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Background and purpose: National joint replacement registries were developed for prospective monitoring of outcomes and post-market surveillance of implants. Increasingly registry data informs practice. However, analysis of a registry can only be as good as the data it captures on the population of interest. We aimed to analyze completeness of reporting of hip and knee replacement procedures for all national registries worldwide. Methods: We analyzed annual reports and data provided following written requests to all active national hip and knee replacement registries. Coverage was defined as the proportion of hospitals in the country that participate in the registry. Procedure completeness was defined as the proportion of procedures successfully captured by the registry. Results: 14 national registries were included, spanning years 2004 to 2022. Coverage was complete in 10. Median procedure completeness for primary hip and knee replacement across all years was 96.5% (interquartile range [IQR] 94.0–97.7%). Median procedure completeness for revisions was 88.5% (IQR 81.0–92.5%). The terminology used and method of calculation of completeness estimates in the registries were variable. Conclusion: National hip and knee replacement registry data generally reflects excellent coverage (full in 10 of 14 registries) and completeness (primary procedures 96.5% and revisions 88.5%) over the last 2 decades.

Background and purpose: Prosthetic joint infection (PJI) following total hip arthroplasty (THA) has a severe impact on patients. We investigated the risk of second revision and mortality following first-time revision due to PJI. Methods: We identified 1,669 first-time revisions including 416 treated with debridement, antibiotics, and implant retention (DAIR) from the Danish Hip Arthroplasty Register (DHR). First-time revision due to PJI was defined as a revision with ≥ 2 culture-positive biopsies for the same bacteria or re-ported as PJI to the DHR within 1 year after primary THA with non-PJI revisions as controls. We retrieved information on Charlson Comorbidity Index (CCI), death, cohabitation status, and cultures from intraoperative biopsies. The adjusted relative risk (RR) with 95% confidence interval (CI) was calculated by first-time revision (PJI or non-PJI). Patients were followed from first-time revision until end of study. Results: PJI was found in 140 of 280 patients having a second revision following any first-time revision. Of these 280 patients, 200 were treated with DAIR as second revision. Patients with first-time revision due to PJI had an increased risk of second revision compared with first-time revision for non-PJI with an adjusted RR for second revision due to any cause of 2.7 (CI 1.9–3.8) and second revision due to PJI of 6.3 (CI 4.0–10). The 10-year adjusted RR for mortality for patients with first-time revision due to PJI compared with non-PJI was 1.8 (CI 0.7–4.5). Conclusion: The risk of second revision was increased both for second revision due to any reason and due to PJI following first-time revision due to PJI. Mortality risk following first-time revision due to PJI was increased, but not statistically significant.

Background and purpose: The low-dose EOS Imaging System is an emerging tool for 3-dimensional measurements in orthopedics. The clinical feasibility for measuring total hip arthroplasty (THA) liner wear has not yet been investigated. We aimed to evaluate the feasibility of using EOS to measure THA liner wear by examining the experimental accuracy using a THA phantom and clinical precision of patients with THA, considering a clinically relevant precision at the 95% repeatability limit to be 0.2 mm. Methods: An experimental THA phantom with movable stem and a fixed cup with a plastic liner was constructed to simulate progressive 3D liner wear. Series of 11 pairs of radiographs with 50 μm femoral movement in between were obtained for each 3D axis in EOS. 30 patients with a THA were scanned twice using EOS to assess precision. Model-based radiostereometric analysis (RSA) was used for wear measurement. Results: The mean difference (true minus simulated wear) with standard deviation (SD) and 95% limits of agreement for experimental THA wear were 0.005 (0.037) and [–0.069 to 0.079] mm for the vertical (y) axis. The mean (SD) and 95% repeatability limit for precision for clinical measurement were –0.029 (0.105) and 0.218 mm. Conclusion: Experimental THA liner wear using EOS was within clinically relevant tolerances and without bias. The clinical precision was just outside our defined clinically relevant precision. Compared with conventional RSA, EOS is less accurate and precise but may still be of value for certain clinical applications, provided larger sample size or longer follow-up are available.

Background and purpose: Dislocation is a severe complication following total hip arthroplasty (THA). Hip precautions have been recommended in the initial postoperative period but evidence supporting this practice is limited. We therefore conducted a population-based study to evaluate the association between discontinuing recommending postoperative hip precautions and the risk of early dislocation. Methods: This is a cohort study with data from the Danish Hip Arthroplasty Register and the Danish National Patient Register. We included patients who underwent primary THA for osteoarthritis in 2004–2019 in public hospitals in the Capital Region of Denmark. The cohort was divided into the hip precautions group, comprising patients operated on between 2004 and 2009, and the no-precautions group operated on between 2014 and 2019. The primary outcome was the difference in the absolute risk of dislocation within 3 months post-surgery. The secondary outcome assessed the same risk within 2 years. We evaluated the difference in absolute risk using absolute risk regression (ARR). Results: The cumulative incidence of dislocation within 3 months was 2.9% (confidence interval [CI] 2.5–3.3) in the hip precautions group and 3.5% (CI 3.1–3.9) in the no-precautions group. The risk of dislocation was higher in the no-precautions group but failed to reach statistical significance in the crude (ARR 1.2, CI 0.9–1.6) and multivariate model (ARR 1.4, CI 0.9–2.2). Conclusion: We found a higher but statistically insignificant increase in the risk of early dislocation in the no-precautions group. The lack of significance in the association may be explained by the increased use of 36-mm femoral heads after the guideline revision.

Background and purpose: Dislocations continue to be a serious complication after primary total hip arthroplasty (THA). Our primary aim was to report the “true” incidence of dislocations in Denmark and secondarily to validate a previously developed algorithm designed to identify THA dislocations in the updated version of the Danish National Patient Register (DNPR), based on data from the Danish Hip Arthroplasty Register (DHR). Methods: We included 5,415 primary THAs from the DHR performed from July 1 to December 31, 2019. Version 3 of the DNPR was launched in February 2019, and a combination of data from the DNPR and a comprehensive national review of 1,762 hospital contacts enabled us to identify every dislocation occurring during the 1st year after THA to determine the “true” 1-year incidence of dislocation. The results were presented as proportions with 95% confidence intervals (CI), and validation was performed by calculating sensitivity and predictive values. Results: The “true” 1-year incidence of dislocation was 2.8% (CI 2.4–3.3). Of these, 37% suffered recurrent dislocations during the follow-up period. Between-hospital variation ranged from 0.0% to 9.6%. The algorithm demonstrated a sensitivity close to 95%, while maintaining a positive predictive value of above 94%. Conclusion: The “true” 1-year incidence of dislocation of 2.8% is comparable to earlier findings, and large variation among hospitals continues to be evident. We have proven the algorithm to be valid in the latest DNPR (version 3), enabling it to be employed as a new quality indicator in future annual DHR reports.

Abstract Background Several factors might be associated with risk of dislocating following uncemented hemiarthroplasty (HA) due to femoral neck fracture (FNF). Current evidence is limited with great variance in reported incidence of dislocation (1–15%). Aim of this study was to identify the cumulative incidence of first-time dislocation following HA and to identify the associated risk factors. Method We performed a retrospective cohort study of patients receiving an HA (BFX Biomet stem, posterior approach) at Copenhagen University Hospital, Bispebjerg, in 2010–2016. Patients were followed until death or end of study (dec 2018). Dislocation was identified by code extraction from the Danish National Patient Registry. Variables included in the multivariate model were defined pre-analysis to include: age, sex and variables with a p-value

Background and purpose: Length of hospital stay after hip and knee arthroplasty is about 1 day in Denmark with few patients discharged on the day of surgery. Hence, a protocol for multicenter implementation of discharge on day of surgery has been instituted. We aimed to describe the implementation of outpatient hip and knee arthroplasty in a multicenter public healthcare setting. Methods: We performed a prospective multicenter study from 7 public hospitals across Denmark. Patients were screened using well-defined in- and exclusion criteria and were discharged on day of surgery when fulfilling functional discharge criteria. The study period was from September 2022 to February 2023 with variable start of implementation. Data from the same centers in a 6-month period before the COVID pandemic from July 2019 to December 2019 was used for baseline control. Results: Of 2,756 primary hip and knee arthroplasties, 37% (95% confidence interval [CI] 35–39) were eligible (range 21–50% in centers) and 52% (range 24–62%) of these were discharged on day of surgery. 21% (CI 20–23) of all patients (eligible and non-eligible) were discharged on day of surgery with a range of 10–31% within centers. This was an additional 15% (CI 13–17, P < 0.001) compared with patients discharged in the control period (6% in 2019). Conclusion: We found it possible to perform outpatient hip and knee replacement in 21% of patients in a public healthcare setting, probably to be increased with further center experience.

