
Sports Orthopedic Research Center – Copenhagen (SORC-C), Department of Orthopedic Surgery, Copenhagen University Hospital Amager & Hvidovre, Denmark

Background: High Tibial Osteotomy (HTO) is used in treatment of patients with medial knee osteoarthritis (OA). A simple clinical test to select the patients most likely to benefit from the procedure is suggested by MD Robert Teitge - the ‘grand old man’ of osteotomy.
Aim: To investigate the interrater reliability of ‘The Teitge test’.
Materials and Methods: The study was performed as a reliability study with two experienced orthopedic surgeons performing the Teitge test blinded to each other’s results. The Teitge test consists of a varus stress test to provoke the patient´s known symptoms followed by a valgus stress test to relieve pressure from the medial compartment of the knee and to simulate the realignment achieved by HTO. The test is considered positive if valgus stress relieves pain and/or makes the knee move mechanically smoother. Prior to enrolment the investigators practiced together, by performing the test on 5 healthy individuals. Testing was standardized following a written procedure. Inclusion criteria were: unicompartmental knee arthrosis, pain at the medial joint line, varus malalignment on long weight bearing x-rays, BMI 20-40, age 30-70 and English or Danish proficiency. Reliability was determined using Cohens kappa (κ).
Results: A total of 18 patients, mean age (SD) 56.7 (8.6), male/female 6/12 were included resulting in 18 knees tested. Positive/negative agreement between investigators was found in 12 out of 18 cases, resulting in κ = 0.2, 95% CI = [- 0.29,0.72]. Due to a weighted number of positive test results (11/18 and 15/18 respectively) prevalence adjusted bias adjusted kappa (PABAK) was applied, reaching κ = 0.3, 95% CI = [-0.1,0.76].
Interpretation / Conclusion: Slight to fair agreement was found for the Teitge test. Clinicians should be careful when interpretating the test due to the low agreement between raters.

170. Patient reported outcome for the medial Oxford knee is better for younger specialist than super seniors
Lasse E. Rasmussen, Per W. Kristensen
Dept. of Orthopaedics Sygehus Lillebælt, Vejle

Background: Our unit consist of surgeons with different levels of experience as dedicated knee replacement surgeons. The 3 super seniors have more than 20 years of experience and the younger surgeons has less than 5 years’ experience. This study describes the forgotten joint score (FJS) and revision for the medial oxford unicompartmentel knee replacement for patients treated by the super seniors and the less experienced younger sugerons. All surgeons had participated in an education program provided by the manufacturer (Zimmer)
Aim: To determine if FJS is dependent on experience for the medial Oxford knee.
Materials and Methods: Retrospective cohort study from our institution with all patients treated with a medial uni in 2018-2020. Preoperative, 1 year oxford knee score and 1 year FJS was measured and compared between the two groups. Revisions for any cause within the first postoperative year was compared between the two groups.
Results: Usage, measured as percentage of medial oxford primary knee replacements, was similar between the groups (Seniors 31%; Young 30%). No difference was observed regarding ASA score, BMI and age as no difference was observed in preoperative oxford knee score between the groups. Surgical duration was significantly faster for the seniors (40 min vs. 51 mins; t-test; P = 0.0003). Median FJS after 1 year was significantly higher for Young consultants (79 points vs. 69 points, P = 0.0001; Mann Whitney test). Revision for any reason was similar between the groups. No difference in FJS was observed for total knee replacements when comparing outcome for Super Seniors versus Young Consultants (60 points vs. 63 points, P = 0.3, Mann Whitney test).
Interpretation / Conclusion: Since the patients operated in both groups appears to be similar, it is doubtful that the faster operation time by the seniors results in poorer outcome, since the risk of revision is also equal in the two groups. Yet, surgical technique could account for part of the difference, but more likely patient approach and shared decision making could be the main factor in understanding the better outcome for patients operated by a young specialist.

181. Failure of meniscal suture and predictive factors
Christopher Holst Hansen¹, Bjørn Borsøe Christensen¹, Anders El-Galaly²
Department of Orthopaedics, Horsens Regional Hospital¹; Department of Orthopaedics, Aarhus University Hospital²

Background: This study was made as a pilot project to identify potential predictors for failure of meniscal suture.
Aim: The aim of the study was to see if predictors such as body mass index (BMI), smoking status at time of operation, sex and age had any correlations to failure of meniscal repair by suture.
Materials and Methods: This study is a single center retrospective study. Patients, who had undergone operation with arthroscopic meniscal repair at the department of orthopedic surgery at Horsens Hospital were identified through data on operations during a periode from 2014 to 2022. Each individual surgical protocol was reviewed and the data was collected. The study endpoint was failure of meniscal repair defined as a need for reoperation with meniscal resection. The data was analyzed by cox regression and a Kaplan-Meier analysis was made to estimate meniscal repair survival.
Results: This study is a single center retrospective study. Patients, who had undergone operation with arthroscopic meniscal repair at the department of orthopedic surgery at Horsens Hospital were identified through data on operations during a periode from 2014 to 2022. Each individual surgical protocol was reviewed and the data was collected. The study endpoint was failure of meniscal repair defined as a need for reoperation with meniscal resection. The data was analyzed by cox regression and a Kaplan-Meier analysis was made to estimate meniscal repair survival.
Interpretation / Conclusion: This study showed a 5 year failure rate of 32,2% for arthroscopic meniscal repair. This study showed no significant correlation between age, sex, BMI or smoking status on failure of meniscal repair.

Poster Walk 5: Upper extremity
Chair: Eske Brand / Jens-Christian Vedel

152. The prevalence of concurrent musculoskeletal complaints in elbows, shoulders, and neck in patients after an isolated hand and forearm complaint.
Lukasz Maciej Winiarski¹ , Jane Dorthea Livoni¹ , Poul Verner Madsen² , Michael Skovdal Rathleff¹ ³ , Peter Larsen¹ ²
Physiotherapy and Occupational Therapy Department, Aalborg University Hospital, Aalborg, Denmark¹;Department of Orthopaedic Surgery, Aalborg University Hospital, Aalborg, Denmark²;Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Aalborg, Denmark³.

Background: Isolated hand and forearm complaints are common in the emergency and orthopedic departments. So far, little is known about whether these patients suffer from concurrent musculoskeletal complaints (MSCs) besides their hand and forearm complaints. Neglecting concurrent MSCs in the upper limbs and neck could hamper rehabilitation and prolong the time taken to return to daily activities.
Aim: The aim of this study was to investigate the prevalence of self-reported concurrent MSCs in the elbow, shoulder, and neck in patients with common hand and/or forearm complaints.
Materials and Methods: This cross-sectional study included 600 patients with any type of diagnoses referred to hand therapy in relation to a hand and/or forearm complaint. Eligibility was determined based on clinical interviews and self-report questionnaires. Patient characteristics, diagnoses, and location of symptoms were registered and analyzed.
Results: The patient group consisted of women (68%, mean age 53 (18 SD)) and men (32%, mean age 48 (16 SD)). The largest diagnostic groups were distal radius and ulna fractures (25%), ligament lesions and ruptures in fingers (16%), and finger fractures (14%). The overall prevalence of concurrent MSCs was 40% (95% CI: 36%-44%). The most common location of concurrent MSCs was the shoulder, 62% (95% CI: 56%-68%), followed by the elbow, 49% (95% CI:43%-55%), and the neck 32% (95% CI: 26%-38%). Thirty- eight percent (95% CI: 32%-44%) of all patients reported concurrent MSCs in two or three regions of the upper limb or neck. Twenty-eight percent (95% CI: 24%-31%) of the whole sample developed concurrent MSCs after the hand and forearm complaint.
Interpretation / Conclusion: The present results suggest, that MSCs from the elbows, shoulders, or neck are very common in patients with hand and/or forearm complaints. Clinicians managing patients with isolated hand and forearm complaints should be aware of the high prevalence of concurrent MSCs. Future research should investigate if specific management strategy, addressing concurrent MSCs, may improve the outcome in this population.

