Crosswalks between the Oxford hip and knee scores and the HOOS-12 and KOOS-12 instruments.

OBJECTIVE: To develop and validate bi-directional crosswalks between the Oxford Hip Score (OHS) and HOOS-12 summary impact score, and between the Oxford Knee Score (OKS) and KOOS-12 summary impact score. METHODS: Data were sourced from the Australian Orthopaedic Association National Joint Replacement Registry Patient-Reported Outcome Measures Program. Patients undergoing primary joint replacement for osteoarthritis who completed the OHS and HOOS-12 or OKS and KOOS-12 instruments were included in the analysis. An equipercentile method was used to create four crosswalks, with the distribution of scores smoothed using log-linear models prior to equating. Crosswalk validity was assessed through comparison of actual vs derived scores, Pearson correlation coefficients, root mean square errors (RMSE) and Bland-Altman plots. RESULTS: Paired OHS/HOOS-12 data and paired OKS/KOOS-12 data were available for 4,513 patients undergoing total hip replacement and 5,942 patients undergoing total knee replacement, respectively. Minimal differences were observed between actual and crosswalk-derived mean scores (actual OHS 27.55 vs derived OHS 27.56; actual HOOS-12 53.28 vs derived HOOS-12 53.31; actual OKS 27.34 vs derived OKS 27.34; actual KOOS-12 50.51 vs derived KOOS-12 50.58). High correlation was observed between actual and derived scores (Pearson's r for hip-specific instruments: 0.943-0.946; Pearson's r for knee-specific instruments: 0.925-0.931). Plotted actual vs mean derived scores also indicated robust concordance across the breadth of the instrument scales. CONCLUSION: These crosswalks provide close approximations of actual OHS, OKS, HOOS-12 and KOOS-12 scores, as indicated by multiple validation metrics. They offer a resource for clinicians, researchers and arthroplasty registries to support PROMs score conversion and data harmonisation efforts.

The burden of end-stage osteoarthritis in Australia: a population-based study on the incidence of total knee replacement attributable to overweight/obesity.

OBJECTIVES: To determine the risk of total knee replacement (TKR) for primary osteoarthritis (OA) associated with overweight/obesity in the Australian population. METHODS: This population-based study analyzed 191,723 cases of TKR collected by the Australian Orthopaedic Association National Joint Registry and population data from the Australian Bureau of Statistics. The time-trend change in incidence of TKR relating to BMI was assessed between 2015 and 2018. The influence of obesity on the incidence of TKR in different age and gender groups was determined. The population attributable fraction (PAF) was then calculated to estimate the effect of obesity reduction on TKR incidence. RESULTS: The greatest increase in incidence of TKR was seen in patients from obese class III. The incidence rate ratio for having a TKR for obesity class III was 28.683 at those aged 18-54 years but was 2.029 at those aged >75 years. Females in obesity class III were 1.7 times more likely to undergo TKR compared to similarly classified males. The PAFs of TKR associated with overweight or obesity was 35%, estimating 14,287 cases of TKR attributable to obesity in 2018. The proportion of TKRs could be reduced by 20% if overweight and obese population move down one category. CONCLUSIONS: Obesity has resulted in a significant increase in the incidence of TKR in the youngest population in Australia. The impact of obesity is greatest in the young and the female population. Effective strategies to reduce the national obese population could potentially reduce 35% of the TKR, with over 10,000 cases being avoided.

Predictors of total hip replacement in community based older adults: a cohort study.