Introduction Perioperative glycaemic control is important. However, the complexity of guidelines for perioperative diabetes management is complicated due to different and novel antihyperglycaemic medications, limited procedure-specific data and lack of data from implemented fast-track regimens which otherwise are known to reduce morbidity and glucose homeostasis disturbances. Consequently, outcome in patients with diabetes mellitus (DM) after surgery and the influence of perioperative diabetes management on postoperative recovery remains poorly understood.Methods and analysis A prospective observational multicentre study involving 8 arthroplasty centres across Denmark with a documented implemented fast-track programme (median length of hospitalisation (LOS) 1 day). We will collect detailed perioperative data including preoperative haemoglobin A1c and antidiabetic treatment in 1400 unselected consecutive patients with DM undergoing hip and knee arthroplasty from September 2022 to December 2025, enrolled after consent. Follow-up duration is 90 days after surgery. The primary outcome is the proportion of patients with DM with LOS >4 days and 90-day readmission rate after fast-track total hip arthroplasty (THA), total knee arthroplasty (TKA) and unicompartmental knee arthroplasty (UKA). The secondary outcome is the association between perioperative diabetes treatment and LOS >2 days, 90-day readmission rate, other patient demographics and Comprehensive Complication Index for patients with DM after THA/TKA/UKA in a fast-track regimen.Ethics and dissemination The study will follow the principles of the Declaration of Helsinki and ICH-Good Clinical Practice guideline. Ethical approval was not necessary as this is a non-interventional observational study on current practice. The trial is registered in the Region of Southern Denmark and on ClinicalTrials.gov. The main results and all substudies of this trial will be published in peer-reviewed international medical journals.Trial registration number NCT05613439.

Minimal joint space width (mJSW) is a radiographic measurement used in the diagnosis of hip osteoarthritis. A large variance when measuring mJSW highlights the need for a supporting diagnostic tool. This study aimed to estimate the reliability of a deep learning algorithm designed to measure the mJSW in pelvic radiographs and to estimate agreement between the algorithm and orthopedic surgeons, radiologists, and a reporting radiographer. The algorithm was highly consistent when measuring mJSW with a mean difference at 0.00. Human readers, however, were subject to variance with a repeatability coefficient of up to 1.31. Statistically, although not clinically significant, differences were found between the algorithm’s and all readers’ measurements with mean measured differences ranging from −0.78 to −0.36 mm. In conclusion, the algorithm was highly reliable, and the mean measured difference between the human readers combined and the algorithm was low, i.e., −0.5 mm bilaterally. Given the consistency of the algorithm, it may be a useful tool for monitoring hip osteoarthritis.

With the implementation of the new MDR 2017/745 by the European Parliament, more robust clinical and pre-clinical data will be required due to a more stringent approval process. The EFORT Implant and Patient Safety Initiative WG1 ‘Introduction of Innovation’, combined knowledge of orthopaedic surgeons, research institutes, orthopaedic device manufacturers, patient representatives and regulatory authorities to develop a comprehensive set of recommendations for the introduction of innovations in joint arthroplasty within the boundaries of MDR 2017/745. Recommendations have been developed to address key questions about pre-clinical and clinical requirements for the introduction of new implants and implant-related instrumentation with the participation of a steering group, invited by the EFORT Board in dialogue with representatives from European National Societies and Speciality Societies. Different degrees of novelty and innovation were described and agreed on in relation to when surgeons can start, using implants and implant-related instrumentation routinely. Before any clinical phase of a new implant, following the pre-market clinical investigation or the equivalent device PMCF pathway, it is a common understanding that all appropriate pre-clinical testing (regulatory mandatory and evident state of the art) – which has to be considered for a specific device – has been successfully completed. Once manufacturers receive the CE mark for a medical device, it can be used in patients routinely when a clinical investigation has been conducted to demonstrate the conformity of devices according to MDR Article 62 or full equivalence for the technical, biological and clinical characteristics has been demonstrated (MDR, Annex XIV, Part A, 3.) and a PMCF study has been initiated.

The objectives of the 1st EFORT European Consensus on ‘Medical and Scientific Research Requirements for the Clinical Introduction of Artificial Joint Arthroplasty Devices’ were foremost to focus on patient safety by establishing performance requirements for medical devices. The 1st EFORT European Consensus applied an a priori-defined, modified Delphi methodology to produce unbiased, high-quality recommendation statements, confirmed by consensus voting of a European expert panel. Intended key outcomes are practical guidelines justified by the current stage of knowledge and based on a broad European Expert Consensus, to maintain innovation and optimisation of orthopaedic devices within the boundaries of MDR 2017/745. Twenty-one main research areas of relevance were defined relying on input from the EFORT IPSI WG1 ‘Introduction of Innovation’ recommendations and a related survey. A modified Delphi approach with a preparatory literature review and work in small groups were used to prepare answers to the research questions in the form of 32 draft Consensus statements. A Consensus Conference in a hybrid format, on-site in the Carl Gustav Carus University of Dresden was organised to further refine the draft statements and define consensus within the complete group of participants by final voting, intended to further quantify expert opinion knowledge. The modified Delphi approach provides practical guidelines for hands-on orientation for orthopaedic surgeons, research institutes and laboratories, orthopaedic device manufacturers, patient representatives, Notified Bodies, National Institutes and authorities. For the first time, initiated by the EFORT IPSI (WG1 ‘Introduction of Innovation’), knowledge of all related stakeholders was combined in the 1st EFORT European Consensus to develop guidelines and result in a comprehensive set of recommendations.

Purpose We aimed to illuminate the lived experiences and the path of recovery for adults sustaining a hip fracture before the age of 60. Methods Participants were purposively sampled from a prospective multicenter cohort study in Sweden and Denmark, and narrative interviews were conducted with 19 individuals 0.7–3.5 years after the fracture. We used a phenomenological hermeneutic method to describe the participants’ expressed essential meaning. Results The experience of sustaining a hip fracture was expressed as a painful and protracted process of regaining self-confidence, function, and independence. It also implied a sense of growing old from one day to the next. Participants were afraid of new falls and fractures, resulting in an increased wariness. When expressing fears and persisting symptoms, participants described being neglected and marginalized by the healthcare system, which was perceived as non-receptive and routinely driven by a notion that hip fractures affect only the elderly. Rehabilitation targeted towards needs different from those of elderly individuals was requested. Conclusion The lived experience of sustaining a hip fracture in individuals under 60 includes substantial challenges in everyday life, even up to 3.5 years after the injury. Rehabilitation pathways tailored to the needs of younger patients are requested.

Introduction A feared complication after total hip arthroplasty (THA) is prosthetic joint infection (PJI), associated with high morbidity and mortality. Prophylactic antibiotics can reduce the risk of PJI. However, there is no consensus on the dosages and current recommendations are based on a low evidence level. The objective is to compare the effect of a single versus multiple doses of prophylactic antibiotics administered within 24 hours on PJI.Methods and analysis The study is designed as a cross-over, cluster randomised, non-inferiority trial. All clinical centres use both antibiotic practices (1 year of each intervention). All Danish orthopaedic surgery departments will be involved: Based on quality databases, 2-year cohorts of approximately 20 000 primary THAs conducted at 39 public and private hospitals, will be included. Inclusion criteria: age ≥18 years, all indications for THA except patients operated due to acute or sequelae from proximal femoral or pelvic fractures or bone tumour or metastasis. The primary outcome is PJI within 90 days after primary THA. Secondary outcomes include (1) serious adverse events, (2) potential PJI, (3) length of hospitalisation stay, (4) cardiovascular events, (5) hospital-treated infections, (6) community-based antibiotic use, (7) opioid use and (8) use of acetaminophen and non-steroidal anti-inflammatory drugs. All outcome measures will be extracted from national databases. Analyses will be based on the intention-to-treat population. Non-inferiority will be shown if the upper limit of the two-sided 95% CI for the OR is less than 1.32 for the single dose as compared with multiple doses. The results will establish best practice on antibiotic prophylaxis dosages in the future.Ethics and dissemination This study has been approved by Committees on Health Research Ethics for The Capital Region of Denmark (21069108) and The Danish Medicines Agency (2021091723). All results will be presented in peer-reviewed medical journals and international conferences.Trial registration number NCT05530551.