153. Intratendinous ganglion and synovial cysts in the extensor digitorum communis tendon: A case report
Trine Brønden Kongensgaard, Niels Henrik Søe
Department of Hand Surgery, Herlev/Gentofte University Hospital of Copenhagen, Hellerup, Denmark.

Background: Introduction: Intratendinous ganglion cyst is a rare condition and only a few cases are described in literature.
Aim: We present, to our knowledge, the first case report of both intratendinous ganglion and synovial cyst in the extensor digitorum tendon to the 3th finger.
Materials and Methods:
Results: Case report: A 71-year old woman presented with left-sided localized swelling on the dorsal site of the hand and a hard nodule in relation to EDC 3-tendon. Ultrasound and MRI scans describe tenosynovitis in the 4th extensor compartment with two intratendinous cysts in EDC 3. Open surgical synovectomy and excision of four cysts in total, one cyst proximal to RC joint and three distal at the level of os capitatum; one large and two minor. The cysts resulted in longitudinal tendon split without the need of repair. Histological analysis showed that that two types of cysts were present; ganglion cyst and synovial cyst. Post-operative recovery proceeded according to plan.
Interpretation / Conclusion: Intratendinous ganglion cysts are a rare condition, and most frequently described in the extensor tendon. As in other cases the patient present with tenosynovitis as localized swelling. The previously described cases find only ganglion cysts, and this case is to our knowledge the first report of two types of cysts in the same tendon; ganglion and synovial. The pathogenesis of intratendinous cysts are still unknown and different theories have been suggested, accordingly further investigation into the origin of intratendinous cysts are required.

154. Management of everyday life after a hand operation – a qualitative study of patients with a weak sense of coherence
Alice Ørts Hansen¹ ² ³ , Kamilla Kielsgaard³, Stina Meyer Larsen² ³ 4
Department of Orthopaedic Surgery and Traumatology, Odense University Hospital and Svendborg Hospital, Odense, Denmark¹ Department of Clinical Research, University of Southern Denmark, Odense, Denmark² Competence Centre for Rehabilitation, REPHA, Danish Centre for Rehabilitation and Palliative Care, Odense University Hospital, Odense, Denmark³ Health Sciences Research Center, UCL University College, Odense Denmark4

Background: Psychosocial factors, such as sense of coherence (SOC) are thought to influence rehabilitation outcomes in hand therapy, including functioning. A greater impact on participation in everyday life occupations has also been found for patients with a weak SOC compared to those with a strong SOC.
Aim: To explore how patients with hand-related disorders and a weak SOC experience and manage everyday life after an operation.
Materials and Methods: In-depth interviews were conducted with five women and three men between the ages of 48 and 65 operated for a hand-related disorder who had a weak SOC (SOC-13 score < 52). Participants were enrolled from a large cohort study. All eligible patients operated from December 2020 - March 2021 were invited. Participants were interviewed once between six and 13 weeks after operation. Data were analysed based on a hermeneutic approach.
Results: The preliminary analyses resulted in two themes, the first of which was Feeling sort of impaired with the subthemes lots of small streams make a big river and challenges in everyday living. Besides the hand-related disorder, participants had several other circumstances that challenged their everyday life. Some participants did not mention ‘loss of roles’; they had already adapted and simplified life because of life circumstances beyond the hand disorder. The participants mentioned several strategies that they used to manage everyday life, such as: adapt the environment, ask for help, postpone activities, spread activities throughout the day and compensatory solutions. The second theme was Uncertainty and confident, with the subthemes expectations and information. The participants felt uncertain and insecure about the future and whether they are doing things right, e.g., their rehabilitation. This was set in contrast to the feeling of confident and security in getting adequate information about what to do and what to expect after the operation and for the future.
Interpretation / Conclusion: The conclusion and the final results will be presented at DOS 2022.

192. Complications after volar locking plate fixation of distal radius fractures: a retrospective study in 822 patients
Søren Perregaard, Rasmus Wejnold Jørgensen, Marcus Landgren
Department of Orthopedic surgery, Hand Surgery Unit, Herlev and Gentofte, Gentofte, Denmark

Background: With the current routine use of volar locking plates as the preferred surgical treatment method of distal radial fracture the purpose of this work was to investigate the complication rate following surgery.
Aim: The aim was to investigate the incidence of complications following surgery using a volar locking plate for a distal radial fracture.
Materials and Methods: A retrospective review of the medical records of all patients treated with open reduction and internal fixation with volar locking plate (VLP) for a distal radial fracture. Nine-hundred and nine distal radial fractures, in 902 surgically treated patients were identified between year 2017 and 2019 at Herlev and Gentofte Hospital. Eighty- seven patients were excluded mainly due to incorrect coding and surgically treated with other methods than a VLP. Hence, 822 patients were deemed eligible for inclusion and postoperative complications attributable to the surgical treatment were recorded with a mean follow-up time of 2.8 years
Results: The mean age of the study population was 63 years (18 to 94) and 81% were female. We identified an overall postoperative complication incidence was 14.2% (116 in 822 patients). With 8.2% (67/822) major complications and 6.0% (49/822) defined as minor complications. The most frequently observed complications was pain and reduced range of motion leading to hardware removal (n = 23, 2.8%), skin adherence not requiring surgical revision (n = 18, 2.2%), and carpal tunnel syndrome (n = 16, 1.9%), 13 underwent carpal tunnel release. Secondary surgery was performed in 9.9% (81 procedures in 87 patients), including preoperatively planned removal of hardware.
Interpretation / Conclusion: The incidence of complications following open reduction and internal fixation of distal radial fractures was low, however patients are at risk of developing both major and minor complications postoperatively. Despite being a safe and efficient treatment for distal radius fractures where surgery is deemed necessary, there is a need for a better understanding of subpopulations at risk of experiencing complications following surgery.

205. Exploring patient experiences after treatment of humeral shaft fractures: A qualitative study
Dennis Karimi¹, Line Houkjær², Anders Skive³, Camilla Holmenlund³, Stig Brorson², Bjarke Viberg¹, Charlotte Abrahamsen4
Department of Orthopaedics, Kolding Hospital¹; Department of Orthopaedics, Zealand University Hospital²; Department of Orthopaedics, Hvidovre University Hospital³; Department of Regional Health Research, University of Southern Denmark4

Background: Humeral shaft fracture treatment can induce serious morbidities, and fractures are notoriously difficult to handle in the emergency department as well as in the outpatient clinic. It is unclear how patients experience their treatment course and how different morbidities impact patients.
Aim: To gain in-depth knowledge, we explored how patients experience humeral shaft fractures and the subsequent treatment course.
Materials and Methods: A qualitative study was performed using semi- structured individual interviews. A purposive sampling approach was conducted to recruit patients with traumatic isolated humeral shaft fractures; the patients’ ages, genders, primary treatments, and complications varied. Data saturation was met after the data of 12 patients were analyzed using Malterud Systematic Text Condensation.
Results: Eight women and four men with a median age of 48.5 years (range: 22–83 years) were interviewed. The median time from injury to interview was 12.5 months (range: 8–18 months). Ten out of twelve patients were treated non-surgically; of those ten, four patients experienced major complications from the primary treatment. During the analysis, five overarching themes were identified: expectations, physical changes, support and independence, psychological impact, and the specific treatment and recovery. Within these themes patients experienced feeling trivialized by personnel, lacked quality information, and were severely impaired in their mobility and independence.
Interpretation / Conclusion: First, patients with humeral shaft fractures expressed frustration with treatment in the emergency department. Second, gross fracture movement and pain were central symptoms that led to the loss of basic capabilities. Third, patient preferences were included in the treatment decision-making process and could change throughout the treatment course. Fourth, patients required massive support to perform basic activities of daily living.

