Session 8: Hip Arthroplasty

Kristine Ifigenia Bunyoz¹, Georgios Tsikandylakis^{2, 3}, Kristian Mortensen¹, Kirill Gromov¹, Maziar Mohaddes^{2, 3}, Henrik Malchau^{3, 4}, Anders Troelsen¹
1. Department of Orthopaedic Surgery, Copenhagen University Hospital, Hvidovre, Denmark 2. Department of Orthopaedics, Sahlgrenska University Hospital, Gothenburg, Sweden 3. Department of Orthopaedics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Sweden 4. Harris Orthopaedic Laboratory, Department of Orthopaedics, Massachusetts General Hospital, Boston, USA

Background: In metal-on-polyethylene (MoP) THA large femoral metal heads are designed to increase stability and reduce dislocation risk. Theoretically, the increased head size could lead to increased taper corrosion with the release of metal ions and adverse reactions.
Aim: Using blood ion measurements, we aim to investigate the potential association between femoral head size and metal-ion release after MoP THA.
Materials and Methods: 96 patients were enrolled at two different centers and randomized to receive either a 32-mm metal head or a 36-44 mm metal head (the largest possible fitting the thinnest available polyethylene insert). Blood metal ions and PROMs (OHS, UCLA) were measured at two- and five-year follow-ups.
Results: Both 2- and 5-year median chrome, cobalt, and titanium levels were below taper corrosion indicative ion levels. At 5 years, median chrome, cobalt, and titanium levels were 0.5 µg/L (0.50-0.62), 0.24 µg/L (0.18-0.30), and 1.16 µg/L (1.0-1.68) for the 32-mm group, and 0.5 µg/L (0.5-0.54), 0.23 µg/L (0.17- 0.39), and 1.30 µg/L (1-2.05) for the 36-44 mm group, with no difference between groups (p=0.825, p=1.000, p=0.558). At 2 years, 7 versus 4 patients had elevated ions in the 32-mm versus 36-44 mm group. At 5 years, 6 versus 7 patients had elevated ions in the 32-mm versus 36-44 mm group. At 5 years, median UCLA score was lower in the 36-44 mm group (p=0.020). The remaining PROMs showed no differences between groups.
Interpretation / Conclusion: 5 years after the insertion of MoP THAs, we found no differences in the blood metal ion levels between 32 mm heads and 36-44 mm heads and no corrosion-related revisions. As taper corrosion can debut after 5 years, there is still a need for long-term follow-up studies on the association between head size and corrosion in MoP THA.

Rajzan Joanroy^1,2, Jens K Møller^2,3, Sophie Gubbels⁴, Søren Overgaard⁵, Claus Varnum^1,2
1.Department of Orthopaedic Surgery, Lillebaelt Hospital - Vejle, Denmark 2.Department of Regional Health Research, University of Southern Denmark, Denmark 3.Department of Clinical Microbiology, Lillebaelt Hospital - Vejle, Denmark 4.Division of Infectious Disease Preparedness, Statens Serum Institut, Denmark 5.Department of Orthopedic Surgery and Traumatology, Copenhagen University Hospital, Bispebjerg, Denmark 6.Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen

Background: The most devastating complication after total hip arthroplasty (THA) is prosthetic joint infection (PJI). Published danish surveillance data from the Healthcare-Associated Infections Database have indicated seasonal variation in primary THA and risk of PJI revision with a higher incidence during summer season.
Aim: We investigated the association between season and risk of PJI revision and any revision following primary THA.
Materials and Methods: This nation-wide register-based cohort study identified 58,449 patients from the Danish Hip Arthroplasty Register (DHR) with unilateral primary THA performed due to osteoarthritis from 2010-2018. From Danish health registries, we retrieved information on Charlson Comorbidity Index (CCI), immigration, death, microbiological data on intraoperative biopsies, cohabitation status and meteorological data from The Danish Meteorological Institute. Summer was defined as June-September, and THAs performed during winter (October-May) were used as controls. The follow-up for all patients was 1 year. Primary outcome was revision due to PJI confirmed or likely: the composite of revision with any culture-positive biopsy or reported PJI to DHR. The secondary outcome was any revision. The cumulative incidences and the adjusted relative risk (RR) with 95% confidence intervals (CI) were calculated by season of the primary THA. We adjusted for age, sex, CCI, cohabitation status, fixation type and duration of antibiotic treatment in relation to primary THA.
Results: At 1-year follow-up, 1,507 patients were revised, of which 632 were due to PJI. The cumulative incidence of PJI for THAs performed during summer and winter was 1.1% (CI 1.0-1.3) and 1.1% (CI 1.0-1.2) and for any revision 2.7% (CI 2.5-3.0) and 2.5% (CI 2.4-2.7), respectively. The adjusted RR for PJI revision was 1.1 (CI 0.9 – 1.3) and for any revision 1.1 (CI 1.0-1.2) for THAs performed during summer vs. winter.
Interpretation / Conclusion: We found no association between summer and the risk of PJI revision or any revision for patients with primary THA. Hence, the published surveillance data could not be verified in the present study. It seems safe to perform primary THA during the summer season.