Background and purpose: The incidence of periprosthetic joint infection after total hip arthroplasty (THA) may be increasing. We performed time-trend analyses of risk, rates, and timing of revision due to infection after primary THAs in the Nordic countries from the period 2004–2018. Patients and methods: 569,463 primary THAs reported to the Nordic Arthroplasty Register Association from 2004 to 2018 were studied. Absolute risk estimates were calculated by Kaplan–Meier and cumulative incidence function methods, whereas adjusted hazard ratios (aHR) were assessed by Cox regression with the first revision due to infection after primary THA as primary endpoint. In addition, we explored changes in the time span from primary THA to revision due to infection. Results: 5,653 (1.0%) primary THAs were revised due to infection during a median follow-up time of 5.4 (IQR 2.5–8.9) years after surgery. Compared with the period 2004–2008, the aHRs for revision were 1.4 (95% confidence interval [CI] 1.3–1.5) for 2009–2013, and 1.9 (CI 1.7–2.0) for 2014–2018. The absolute 5-year rates of revision due to infection were 0.7% (CI 0.7–0.7), 1.0% (CI 0.9–1.0), and 1.2% (CI 1.2–1.3) for the 3 time periods respectively. We found changes in the time span from primary THA to revision due to infection. Compared with 2004–2008, the aHR for revision within 30 days after THA was 2.5 (CI 2.1–2.9) for 2009–2013, and 3.4 (CI 3.0–3.9) for 2013–2018. The aHR for revision within 31–90 days after THA was 1.5 (CI 1.3–1.9) for 2009–2013, and 2.5 (CI 2.1–3.0) for 2013–2018, compared with 2004–2008. Conclusion: The risk of revision due to infection after primary THA almost doubled, both in absolute cumulative incidence and in relative risk, throughout the period 2004–2018. This increase was mainly due to an increased risk of revision within 90 days of THA. This may reflect a “true” increase (i.e., frailer patients or more use of uncemented implants) and/or an “apparent” increase (i.e., improved diagnostics, changed revision strategy, or completeness of reporting) in incidence of periprosthetic joint infection. It is not possible to disclose such changes in the present study, and this warrants further research.

Background and purpose: The bearings with the best survivorship for young patients with total hip arthroplasty (THA) should be identified. We compared hazard ratios (HR) of revision of primary stemmed cementless THAs with metal-on-metal (MoM), ceramic-on-ceramic (CoC), and ceramic-on-highly-crosslinked-polyethylene (CoXLP) with that of metal-on-highly-crosslinked-polyethylene (MoXLP) bearings in patients aged 20–55 years with primary osteoarthritis or childhood hip disorders. Patients and methods: From the Nordic Arthroplasty Register Association dataset we included 1,813 MoM, 3,615 CoC, 5,947 CoXLP, and 10,219 MoXLP THA in patients operated on between 2005 and 2017 in a prospective cohort study. We used the Kaplan–Meier estimator for THA survivorship and Cox regression to estimate HR of revision adjusted for confounders (including 95% confidence intervals [CI]). MoXLP was used as reference. HRs were calculated during 3 intervals (0–2, 2–7, and 7–13 years) to meet the assumption of proportional hazards. Results: Median follow-up was 5 years for MoXLP, 10 years for MoM, 6 years for CoC, and 4 years for CoXLP. 13-year Kaplan–Meier survival estimates were 95% (CI 94–95) for MoXLP, 82% (CI 80–84) for MoM, 93% (CI 92–95) for CoC, and 93% (CI 92–94) for CoXLP bearings. MoM had higher 2–7 and 7–13 years’ adjusted HRs of revision (3.6, CI 2.3–5.7 and 4.1, CI 1.7–10). MoXLP, CoC, and CoXLP had similar HRs in all 3 periods. The 7–13-year adjusted HRs of revision of CoC and CoXLP were statistically non-significantly higher. Conclusion: In young patients, MoXLP for primary cementless THA had higher revision-free survival and lower HR for revision than MoM bearings. Longer follow-up is needed to compare MoXLP, CoC, and CoXLP.

Background and purpose: Previous studies on hip survival following periacetabular osteotomy (PAO) have reported isolated data for the treatment of 1 underlying condition, making comparison between patient groups difficult. We report the hip survival after PAO in patients with acetabular dysplasia (AD), acetabular retroversion (AR), congenital dislocation of the hip (CDH), and Legg-Calvé-Perthes disease (LCPD) with total hip arthroplasty (THA) as primary endpoint and secondarily the risk of subsequent hip-related operations other than THA. Patients and methods: From 1997 to December 2021, 1,501 hips (1,203 patients) underwent PAO in a single center (Odense University Hospital). We identified conversions to THA and other subsequent hip-related operations through patient files and the Danish National Patient Registry (DNPR). Results: 123 (8.2%) of the total cohort of 1,501 hips were converted to THA within the study period. The overall Kaplan–Meier hip survival rate was 71% (95% confidence interval [CI] 61–79) at 24 years with a mean follow-up of 7.6 years (range 0.02–25). The individual Kaplan–Meier hip survival rates at 15 years were 81% (CI 76–86) for AD, 94% (CI 91–96) for AR, 84% (CI 66–93) for CDH, and 66% (CI 49–79) for LCPD. In total, the overall risk of additional hip-related operations was 48% (of which 92% were screw removal). Conclusion: Encouragingly, 71% of hips were preserved 24 years after PAO. We found that AR patients had the highest (94%) PAO survivorship at 15 years compared with the other underlying hip conditions. Almost half of PAO patients may undergo later additional surgery, of which screw removal is the primary intervention. Overall long-term survival, risk factors for conversion to THA, and risk of additional surgery are relevant information for shared decision-making.

Objective To explore patient, clinician and decision-maker perceptions on a clinical trial evaluating the effectiveness of total hip arthroplasty (THA) compared with exercise to inform the trial protocol.Design This is an exploratory qualitative case study using a constructivist paradigm.Setting and participants Participants were enrolled into three key stakeholder groups: patients eligible for THA, clinicians, and decision makers. Focus group interviews were conducted in undisturbed conference rooms at two hospitals in Denmark, according to group status using semi-structured interview guides.Analysis Interviews were recorded, transcribed verbatim and thematic analysed using an inductive approach.Results We conducted 4 focus group interviews with 14 patients, 1 focus group interview with 4 clinicians (2 orthopaedic surgeons and 2 physiotherapists) and 1 focus group interview with 4 decision-makers. Two main themes were generated. ‘Treatment expectations and beliefs impact management choices’ covered three supporting codes: Treatment without surgery is unlikely to lead to recovery; Clinician authority impacts the management narrative; The ‘surgery vs exercise’ debate. ‘Factors influencing clinical trial integrity and feasibility’ highlighted three supporting codes: Who is considered eligible for surgery?; Facilitators and barriers for surgery and exercise in a clinical trial context; Improvements in hip pain and hip function are the most important outcomes.Conclusions Based on key stakeholder treatment expectations and beliefs, we implemented three main strategies to improve the methodological rigorousness of our trial protocol. First, we added an observational study investigating the generalisability to address a potential low enrolment rate. Second, we developed an enrolment procedure using generic guidance and balanced narrative conveyed by an independent clinician to facilitate communication of clinical equipoise. Third, we adopted change in hip pain and function as the primary outcome. These findings highlight the value of patient and public involvement in the development of trial protocols to reduce bias in comparative clinical trials evaluating surgical and non-surgical management.Trial registration number NCT04070027 (pre-results).

Background and purpose: Hip precautions are routinely prescribed to patients with osteoarthritis to decrease dislocation rates after total hip arthroplasty (THA) using a posterior approach. However, recommendations have been based on very low certainty of evidence. We updated the evidence on the influence of hip precautions on early recovery following THA by this systematic review. Materials and methods: We performed systematic searches for randomized controlled trials (RCT) and non-randomized (NRS) studies in MEDLINE, Embase, PEDro, and CINAHL published from 2016 to July 2022. 2 reviewers independently included studies comparing postoperative precautions with minimal or no precautions, extracted data, and assessed the risk of bias. Random effects meta-analyses were used to synthesize the results. The certainty of the evidence was rated by the Grading of Recommendations Assessment and Evaluation approach. The critical outcome was the risk of hip dislocations within 3 months of surgery. Other outcomes were long-term risk of dislocation and reoperation, self-reported and performance-based assessment of function, quality of life, pain, and time to return to work. Results: 4 RCTs and 5 NRSs, including 8,835 participants, were included. There may be no or negligible difference in early hip dislocations (RCTs: risk ratio [RR] 1.8, 95% confidence interval [CI] 0.6–5.2; NRS: RR 0.9, CI 0.3–2.5). Certainty in the evidence was low for RCTs and very low for NRSs. Finally, precautions may reduce the performance-based assessment of function slightly, but the evidence was very uncertain. For all other outcomes, no differences were found (moderate to very low certainty evidence). Conclusion: The current evidence does not support routinely prescribing hip precautions post-surgically for patients undergoing THA to prevent hip dislocations. However, the results might change with high-quality studies.