180. Accuracy and reliability of a new non-invasive model for dynamic measurements of glenohumeral translation
Catarina Malmberg¹, Stefan E Jensen¹, Benjamin Michaud², Per Hölmich¹, Kristoffer W Barfod¹, Jesper Bencke¹ ³
Sports Orthopedic Research Center – Copenhagen (SORC-C), Department of Orthopedic Surgery, Copenhagen University Hospital Amager & Hvidovre, Denmark¹; Laboratoire de simulation et modélisation du mouvement (S2M), École de kinésiologie et des sciences de l’activité physique, Université de Montréal, Québec²; Human Movement Analysis Laboratory, Department of Orthopedic Surgery, Copenhagen University Hospital Amager & Hvidovre, Denmark³

Background: Shoulder conditions are often directly connected to glenohumeral joint pathology and can lead to abnormal joint kinematics, described as glenohumeral translation. A skin marker-based motion capture model for measurements of glenohumeral translation was recently developed.
Aim: To investigate the concurrent validity and the interrater reliability of a new model for analysis of glenohumeral translation.
Materials and Methods: Twelve infrared cameras were used to track reflections from moving skin markers in the motion capture model. A strict protocol for placement of the skin markers was followed. Shoulder range of motion (ROM) and activities of daily living (ADL) were tested. To investigate the validity, the skin marker-based model was compared to gold standard through simultaneous data collection from markers fitted to intracortical pins in the humerus and the scapula of healthy volunteers. Reliability was tested by comparing two investigators performing the skin marker-based protocol in a different group of healthy volunteers. The mean Root Mean Square Error (RMSE) was calculated for each tested motion to determine the validity. The interrater reliability was determined as Intraclass Correlation (ICC2,1) for each tested motion.
Results: Four subjects were included in the validity test: F/M=2/2, mean age 35 (range 31-38), mean BMI 23.2 (SD2.70). The RMSE for anterior-posterior translation ranged 5.8-8.1 mm during ROM and 5.5- 8.0 mm during ADL. For superior-inferior translation, the RMSE ranged 3.3-6.8 mm during ROM and 3.4- 4.8 mm during ADL. In the reliability experiment, 20 subjects were included: F/M=8/12, mean age 31 (range 23-37), mean BMI 22.9 (SD1.74). The ICC for anterior-posterior translation ranged 0.13-0.51 during ROM, 0.25-0.63 during ADL. Correspondingly, the ICC for superior-inferior translation ranged 0.08-0.50 and 0.05-0.55.
Interpretation / Conclusion: The inaccuracy of the skin marker-based model exceeded physiological values of glenohumeral translation for all tested movements. The reliability of the model was task dependent, but the limited study sample complicates interpretation of data. The skin marker-based model cannot be recommended for measurements of glenohumeral translation.

175. Stemmed hemiarthroplasty with a suture collar and a common platform system for acute proximal humeral fractures
Jeppe Vejlgaard Rasmussen¹, Alexander Amundsen¹, Marc Randall Nyring¹, John Kloth Petersen², Zaid Issa², Bo Sanderhoff Olsen¹
Department of Orthopedic Surgery, Herlev-Gentofte Hospital¹; Department of Orthopedic Surgery, Zealand University Hospital, Køge²

Background: Hemiarthroplasty for acute proximal humeral fractures gives disappointing results, often due to rotator cuff insufficiency. Better tuberosity fixation might improve results.
Aim: Therefore, the aim of this study was to: 1) report the outcome of a stemmed hemiarthroplasty with a common platform system and a modular suture collar; 2) to compare the outcome with that of a standard stemmed hemiarthroplasty; 3) to report the feasibility of revision arthroplasty with retention of the stem and; 4) to evaluate the association between tuberosity healing and functional outcome.
Materials and Methods: Forty-four fractures that were deemed not suitable for non-surgical treatment or open-reduction and internal fixation were treated with the Global Unite fracture system between January 2017 and July 2019. The functional and radiographic results at 2 years were compared with the results of 44 Global Fx arthroplasties. The results of patients who had adequate healing of the greater tuberosity were compared with the results of patients who had severe malunion or non-union (resorption).
Results: Mean Oxford Shoulder Score (OSS), Constant- Murley Score (CMS) and Western Ontario Osteoarthritis of the Shoulder index (WOOS) was 33 (range 10 to 48), 40 (range 10 to 98), and 68 (range 18 to 98) at 2 years. There were no differences in functional outcome scores or in the risk of inadequate healing of the greater tuberosity between the Global Unite and the Global Fx systems. Five (11%) patients underwent revision surgery with retention of the stem. Inadequate tuberosity healing was associated with an inferior CMS (mean difference: 6; 95% CI: 1 to 10, P=0.01) and an inferior OSS (mean difference: 9; 95% CI: 1 to 16, P=0.03).
Interpretation / Conclusion: The use of stemmed hemiarthroplasty with a suture collar did not improve healing of the greater tuberosity nor the functional outcome. Five arthroplasties were revised with retention of the stem and the common platform system could be arguments for using the Global Unite system when a stemmed hemiarthroplasty is used for acute proximal humeral fractures.

Poster Walk 6: Paediatrics
Chair: Martin Gottliebsen / Peter Buxbom

171. Construct validity of a novel simulator for pinning of supracondylar humeral fractures
Jan Duedal Rölfing¹ ², Steven Long ³, Ahmed Abood ², Emily Connor ³, Emily Wagstrom 4, Geb Thomas 5, Donald Anderson ³, Heather Kowalski ³
¹ Corporate HR, MidtSim, Central Denmark Region ² Dept. of Orthopaedics, Aarhus University Hospital, ³ Dept. of Orthopedics and Rehabilitation, University of Iowa, USA 4 Dept. of Orthopedics, University of Minnesota, Minneapolis, USA 5 Department of Industrial and Systems Engineering, University of Iowa, USA

Background: Dislocated supracondylar humerus fractures (SCH) in children are often treated by diverging Kirschner wires across the fracture to provide stable fixation. Building on a validated simulator for hip fractures, we developed an augmented reality simulator to train orthopedic residents in pinning SCH.
Aim: The aim of this study was to assess the construct validity of the SCH simulator that means its ability to distinguish surgical expertise.
Materials and Methods: 43 surgeons from the University of Iowa, University of Minnesota, and University of Aarhus, Denmark were included. 21 novices (first- or second-year residents), 11 intermediate surgeons (third- or fourth-year residents), and 11 advanced surgeons (fifth-year residents or faculty) participated. Surgical performance was graded on wire divergence, use of fluoroscopy, and overall time. Differentiating features of the simulator include: (1) camera-based tracking of a wire replaces fluoroscopic radiation exposure and (2) a plastic Sawbone replicates the feel of drilling through actual bone. After a warm-up exercise, participants were exposed to a reduced SCH and asked to place 3 diverging lateral wires based on haptic and radiological feedback by the simulator.
Results: Advanced and intermediate surgeons achieved significantly greater pin spread than the novice group (advanced 49%, intermediate 40%, novice 29%). The advanced group used significantly less fluoroscopy than the intermediate and novice groups (advanced 27+/-6 images, intermediate 41+/-17, and novice 52+/-18). The advanced participants required significantly less time to place the 3- wire construct (advanced 321+/-74 seconds, intermediate 448+/-137, novice 592+/-196). All results were statistically significant, p<0.05.
Interpretation / Conclusion: Treating SCH is a critical skill that orthopedic surgeons must acquire. This study shows that the novel simulator can clearly distinguish between the 3 groups: novice, intermediate, and advanced performance. Future studies will investigate how simulator training can improve the surgical skill of novice and intermediate residents.

