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Evidence on the comparative effectiveness of osteoporosis treatments is heterogeneous. This may be attributed to different populations and clinical practice, but also to differing methodologies ensuring comparability of treatment groups before treatment effect estimation and the amount of residual confounding by indication. This study assessed the comparability of denosumab vs oral bisphosphonate (OBP) groups using propensity score (PS) methods and negative control outcome (NCO) analysis. A total of 280 288 women aged ≥50 yr initiating denosumab or OBP in 2011-2018 were included from the UK Clinical Practice Research Datalink (CPRD) and the Danish National Registries (DNR). Balance of observed covariates was assessed using absolute standardized mean difference (ASMD) before and after PS weighting, matching, and stratification, with ASMD >0.1 indicating imbalance. Residual confounding was assessed using NCOs with ≥100 events. Hazard ratio (HR) and 95%CI between treatment and NCO were estimated using Cox models. Presence of residual confounding was evaluated with 2 approaches (1) >5% of NCOs with 95% CI excluding 1, (2) >5% of NCOs with an upper CI <0.75 or lower CI >1.3. The number of imbalanced covariates before adjustment (CPRD 22/87; DNR 18/83) decreased, with 2%–11% imbalance remaining after weighting, matching, or stratification. Using approach 1, residual confounding was present for all PS methods in both databases (≥8% of NCOs), except for stratification in DNR (3.8%). Using approach 2, residual confounding was present in CPRD with PS matching (5.3%) and stratification (6.4%), but not with weighting (4.3%). Within DNR, no NCOs had HR estimates with upper or lower CI limits beyond the specified bounds indicating residual confounding for any PS method. Achievement of covariate balance and determination of residual bias were dependent upon several factors including the population under study, PS method, prevalence of NCO, and the threshold indic

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 me, 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-revie

Jakob Bie Granild-Jensen,1,2 Alma Becic Pedersen,2,3 Eskild Bendix Kristiansen,3 Bente Langdahl,2,4 Bjarne Møller-Madsen,2,5 Charlotte Søndergaard,6 Stense Farholt,7 Esben Thyssen Vestergaard,1,2 Gija Rackauskaite8 1Department of Child and Youth, Randers Regional Hospital, Randers, Denmark; 2Department of Clinical Medicine, Aarhus University, Aarhus, Denmark; 3Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark; 4Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark; 5Department of Children’s Orthopedics, Aarhus University Hospital, Aarhus, Denmark; 6Department of Pediatrics and Adolescent Medicine, Gødstrup Regional Hospital, Gødstrup, Denmark; 7Centre for Rare Diseases - Department of Pediatrics and Adolescent Medicine, Aarhus University Hospital, Aarhus, Denmark; 8Department of Pediatrics and Adolescent Medicine, Aarhus University Hospital, Aarhus, DenmarkCorrespondence: Jakob Bie Granild-Jensen, Department of Child and Youth, Randers Regional Hospital, Oestervangsvej 54, Randers, NE, 8930, Denmark, Email jakobgranild@dadlnet.dkBackground: In children with cerebral palsy (CP), fracture rates have been reported to be higher than in the general population but age-specific fracture rates have not been directly compared and the effect of comorbid epilepsy needs elucidation. This impairs decision-making regarding bone health interventions.Aim: We aimed to establish the age-specific fracture rates in children with CP with and without epilepsy in Denmark.Materials and Methods: Data from Danish registers were combined to establish cohorts of children with and without CP born in Denmark from 1997 to 2007. Fracture rates were calculated for 1997– 2016.Results: We identified 1,451 children with CP and 787,159 without CP. Female/male fracture rates per 1,000 person-years were 23/27 with CP and 23/29 without CP. Male sex, epilepsy and anti-seizure medication, but not the diagnosis of CP or GMFCS-lev

Background and purpose — Unicompartmental knee arthroplasty (UKA) has increased in use. We investigated changes to UKA revision risk over the last 20 years compared with total knee arthroplasty (TKA), examined external and patient factors for correlation to UKA revision risk, and described the survival probability for current UKA and TKA practice. Patients and methods — All knee arthroplasties reported to the Danish Knee Arthroplasty Register from 1997 to 2017 were linked to the National Patient Register and the Civil Registration System for comorbidity, emigration, and mortality information. All primary UKA and TKA patients with primary osteoarthritis were included and propensity score matched 4 TKAs to 1 UKA. Revision and mortality were analyzed using competing risk cox regression with a shared gamma frailty component. Results — The matched cohort included 48,195 primary knee arthroplasties (9,639 UKAs). From 1997–2001 to 2012–2017 the 3-year hazard ratio decreased from 5.5 (95% CI 2.7–11) to 1.5 (CI 1.2–1.8) due to increased UKA survival. Cementless fixation, a high percentage usage of UKA, and increased surgical volume decreased UKA revision risk, and increased in occurrence parallel to the decreasing revision risks. Current UKA practice using cementless fixation at a high usage unit has a 3-year implant survival of 96% (CI 97–95), 1.1% lower than current TKA practice. Interpretation — UKA revision risk has decreased over the last 20 years, nearing that of TKA surgery. High usage rates, surgical volume, and the use of cementless fixation have increased during the study and were associated with decreased UKA revision risks.