Background and purpose: Little is known on the use of metal artifact reduction sequence (MARS) MRI to diagnose osteonecrosis of the femoral head (ONFH) after fixation of femoral neck fractures (FNF) with conventional metal implants present. We compared MARS MRI with radiography in diagnosing ONFH. Secondarily, we determined whether signs of ONFH on MARS MRI correlate with patient-reported outcomes (PROs) via Oxford Hip Score (OHS) and pain (VAS). Patients and methods: 30 adults under 60 years treated with internal fixation after FNF were prospectively included (2015–2018) at 2 hospitals. They were followed up with radiography and PROs at 4, 12, and 24 months and MARS MRI at 4 and 12 months. OHS < 34 or VAS pain > 20 was considered significant. Results: At 12 months, 14 patients had a pathological MRI. 3 of 14 had ONFH on radiographs at 12 months, increasing to 5 at 24 months, and 4 had unfavorable PROs. 2 of 5 patients with ONFH signs on both MRI and radiography had unfavorable PROs. 1 of 10 patients with normal MRI and radiography had unfavorable 2-year PROs. 4 patients had inconsistent MRI results, of which 1 developed ONFH. 1 patient dropped out. Conclusion: Information from a pathological MRI was not useful, as a majority remained free from symptoms and ONFH signs on radiographs. Furthermore, PROs did not correlate with imaging results. MARS MRI findings must be better understood before being taken into clinical practice. However, a normal MARS MRI seems to be a good prognostic finding.

Background and purpose: Limited data exists on the implementation process and safety of discharge on the day of surgery after primary hip and knee arthroplasty in a multicenter setting. We report our study protocol on the investigation of the feasibility, safety, and socioeconomic aspects following discharge on day of surgery after hip and knee arthroplasty across 8 fast-track centers. Patients and methods: This is a study protocol for a prospective cohort study on discharge on day of surgery from the Center for Fast-track Hip and Knee Replacement. The collaboration includes 8 centers covering 40% of the primary hip and knee arthroplasty procedures undertaken in Denmark. All patients scheduled for surgery are screened for eligibility using well-defined inclusion and exclusion criteria. Eligible patients fulfilling discharge criteria will be discharged on day of surgery. We expect to screen 9,000 patients annually. Duration and outcome: Patients will be enrolled over a 3-year period from September 2022 and reporting of results will run continuously until December 2025. We shall report the proportion of eligible patients and patients discharged on day of surgery as well as limiting factors. Readmissions and complications within 30 days are recorded with real-time follow-up by research staff. Furthermore, patient-reported information on willingness to repeat discharge on day of surgery, contacts with the healthcare system, complications, and workability is registered 30 days postoperatively. EQ-5D, Oxford Knee Score, and Oxford Hip Score are completed preoperatively and after 3 months and 1 year. Finally, outcome data will be used in the development of a prediction model for successful discharge on the day of surgery.

Background and purpose: Joint stability after hip replacement (HR) in patients with metastatic bone disease (MBD) is of special importance. Dislocation is the second leading cause of implant revision in HR, while survival after MBD surgery is poor with an expected 1-year survival of around 40%. As few studies have investigated the dislocation risk across different articulation solutions in MBD, we conducted a retrospective study on primary HR for patients with MBD treated in our department. Patients and methods: The primary outcome is the 1-year cumulative incidence of dislocation. We included patients with MBD who received HR at our department in 2003–2019. We excluded patients with partial pelvic reconstruction, total femoral replacement, and revision surgery. We assessed the incidence of dislocation with competing risk analysis with death and implant removal as competing risks. Results: We included 471 patients. Median follow-up was 6.5 months. The patients received 248 regular total hip arthroplasties (THAs), 117 hemiarthroplasties, 70 constrained liners, and 36 dual mobility liners. Major bone resection (MBR), defined as resection below the lesser trochanter, was performed in 63%. The overall 1-year cumulative incidence of dislocation was 6.2% (95% CI 4.0–8.3). Dislocation stratified by articulating surface was 6.9% (CI 3.7–10) for regular THA, 6.8% (CI 2.3–11) for hemiarthroplasty, 2.9% (CI 0.0–6.8) for constrained liner, and 5.6% (CI 0.0–13) for dual mobility liners. There was no significant difference between patients with and without MBR (p = 0.5). Conclusion: The 1-year cumulative incidence of dislocation is 6.2% in patients with MBD. Further studies are needed to determine any real benefits of specific articulations on the risk of postoperative dislocation in patients with MBD.

Abstract Background The Oxford Hip Score is used to evaluate the outcome after total hip arthroplasty. The Oxford Hip Score was developed more than 20 years ago with only some degree of patient involvement. We question if the Oxford Hip Score is still relevant for the present-day total hip artrhoplasty patients. We aimed to determine whether the Oxford Hip Score contains items that are relevant for present-day patients with osteoarthritis undergoing total hip arthroplasty, thus investigating the content validity. Methods Patients aged 60–75 years, undergoing total hip arthroplasty for primary osteoarthritis were recruited to participate in focus group interviews preoperatively and at 3 and 12 months after primary total hip arthroplasty. We conducted 6 focus group interviews in which 30 patients participated. The interviews were audio-recorded and transcribed verbatim. Using Interpretative Phenomenological Analysis, we inductively organised the interview transcripts into particular items/themes which we then compared to items in the Oxford Hip Score. Results We identified 6 general items with 41 sub-items. The 6 general items were pain, walking, physical activities, functional abilities, quality of life and psychological health. We found that items in the Oxford Hip Score were all in some way relevant to the patients but that the Oxford Hip Score lacks several important items relevant for present-day total hip artrhoplasty patients, including several physical activities, functional abilities and certain aspects of quality of life and psychological health. Conclusion We found that the Oxford Hip Score lacks important items for present-day patients in our population. Due to findings regarding several additional items that are not present in the Oxford Hip Score, particularly concerning physical activities and quality of life, we question the content validity of the Oxford Hip Score for a present-day population. Our findings indicate a need for a revision of the Oxford Hip Score.

Background and purpose — Socioeconomic inequality in health is recognized as an important public health issue. We examined whether socioeconomic status (SES) is associated with revision and mortality rates after total hip arthroplasty (THA) within 90 and 365 days. Patients and methods — We obtained SES markers (cohabitation, education, income, and liquid assets) on 103,901 THA patients from Danish health registers (year 1995–2017). The outcomes were any revision (all revisions), specified revision (due to infection, fracture, or dislocation), and mortality. We used Cox regression analysis to estimate adjusted hazard ratio (aHR) of each outcome with 95% confidence interval (CI) for each SES marker. Results — Within 90 days, the aHR for any revision was 1.3 (95% CI 1.1–1.4) for patients living alone vs. cohabiting. The aHR was 2.0 (CI 1.4–2.6) for low-income vs. high-income among patients < 65 years. The aHR was 1.2 (CI 0.9–1.7) for low liquid assets among patients > 65 years. Results were consistent for any revision within 365 days as well as for revisions due to infection, fracture, and dislocation. The aHR for mortality was 1.4 (CI 1.2–1.6) within 90 days and 1.3 (CI 1.2–1.5) within 365 days for patients living alone vs. cohabiting. Low education, low income, and low liquid assets were associated with increased mortality rate within both 90 and 365 days. Interpretation — Our results suggest that living alone, low income, and low liquid assets were associated with increased revision and mortality up to 365 days after THA surgery. Optimizing medical conditions prior to surgery and implementing different post-THA support strategies with a focus on vulnerable patients may reduce complications associated with inequality.

Background and purpose — Hip dysplasia in adults is a deformity in which the acetabulum inadequately covers the femoral head. The prevalence is sparingly described in the literature. We investigated the prevalence in Malmö (Sweden) and assessed whether the condition was recognized in the radiology reports. Subjects and methods — All pelvic radiographs performed in Malmö during 2007–2008 on subjects aged 20–70 years with a Swedish personal identity number were assessed. 1,870 digital radiographs were eligible for analysis. The lateral center-edge angle (LCEA) and acetabular index angle (AIA) were measured. Hip dysplasia was defined as an LCEA ≤ 20°. Intraclass correlation coefficients (ICC) for intra-observer measurements ranged from 0.87 (AIA, 95% CI 0.78–0.93) to 0.98 (LCEA, CI 0.97–0.99). Results — The prevalence of hip dysplasia (LCEA ≤ 20°) was 5.2% (CI 4.3–6.3), (98/1,870). There was no statistically significant difference between the sexes for either prevalence of hip dysplasia or mean LCEA. The mean AIA was 0.9° (CI 0.3–1.3) higher in men (4.1 SD 5.5) compared with women (3.2 SD 5.4). The radiologists had reported hip dysplasia in 7 of the 98 cases. Interpretation — The prevalence of hip dysplasia in Malmö (Sweden) is similar to previously reported data from Copenhagen (Denmark) and Bergen (Norway). Our results indicate that hip dysplasia is often overlooked by radiologists, which may influence patient treatment.