172. Evaluating Inter-rater reliability of the Modified Gordon Score for pin site infection
Marie Fridberg, Arash Ghaffari, Hans-Christen Husum, Ole Rahbek, Søren Kold
Interdisciplinary Orthopaedics, Aalborg University Hospital, Denmark

Background: There is no consensus on how to evaluate and grade pin site infections, the most common complication in external fixation. Pin site infection is diagnosed from clinical symptoms (erythema, swelling, pain, drainage, pus). A precise, objective and reliable pin site infectious score is warranted to improve post-surgical care
Aim: The aim was to test the reliability of the Modified Gordon Infection Score (MGS). The observed agreement and inter-rater reliability were investigated between nurse and doctors
Materials and Methods: MGS: 0=clean 1=Serous drainage, no erythema 2=Erythema, no drainage 3=Erythema and serous drainage 4=Erythema and purulent drainage 5=Erythema, purulent drainage, radiographic osteolysis 6=Ring sequestrum or osteomyelitis. To differentiate between grade 4 and 5 radiographs are needed to identify osteomyelitis. MGS score was performed in the outpatient clinic at Aalborg University Hospital, Denmark on 1472 pin sites in 119 patients by one nurse and one of three orthopaedic surgeons blinded to each other’s judgement. The data was stored in a Red Cap Database for further statistical analysis. The observed agreement between the nurse and the 3 orthopaedic surgeons was evaluated with a one-way random-effect model with interclass correlation with absolute agreement. Furthermore the observed agreement for each of the 3 surgeons with the nurse was calculated
Results: The distribution of MGS infection grade in the 1472 pin sites was: Grade 0; n=1372, Grade 1; n=32, Grade 2; n=39, Grade 3; n=24, Grade 4; n=5, Grade 5; n=0, Grade 6; n=0. The observed agreement between the nurse and the surgeons was calculated as 98%. The ICC estimated between nurse and the surgeons was 0,8943 (ICC >0,85 = reliable). The grading was done by three different doctors with an agreement with the nurse as follows. Rater1 (n=239) =99,5 % , Rater2 (n=649) =97,4%, Rater3 (n=384) =96,6%
Interpretation / Conclusion: A limitation to this study is that the dataset represents mostly clean pin sites MGS 0. Only 100 pin sites had signs of superficial infection MGS 1-4 and no sites with deep infection were observed. We found that the MGS infection score is highly reliable for low grade infections, but we cannot conclude on reliability in severe infections

173. Therapist-led interventions to prevent hip dislocation and uncorrectable scoliosis among children with cerebral palsy
Lærke Hartvig Krarup¹, Pia Kjær Kristensen¹ ², Martin Bækgaard¹ ² Stisen, Kirsten Nordbye-Nielsen¹ ² ³, Inger Mechlenburg¹ ²
Department of Orthopaedic Surgery, Aarhus University Hospital, Aarhus, Denmark¹; Department of Clinical Medicine, Aarhus University, Aarhus, Denmark²; CPNorth: Living Life With Cerebral Palsy in the Nordic Countries, Aarhus, Denmark³.

Background: Prevention of hip displacement and scoliosis is a key concern among children with cerebral palsy. Therapist-led interventions may prevent aggravation of the diseases and reduce or postpone the need for surgery.
Aim: The aim of this study was to determine the prevalence of hip displacement and correctable scoliosis and the incidence of hip dislocation and uncorrectable scoliosis among children with cerebral palsy. Moreover, to describe the variation in type and frequency of therapist-led interventions in the time period from identification of hip displacement or correctable scoliosis until the following physiotherapeutic assessment.
Materials and Methods: This population-based descriptive cohort study was based on data from the Danish Cerebral Palsy Follow-up Program. We included all children registered with radiographic and physiotherapeutic assessment. We estimated the prevalence of children with hip displacement and correctable scoliosis and the incidence of hip dislocation and uncorrectable scoliosis in the time period 2010-2020. Type, frequency, intensity and aim of therapist-led interventions were descriptively compared across the cohorts.
Results: The prevalence of hip displacement was 22% (95% CI: 0.19-0.23) and the prevalence of correctable scoliosis was 26% (95% CI: 0.24-0.28). The incidence of hip dislocation was 1% (95% CI: 0.00-0.02) and the incidence of uncorrectable scoliosis was 5% (95% CI: 0.03-0.06). The proportion of children who received intensive treatment was higher among children with hip displacement than children with correctable scoliosis. In both cohorts the primary aim of the therapist-led interventions was to increase joint range of motion. The use of a standing aid among children with hip displacement was frequent, whereas the use of a spinal brace among children with correctable scoliosis was rare.
Interpretation / Conclusion: Hip displacement and correctable scoliosis are highly prevalent in children with CP, whereas the incidence of hip dislocations and uncorrectable scoliosis is low. For both cohorts a smaller proportion than to be expected received intensive treatment. The proportion of children with correctable scoliosis who used of a spinal brace was surprisingly low.

174. Congenital pseudarthrosis of the tibia. Early experiences with the Paley protocol
Søren Kold, Ole Rahbek
Department of Orthopaedics, Aalborg University Hospital

Background: Limb preserving surgery for congenital pseudarthrosis of the tibia has historically carried very high rates of non-union and refracture. A new treatment algorithm by Paley has in a case-series of 17 patients with an average follow-up of 3.7 years resulted in a calculated probability of 100% to achieve union without refracture using external fixators. The method has recently been improved to allow for treatment without external fixator. However, results from this surgery performed outside the Paley Institute are currently not available.
Aim: This study reports preliminary results with the Paley algorithm for CPT.
Materials and Methods: 2 patients with Crawford type IV congenital pseudarthrosis of the tibia. The age at time of surgery was 21 and 30 months. Both patients received preoperative injections of zoledronic acid to protect the autogenous bone graft from resorption after implantation. The surgery included: 1) resection of hamartoma and resection of tibial and fibular bone to vital bone; 2) angular correction of the deformities; 3) recanalization of tibial medullary canal and stabilization with Fascier-Duval telescopic nail combined with locking plate stabilization of the tibia; 4) autogeneous cancellous bone graft and periosteal grafting from the pelvis in combination with recombinant bone morphogenetic protein; 5) intramedullary fixation of the fibula. The patients were kept in a long leg cast for 2 weeks after surgery and hereafter in a low leg cast until union. After union an orthosis is applied for out-door activities.
Results: Patients became fully weightbearing and ambulatory shortly after conversion to a low leg cast 2 weeks postoperatively. Both patients have succesful cross-sectional union between the tibia and fibula. The telescopic nails function in both patients. No refracture has occurred with a follow-up of 5 and 26 months after primary surgery.
Interpretation / Conclusion: Preliminary results of the Paley protocol for CPT in a Danish setting achieved 100% union without use of external fixators. The low age at surgery allows for surgical treatment prior to proximal migration of the distal fibula. Long-term follow up is warranted.