Jens Laigaard^1,2,3, Anders Peder Højer Karlsen^2,4, Mathias Maagaard^2,3, Troels Haxholdt Lunn^3,4, Ole Mathiesen^2,3, Søren Overgaard^1,3
1) Dept. of Orthopaedic Surgery and Traumatology, Copenhagen University Hospital Bispebjerg and Frederiksberg, Copenhagen, Denmark; 2) Centre for Anaesthesiological Research, Dept. of Anesthesiology, Zealand University Hospital, Køge, Denmark; 3) Dept. of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark; 4) Dept. of Anesthesia and Intensive care, Copenhagen University Hospital Bispebjerg and Frederiksberg, Denmark.

Background: Pain during rehabilitation from surgery is associated with persistent pain. This occurs in around 9 to 20% of patients after total hip or knee arthroplasty (THA/KA). The main reason for this, is believed to be central sensitisation, where the pain centres become hypersensitive after experiencing intense pain.
Aim: To investigate the effect of perioperative analgesic interventions in reducing persistent pain after THA and KA.
Materials and Methods: This was a systematic review and meta-analysis of randomised trials on perioperative analgesic interventions for osteoarthritis patients undergoing elective THA/KA. The protocol was registered (CRD42021284175) and published (PMID 35325472). Two authors independently screened records, extracted data, and assessed risk of bias. The primary outcome was pain scores 3-24 months postsurgically, reported as absolute mean differences (95% confidence interval) on the 0-100 visual analogue scale.
Results: We searched CENTRAL, MEDLINE, and Embase up to October 19, 2021, and identified 38,202 unique records. We screened 892 articles and found 725 eligible trials, but pain outcomes 3-24 months postsurgically was only available from 37 trials, despite contact to authors of all eligible trials. All 37 trials were at high risk of bias. Most included trials investigated glucocorticoids (10 trial arms, 5369 patients), local infiltration analgesia (7 trial arms, 1932 patients), and gabapentinoids (6 trial arms, 1770 patients). We found no effect of glucocorticoids (-0.3 mm [95% CI -0.8 to 0.3]), local infiltration analgesia (0.0 mm [-0.4 to 0.4)) or gabapentinoids (-3.0 mm [-27.9 to 21.9]) on pain assessed at rest after 3-24 months. Similarly, we found no effect of glucocorticoids (0.2 mm [-0.4 to 0.7]), local infiltration analgesia (-1.4 mm [-4.0 to 1.1]) or gabapentinoids (2.8 mm [-1.3 to 6.8]) on pain assessed during movement. Other outcomes of interest, including serious adverse events, were rarely reported.
Interpretation / Conclusion: Few trials on analgesic interventions for THA/KA reported long-term pain outcomes. All trials were at high risk of bias, and we did not find any evidence for or against perioperative analgesic interventions for reduction of persistent postsurgical pain.