Background and purpose: There are concerns that bleeding following primary total hip arthroplasty (THA) contributes to prolonged wound drainage and prosthetic joint infection (PJI). We examined whether short (1–5 days), medium (6–14 days), and extended (≥ 15 days) duration of thromboprophylaxis is associated with the 5-year revision rate after THA due to osteoarthritis. Patients and methods: We performed a cohort study based on data from hip arthroplasty and administrative registries in Denmark and Norway (2008–2014). The outcome was revision surgery due to PJI, aseptic loosening or any cause, and patient mortality. Adjusted cause-specific hazard ratios (HRs) were analyzed with Cox regression analyses. Results: Among 50,482 THA patients, 8,333 received short, 17,009 received medium, and 25,140 received extended thromboprophylaxis. The HRs for revision due to PJI within 5 years were 1.0 (95%CI 0.7–1.3) and 1.1 (CI 0.9–1.3) for short and extended vs. medium treatment, whereas HR for extended vs. medium prophylaxis was 1.5 (CI 1.2–2.0) within 3 months. The HRs for revision due to aseptic loosening within 5 years were 1.0 (CI 0.7–1.4) and 1.1 (CI 0.9–1.4) for short and extended vs. medium treatment. The HRs for any revision within 5 years were 0.9 (CI 0.8–1.1) and 0.9 (CI 0.8–1.0) for short and extended vs. medium treatment. Extended vs. medium prophylaxis was associated with a decreased 0–3 month mortality. The absolute differences at 5 years were ≤ 1%. Conclusion: Our data suggests no association between duration of anticoagulant thromboprophylaxis and revision rate within 5 years of primary THA. The extended thromboprophylaxis might be associated with early increased revision rate due to PJI but also with lower mortality; however, the clinical relevance of this finding requires further research.

Background and purpose: Patients receiving a total hip arthroplasty (THA) are subsequently at an increased risk of cardiovascular disease (CVD). Further, socioeconomic status (SES) has an effect on CVD. We evaluated whether low SES is associated with a higher risk of readmission due to CVD after THA within 90 days in a setting with universal tax-supported healthcare. Patients and methods: We performed a nationwide population-based cohort study using Danish health registries from 1995 to 2017. Individual-based information on SES markers (cohabitation, education, income, and liquid assets) was obtained for all participants. The outcome was any hospital-treated CVD. The data was transformed using the pseudo-observation method to enable an estimation of the adjusted risk ratios (RRs) with 95% confidence intervals (CI) for each marker using generalized linear regression. Results: Among 103,286 THA patients, 452 were hospitalized with CVD within 90 days after surgery. Low SES seemed to be associated with a small increased risk of CVD, as the RRs for any CVD were 1.1 (95% CI 0.7–1.7) for patients living alone vs. cohabiting, 1.3 (CI 0.7– .3) for low education vs. high, 1.4 (CI 0.8–2.6) for low income vs. high, and 1.3 (CI 0.8–2.1) for low liquid assets vs. high. Conclusion: Living alone, low education, low income, and low liquid assets seem to be associated with a small increased risk of readmission due to CVD 90 days after THA. Wide confidence intervals in risk should be considered when interpreting the study results.

Introduction Multimodal analgesia with paracetamol, non-steroidal anti-inflammatory drug and glucocorticoid is recommended for hip arthroplasty, but with uncertain effects of the different combinations. We aim to investigate benefit and harm of different combinations of paracetamol, ibuprofen and dexamethasone following total hip arthroplasty.Methods and analysis RECIPE is a randomised, placebo-controlled, parallel 4-group, blinded trial with 90-day and 1-year follow-up performed at nine Danish hospitals. Interventions are initiated preoperatively and continued for 24 hours postoperatively. Eligible participants undergoing total hip arthroplasty are randomised to:group A: oral paracetamol 1000 mg × 4+oral ibuprofen 400 mg × 4+intravenous placebo; group B: oral paracetamol 1000 mg × 4+intravenous dexamethasone 24 mg+oral placebo; group C: oral ibuprofen 400 mg × 4+intravenous dexamethasone 24 mg+oral placebo; group D: oral paracetamol 1000 mg × 4+oral ibuprofen 400 mg × 4+intravenous dexamethasone 24 mg.Primary outcome is cumulative opioid consumption at 0–24 hours. Secondary outcomes are pain at rest, during mobilisation and during a 5 m walk and adverse events. Follow-up includes serious adverse events and patient reported outcome measures at 90 days and 1 year. A total of 1060 participants are needed to demonstrate a difference of 8 mg in 24-hour morphine consumption assuming an SD of 24.5 mg, a risk of type I errors of 0.0083 and a risk of type 2 errors of 0.2. Primary analysis will be a modified intention-to-treat analysis.With this trial we aim to verify recommendations for pain treatment after total hip arthroplasty, and investigate the role of dexamethasone as an analgesic adjuvant to paracetamol and ibuprofen.Ethics and dissemination This trial is approved by the Region Zealand Committee on Health Research Ethics (SJ-799). Plans for dissemination include publication in peer-reviewed journals and presentation at scientific meetings.Trial registration number NCT04123873.

Objectives: We quantify 3-D microarchitectural properties of femoral head cancellous bones from patients with rheumatoid arthritis (RA, n ​= ​12), osteoarthritis (OA, n ​= ​15), osteoporosis (OP, n ​= ​24), or donor controls (CNT, n ​= ​8); and investigate their rod- and plate-like trabecular morphometric properties of trabecular bone tissues and compare these properties between them. Methods: Femoral heads were harvested during total hip replacement surgeries or collected from donors. Four cubic cancellous bone samples produced from each femoral head were micro-CT scanned to quantify their microarchitectural and rod- and plate-like trabecular properties. The samples were then tested in compression to determine mechanical properties. Results: The microarchitectural properties of femoral head cancellous bone revealed significant differences among the 4 groups, but not between RA and OA. Bone volume fraction was significantly greater in the RA and the OA than in the OP and the CNT. Structure model index was significantly lower in the RA and the OA than in the OP. Number of rods in the RA was significantly greater than in the other 3 groups. Number of plates and plate volume density in the RA and the OA were significantly greater than in the OP and the CNT. Mechanical properties were significantly greater in the RA and the OA than in the OP. The single best determinant for mechanical properties was bone volume fraction. Conclusions: This study demonstrates significant differences in 3-D microarchitectural properties and rod- and plate-like trabecular morphometric properties among patients with RA, OA, or OP. The RA and OA cancellous bones displayed similar patterns of microarchitectural degeneration and pronounced different microarchitectures from the OP. The OP group revealed the weakest cancellous bone strength, while the RA and OA groups exhibited a compensatory effect that maintains bone tissues, and hence mechanical properties. The translational potential of this article: The study enhances the understanding of microarchitectural degeneration of diseased cancellous bone. The OP group had the weakest cancellous bone strength, while the RA and OA groups exhibited a compensatory effect that maintains bone tissues, and hence mechanical properties. These results are particularly important for design and survival of joint prosthesis.

Abstract Background Several malreduction criteria have been proposed for ankle surgery, but the criteria of most importance for functional outcome remain undetermined. Furthermore, the acute inflammatory response in the ankle joint after fracture is hypothesized to result in osteoarthritis development, but no study has investigated the correlation between the levels of these inflammatory cytokines and post-surgical functional outcomes. We aimed to identify malreduction criteria and inflammatory cytokines associated with functional outcome after ankle surgery. Methods During surgery, synovial fluid from the fractured and healthy contralateral ankles of 46 patients was collected for chemiluminescence analysis of 22 inflammatory cytokines and metabolic proteins. The quality of fracture reduction was based on 9 criteria on plain X-rays and 5 criteria on weight-bearing computed tomography (WBCT) scans. After 3 and 12 months, we recorded scores on American Orthopedic Foot and Ankle Society (AOFAS) scale, the Danish version of Foot Function Index (FFI-DK), EQ-5D-5L index score, the Kellgren-Lawrence score, and joint space narrowing. Results Tibiofibular (TF) overlap (p = 0.02) and dime sign (p = 0.008) correlated with FFI-DK. Tibiotalar tilt correlated positively with joint space narrowing at 3 months (p = 0.01) and 12 months (p = 0.03). TF widening correlated with FFI-DK (p = 0.04), AOFAS (p = 0.02), and EQ-5D-5L (p = 0.02). No consistent correlations between synovial cytokine levels and functional outcomes were found at 12 months. Conclusions Malreduction of TF overlap, TF widening, and tibiotalar tilt were the most important criteria for functional outcome after ankle surgery. Increased inflammatory cytokine levels after fracture did not affect functional outcome at 12 months. Trial registration This cohort study is registered the 10th of December 2018 at ClinicalTrials.gov ( NCT03769909 ), was approved by the local committee on health ethics (The Regional Committees on Health Research Ethics for Southern Denmark: J.No. S-20170139), and was reported to the National Danish Data Protection Agency (17/28505).