Poster Walk 7: Trauma
Chair: Joakim Jensen / Frederik Borup Danielsson

182. Higher Rate Of Nonunion In Bicondylar Tibial Plateau Fractures With A Tibial Tubercle Fragment
Derek Stenquist, Tyler Caton, Eric Chen , Selzer Faith, Marilyn Heng, Michael Weaver, Arvind von Keudell
a Harvard Medical School Orthopedic Trauma Initiative, Boston, MA b Harvard Combined Orthopaedic Residency Program, Boston, MA c Brigham and Women’s Hospital, Department of Orthopaedic Surgery, Boston, MA dDepartment of Orthopaedic Surgery, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark

Background: A separate tibial tubercle fragment (TF) is found in up to half of all bicondylar tibial plateau (BTP) fractures. Techniques to address the TF include lag screws, plate fixation, or cerclage wiring. Adequate healing of the TF is required to reconstitute the extensor mechanism of the knee.
Aim: The purpose of this study was to compare functional outcomes and complications after ORIF (Open reduction and internal fixation) of BTP fractures with and without a TF.
Materials and Methods: This is a retrospective cohort study of adult patients undergoing ORIF of an AO/OTA 41- C or Schatzker V/VI BTP fracture at two Level 1 trauma centers. Radiographs and computerized tomography (CT) scans were reviewed to determine the presence of a separate tubercle fragment (TF) and mode of fixation if addressed. Primary outcomes were the Patient-Reported Outcomes Measurement Information System Physical Function (PROMIS PF) score and EUROQUOL-(EQ)-5D-3L. Secondary outcomes included rates of infection, reoperation, and nonunion.
Results: This analysis was comprised of 189 patients (mean follow-up 8.1 years, range 1.1-16.5) and TF was identified in 55 patients (29%). Compared to NTF patients, those in the TF group had more open fractures (16% vs 5%, p=0.02) and more 41C3 fractures (65% vs 44%, p=0.01) but there was no significant difference in the rates of deep infection (15% vs 8%, p=0.19) or reoperation (23% vs 13%, p=0.09) between the two groups. There was no difference in PROMIS PF (48.1 vs 47.5, p=0.45) or EQ-5D scores (0.82 vs 0.83, p=0.32) between the TF and NTF groups. Furthermore, there was no difference in functional outcome according to management of the TF. There was a higher rate of nonunion in the TF cohort compared to the NTF cohort (11% vs 2%, p=0.02) but no difference in nonunion rate according to mode of TF management (no repair 0% vs screws 6% vs cerclage 15%, p=0.85).
Interpretation / Conclusion: In this retrospective cohort study of patients with bicondylar tibial plateau fractures, patients with a TF experienced more severe injuries but no difference in functional outcomes were detected compared patients without a TF.

186. Risk Assessment of Accidents Involving Stand-up Electric Scooter Riders in Odense, Southern Denmark, in the Period of July 2019 to December 2021
Eva Lindhardt Hansen, Jens Lauritsen, Martin Lindberg-Larsen, Niels Dieter Röck
The Research Unit of Orthopaedic Surgery, Department of Orthopaedic Surgery, Odense University Hospital; Accident Analysis Group, Department of Orthopaedic Surgery, Odense University Hospital; Department of Clinical Research, University of Southern Denmark.

Background: Electric scooters (e-scooters), a new form of personal transport device, was introduced in rental programmes in Odense, Denmark, in 2019. E-scooter riders are vulnerable road users, who can legally travel at 20 km/h with little noise and, prior to 2022, no required safety gear. The risk of sustaining a trauma riding an e-scooter has been shown to be 8-10 times the risk of riding a bicycle. The safety of e- scooters in an urban setting must be examined to assess risk of accidents and the severity of injuries. Both to inform the e- scooter riders, the legislators and the health personnel that care for the injured.
Aim: We aim to assess the number, characteristics and severity of accidents involving riders of e- scooters in Odense from their introduction July 2019 to December 2021.
Materials and Methods: All contacts to the emergency department of Odense University Hospital are routinely registered. We used this registry to identify all injuries involving e-scooters from July 1st 2019 to December 31st 2021. Resulting in 350 total contacts, 320 involving riders of e-scooters. The time of accident, sex, age and acquired injuries were anonymously extracted and processed with EpiData.
Results: Men comprised 2/3 of injured riders. The average age of patients was 25 years old. 55 % of accidents happened from Friday to Sunday. Saturday night accounted for 11 % of total accidents. The most common injuries were to the upper extremities (47 %), seconded by head and neck (33 %). 13 % wore a helmet at the time of the accident. The injuries were of major severity in 15 % of the cases and out-patient treatment was most common (96 %). There were no fatalities in the period.
Interpretation / Conclusion: From July 2019 to December 2021 there were total 320 accidents involving riders of e- scooters. The number increased every year. Most accidents involved men, occurred in the summer, during the weekend and at night. Upper extremities, head and neck were the most common injuries sites. Less than 1 in 7 riders wore a helmet with no significant increase from 2019 to 2021. Most injuries were of minor severity and there were no fatalities. Helmet-requirement was introduced by January 2022, follow-up is needed to see the effects of this new legislation.

187. Management of Aseptic Failure after ORIF of Complete Articular Tibial Plateau Fractures
Andrew Hresko, Mihir Dekhne, Phil Grisdela, Sravya Challa, Theodor Guild, Derek Stenquist, Arvind von Keudell a,b,c
aHarvard Orthopaedic Trauma Initiative, Harvard Medical School, Boston, Massachusetts, USA bDepartment of Orthopaedic Surgery, Brigham and Women's Hospital, Boston, Massachusetts, USA cDepartment of Orthopaedic Surgery, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark

Background: Bicondylar tibial plateau (BTP) fractures are complex injuries associated with high complication rates following fixation. While infection has received the greatest focus in existing literature, aseptic failures after ORIF such as loss of reduction, nonunion, and symptomatic malunion have also been reported and necessitate reoperation with potential morbidity.
Aim: The primary aim of this study was to review the clinical course associated with aseptic failure following open reduction internal fixation (ORIF) for BTP fracture.
Materials and Methods: This is a retrospective case series of adult patients who underwent fixation of AO/OTA 41-C (Schatzker 6) BTP fractures at two Level 1 trauma centers between 2001-2018 and developed aseptic failure (nonunion, symptomatic malunion, loss of reduction, or hardware failure) requiring reoperation. Patients with deep surgical site infection were excluded. Demographic, injury, fracture, and initial fixation characteristics were collected. Clinical course following diagnosis of the index complication was reviewed. Revision operation surgical details, timing, and outcomes were recorded.
Results: 508 AO/OTA 41C fractures were identified, with 26 experiencing aseptic failure of fixation (5%): 15 nonunion, 6 symptomatic malunion, 3 loss of reduction, 1 hardware failure, and 1 fracture fragment osteonecrosis. Mean age 52.7 years (standard error [SE] 2.4), 50% female, mean follow-up 4.0 years (SE 0.8). Regarding initial injury, 3 (11.5%) were open fractures, 6 (23.1%) were staged with external fixation, and 4 (15.4%) required flap coverage. After diagnosis of the index complication, 15 (57.7%) underwent revision ORIF.
Interpretation / Conclusion: BTP fractures are complex injuries that require prolonged monitoring of bony healing. Aseptic failure encompasses a range of complications and is relatively rare but can lead to a protracted treatment course requiring multiple operations. Revision ORIF for septic nonunion presents particular challenges and was successful in only half of cases in this series. A high percentage of non-united fractures required eventual TKA.