OBJECTIVE: The purpose of this study is to describe predictors of total hip replacement (THR) in community dwelling older adults. A better understanding of predictors of THR can aid in triaging patients and researching preventative strategies. DESIGN: At baseline, participants had assessment of radiographic OA and cam morphology (from pelvic radiographs), shape mode scores and hip bone mineral density (BMD; from dual energy X-ray absorptiometry (DXA)). After 2.6 and 5 years, participants reported hip pain using WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index), and had hip structural changes assessed using magnetic resonance imaging (MRI). Risk of THR was analysed using mixed-effect Poisson regression. RESULTS: Incidence of THR for OA over 14 years was 4.6% (37/801). As expected, WOMAC hip pain and hip radiographic OA both predicted risk of THR. Additionally, shape mode 2 score (decreasing acetabular coverage) (RR 1.83/SD; 95% CI 1.1-3.04), shape mode 4 score (non-spherical femoral head) (RR 0.59/SD; 95% CI 0.36-0.96), cam morphology (α > 60°) (RR 2.2/SD; 95% CI 1.33-3.36), neck of femur BMD (RR 2.09/SD, 95% CI 1.48-2.94) and bone marrow lesions (BMLs) increased risk of THR (RR 7.10/unit; 95% CI 1.09-46.29). CONCLUSION: In addition to hip pain and radiographic hip OA, measures of hip shape, cam morphology, BMD and BMLs independently predict risk of THR. This supports the role of hip bone geometry and structure in the pathogenesis of end stage hip OA and has identified factors that can be used to improve prediction models for THR.

Implications for research and clinical use from a Rasch analysis of the HOOS-12 and KOOS-12 instruments.

OBJECTIVE: To evaluate the structural validity of the 12-item Hip disability and Osteoarthritis Outcome Score (HOOS-12) and 12-item Knee injury and Osteoarthritis Outcome Score (KOOS-12) using Rasch analysis and consider psychometric implications for research and clinical use. METHOD: Individual-level HOOS-12 and KOOS-12 data from the Australian Orthopaedic Association National Joint Replacement Registry, collected before and after primary total hip and knee replacement, were used for this analysis. Using the Rasch analytic approach, overall model fit and item fit were examined, together with potential reasons for misfit including response threshold ordering, differential item functioning, internal consistency, unidimensionality and item targeting. RESULTS: Overall misfit to the Rasch model was evident for both instruments. A degree of item misfit was also observed, although most items demonstrated logical sequencing of response options. Only two items (hip/knee pain frequency and awareness of hip/knee problems) displayed disordered response thresholds. The pain, function, and quality of life domains of the HOOS-12 and KOOS-12 demonstrated excellent internal consistency reliability (person separation index: 0.80-0.93) and unidimensionality. A mismatch between item difficulty and person ability scores at the highest end of the HOOS-12 and KOOS-12 scales contributed to post-operative ceiling effects (mean logit for HOOS-12: 3.57; KOOS-12: 2.58; ≈0 indicates well-targeted scale). CONCLUSION: We found evidence to support the structural validity of the three HOOS-12 and KOOS-12 domains for evaluating joint replacement outcomes. However, there may be missing content in both instruments particularly for high-functioning patients. Minor refinement of some response options may be warranted to improve item performance.

Performance of the HOOS-12 and KOOS-12 instruments for evaluating outcomes from joint replacement surgery.

OBJECTIVE: To evaluate the psychometric properties of the 12-item Hip disability and Osteoarthritis Outcome Score (HOOS-12) and Knee injury and Osteoarthritis Outcome Score (KOOS-12) for use in evaluating outcomes after joint replacement for osteoarthritis. DESIGN: Patient-reported outcomes data collected by the Australian Orthopaedic Association National Joint Replacement Registry were used for this analysis. HOOS-12 and KOOS-12 domain (pain, function, quality of life) and summary impact data were available. The Oxford Hip Score (OHS), Oxford Knee Score (OKS) and EQ-5D-5L were used as comparators. Instruments were administered pre-operatively and at 6 months post-operatively. Internal consistency reliability, floor and ceiling effects, convergent validity, known groups validity, and responsiveness were evaluated using standard psychometric techniques. RESULTS: Baseline HOOS-12 and KOOS-12 data were available for 3,023 patients undergoing primary total hip replacement and 4,010 patients undergoing primary total knee replacement. At baseline, high internal consistency was demonstrated for all domains and summary scores (Cronbach's alpha: HOOS-12 = 0.81-0.93; KOOS-12 = 0.82-0.92). Post-operative ceiling effects (>15% of patients scoring the best possible score) were identified for the HOOS-12 pain (46%), function (39%) and quality of life domains (26%) and summary score (17%), and for the KOOS-12 pain (21%) and function domains (18%). The HOOS-12 and KOOS-12 could differentiate between two known groups (lowest/highest OHS or OKS quartiles post-operatively; p < 0.001) and were highly responsive to change (effect sizes for HOOS-12: 2.20-2.83; KOOS-12: 1.82-2.35). CONCLUSION: The HOOS-12 and KOOS-12 have good psychometric properties for capturing joint replacement outcomes including excellent responsiveness, although ceiling effects may limit monitoring of post-operative improvement.