Background and purpose — Dislocation of total hip arthroplasties (THA) is often treated with closed reduction and traditionally not registered in orthopedic registers. This study aimed to create an algorithm designed to identify cases of dislocations of THAs with high sensitivity, specificity, and positive predictive value (PPV) based on codes from the Danish National Patient Register (DNPR). Patients and methods — All patients (n = 31,762) with primary osteoarthritis undergoing THA from January 1, 2010 to December 31, 2014 were included from the Danish Hip Arthroplasty Register (DHR). We extracted available data for every hospital contact in the DNPR during a 2-year follow-up period, then conducted a comprehensive nationwide review of 5,096 patient files to register all dislocations and applied codes. Results — We identified 1,890 hip dislocations among 1,094 of the included 31,762 THAs. More than 70 different diagnoses and 55 procedural codes were coupled to the hospital contacts with dislocation. A combination of the correct codes produced a sensitivity of 63% and a PPV of 98%. Adding alternative and often applied codes increased the sensitivity to 91%, while the PPV was maintained at 93%. Additional steps increased sensitivity to 95% but at the expense of an unacceptable decrease in the PPV to 82%. Specificity was, in all steps, greater than 99%. Interpretation — The developed algorithm achieved high and acceptable values for sensitivity, specificity, and predictive values. We found that surgeons in most cases coded correctly. However, the codes were not always transferred to the discharge summary. In perspective, this kind of algorithm may be used in Danish quality registers.

Background and purpose — Hemiarthroplasty has lower reoperation frequency and better mobilization compared with internal fixation (IF) in patients with undisplaced femoral neck fractures (FNF), which might translate into lower mortality. In this population-based cohort study we compare the risk of mortality and reoperation in undisplaced FNF treated with IF and displaced FNF treated with arthroplasty in patients older than 70 years old. We assume that, per se, there is no difference in mortality risk between patients with a displaced and an undisplaced FNF. Patients and methods — Hip fracture patients were identified in the Danish Multidisciplinary Hip Fracture Registry during 2005–2015. Data on medication, comorbidities, reoperation, and mortality were retrieved from other Danish medical databases. IF and arthroplasty patients were compared with regards to mortality and reoperation up to 5 years postoperatively. We calculated hazard ratios (HR) with 95% confidence intervals (CI) adjusting for relevant confounders. Results — We included 19,260 FNF treated with arthroplasty and 10,337 FNF with IF. There was an increased risk of mortality for arthroplasty within 30 days, HR 1.3 (95% CI 1.3–1.4), compared with IF but not after 1 and 5 years. Arthroplasty patients had adjusted HRs for reoperation of 0.8 (0.8–0.9) within 1 year, 0.8 (0.7–0.9) within 2 years, and 0.8 (0.8–0.9) within 5 years postoperatively compared with IF. Interpretation — Patients treated for a displaced FNF with arthroplasty had a higher risk of 30-day mortality compared with patients who had an undisplaced FNF treated with IF. It has to be considered that there were baseline differences in the groups but there was no difference in mortality risk up to 5 years post-surgery. Concerning reoperation, patients with a displaced FNF treated with arthroplasty had a lower risk of reoperation compared with IF for undisplaced FNF.

Background and purpose: Results regarding the impact of anticoagulants on revision rate are conflicting. We examined the association between the use of low molecular weight heparin (LMWH) or non-vitamin K oral anticoagulants (NOACs) as thromboprophylaxis after primary total hip arthroplasty (THA) and the revision rate due to infection, aseptic loosening, and all causes. Patients and methods: We conducted a cohort study (n = 53,605) based on prospectively collected data from the national hip arthroplasty registries from Denmark and Norway. The outcome was time to revision due to infection, aseptic loosening, and all causes, studied separately. Kaplan–Meier (KM) survival analysis and a Cox proportional hazard model was used to estimate implant survival and cause-specific hazard ratios (HRs) with 95% confidence intervals (CI) adjusting for age, sex, Charlson Comorbidity Index, fixation type, start, and duration of thromboprophylaxis, and preoperative use of Vitamin K antagonists, NOAC, aspirin, and platelet inhibitors as confounders. Results: We included 40,451 patients in the LMWH group and 13,154 patients in the NOAC group. Regarding revision due to infection, the 1-year and 5-year KM survival was 99% in both the LMWH group and in the NOAC group. During the entire follow-up period, the adjusted HR for revision due to infection was 0.9 (CI 0.7–1.1), 1.6 (CI 1.3–2.1) for aseptic loosening, and 1.2 (CI 1.1–1.4) for all-cause revision for the NOAC compared with the LMWH group. The absolute differences in revision rates between the groups varied from 0.2% to 1%. Interpretation: Compared with LMWH, NOACs were associated with a slightly lower revision rate due to infection, but higher revisions rates due to aseptic loosening and all-cause revision. The absolute differences between groups are small and most likely not clinically relevant. In addition, the observed associations might partly be explained by selection bias and unmeasured confounding, and should be a topic for further research.

Background and purpose — Current literature indicates no difference in 90-day mortality after cemented compared with cementless total hip arthroplasty (THA). However, previous studies are hampered by potential selection bias and suboptimal adjustment for comorbidity confounding. Therefore, we examined the comorbidity-adjusted mortality up to 90 days after cemented compared with cementless THA performed due to osteoarthritis. Patients and methods — Using the Nordic Arthroplasty Register Association database, 2005–2013, we included 108,572 cemented and 80,034 cementless THA due to osteoarthritis. We calculated the Charlson comorbidity index of each patient based on data from national patient registers. The Kaplan–Meier method was used to estimate unadjusted all-cause mortality. Cox regression was used to estimate hazard ratios (HR) with 95% confidence intervals (CI) for 14, 30-, and 90-day mortality comparing cemented with cementless THA, adjusting for age, sex, comorbidity, nation, and year of surgery. Results — Cumulative all-cause mortality within 90 days was 0.41% (CI 0.37–0.46) after cemented and 0.26% (CI 0.22–0.30) after cementless THA. The adjusted HR for cemented vs. cementless fixation was 0.97 (CI 0.79–1.2), and similar risk estimates were obtained for mortality within 14 (adjusted HR 0.91 [CI 0.64–1.3]) and 30 days (adjusted HR 0.94 [CI 0.71–1.3]). We found no clinically relevant differences in mortality between cemented and cementless THA in analyses stratified by age, sex, Charlson comorbidity index, or year of surgery. Interpretation — After adjustment for comorbidity as an important confounder, we observed similar early mortality between the 2 fixation techniques.

Background and purpose — Collaborations between arthroplasty registries are important in order to create the possibility of detecting inferior implants early and improve our understanding of differences between nations in terms of indications and outcomes. In this registry study we compared patient and procedure characteristics, and revision rates in the Nordic Arthroplasty Register Association (NARA) database and the Dutch Arthroplasty Register (LROI). Patients and methods — All total hip arthroplasties (THAs) performed in 2010–2016 were included from the LROI (n = 184,862) and the NARA database (n = 290,823), which contains data from Denmark, Norway, Sweden, and Finland. Descriptive statistics and Kaplan–Meier survival analyses based on all reasons for revision and stratified by fixation were performed and compared between countries. Results — In the Netherlands, the proportion of patients aged < 55 years (9%) and male patients (34%) was lower than in Nordic countries (< 55 years 11–13%; males 35–43%); the proportion of osteoarthritis (OA) (87%) was higher compared with Sweden (81%), Norway (77%), and Denmark (81%) but comparable to Finland (86%). Uncemented fixation was used in 62% of patients in the Netherlands, in 70% of patients in Denmark and Finland, and in 28% and 19% in Norway and Sweden, respectively. The 5-year revision rate for THAs for OA was lower in Sweden (2.3%, 95% CI 2.1–2.5) than in the Netherlands (3.0%, CI 2.9–3.1), Norway (3.8%, CI 3.6–4.0), Denmark (4.6%, CI 4.4–4.8), and Finland (4.4%, CI 4.3–4.5). Revision rates in Denmark, Norway, and Finland were higher for all fixation groups. Interpretation — Patient and THA procedure characteristics as well as revision rates evinced some differences between the Netherlands and the Nordic countries. The Netherlands compared best with Denmark in terms of patient and procedure characteristics, but resembled Sweden more in terms of short-term revision risk. Combining data from registries like LROI and the NARA collaboration is feasible and might possibly enable tracking of potential outlier implants.