Rasmus Reinholdt Sørensen¹, Signe Timm¹, Lasse Enkebølle Rasmussen¹, Claus Lohman Brasen², Claus Varnum¹
1. Department of Orthopaedic Surgery, Lillebaelt Hospital - Vejle; 2. Department of Biochemistry and Immunology, Lillebaelt Hospital - Vejle

Background: Metabolic syndrome (MetS) is a common term used for metabolic deficiencies that can lead to cardiovascular disease, diabetes and other lifestyle-related conditions. Estimations are that 30% of the middle-aged population in Denmark suffers from MetS. It is unknown how MetS influences the outcome after hip and knee arthroplasty.
Aim: Primary aim was to investigate the change in patient-reported outcome (PRO) from baseline to 12 months after hip and knee arthroplasty in patients with MetS compared to patients without MetS. Secondly, PRO was compared at baseline, 3 and 24 months after surgery.
Materials and Methods: During May 1st, 2017 to November 30th, 2019 a cohort of 2,760 patients undergoing 2,901 hip and knee arthroplasties was established. Data from national registries and a local database were used to determine the presence of MetS and the patients´ scores on Oxford Hip Score (OHS) or Oxford Knee Score (OKS), UCLA Activity Score (UCLA), Forgotten Joint Score (FJS) and EQ-5D-5L score at baseline, 3, 12 and 24 months after surgery. Primary outcome was the change from baseline to 12 months in OHS and OKS. Secondary outcome was OHS and OKS at 3 and 24 months as well as UCLA, EQ5D-5L and FJS at 3, 12 and 24 months after surgery. Mixed effect linear regression, adjusted for age, sex, comorbidity and smoking, was applied to present marginal mean and associated 95% confidence intervals.
Results: fifty-two percent of the cohort met the criteria for MetS. Both groups showed an increase in OHS (MetS group 23 (22-23), non-MetS group 21 (21- 23)) and OKS (MetS-group 18 (18-19), non-MetS group 18 (18-19)) at 12 months follow-up. The difference between groups did not reach statistical significance (OHS p=0.39 and OKS p=0.97). Similar improvements were seen in UCLA, FJS and EQ-5D-5L at every time point.
Interpretation / Conclusion: Patients with metabolic deficiencies meeting the criteria for MetS reach the same improvement in PRO as individuals without MetS up to 24 months after hip and knee arthroplasty.

Martin Peter Nielsen¹, Janus D Christensen¹, Thomas Jakobsen¹, Poul Torben Nielsen
1. Department of Orthopaedics, Aalborg University Hosptial;

Background: Using radio stereometric analysis (RSA), we have previously shown good fixation of the ultra-short stem Primoris® at midterm follow-up (5 years). Bone mineral density (BMD) evaluations have shown promising results with preservation of proximal bone stock. Few studies have evaluated long term follow up on BMD, migration and patient satisfaction of an ultra-short stem.
Aim: The aim of this study was to investigate bone remodeling, implant migration analysis (RSA) and patient related outcome measures (PROMs) in patients treated with the Primoris ® stem with a 10- year follow-up
Materials and Methods: 50 patients (5 females and 45 males), mean age of 52 with end-stage osteoarthritis were treated with the Primoris® between 2011-13. Using DEXA scans we analyzed bone mineral density (BMD) in four different regions of interest (ROI). Implant migration was assessed using RSA. PROMs were evaluated with Harris Hip score, Oxford Hip score, WOMAC, EQ-5D score and UCLA activity score at the same follow up intervals. Follow up examinations were performed at day 1, 6 weeks, 6 months, 12 months, 2 years, 5 years and 10 years postoperatively.
Results: BMD showed a decrease in ROI1 (10.7%), ROI2 (12.7%), ROI3 (12.5%), ROI4 (4,.%) from day 0 to 10 years. Patient satisfaction at 10-year follow-up remained high with median values of Harris Hip score 98, Oxford Hip score 47, WOMAC 97 , EQ-5D score 1, UCLA activity score 7. RSA analysis showed minimal migration of the prosthesis in translation(X,Y,Z) and rotation(X,Y,Z) with a mean maximum total point motion at 10 years only of 0,79 mm.
Interpretation / Conclusion: This 10-year follow up study of the Primoris® stem revealed minimal migration, which is in accordance with migration patterns of traditional uncemented stems. In regards to preserving proximal bone stock for eventual later revision and the risk of fracture, results are encouraging with only minimal stress- shielding and PROMs comparable to patients treated with a standard uncemented stem.

Arash Ghaffari¹, Pernille Damborg Clasen¹, Rikke Vindberg Boel¹, Andreas Kappel¹, Thomas Jakobsen¹, Søren Kold¹, Ole Rahbek¹
1. Interdisciplinary Orthopaedics, Aalborg University Hospital.