Jeppe Damgren Vesterager, Morten Madsen, Thomas Johannesson Hjelholt, Pia Kjær Kristensen, Alma Becic Pedersen Department of Clinical Epidemiology, Aarhus University Hospital and Department of Clinical Medicine, Aarhus University, Aarhus, DenmarkCorrespondence: Alma Becic Pedersen, Tel +45 87167212, Fax +45 87167215, Email abp@clin.au.dkObjective: Comorbidity has an important role in risk prediction and risk adjustment modelling in observational studies. However, it is unknown which comorbidity index is most accurate to predict mortality in hip fracture patients. We aimed to evaluate the prediction ability, including discrimination and calibration of Charlson comorbidity index (CCI), Elixhauser comorbidity index (ECI) and Rx-risk index for 30 day- and 1 year mortality in a population-based cohort of hip fracture surgery patients.Methods: Using the Danish Multidisciplinary Hip Fracture Registry in the period 2014– 2018, 31,443 patients were included. CCI and ECI were based on discharge diagnoses, while Rx-Risk index was based on pharmacy dispensings. We used logistic regression to assess discrimination of the different indices, individually and in combinations, by calculating c-statistics and the contrast in c-statistic to a base model including only age and gender with 95% confidence intervals (CI).Results: The study cohort were primarily female (69%) and older than 85 years (42%). The 30-day mortality was 10.1% and the 1-year mortality was 26.6%. Age and gender alone had a good discrimination ability for 30-day and 1-year mortality (c-statistic=0.70, CI: 0.69– 0.71 and c-statistic=0.68, CI: 0.67 − 0.69, respectively). By adding indices individually to the base model, Rx-risk index had the best 30-day and 1-year mortality discrimination ability (c-statistic=0.73, CI: 0.72– 0.74 and 0.71 CI: 0.71– 0.72, respectively). By adding combination of indices to the base model, a combination of CCI and the Rx-risk index had a 30-day and 1-year mortality discriminat

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 fo

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 <18.5 (adjusted OR (aOR) 1.22, 95% CI 1.09 to 1.36), BMI of 25.0-29.9 (aOR 1.12, 95% CI 1.04 to 1.21) and BMI of ≥30 (aOR 1.57, 95% CI 1.40 to 1.76) with BMI 18.6-24.9 as reference, a pertrochanteric/subtrochanteric fracture (aOR 1.27, 95% CI 1.20 to 1.34) with femoral neck fracture as reference, preoperative use (vs no-use) of non-steroidal anti-inflammatory drug (aOR 1.68, 95% CI 1.55 to 1.83), selective serotonin reuptake inhibitor (aOR 1.42, 95% CI 1.32 to 1.53), antidepressants (aOR 1.36, 95% CI 1.24 to 1.49), antipsychotics (aOR 1.21, 95% CI 1.07 to 1.35), corticosteroids (aOR 1.54, 95% CI 1.35 to 1.76), statins (aOR 1.09, 95% CI 1.02 to 1.18), antibiotics (aOR 1.32, 95% CI 1.22 to 1.42), antiosteoporosis drugs (aOR 1.33, 95% CI 1.19 to 1.49) and anticoagulatives (aOR 1.24, 95% CI 1.17 to 1.32). Presence of cardiovascular comorbidities, diabetes, gastrointestinal diseases, dementia, chronic obstructive pulmonary disease or renal diseases was further identified as a risk factor. Conclusion In this large nationwide cohort study, we identified several risk factors associated with new chronic opioid use after hip fracture surgery among

Background and purpose - Knee fracture treatment burden remains unknown, impeding proper use of hospital resources. We examined 20-year trends in incidence rates (IRs) and patient-, fracture-, and treatment-related characteristics of knee fracture patients.Patients and methods - This nationwide cohort study of prospectively collected data including patients with distal femoral, patellar, and proximal tibial fractures from the Danish National Patient Registry during 1998-2017, assesses IRs of knee fractures (per 105 inhabitants) as well as patient-, fracture-, and treatment-related characteristics of knee fracture patients.Results - During 1998-2017, 60,823 patients (median age 55; 57% female) sustained 74,106 knee fractures. 74% of the study population had a Charlson Comorbidity Index (CCI) of 0 and 18% a CCI of ≥ 2. 51% were proximal tibial fractures, 31% patellar fractures, and 18% distal femoral fractures. At the time of knee fracture, 20% patients had concomitant near-knee fractures (femur/tibia/fibula shaft/hip/ankle), 13% concomitant fractures (pelvic/spine/thorax/upper extremities), 5% osteoporosis, and 4% primary knee osteoarthritis. Over 1/3 knee fractures were surgically treated and of these 86% were open-reduction internal fixations, 9% external fixations, and 5% knee arthroplasties. The most common surgery type was proximal tibia plating (n = 4,868; 60% female). Knee fracture IR increased 12% to 70, females aged > 51 had the highest knee fracture IR, proximal tibial fracture had the highest knee fracture type IR (32) and surgically treated knee fracture IR increased 35% to 23.Interpretation - Knee fracture IRs, especially of surgically treated knee fractures, are increasing and proximal tibial fracture has the highest knee fracture type IR. Females aged > 51 and patients with comorbidity are associated with knee fracture, proximal tibial fracture, proximal tibial fracture surgery, and posttraumatic knee arthroplasty.