Background and purpose — In Denmark, all citizens are guaranteed free access to medical care, which should minimize socioeconomic status (SES) inequalities. We examined the association between SES and the utilization of total hip arthroplasty (THA) by age and over time. Patients and methods — Data on education, income, liquid assets, and occupation on 104,055 THA cases and 520,275 population controls were obtained from Danish health registers. We used logistic regression to estimate adjusted odds ratios (aOR) for THA with 95% confidence intervals (CI). Results — Risk (CI) of THA was higher for 45–55-year-olds with lowest vs. highest education (aOR 1.4 [1.3–1.5]), and for those with lowest vs. highest income (aOR 1.1 [1.0–1.2]). The association between education and income and higher risk of THA decreased with increasing age. The risk of THA was lower for persons with lowest vs. highest liquid assets in all age groups and time periods. The risk of THA was higher for persons with lowest education in 1995–2000 (aOR 1.2 [1.1-1.3]), but diminished in 2013–2017 (aOR 1.0 [1.0–1.0]). For those on lowest income there was a higher risk of THA in 1995–2000 (aOR 1.2 [1.1–1.3]), changing to lower risk in 2013–2017 (aOR 0.8 [0.8–0.9]). Interpretation — In a society where all citizens are guaranteed free access to medical care, we observed a social inequality in regard to the risk of THA with a development over time and in relation to age in most of our SES markers, showing a need for more patient involvement by implementing more focused interventions targeted to the most vulnerable patient groups identified as currently living alone, on low income, and with a low level of liquid assets.

Abstract Background Children with cerebral palsy often exhibit an altered gait pattern; however, it is uncertain whether the use of an instrumented gait analysis in interdisciplinary interventions affects the perceived experience of family-centered service (FCS) and/or gross motor function. The aim of this study is to investigate whether individually tailored interdisciplinary interventions, based on an instrumented gait analysis report, has a superior effectiveness on perceived FCS and gross motor function in children with cerebral palsy, compared to ‘care as usual’ without the use of instrumented gait analysis. Furthermore, to investigate potential associations between perceived FCS and gross motor function improvement with the goal of improving future therapy on gross motor function. Method This is a sequel analysis on tertiary outcome measures from a prospective, single blind, randomized, parallel group study including two groups of 30 children aged 5–8 years with spastic cerebral palsy at Gross Motor Function Classification System levels I-II (n = 60). The intervention group underwent a three-dimensional gait analysis, from which a clinical report was written with recommendations on interdisciplinary interventions, such as physical therapy, orthopedic surgery, orthotics or spasticity management. To assess effectiveness on perceived FCS and gross motor function, at baseline, 26 weeks and 52 weeks, the five domains in the Measure of Processes of Care (MPOC-20) (Enabling and partnership, Providing general information, Providing specific information about the child, Respectful and supportive service, and Coordinated and comprehensive care) and the Gross Motor Function Measurement (GMFM-66) were used as outcome measures. Results No significant differences in between-group change scores in any of the five MPOC-20 domains were observed (p = 0.40–0.97). In favor of the intervention group a significantly higher between-group change score in GMFM-66 (mean difference: 3.05 [95%CI: 1.12–4.98], p = 0.003) after 52 weeks was observed. Conclusion The addition of an instrumented gait analysis report to ‘care as usual’ did not improve the parents’ perceptions of FCS in treatment of children with cerebral palsy. However, superior improvement in the GMFM-66 was observed in the intervention group, suggesting meaningful gross motor function improvement. Trial registration Clinical Trials, NCT02160457 . Registered June 10th 2014.

Background and purpose — 32-mm heads are widely used in total hip arthroplasty (THA) in Scandinavia, while the proportion of 36-mm heads is increasing as they are expected to increase THA stability. We investigated whether the use of 36-mm heads in THA after proximal femur fracture (PFF) is associated with a lower risk of revision compared with 32-mm heads. Patients and methods — We included 5,030 patients operated with THA due to PFF with 32- or 36-mm heads from the Nordic Arthroplasty Register Association database. Each patient with a 36-mm head was matched with a patient with a 32-mm head, using propensity score. The patients were operated between 2006 and 2016, with a metal or ceramic head on a polyethylene bearing. Cox proportional hazards models were fitted to estimate the unadjusted and adjusted hazard ratio (HR) with 95% confidence intervals (CI) for revision for any reason and revision due to dislocation for 36-mm heads compared with 32-mm heads. Results — 36-mm heads had an HR of 0.9 (CI 0.7–1.2) for revision for any reason and 0.8 (CI 0.5–1.3) for revision due to dislocation compared with 32-mm heads at a median follow-up of 2.5 years (interquartile range 1–4.4). Interpretation — We were not able to demonstrate any clinically relevant reduction of the risk of THA revision for any reason or due to dislocation when 36-mm heads were used versus 32-mm. Residual confounding due to lack of data on patient comorbidities and body mass index could bias our results.

Background and purpose — The use of cementless total hip arthroplasty (THA) in elderly patients is debated because of increased risk of early periprosthetic femoral fractures. However, cemented femoral components carry a risk of bone cement implantation syndrome. Hence, we compared in-hospital complications, complications leading to readmission and mortality ≤ 30 days postoperatively between hybrid/cemented (cemented femoral component) vs. cementless THA in osteoarthritis patients > 70 years. Patients and methods — This is a prospective observational cohort study in 9 centers from January 2010 to August 2017. We used 30-day follow-up from the Danish National Patient Registry, patient records, and data from the Danish Hip Arthroplasty Register. Only THAs performed as a result of osteoarthritis were included. Results — 3,368 (42%) of the THAs were cemented/hybrid and 4,728 (58%) cementless. The in-hospital complication risk was 7.7% after cemented/hybrid vs. 5.3% after cementless THA (< 0.001), statistically not significant when adjusting for comorbidities (p = 0.1). There were similar risks of complications causing readmission (5.7% vs. 6.2%) and mortality ≤ 30 days (0.2% vs. 0.3%). 15 cases (0.4%) of pulmonary embolism (PE) were found after cemented/hybrid vs. 4 (0.1%) after cementless THA (p = 0.001); none occurred within 24 hours postoperatively. 2 of the PEs after cementless THA led to mortality. Cemented/hybrid THA remained significantly associated with risk of PE (RR 3.9, p = 0.02), when adjusting for comorbidities. BMI > 35 was associated with highest risk of PE (RR 5.7, p = 0.003). The risk of periprosthetic femoral fracture was 0.2% after cemented/hybrid vs. 1.5% after cementless THA (p < 0.001) and the risk of dislocations was 1.2% after cemented/hybrid THA vs. 1.8% after cementless THA (p = 0.04). Interpretation — The higher risk of PE after cemented/hybrid THA and higher risk of periprosthetic femoral fractures and dislocations after cementless THA highlights that both medically and surgically complications are related to fixation technique and have to be considered.

Introduction Hip osteoarthritis (OA) is the leading cause for total hip arthroplasty (THA). Although, being considered as the surgery of the century up to 23% of the patients report long-term pain, and deficits in physical function and muscle strength may persist after THA. Progressive resistance training (PRT) appears to improve multiple outcomes moderately in patients with hip OA. Current treatment selection is based on low-level evidence as no randomised controlled trials have compared THA to non-surgical treatment. The primary aim of this trial is to investigate whether THA followed by standard care is superior to 12 weeks of supervised PRT followed by 12 weeks of optional unsupervised PRT for improving hip pain and function in patients with severe hip OA.Methods and analysis This is a protocol for a multicentre, parallel-group, assessor-blinded, randomised controlled superiority trial conducted at four hospitals across three healthcare regions in Denmark. 120 patients aged ≥50 years with clinical and radiographic hip OA found eligible for THA by an orthopaedic surgeon will be randomised to THA followed by standard care, or 12 weeks of PRT (allocation 1:1). The primary outcome will be change in patient-reported hip pain and function, measured using the Oxford Hip Score, from baseline to 6 months after initiating the treatment. Key secondary outcomes will be change in the Hip disability and Osteoarthritis Outcome Score subscales, University of California Los Angeles Activity Score, 40 m fast-paced walk test, 30 s chair stand test and occurrence of serious adverse events. Patients declining participation in the trial will be invited into a prospective observational cohort study.Ethics and dissemination The trial has been approved by The Regional Committees on Health Research Ethics for Southern Denmark (Project-ID: S-20180158). All results will be presented in peer-reviewed scientific journals and international conferences.Trial registration number ClinicalTrials.gov (NCT04070027).

Hip dysplasia (HD) is a frequent cause of hip pain in skeletally mature patients and may lead to osteoarthritis (OA). An accurate and early diagnosis may postpone, reduce or even prevent the onset of OA and ultimately hip arthroplasty at a young age. The overall aim of this study was to assess the reliability of an algorithm, designed to read pelvic anterior-posterior (AP) radiographs and to estimate the agreement between the algorithm and human readers for measuring (i) lateral center edge angle of Wiberg (LCEA) and (ii) Acetabular index angle (AIA). The algorithm was based on deep-learning models developed using a modified U-net architecture and ResNet 34. The newly developed algorithm was found to be highly reliable when identifying the anatomical landmarks used for measuring LCEA and AIA in pelvic radiographs, thus offering highly consistent measurement outputs. The study showed that manual identification of the same landmarks made by five specialist readers were subject to variance and the level of agreement between the algorithm and human readers was consequently poor with mean measured differences from 0.37 to 9.56° for right LCEA measurements. The algorithm displayed the highest agreement with the senior orthopedic surgeon. With further development, the algorithm may be a good alternative to humans when screening for HD.