Background: Wearable inertial sensors can detect abnormal gait associated with knee or hip osteoarthritis (OA). However, few studies have compared sensor-derived gait parameters between patients with hip and knee OA or evaluated the efficacy of sensors suitable for remote monitoring in distinguishing between the two.
Aim: Our study seeks to examine the differences in accelerations captured by low-frequency wearable sensors in patients with knee and hip OA and classify their gait patterns.
Materials and Methods: We included patients with unilateral hip and knee OA. Gait analysis was conducted using an accelerometer ipsilateral with the affected joint on the lateral distal thighs. Statistical parametric mapping (SPM) was used to compare acceleration signals. The k-Nearest Neighbor (k- NN) algorithm was trained on 80% of the signals’ Fourier coefficients and validated on the remaining 20% using 10-fold cross-validation to classify the gait patterns into hip and knee OA.
Results: We included 42 hip OA patients (19 females, age 70 [63-78], BMI of 28.3 [24.8-30.9]) and 59 knee OA patients (31 females, age 68 [62- 74], BMI of 29.7 [26.3-32.6]). The SPM results indicated that one cluster (12-20%) along the vertical axis had accelerations exceeding the critical threshold of 2.956 (p=0.024). For the anteroposterior axis, three clusters were observed exceeding the threshold of 3.031 at 5-19% (p = 0.0001), 39- 54% (p=0.00005), and 88-96% (p = 0.01). Regarding the mediolateral axis, four clusters were identified exceeding the threshold of 2.875 at 0-9% (p = 0.02), 14-20% (p=0.04), 28-68% (p < 0.00001), and 84-100% (p = 0.004). The k-NN model achieved an AUC of 0.79, an accuracy of 80%, and a precision of 85%.
Interpretation / Conclusion: In conclusion, the Fourier coefficients of the signals recorded by wearable sensors can effectively discriminate the gait patterns of knee and hip OA. In addition, the most remarkable differences in the time domain were observed along the mediolateral axis.

Edwards Nina M.¹, Klenø André S.², Pedersen Alma B.²
1. Department of Orthopaedic Surgery, Regionshospitalet Horsens, Denmark; 2. Department of Clinical Epidemiology, Department of Clinical Medicine, Aarhus University and Aarhus University Hospital, Aarhus, Denmark.

Background: Opioids are commonly used to treat pain after total hip arthroplasty (THA) surgery, however continued opioid use is seen in 16 % of patients 12 months after THA surgery. Increasing evidence show that psychological factors can affect pain and opioid use after surgery. However, little is known regarding the impact of a history of stress on opioid use after THA.
Aim: To examine the association between perceived stress and the risk of continued opioid use after THA in patients with osteoarthritis.
Materials and Methods: The 2013 and 2017 nationwide population-based health survey was used to identify 1,729 patients who completed a self-reported Perceived Stress Scale and who later on received a primary THA, identified through the Danish Hip Arthroplasty Registry. Patients were categorized into two groups: high level of stress and low level of stress (including no stress). The outcome was continued opioid use defined as = 2 opioid dispensing 1-12 months after THA identified in the Danish National Health Service Prescription Database. We calculated prevalences of continued opioid use. We calculated the adjusted prevalence ratios (aPR) with 95% confidence intervals using log-binomial regression and adjusting for sex, age, comorbidities, and education. We calculated median morphine milligram equivalents (MME) for the entire year as the opioid dose multiplied by an MME conversion factor.
Results: Overall, 258 (15%) patients reported high level of perceived stress, and 26% of these had continued opioid use. 1,471 (85%) patients reported low level or no stress, and 15% of these had continued opioid use. The aPR for continued opioid use was 1.42 (1.11-1.80). The MME dose was 1000 for patients, who reported high level of perceived stress and 645 for patients, who reported low level or no stress.
Interpretation / Conclusion: Patients, who report high level of perceived stress before THA have a higher risk of continued opioid use and consume higher MME dose in the first post-operative year after THA than patients, who report low level or no stress. We examined important pre-existing patient characteristics and found important differences contributing to continued opioid use after THA.