Q fever seroprevalence in Australia suggests one in twenty people have been exposed.

Q fever (caused by Coxiella burnetii) is thought to have an almost world-wide distribution, but few countries have conducted national serosurveys. We measured Q fever seroprevalence using residual sera from diagnostic laboratories across Australia. Individuals aged 1-79 years in 2012-2013 were sampled to be proportional to the population distribution by region, distance from metropolitan areas and gender. A 1/50 serum dilution was tested for the Phase II IgG antibody against C. burnetii by indirect immunofluorescence. We calculated crude seroprevalence estimates by age group and gender, as well as age standardised national and metropolitan/non-metropolitan seroprevalence estimates. Of 2785 sera, 99 tested positive. Age standardised seroprevalence was 5.6% (95% confidence interval (CI 4.5%-6.8%), and similar in metropolitan (5.5%; 95% CI 4.1%-6.9%) and non-metropolitan regions (6.0%; 95%CI 4.0%-8.0%). More males were seropositive (6.9%; 95% CI 5.2%-8.6%) than females (4.2%; 95% CI 2.9%-5.5%) with peak seroprevalence at 50-59 years (9.2%; 95% CI 5.2%-13.3%). Q fever seroprevalence for Australia was higher than expected (especially in metropolitan regions) and higher than estimates from the Netherlands (2.4%; pre-outbreak) and US (3.1%), but lower than for Northern Ireland (12.8%). Robust country-specific seroprevalence estimates, with detailed exposure data, are required to better understand who is at risk and the need for preventive measures.

Practice variation in total hip arthroplasty versus hemiarthroplasty for treatment of fractured neck of femur in Australia.

AIMS: Displaced femoral neck fractures (FNF) may be treated with partial (hemiarthroplasty, HA) or total hip arthroplasty (THA), with recent recommendations advising that THA be used in community-ambulant patients. This study aims to determine the association between the proportion of FNF treated with THA and year of surgery, day of the week, surgeon practice, and private versus public hospitals, adjusting for known confounders. PATIENTS AND METHODS: Data from 67 620 patients in the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) from 1999 to 2016 inclusive were used to generate unadjusted and adjusted analyses of the associations between patient, time, surgeon and institution factors, and the proportion of FNF treated with THA. RESULTS: Overall, THA was used in 23.7% of patients. THA was more frequently used over time, in younger patients, in healthier patients, in cases performed on weekdays (adjusted odds ratio (OR) 1.27; 95% confidence interval (CI) 1.14 to 1.41), in private hospitals (adjusted OR 4.34; 95% CI 3.94 to 4.79) and by surgeons whose hip arthroplasty practice has a relatively higher proportion of elective patients (adjusted OR 1.65; 95% CI 1.49 to 1.83). CONCLUSION: Practice variation exists in the proportion of FNF patients treated with THA due to variables other than patient factors. This may reflect variation in resources available and surgeon preference, and uncertainty regarding the relative indication.

Relationship of weight and obesity with the risk of knee and hip arthroplasty for osteoarthritis across different levels of physical performance: a prospective cohort study.