189. Gait recovery is not associated to soft tissue injury in patients with lateral tibial plateau fractures
Petrer Larsen1,2, Rasmus Elsoe2
1 Department of Occupational Therapy and Physiotherapy, Aalborg University Hospital, Denmark. 2 Department of Orthopaedic Surgery, Aalborg University Hospital, Denmark.

Background: Although soft tissue injuries following lateral tibial plateau fractures are common, little is known regarding functional recovery and postoperative development in specific gait patterns.
Aim: The aim of the present study was to report 12-month gait recovery in patients with lateral tibial plateau fractures divided into groups with and without conservatively managed MRI-verified soft tissue injuries.
Materials and Methods: The study design was a prospective cohort study. Included were patients treated following a lateral tibial plateau fracture (AO-41B) between December 2013 and November 2016. The primary outcome score was gait patterns.
Results: Fifty-six patients were included. The mean age of the patients at the time of fracture was 56 years (range 22-86). Thirty-three patients (59 %) were female. Twenty-eight patients (50 %) presented with preoperative soft tissue injuries. Basic characteristics of the gait show a mean gait speed of 125.7 (SD31.3) cm/sec. for patients with soft tissue injuries and 125.2 (SD31.1) cm/sec. for patients without soft tissue injuries (P=0.96). Patients with and without soft tissue injuries show no significant difference in % asymmetry of gait function, although gait asymmetry was common in both groups.
Interpretation / Conclusion: Twelve months of gait recovery following lateral tibial plateau fractures were not associated with MRI-verified soft tissue injuries. More research is needed to investigate the effects of treatment strategies and rehabilitation.

Peter Larsen 1,2, Oscar Plazer3, Lærke Lollergaard3, Samuel Pedersen3, Peter Nielsen3, Michael Rathleff1,3, Thomas Bandholm4, Stefan Jensen2, Rasmus Elsoe2
1 Department of Occupational Therapy and Physiotherapy, Aalborg University Hospital, Aalborg Denmark. 2 Department of Orthopaedic Surgery, Aalborg University Hospital, Aalborg Denmark. 3 Department of Health Science and Technology, Aalborg University, Aalborg, Denmark. 4 Physical Medicine & Rehabilitation Research – Copenhagen (PMR-C), Department of Physio- and Occupational Therapy, Department of Orthopaedic Surgery, Department of Clinical Research, Copenhagen University Hospital, Amager and Hvidovre, Copenhagen, Denmark.

Background: Blood flow restricted exercise (BFRE) is characterized by muscle strength training with low external weight loads (20-30% of one-repetition maximum (1RM)) combined with a pneumatic cuff inflation that partly reduces arterial blood flow and limits venous return, thus, elevating metabolic stimulus in the working muscles. Due to the low external weight needed, BFRE seems useful in the rehabilitation of patients with ankle fractures, and may reduce the negative effects of immobilization.
Aim: The objective was to investigate the feasibility of blood flow restricted exercise (BFRE) as a rehabilitation modality in patients with a unilateral ankle fracture.
Materials and Methods: Feasibility study with a prospective cohort design. Inclusion criteria were above 18 years of age and unilateral ankle fractures. Exclusion criteria: history of cardiac or embolic diseases, cancer, diabetes, hypertension and family history of cardio or vascular diseases. The predefined feasibility outcome was based on three criteria regarding patients experience with participating in the BFRE protocol and the absence of any serious adverse events.
Results: Eight patients were included. Median age was 33 years (range: 23-60). All eight patients reported maximum satisfaction on the two questions regarding patient’s perception of the overall experience with BFRE training and the feasibility to introduce BFRE as an intervention.
Interpretation / Conclusion: Early use of BFRE in patients with unilateral ankle fractures seems feasible in patients without comorbidity.

193. Complications and Soft Tissue Coverage After Complete Articular, Open Tibial Plateau Fractures
Phillip Grisdela, Jeffrey Olson, Theodore Guild, Mihir Dekhne, Andrew Hresko, Upender Singh, Michael Weaver, Arvind Von Keudell, Derek Stenquist
Harvard Combined Orthopaedic Residency Program 1,2,3,5,9; Harvard Medical School 4; Rigshospitalet, Department of Orthopaedic Surgery, Copenhagen University 6; Brigham and Women's Hospital 7,8

Background: Bicondylar tibial plateau (BTP) fractures are associated with high-energy mechanisms and open fractures are reported in 11-16%. The optimal timing of definitive fixation and soft tissue coverage is still debated.
Aim: The primary aim was to evaluate the incidence of complications following these injuries. The secondary aim was to study the effect of timing of fixation and timing of flap coverage on deep infection rates following open reduction internal fixation (ORIF).
Materials and Methods: This is a retrospective case series of adult patients who had ORIF of Schatzker 6 open, BTP fractures at two Level 1 trauma centers between 2001-2018. Demographic, injury, and fracture data were collected. Surgical details including number of debridements, timing of definitive ORIF and soft tissue coverage relative to injury were recorded. Primary outcomes included rates of deep infection and unplanned reoperation.
Results: 508 BTP fractures were identified, with 51 open fractures: mean (SD) age 45.7 (12.3) years, 72% male, mean (SD) follow up of 4.3 (39.8) years. Forty-two (82%) were Gustilo-Anderson type III open injuries. A median (IQR) of 2 (1-3) debridements were required prior to closure. Twenty-four (47%) patients underwent acute ORIF (<24 hours). Twelve patients (24%) received a primary flap at mean (SD) 6.4 (3.9) days following injury. Five (35%) were simultaneous “fix and flap” procedures. Another 14 (27%) required a secondary flap for wound complications. The overall deep infection rate was 39% and unplanned reoperation 86%. Among patients with type IIIB and C injuries, rates of deep infection (83% vs 17%, p = 0.02) and reoperation (83% vs 33%, p = 0.08) were higher in patients treated with delayed (>7 days) versus early flap coverage. There was no difference in infection (29 vs. 48%, p=0.16) and unplanned reoperation (33 vs. 52%, p=0.18) rates between acute (<24hrs) and delayed fixation.
Interpretation / Conclusion: Time to flap coverage greater than 7 days was associated with higher rates of deep infection and unplanned reoperation in this cohort. Patients with these injuries should be counseled about the high rate of complications. Definitive soft tissue coverage should be accomplished as soon as feasible.