Lars L. Hermansen^1,2, Thomas F. Iversen², Pernille Iversen³, Søren Overgaard^4,5
1. Department. of Orthopedics, University Hospital of Southern Denmark, Esbjerg; 2. Department of Regional Health Research, University of Southern Denmark, Odense; 3. The Danish Clinical Quality Program and Clinical Registries; 4. Department of Orthopedic Surgery and Traumatology, Copenhagen University Hospital, Bispebjerg; 5. Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen;

Background: Dislocation is one of the leading indications for hip revision, but most patients are still treated by closed reduction only. The true burden of this complication has historically been difficult to measure truthfully. In 2019, we presented the true dislocation risk from 2010-2014 after conducting a nationwide review of patient files, and we initiated the work of implementing a new quality indicator in the Danish Hip Arthroplasty Register (DHR) based on the new Danish National Patient Register (DNPR - LPR3 version).
Aim: Prior to planned onset of the dislocation indicator in the 2022-annual DHR report, our aim with this study was to present the current national status of the true one-year dislocation risk after primary THA.
Materials and Methods: We included 5.415 primary THAs inserted from 1/7 2019 to 31/12 2019 and identified every hospital contact with the Danish healthcare system within the first postoperative year based on data from the DNPR. To identify every dislocation, we manually reviewed patient files containing more than 1.750 hospital contacts. All public hospitals and private clinics were included. Results are presented as proportions with 95% confidence intervals.
Results: We identified 243 dislocations in 152 THAs corresponding to a true one-year dislocation risk of 2.8% (2.4-3.3). During the follow-up, 37% of the patients suffered additional events of dislocation. THA due to osteoarthritis resulted in 2.5% (2.1-3.0) dislocations, while the risk was 4.5% (2.3- 7.7) and 5.3% (2.8-9.1) in patients with acute femoral neck fracture and sequalae after earlier hip fracture surgery, respectively. The results varied within the five regions of Denmark from 1.4% (0.9-2.3) to 5.4% (3.6-7.6), and between hospitals from 0% to 9.6% (3.2-21.0).
Interpretation / Conclusion: The true one-year dislocation risk after primary THA was 2.8%. This level corresponds well with our findings in the 2010-2014 cohort. The next step will be to validate our algorithm based on LPR3-data. The quality indicator in the upcoming DHR annual reports will contribute to identify both hospitals and implant-related factors associated with high dislocation rates and improvement potential.

morten boye petersen¹, mikkel Rathsach andersen¹
1. Department of Orthopaedics, Gentofte, Gentofte-Herlev University Hospital

Background: Diagnostics of possible infection in revision hip or knee arthroplasty, has so far essentially been by taking five tissue biopsies, as described by Kamme 1981. However, it is often experienced that tissue samples are without significant bacterial diagnostics, even though the surgeon's experience is that the field is infected. Based on knowledge of biomembrane formation, sonication has been developed as a method for diagnosing periprosthetic infection (PJI).
Aim: To evaluate results with the first 49 cases using sonication, the sonication result was compared with the results of culture of tissue biopsies.
Materials and Methods: 49 implants removed during hip or knee revision of all courses from 2017 to 2023 were sent for sonication. According to EBJIS classification, preoperative 24 cases were with unlikely infection, 21 with infection likely and 4 with confirmed infection. If significant bacterial growth was found when culturing the sonication liquid, this was taken as diagnostic of bacterial infection. For all cases, five biopsies were taken a.m. Kamme. If two or more tissue biopsies showed growth of the same bacteria, this was taken as diagnostic for bacterial infection. Results after the two analysis methods were compared.
Results: In 28 operations, neither tissue biopsies nor sonication found diagnostic signs of bacteria. In 14 cases, sonication found bacteria, typically low virulence bacteria, with no growth in tissue samples. In 6 cases, both sonication and tissue samples found bacteria, and in all 6 cases, the same bacterial strain. In 1 operation, sonication found no growth, while tissue biopsies (3/5) found growth of Staphylococcus aureus
Interpretation / Conclusion: Sonication seems to have a role in bacterial diagnostic in revision surgery for PJI. Typically, low-virulence biomembrane forming bacteria such as e.g. Staph. Epidermidis is detected. In 14 cases (28%), bacteria could be detected by sonication, where tissue biopsies found no bacteria. In the cases where there was both growth by sonication and 2 of 5 possitve tissue cultures , there was good agreement in the bacterial diagnosis. However, in its current structure, the method is expensive and resource-demanding, which gives limitations to its use.