OBJECTIVE: To examine the association between obesity and knee and hip arthroplasty for osteoarthritis across a range of physical performance. METHOD: The body mass index and physical performance (on the 36-item Short Form Health Survey) of 9135 Australian Diabetes, Obesity and Lifestyle Study participants were measured in 1999-2000. The incidence of knee and hip arthroplasty during 2002-2011 was determined by linking the cohort records to the Australian Orthopaedic Association National Joint Replacement Registry. RESULTS: Over 9.1 ± 2.3 years (mean ± sd)) of follow-up, 317 participants had knee and 202 had hip arthroplasty for osteoarthritis. Using those with neither obesity nor significantly impaired physical performance as the reference group, participants with both obesity and significantly impaired physical performance had a higher knee arthroplasty risk [hazard ratio (HR) = 5.25, 95% confidence interval (CI) 3.85-7.14] than those with obesity alone (HR = 2.49, 95% CI 1.81-3.44) or impaired physical performance alone (HR = 2.19, 95% CI 1.59-3.02). Similar results were observed for hip arthroplasty (obesity and impaired physical performance: HR = 2.67, 95% CI 1.72-4.15; obesity alone: HR = 1.65, 95% CI 1.08-2.51; impaired physical performance alone: HR = 1.83, 95% CI 1.26-2.66). Among overweight/obese patients, 5 kg greater baseline weight increased the knee arthroplasty risk across all levels of physical performance, and hip arthroplasty risk in those with the highest level of physical performance. CONCLUSION: Although impaired physical performance is an independent risk factor for knee and hip arthroplasty, greater weight increased knee arthroplasty for overweight/obese participants at all levels of physical performance, but hip arthroplasty only in those with good physical performance. Targeting weight loss has the potential to reduce the risk of knee arthroplasty and improve patient outcomes, even in those with poor physical performance.

Patellar tendon enthesis abnormalities and their association with knee pain and structural abnormalities in older adults.

OBJECTIVE: To describe associations between presence of patellar tendon enthesis (PTE) abnormalities and symptoms, structural abnormalities, and total knee replacement (TKR) in older adult cohort. METHODS: PTE abnormalities (presence of abnormal bone signal and/or bone erosion), were measured on T2-weighted magnetic resonance (MR) images at baseline in 961 community-dwelling older adults. Knee pain and function limitation were assessed using Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Bone marrow lesions (BMLs), cartilage volume and defects score, and infrapatellar fat pad (IPFP) area were measured using validated methods. Incidence of TKR was determined by data linkage. RESULTS: Participants with abnormal PTE bone signal and/or erosion was 20%. Cross-sectionally, presence of PTE abnormalities was associated with greater pain intensity while going up and down stairs (ß = 0.22 (95% confidence interval (CI); 0.03, 0.41)), greater risk of femoral BMLs (RR = 1.46 (1.12, 1.90)) and worse tibial cartilage defects score (RR = 1.70 (1.16, 2.47), and smaller IPFP area (ß = -0.27 (-0.47, -0.06) cm2), after adjustment of confounders. Longitudinally, presence of baseline PTE abnormalities was associated with a deleterious increase in tibial BML size (RR = 1.52 (1.12, 2.05)) over 10.7 years but not symptoms, other structural changes, or TKR. CONCLUSION: PTE abnormalities are common in older adults. Presence of cross-sectional but not longitudinal associations suggests they are commonly co-exist with other knee structural abnormalities but may not play a major role in symptom development or structural change, excepting tibial BMLs.

Cross-Linked Polyethylene for Total Hip Arthroplasty Markedly Reduces Revision Surgery at 16 Years.