198. Outcomes after ORIF of Bicondylar Schatzker VI (AO Type C) Tibial Plateau Fractures in an Elderly Population
Mihir Dekhne, Derek Stenquist, Nishant Suneja, Michael Weaver, Michael Moerk Petersen, Anders Odgaard, Arvind von Keudell
Mihir S. Dekhne(a,b), Derek Stenquist(b,c), Nishant Suneja(b,c), Michael Weaver(b,c), Michael Moerk Petersen(d,e), Anders Odgaard(d,e), Arvind von Keudell (b,c,d) aHarvard Medical School, Boston, Massachusetts, USA bHarvard Orthopaedic Trauma Initiative, Harvard Medical School, Boston, Massachusetts, USA cDepartment of Orthopaedic Surgery, Brigham and Women's Hospital, Boston, Massachusetts, USA dDepartment of Orthopaedic Surgery, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark eDepartment of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark

Background: The surgical management of bicondylar tibial plateau (BTP) fractures in elderly patients aims to restore knee stability while minimizing soft tissue complications.
Aim: The purpose of this study was to compare injury characteristics and surgical outcomes after ORIF of BTP fractures (AO/OTA 41-C (Schatzker VI)) in young (< 50 years) versus elderly (> 65 years) patients.
Materials and Methods: A retrospective cohort study was conducted using data from two American College of Surgeons (ACS) level I trauma centers. Inclusion criteria were: (1) age 18 years or older, (2) bicondylar tibial plateau fracture (AO/OTA 41-C or Schatzker VI), (3) treatment with ORIF, and (4) minimum of 6 months follow-up. Patients between 50 and 65 years of age were excluded. Data collection was performed by reviewing electronic medical records, operative reports, and radiology reports.
Results: We identified 323 patients (61% male) with 327 BTP fractures and a median follow-up of 685 days. There were 230 young patients (71%) < 50 years and 93 elderly patients (29%) >6 5 years at time of presentation. Elderly patients were significantly more likely to have a low energy mechanism of injury (44.6 vs. 16.2%, p < 0.001), and present with diabetes (19.4 vs. 4.4%, p < 0.001) or coronary artery disease (12.9 vs. 1.3%, p < 0.001). Elderly patients were also significantly less likely to undergo staged management with initial knee-spanning external fixation followed by delayed ORIF (19.2 vs. 33.9%, p = 0.008). Elderly patients had a lower arc of motion at final follow-up (105 vs. 113, p < 0.001) and reduced PROMIS-10 function scores (43.8 vs. 49.8, p=0.013). No differences were observed in rates of superficial infection, deep infection, reoperation, or EQ-5D scores.
Interpretation / Conclusion: This is the largest study to compare injury characteristics and outcomes after ORIF of BTP fractures according to age. Elderly patients (age > 65 years) sustained BTP fractures by lower energy mechanisms than their younger counterparts with similar fracture patterns and were often managed with ORIF. The results of this study suggest that ORIF of BTP fractures in elderly patients is associated with similar complication rates and outcomes as in younger patients.

Simon Comtesse 1, Arvind von Keudell 2,3, Stephen Ferguson, Thomas Zumbrunn
1. Institute for Biomechanics, ETH Zurich, Switzerland; 2. Department of Orthopaedic Trauma, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA; 3.Department of Orthopaedic Surgery, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark

Background: For complex peri-articular fractures, it is often unclear how the screws and plates should be positioned to achieve maximum stability. Postoperative immobilization is often depended on this. Hence, outcomes may heavily depend on the surgeon’s experience.
Aim: Our goal is to introduce a method for quantitative evaluation of fracture-fixation stability, by means of finite element analysis and musculoskeletal modelling.
Materials and Methods: Based on a pre-operative computed tomography (CT) scan, ten bone fragments of a right proximal bicondylar tibia fracture (Schatzker 6) were segmented and aligned to achieve adequate fracture reduction. Bone material properties were assigned from Hounsfield Units based on internal density calibration. According to the post- operative CT scan, 3D models of the implanted stainless-steel screws were designed and aligned to the bone fragments thereby reverse-engineering the clinical reconstruction. Knee joint reaction forces and muscle forces were imported from a subject-specific musculoskeletal gait model during mid- stance phase (AnyBody Technology, Denmark) and implemented in the Finite Element Model
Results: A maximum displacement of 1.62mm was found at the proximal aspect of the lateral fragment. The maximum von Mises stress (423MPa) was located on the most distal lateral screw,
Interpretation / Conclusion: After validation of the model, fragment movement could be related to fracture healing and serve as a predictive tool for clinical outcome. Possible hardware failure could be predicted by means of von Mises stresses in the screws. Furthermore, this process may enable development of more effective patient-specific implants in the future.

Poster Walk 8: Tumor - Spine
Chair: Michael Bendtsen / Dennis Hallager

209. Effect of negative pressure wound therapy after surgical removal of deep-seated high-malignant soft tissue sarcomas of the extremities and trunk wall – study protocol for a randomized controlled trial
Andrea Pohly Thorn¹ , Yilmaz Müjgan¹ , Skovlund Michala², Jensen Claus Lindkær¹ , Michael Mørk Petersen¹
¹ Rigshospitalet – University of Copenhagen, Department of Orthopaedic Surgery ² Bispebjerg Hospital - Department of Orthopaedic Surgery

Background: Sarcomas are a heterogeneous group of rare malignant tumors in the musculoskeletal system. The reported incidence is 300 cases per year in Denmark (250 Soft tissue sarcomas (STS) including 100 retroperitoneal/abdominal STS and 50 bone sarcomas). The main treatment principles is surgery supplemented with adjuvant radiotherapy depending on subtype and stage. STS surgery is often combined with pre- or postoperative radiation therapy and is a high-risk procedure concerning wound complications and postoperative infections. A previous retrospective study showed that Negative Pressure Wound Therapy (NPWT) reduced the risk of wound complications in patients with lower extremity STS..
Aim: The aim of this research project is to improve the surgical treatment of STS treatment. We want to evaluate the effect of the use of NPWT versus a conventional wound dressing on postoperative wound complications after surgical removal of deep- seated high-malignant STS of the extremities or trunk wall.
Materials and Methods: RCT (no blinding) where patients will be randomized to wound closure with staples and either NPWT for 7 days or a conventional wound dressing. Randomization sequence will be computer generated and based upon sample size calculation, using previously published data, we have decided to include 154 STS patients, 77 in each group, and to make allowance for dropouts we plan to include 160 patients. Patient's wounds will be followed with photo documentation on day 0, day 7, at definitive wound healing (removal of staples), 4 months postoperatively and in case of major wound complication. Our Primary study endpoint is a major wound complication defined as in O’Sullivan et al. within 4 months after surgery and includes following: Secondary operation under general or regional anesthesia for wound repair, wound management without secondary operation or readmission for wound care.
Results: The study is on-going, and result are not finalized.
Interpretation / Conclusion: Many new medical devises and technical solutions are currently introduced and even though some documentation regarding the use of NPWT e.g. in joint replacement surgery exist it is also important to seek documentation for this treatment principle in STS surgery

210. Sclerotherapy of aneurysmal bone cysts with polidocanol
Kolja Weber, Claus Lindkær Jensen, Michael Mørk Petersen
Department of Orthopaedic Surgery, Rigshospitalet, Copenhagen, Denmark

Background: Aneurysmal bone cysts (ABC) are benign cystic bone lesions, which make up approx. 2% of all primary bone tumors. As an alternative to the primary treatment of choice, which consists of curettage with bone grafting, alternative treatment methods with promising results have been described. At our department we have in recent years used percutaneous sclerotherapy with polidocanol. Here we present our experience with this method.
Aim: To identify the efficacy and safety of sclerotherapy with polidocanol.
Materials and Methods: Sixteen consecutive patients (mean age 12 years; range 4-25) with 17 ABCs treated with sclerotherapy with polidocanol from 2015-2020 were included retrospectively. Under general anesthesia and fluoroscopic guidance, repeated percutaneous injections of 4mg polidocanol/kg body weight were performed. Through review of the electronic medical records, the following were identified: healing and recurrence rate, number of treatments, gender, age, comorbidity, location of the tumor, side effects / complications as well as any previous surgery for ABC. The mean length of radiographic follow up was 20 months.
Results: All ABCs except one healed after a mean of 4 (range 1-8) injections. Complete clinical and radiographic healing was observes in 10 cysts, while partial radiographic healing without clinical symptoms were seen in 6 cases and were considered to be healed. The cyst that failed to heal had previously undergone curettage twice with recurrence. One patient with a pelvic ABC experienced right after two injections, possibly due to an allergic reaction, a sudden drop in blood pressure which could quickly be reversed. Further than that, no complications were observed.
Interpretation / Conclusion: Percutaneous sclerotherapy with polidocanol is an efficient and safe alternative to conventional surgery for the treatment of aneurysmal bone cysts. Our findings corroborate data presented in previous publications.