Pia Kjær Kristensen,1,2 Niels Dieter Röck,3 Helle Collatz Christensen,4 Alma Becic Pedersen1 1Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark; 2Department of Orthopaedic Surgery, Horsens Regional Hospital, Horsens, Denmark; 3Department of Orthopaedic Surgery, Odense University Hospital, Odense, Denmark; 4Danish Clinical Quality Program (RKKP) National Clinical Registries, Frederiksberg Hospital, Frederiksberg, DenmarkCorrespondence: Pia Kjær KristensenDepartment of Clinical Epidemiology, Aarhus University Hospital, Olof Palmes Allé 43-45, Aarhus DK-8200, DenmarkTel +45 87168063Fax +45 87167215Email pkkr@clin.au.dkAim of the Registry: The aim of the Danish Multidisciplinary Hip Fracture Registry (DMHFR) is to collect data on processes of treatment, nursing care and rehabilitation as well as outcomes for patients with hip fracture in Denmark, and thereby monitor and improve the quality.Study Population: Hip fracture patients at age 65 or older that have undergone surgery with arthroplasty or internal fixation since 2004.Main Variables: DMHFR collects quality indicators and descriptive variables. Quality indicators include eight process performance measures within treatment, nursing care and rehabilitation, reflecting recommendations from the national clinical guideline for hip fracture patients, and three outcome measures including survival within 30-days, unplanned acute readmission within 30 days and reoperation within 2 years. Descriptive variables include a number of patient- and surgery-related characteristics. All data are collected prospectively.Results: By the end of 2018, the DMHFR included 86,438 hip fracture patients. Since 2006, all hospital departments in Denmark, treating patients with hip fracture, have reported improvement in quality of care and improvement in survival, and reoperation over time as well as high completeness of variables registration.Conclusion: The DMHFR is a well

OBJECTIVE: To report the 1-year pre and postoperative analgesic use in patients undergoing primary surgery for adult spinal deformity (ASD) and assess risk factors for chronic postoperative opioid use.METHODS: Patients > 18 years undergoing primary instrumented surgery for ASD in Denmark between 2006 and 2016 were identified in the Danish National Patient Registry. Information on analgesic use were obtained from the Danish National Health Service Prescription Database. Use of analgesics was calculated one year before and after surgery for each patient, per quarter (-Q4 to -Q1 before and Q1 to Q4 after). Users were defined as patient with one or more prescriptions in the given quarter.RESULTS: We identified 892 patients. Preoperatively, 28% (n = 246) of patients were opioid users in -Q4 and 33% (n = 295) in -Q1. Postoperatively, 85% (n = 756) of patients were opioid users in Q1 and 31% (n = 280) in Q4. Proportions of users of other analgesics (paracetamol, antidepressants, and anticonvulsants) were stable before and after surgery. Use of nonsteroidal anti-inflammatory drug decreased postoperatively by 40% (-Q1 vs. Q4). 26% of patients had chronic preoperative opioid use (one or more prescriptions in each -Q2 and -Q1) and 24% had chronic postoperative use (prescription each of Q1-Q4). Multivariate logistic regression analysis showed age increment per 10 years and preoperative chronic opioid use as risk factors for chronic postoperative opioid use.CONCLUSION: One year after ASD surgery, opioid use was not reduced compared to preoperative usage.

□ The Nordic Arthroplasty Register Association (NARA) was established in 2007 by arthroplasty register representatives from Sweden, Norway and Denmark with the overall aim to improve the quality of research and thereby enhance the possibility for quality improvement with arthroplasty surgery. Finland joined the NARA collaboration in 2010. □ NARA minimal hip, knee and shoulder datasets were created with variables that all countries can deliver. They are dynamic datasets, currently with 25 variables for hip arthroplasty, 20 for knee arthroplasty and 20 for shoulder arthroplasty. □ NARA has published statistical guidelines for the analysis of arthroplasty register data. The association is continuously working on the improvement of statistical methods and the application of new ones. □ There are 31 published peer-reviewed papers based on the NARA databases and 20 ongoing projects in different phases. Several NARA publications have significantly affected clinical practice. For example, metal-on-metal total hip arthroplasty and resurfacing arthroplasty have been abandoned due to increased revision risk based on i.a. NARA reports. Further, the use of uncemented total hip arthroplasty in elderly patients has decreased significantly, especially in Finland, based on the NARA data. □ The NARA collaboration has been successful because the countries were able to agree on a common dataset and variable definitions. The collaboration was also successful because the group was able to initiate a number of research projects and provide answers to clinically relevant questions. A number of specific goals, set up in 2007, have been achieved and new one has emerged in the process.