BACKGROUND: Total hip arthroplasty (THA) is an effective operation for the management of end-stage hip osteoarthritis, but long-term success can be limited by wear of the polyethylene bearing surface. Cross-linking conventional polyethylene has resulted in lower wear rates and a reduction in bone lysis in both laboratory and clinical studies. The aim of this study was to compare the rates of revision between cross-linked polyethylene (XLPE) and conventional non-cross-linked polyethylene (CPE) at 16 years after THAs performed for the treatment of osteoarthritis. METHODS: We performed an observational study of data, from a national registry, on all patients who underwent THA for osteoarthritis in Australia from 1999 through December 31, 2016. The outcomes of THAs performed with CPE were compared with those of THAs performed with XLPE, along with an analysis of the effect of age, sex, femoral head size, the method of acetabular and femoral component fixation, and the reasons and types of revision. The principal outcome measure was the time to the first revision, determined using Kaplan-Meier estimates of survivorship. RESULTS: CPE was used in 41,171 procedures, and XLPE was used in 199,131. The mean ages of the men and women treated with CPE were 70.0 years (standard deviation [SD] = 9.9 years) and 72.5 years (SD = 9.7 years), respectively, whereas the men and women who received XLPE were slightly younger (mean age, 68.6 years [SD = 10.3 years] and 70.7 years [SD = 9.9 years], respectively. XLPE was associated with a lower rate of revision than CPE at 6 months, and this difference became more apparent with time. The 16-year cumulative percentage of revisions of the primary THAs was 11.7% (95% confidence interval [CI] = 11.1% to 12.3%]) in the CPE group and 6.2% (95% CI = 5.7% to 6.7%) in the XLPE group. The hazard ratio at 9 years was 3.02 (p = 0.001). CONCLUSIONS: The use of XLPE has resulted in a significant reduction in the rate of revision at 16 years following THA for osteoarthritis. This evidence suggests that the longevity of THA is likely to be improved, which may enable younger patients to undergo surgery, confident of a reduced need for revision in the long term. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

The association between ambulatory activity, body composition and hip or knee joint replacement due to osteoarthritis: a prospective cohort study.

OBJECTIVE: To examine the association between ambulatory activity (AA), body composition measures and hip or knee joint replacement (JR) due to osteoarthritis. DESIGN: At baseline, 1082 community-dwelling older-adults aged 50-80 years were studied. AA was measured objectively using pedometer and body composition by dual-energy X-ray absorptiometry. The incidence of primary (first-time) JR was determined by data linkage to the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). Log binomial regression with generalized estimating equations were used to estimate the risk of JR associated with baseline AA and body composition measures, adjusting for age, sex, X-ray disease severity, and pain. RESULTS: Over 13 years of follow-up, 74 (6.8%) participants had a knee replacement (KR) and 50 (4.7%) a hip replacement (HR). AA was associated with a higher risk of KR (RR 1.09/1000 steps/day, 95% CI 1.01, 1.16) and a lower risk of HR (RR 0.90/1000 steps/day, 95% CI 0.81, 0.99). Body mass index (BMI) (RR 1.07/kg/m2, 95% CI 1.03, 1.12), total fat mass (RR 1.03/kg, 95% CI 1.01, 1.06), trunk fat mass (RR 1.05/kg, 95% CI 1.00, 1.09), and waist circumference (RR 1.02/cm, 95% CI 1.00, 1.04) were associated with a higher risk of KR. Body composition measures were not associated with HR. CONCLUSIONS: An objective measure of AA was associated with a small increased risk of KR and a small reduced risk of HR. Worse body composition profiles were associated with KR, but not HR. Altogether this may suggest different causal pathways for each site with regard to habitual activity and obesity.

Prevalence and changes in analgesic medication utilisation 1 year prior to total joint replacement in an older cohort of patients.

OBJECTIVES: To evaluate the prevalence and change in analgesic medications use prior to joint replacement in older patients between 2001 and 2012. METHODS: A population based epidemiological study was conducted. Opioids, non-steroidal anti-inflammatories (NSAIDs), paracetamol, corticosteroid injections, medications for neuropathic pain, hypnotics, and muscle relaxants supplied 1 year prior to total knee replacement (TKR, n = 15,517) and hip replacement (THR, n = 10,018) were assessed. Patient characteristics and surgical indication adjusted prevalence ratios (PRs) and 95% confidence intervals (CI) are provided. RESULTS: From 2001 to 2012, in the TKR cohort (median age 78.9) the prevalence of opioid use prior to surgery increased from 37% to 49% (PR = 1.01, 95% CI 1.00-1.01, P = 0.01), while in the THR cohort (median age 81.1) it increased from 44% to 54% (PR = 1.01, 95% CI 1.01-1.02, P < 0.001). Paracetamol use increased from 52% to 61% (PR = 1.0, 95% CI 1.0-1.0, P = 0.913) in the TKR cohort and from 55% to 67% (PR = 1.01, 95% CI 1.00-1.01, P = 0.005) in the THR cohort. Neuropathic pain medication use increased from 5% to 11% in the TKR cohort (PR = 1.04, 95% CI 1.02-1.06, P < 0.0001) and from 6% to 12% in the THR cohort (PR = 1.06, 95% CI 1.04-1.09, P < 0.0001). NSAID use decreased from 76% to 50% in the TKR cohort (PR = 0.96, 95% CI 0.95-0.96, P < 0.0001), and from 81% to 47% in THR cohort (PR = 0.95, 95% CI 0.94-0.95, P < 0.0001). Corticosteroid injections prevalence also decreased (TKR: 21-18%, PR = 0.97, 95% CI 0.96-0.97, P < 0.001, THR: 18-17%, PR = 0.97, 95% CI 0.96-0.98, P < 0.001). CONCLUSION: Pain medication utilization prior to joint replacement surgery changed significantly in this national older cohort of patients during the 2000s.