Background and purpose — The Mitch proximal epiphyseal replacement (PER) was developed to preserve proximal femoral bone and minimize femoral neck fracture associated with hip resurfacing arthroplasty (HRA). We studied the survival and risk of revision of HRA compared with cementless metal-on-polyethylene (MoP) total hip arthroplasty (THA) and the survival and risk of revision of the Mitch PER compared with MoP THA. Patients and methods — Using propensity score, we matched 1,057 HRA to 1,057 MoP THA and 202 Mitch PER to 1,010 MoP THA from the Danish Hip Arthroplasty Register. To estimate the relative risk (RR) of revision, we used regression with the pseudo-value approach and treated death as a competing risk. Results — The cumulative incidence for any revision of HRA at 10 years’ follow-up was 11% (95% confidence interval [CI] 9.1–13) and 6.4% (CI 5.8–7.0) for MoP THA. The RR of any revision was 1.5 (CI 1.1–2.1) for HRA at 10 years’ follow-up. By excluding the ASR components, the RR of revision at 10 years was 1.2 (CI 0.8–1.7). The cumulative incidence of revision was 9.6% (CI 4.2–18) for Mitch PER and 5.4% (CI 5.1–5.7) for MoP THA at 8 years. The RR of revision was 2.0 (CI 0.9–4.3) for Mitch PER at 8 years’ follow-up. Interpretation — The HRA had increased risk of revision compared with the MoP THA. When excluding ASR, the HRA group had similar risk of revision compared with MoP THA. The Mitch PER did not have a statistically significant increased risk of revision compared with MoP THA.

Background and purpose — The literature is scarce on the outcome of the youngest patients with total hip arthroplasties (THAs). We analyzed register data, revision risk, and related factors in patients 21 years or younger with THAs in the Nordic Arthroplasty Register Association (NARA). Patients and methods — We included all THA patients 21 years or younger reported during 1995 through 2016 to the Danish, Finnish, Norwegian, and Swedish hip arthroplasty registers and merged these into the NARA dataset. Primary outcome was any implant revision. Results — We identified 881 THAs in 747 patients. Mean age at primary surgery was 18 years (9–21). The indications for THA were pediatric hip diseases (33%), systemic inflammatory disease (23%), osteoarthritis (4%), avascular necrosis (12%), hip fracture sequelae (7%), and other diagnoses (21%). Unadjusted 10-year survival for all THAs was 86%. Comparison between indications showed no differences in survival. Uncemented implants were used most frequently. Survival for uncemented and cemented implants was the same adjusted for sex, indication, head size, and time period for primary surgery. Aseptic loosening was the main cause of revision. Interpretation — Both cemented and uncemented fixations seem to be a viable option in this age group, but with a lower implant survival than in older patient groups.

Abstract Background Spinal fusion is a commonly used procedure in spinal surgery. To ensure stable fusion, bone graft materials are used. ABM/P-15 (commercial name i-Factor™ Flex) is an available synthetic bone graft material that has CE approval in Europe. This peptide has been shown to improve bone formation when used in devices with fixation or on bone defects. However, the lack of external stability and large graft size make posterolateral lumbar fusion (PLF) a most challenging grafting procedure. This prospective randomized study was designed to evaluate early spinal fusion rates using an anorganic bovine-derived hydroxyapatite matrix (ABM) combined with a synthetic 15 amino acid sequence (P-15)–ABM/P-15 bone graft, and compared with allograft in an uninstrumented PLF model in sheep. The objective of this study was to assess fusion rates when using ABM/P-15 in uninstrumented posterolateral fusion in sheep. Methods Twelve Texas/Gotland mixed breed sheep underwent open PLF at 2 levels L2/L3 and L4/L5 without fixation instruments. The levels were randomized so that sheep received an ABM graft either with or without P15 coating. Sheep were euthanized after 4.5 months and levels were harvested and evaluated with a micro-CT scanner and qualitative histology. Fusion rates were assessed by 2D sections and 3D reconstruction images and fusion was defined as intertransverse bridging. Results There was 68% fusion rate in the allograft group and an extensive migration of graft material was noticed with a fusion rate of just 37% in the ABM/P-15 group. Qualitative histology showed positive osteointegration of the material and good correlation to scanning results. Conclusions In this PLF fusion model, ABM/P15 demonstrated the ability to migrate when lacking external stability. Due to this migration, reported fusion rates were significantly lower than in the allograft group. The use of ABM/P15 as i-Factor™ Flex may be limited to devices with fixation and bone defects.

Objective To examine the risk factors for new chronic opioid use in elderly patients who underwent hip fracture surgery.Design Prospective population-based cohort study.Setting and participants Using Danish nationwide health registries, we identified all opioid non-user patients aged ≥65 years who had undergone hip fracture surgery from 2005 to 2016 and were alive within the first year following surgery.Main outcome measures New chronic opioid use defined by the dispensing of at least two prescription opioids within two of the last three quarters during the first year following surgery.Results We identified 37 202 opioid non-user patients who underwent hip fracture surgery. Of these, 5497 (15%) developed new chronic opioid user within 1 year of surgery. Risk factors for new chronic opioid use were Body Mass Index (BMI) of

Introduction. Intra-articular fractures are the leading etiology for posttraumatic osteoarthritis (PTOA) in the ankle. Elevation of proinflammatory cytokines following intra-articular fracture may lead to synovial catabolism and cartilage degradation. We aimed to compare cytokine levels in injured and healthy ankle joints, examine the longer-term cytokine levels in fractured ankles, and investigate the association between cytokine levels in fractured ankles and plasma. Materials and Methods. In this cross-sectional study, synovial fluid (SF) and plasma of forty-seven patients with acute intra-articular ankle fractures and eight patients undergoing implant removal were collected prior to surgery. We determined concentrations of sixteen inflammatory cytokines, two cartilage degradation proteins, and four metabolic proteins and compared the levels in acutely injured ankles with those of the healthy contralateral side or during metal removal. Cytokine levels in injured ankles were also compared to serum cytokine levels. Nonparametric Wilcoxon rank-sum and Spearman tests were used for statistical analysis, and a p value below 0.05 was considered significant. Results. Compared to the healthy ankles, the synovial fluid in ankles with acute intra-articular fracture had elevated levels of several proinflammatory cytokines and proteases (IL-1β, IL-2, IL-6, IL-8, IL-12p70, TNF, IFNγ, MMP-1, MMP-3, and MMP-9) and anti-inflammatory cytokines (IL-1RA, IL-4, IL-10, and IL-13). The levels of cartilage degradation products (ACG, CTX-2) and metabolic mediators (TGF-β1 and TGF-β2) were also significantly higher. Synovial concentrations of ACG, IL-12-p70, IFNγ, IL-4, and bFGF correlated with serum levels. While most of the examined synovial cytokines were unchanged after implant removal, IL-4 and IL-6 levels were upregulated. Conclusions. We show that an acute ankle fracture is followed by an inflammatory reaction and cartilage degeneration. These data contribute to the current understanding of the protein regulation behind the development of PTOA and is a further step towards supplementing the current surgical treatment. This cross-sectional study was “retrospectively registered” on the 31th October 2017 at ClinicalTrials.gov (NCT03769909). The registration was carried out after inclusion of the first patient and prior to finalization of patient recruitment and statistical analyses: https://clinicaltrials.gov/ct2/show/NCT03769909?term=NCT03769909&draw=2&rank=1.

Background and purpose — Threshold values defining 3 categories of passive range of motion are used in the Cerebral Palsy follow-Up Program to guide clinical decisions. The aim of this study was to investigate the threshold values by testing the hypothesis that passive range of motion in ankle dorsiflexion is associated with gross motor function and that function differs between the groups of participants in each category. Patients and methods — We analyzed data from 60 ambulatory children (aged 5–9 years) with spastic cerebral palsy. Outcomes were passive range of motion in ankle dorsiflexion with flexed and extended knee and gross motor function (Gait Deviation Index, Gait Variable Score of the ankle, peak dorsiflexion during gait, 1-minute walk, Gross Motor Function Measure, the Pediatric Quality of Life Inventory Cerebral Palsy Module, and Pediatric Outcomes Data Collection Instrument). Results — Significant (p < 0.05) and moderate correlations were documented for range of motion versus Gait Variable Score of the ankle (r = –0.37 and r = –0.37) and range of motion versus peak dorsiflexion (r = 0.49 and r = 0.55). Differences between the groups formed by the categories were shown for Gait Variable Score of the ankle and peak dorsiflexion (p < 0.05). No other significant correlations or differences between the categories were observed. Interpretation — The results suggest that threshold values for ankle dorsiflexion used in the Cerebral Palsy follow-Up Program are of limited clinical value in assessing overall gross motor function, but may be used to identify deviations in ankle-specific gait function.