177. The outcomes after Anterior Lumbar Interbody Fusion(ALIF): Our experience
Ari Demirel, Renata Terzic, Jon Kaspersen, Søren Peter Eiskjær
Department of Orthopaedics, Aalborg University Hospital

Background: ALIF is a well-established treatment for degenerative disc disease. Poly-ether-ether-ketone(PEEK) ALIF cages have many advantages: Relative radiolucency, elasticity closer to bone and showing less subsidence.
Aim: The goal of this study was to determine the radiological outcomes and complications after ALIF surgery.
Materials and Methods: Retrospective review of patients with ALIF(PEEK cage) surgery from 2014 to 2020 in our center. Complications were noted. Bone union determined with Bridwell classification. Pre and post-operative X-rays, X-rays at the last follow-up reviewed. Anterior (A)-posterior (P) disc space height (DSH), segmental lordosis (SL) at the ALIF levels, global lumbar lordosis (GL) measured.
Results: 56 patients (M:25, F:31) and 80 ALIF cages were reviewed. The diagnoses were: 33 discus degeneration, 16 spondylolisthesis, 7 non-union. The respective median age of surgery and follow-up duration(months) for these groups were: 47(37-54) /14(12-24), 45(40-52) /22(14- 27), 57(51-62) /17(16-25). Complications were: 3 venous lesions, 2 misplaced screws, 1 renal dysfunction, 1 rupture of the rectus abdominis and transverse fascia, 1 loose pedical screw, 1 anterior superficial wound infection, 4 relaxations of the left rectus abdominis musculature, 1 posterior deep infection, 2 adjacent level degenerations. Bridwell fusion were: 1 in 72 cages, 2 in 6 cages and 4 in 2 cages. The A- DSH and P-DSH L3/L4, L4/L5, L5/S1 significantly increased from preoperatively to immediately postoperatively and compared to the distance at last follow up. The A-DSH and P- DSH L4/L5, L5/S1 decreased significantly from immediately postoperatively to last follow-up. In L4/L5, the decrease in P-DSH from immediately postoperatively to last follow up was insignificant. Only for the L5/S1 level did the SL increase significantly from preoperatively to immediately postoperatively and compared to the angle at last follow-up. No significant changes noted in the GL.
Interpretation / Conclusion: The use of ALIF(PEEK cage) with posterior fixation resulted in very low non-union rate (2,5%). It generally increased DSH and conserved or increased lordosis. The approach related complications are comparable to the complication rates in the literature.

178. Demineralized cortical fibers are associated with low pseudarthrosis rate in patients undergoing surgery for adult spinal deformity without three-column osteotomy
Martin Heegaard, Tanvir Johanning Bari, Benny Dahl, Lars Valentin Hansen, Martin Gehrchen
Spine Unit, Department of Orthopedic Surgery, Rigshospitalet, Copenhagen University Hospital, Blegdamsvej 9, 2100 Copenhagen, Denmark

Background: Demineralized cortical fibers (DCF) were introduced in 2017 at our institution aiming to reduce pseudarthrosis rate after surgery for adult spinal deformity (ASD). We have previously demonstrated that the use of DCF in ASD patients undergoing procedures including 3COs reduces the risk of pseudarthrosis compared to patients receiving autologous and allogenic bone graft.
Aim: The purpose of the present study was to investigate the effect of DCF on postoperative pseudarthrosis after surgery for ASD without a three-column osteotomy (3CO).
Materials and Methods: All patients undergoing surgery for ASD were retrospectively screened at our institution from 2017- 2019, excluding patients having 3CO surgery. Patients were included if DCF was applied from at least L3-sacrum. All patients had a minimum of 2- year follow-up. The main outcome was CT-verified postoperative pseudarthrosis with implant failure (rod breakage or screw loosening) requiring revision surgery.
Results: Fifty-three patients were included for final analysis. Revision surgery due to CT-verified postoperative pseudarthrosis occurred in 13% (n=7). Nine percent (n=5) of the patients had major postoperative complications.
Interpretation / Conclusion: Our study is the first to investigate the use of DCF in patients undergoing ASD surgery without 3CO. Our results suggest that the use of DCF is associated with a low incidence of postoperative pseudarthrosis requiring revision surgery compared to previously published studies.

179. Definitions of Segmental Instability in the Degenerative Lumbar Spine – a Systematic Review
Signe Forbech Elmose¹, Gustav Østerheden Andersen¹, Leah Yacat Carreon¹, Freyr Gauti Sigmundsson², Mikkel Østerheden Andersen¹
Center for Spine Surgery and Research, Spine Center of Southern Denmark, Lillebaelt Hospital, Oestre Hougvej 55, DK-5500 Middelfart¹ ; Department of Orthopaedic surgery, Örebro University Hospital, Södra Grev Rosengatan, SE-70185 Örebro²

Background: What defines segmental instability of the lumbar spine has been a clinical and scientific question for almost a century. In patients with lumbar degenerative spondylolisthesis (LDS) and spinal stenosis (LSS) the definition of segmental instability has an impact on surgical decision-making, as its presence may require a fusion procedure in addition to decompression. Despite this, the operational definition of segmental instability varies.
Aim: - To collect and group definitions of segmental instability, reported in surgical studies of patients with LSS and/or LDS - To report the frequencies of these definitions - To report on imaging measurement thresholds for instability in patients and compare these to those reported in biomechanical studies and studies of spine healthy individuals - To report on studies that include a reliability study.
Materials and Methods: We conducted a systematic review according to Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Studies eligible for inclusion were clinical and biomechanical studies on adult LDS and/or LSS patients who underwent surgical treatment and with data on diagnostic imaging. A systematic literature search was conducted in relevant databases. Full text screening inclusion criteria was definition of segmental instability or any synonym. Two reviewers independently screened articles in a two-step process. Data synthesis presented by tabulate form and narrative synthesis.
Results: We included 118 studies for data extraction, 69 % were surgical studies with decompression or fusion as interventions, 31 % non-interventional studies. Grouping the definitions of segmental instability according similarities showed that 24% defined instability by dynamic sagittal translation, 26 % dynamic translation and dynamic angulation, 8% used a narrative definition. Comparison showed that non-interventional studies with a healthy population more often had a narrative definition.
Interpretation / Conclusion: To our knowledge this is the largest review of literature on segmental instability. Despite a reputation of non-consensus, segmental instability in the degenerative lumbar spine can radiologically be defined as > 3mm dynamic sagittal translation.