Cyclotron production and radiochemical separation of 55Co and 58mCo from 54Fe, 58Ni and 57Fe targets.

This work presents the production with a cyclotron of the positron emitter 55Co via the 54Fe(d,n) and 58Ni(p,α) reactions and the Auger electron emitter 58mCo via the 57Fe(d,n) reaction after high current (40µA p and 60µA d) irradiation on electroplated targets. High specific activity radionuclides (up to 55.6 GBq/µmol 55Co and 31.8GBq/µmol 58mCo) with high radionuclidic purity (99.995% 55Co from 54Fe, 98.8% 55Co from 58Ni, and 98.7% 58mCo from 57Fe at end of bombardment, EoB), in high activity concentration (final separated radionuclide in < 0.6mL) and with almost quantitative overall activity separation yield (> 92%) were obtained after processing of the irradiated targets with novel radiochemical separation methods based on HCl dissolution and the resin N,N,N',N'-tetrakis-2-ethylhexyldiglycolamide (DGA, branched). One hour long irradiations using 38-65, 110-214 and 59-78mg of enriched 54Fe (99.93%), 58Ni (99.48%) and 57Fe (95.06%), respectively, electroplated over a 1.0cm2 surface, yielded 582 ± 66MBq 55Co, 372 ± 14MBq 55Co and 810 ± 186MBq 58mCo, respectively, decay corrected to EoB. The separation methods allow for the recovery of the costly enriched target materials, which were reconstituted into metallic targets after novel electroplating methods, with an overall recycling efficiency of 93 ± 4% for iron. The produced radionuclides were used to radiolabel the angiogenesis marker antibody TRC105 conjugated to the chelator NOTA as a demonstration of their quality.

Projected increase in total knee arthroplasty in the United States - an alternative projection model.

OBJECTIVE: The purpose of our study was to estimate the future incidence rate (IR) and volume of primary total knee arthroplasty (TKA) in the United States from 2015 to 2050 using a conservative projection model that assumes a maximum IR of procedures. Furthermore, our study compared these projections to a model assuming exponential growth, as done in previous studies, for illustrative purposes. METHODS: A population based epidemiological study was conducted using data from US National Inpatient Sample (NIS) and Census Bureau. Primary TKA procedures performed between 1993 and 2012 were identified. The IR, 95% confidence intervals (CI), or prediction intervals (PI) of TKA per 100,000 US citizens over the age of 40 years were calculated. The estimated IR was used as the outcome of a regression modelling with a logistic regression (i.e., conservative model) and Poisson regression equation (i.e., exponential growth model). RESULTS: Logistic regression modelling suggests the IR of TKA is expected to increase 69% by 2050 compared to 2012, from 429 (95%CI 374-453) procedures/100,000 in 2012 to 725 (95%PI 121-1041) in 2050. This translates into a 143% projected increase in TKA volume. Using the Poisson model, the IR in 2050 was projected to increase 565%, to 2854 (95%CI 2278-4004) procedures/100,000 IR, which is an 855% projected increase in volume compared to 2012. CONCLUSIONS: Even after using a conservative projection approach, the number of TKAs in the US, which already has the highest IR of knee arthroplasty in the world, is expected to increase 143% by 2050.

Thirteen novel canine dog leukocyte antigen-88 alleles identified by sequence-based typing.

Major histocompatibility complex (MHC) genes in mammals include highly polymorphic class I and class II genes that are critical for donor-recipient matching for transplantation. Dogs have served as an effective, directly translatable model for stem/progenitor cell transplantation. Previous analyses of MHC class I genes in dogs point to a single highly polymorphic gene, dog leukocyte antigen (DLA)-88, as an important factor in the success or failure of hematopoietic stem cell transplants. Fifty-nine DLA-88 alleles have been identified and reported so far. Here, we extend this list by presenting 13 novel DLA-88 alleles found in domestic dogs.

The use of femoral stems with exchangeable necks in primary total hip arthroplasty increases the rate of revision.

AIMS: Femoral stems with exchangeable (modular) necks were introduced to offer surgeons an increased choice when determining the version, offset and length of the femoral neck during total hip arthroplasty (THA). It was hoped that this would improve outcomes and reduce complications, particularly dislocation. In 2010, the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) first reported an increased rate of revision after primary THA using femoral stems with an exchangeable neck. The aim of this study was to provide a more comprehensive up-to-date analysis of primary THA using femoral stems with exchangeable and fixed necks. MATERIALS AND METHODS: The data included all primary THA procedures performed for osteoarthritis (OA), reported to the AOANJRR between 01 September 1999 and 31 December 2014. There were 9289 femoral stems with an exchangeable neck and 253 165 femoral stems with a fixed neck. The characteristics of the patients and prostheses including the bearing surface and stem/neck metal combinations were examined using Cox proportional hazard ratios (HRs) and Kaplan-Meier estimates of survivorship. RESULTS: It was found that prostheses with an exchangeable neck had a higher rate of revision and this was evident regardless of the bearing surface or the size of the femoral head. Exchangeable neck prostheses with a titanium stem and a cobalt-chromium neck had a significantly higher rate of revision compared with titanium stem/titanium neck combinations (HR 1.83, 95% confidence interval 1.49 to 2.23, p < 0.001). Revisions were higher for these combinations compared with femoral stems with a fixed neck. CONCLUSION: There appears to be little evidence to support the continued use of prostheses with an exchangeable neck in primary THA undertaken for OA. Cite this article: Bone Joint J 2017;99-B:766-73.

Substantial rise in the lifetime risk of primary total knee replacement surgery for osteoarthritis from 2003 to 2013: an international, population-level analysis.

OBJECTIVE: To estimate and compare the lifetime risk of total knee replacement surgery (TKR) for osteoarthritis (OA) between countries, and over time. METHOD: Data on primary TKR procedures performed for OA in 2003 and 2013 were extracted from national arthroplasty registries in Australia, Denmark, Finland, Norway and Sweden. Life tables and population data were also obtained for each country. Lifetime risk of TKR was calculated for 2003 and 2013 using registry, life table and population data. RESULTS: Marked international variation in lifetime risk of TKR was evident, with females consistently demonstrating the greatest risk. In 2013, Finland had the highest lifetime risk for females (22.8%, 95%CI 22.5-23.1%) and Australia had the highest risk for males (15.4%, 95%CI 15.1-15.6%). Norway had the lowest lifetime risk for females (9.7%, 95%CI 9.5-9.9%) and males (5.8%, 95%CI 5.6-5.9%) in 2013. All countries showed a significant rise in lifetime risk of TKR for both sexes over the 10-year study period, with the largest increases observed in Australia (females: from 13.6% to 21.1%; males: from 9.8% to 15.4%). CONCLUSIONS: Using population-based data, this study identified significant increases in the lifetime risk of TKR in all five countries from 2003 to 2013. Lifetime risk of TKR was as high as 1 in 5 women in Finland, and 1 in 7 males in Australia. These risk estimates quantify the healthcare resource burden of knee OA at the population level, providing an important resource for public health policy development and healthcare planning.