Incidence of Instability Following Primary Total Hip Arthroplasty Continues to Decline in the Medicare Population.

BACKGROUND: Instability has been the primary cause of failure following primary total hip arthroplasty (THA) leading to revision hip surgery. The purpose of this study was to determine if instability rates have further declined following advances in primary THA, including dual mobility articulations, direct anterior approaches, advanced technologies, and improved knowledge of the hip-spine relationships. METHODS: Using the 5% Medicare Part B claims data from 1999 to 2019, we identified 81,573 patients who underwent primary THA for osteoarthritis. Patients who experienced instability at 3 months, 6 months, 1 year, and 2 years were identified. Multivariate cox regression analyses evaluated the effect of patient and procedure characteristics on the risk of instability. RESULTS: Instability at 1 year following primary THA declined from approximately 4% in 2000 to 2.3% in 2010 and 1.6% in 2018. The leading cause of revision surgery was infection (18.6%), followed by periprosthetic fracture (14%), mechanical loosening (11.5%), and instability (9.4%). High-risk groups for instability continue to include increased age, higher Charlson index, obesity, lumbar spine pathology, and neurocognitive disorders. CONCLUSION: Instability is no longer the leading etiology of failure following primary THA with a decline of approximately 40% over the past decade. Infection, periprosthetic fracture, mechanical loosening, and then instability are now the leading causes of failure. Multiple factors may play a role in the decline of instability, including increased use of dual mobility articulations, direct anterior approaches, improved knowledge of the hip-spine relationships, and use of advanced technologies.

Assessment of patients' self-reported levels of adherence to postoperative restrictions following total hip replacement.

BACKGROUND: Postoperative precautions that limit hip movement reduce the incidence of postoperative dislocation following total hip replacement (THR). It is assumed that patients adhere to these precautions, but true adherence is unknown. AIMS: To assess adherence to postoperative precautions, including bending, twisting, crossing of legs, sleeping position and sitting position following primary THR surgery. METHODS: A self-reporting questionnaire explored patient adherence to precautions following primary THR. Questionnaires were sent to 120 patients following elective primary THR at two orthopaedic centres in England between November 2016 and April 2017. Patients were also asked to report the duration of adherence and the difficulty associated with adherence to each of the precautions. RESULTS: Eighty-three percent (99/120) of patients responded. Of these, 56% (56/99) were female and 44% (44/99) were male. Mean age was 66.0 (standard deviation 9.4) years. Seventy-six percent of patients were classified as 'highly adherent' to the precautions in hospital, and this reduced to 68% when patients went home. The median duration of adherence to the precaution to avoid crossing legs was 6 weeks [interquartile range (IQR) 6-6]. For the remaining four precautions, the median duration of adherence was consistently 6 weeks (IQR 4-6). CONCLUSION: High levels of adherence to precautions following THR were identified. However, patients reported difficulty adhering to the precautions, which may explain why 24% of patients were not able to adhere to the precautions> 90% of the time. Patients reported that the most difficult precaution to adhere to was supine sleeping, and the least difficult precautions to adhere to were avoiding crossing legs and using a raised chair.

Treatment patterns and clinical and economic burden of hip dislocation following primary total hip arthroplasty in England.

AIMS: The aim of this study was to estimate the clinical and economic burden of dislocation following primary total hip arthroplasty (THA) in England. METHODS: This retrospective evaluation used data from the UK Clinical Practice Research Datalink database. Patients were eligible if they underwent a primary THA (index date) and had medical records available 90 days pre-index and 180 days post-index. Bilateral THAs were excluded. Healthcare costs and resource use were evaluated over two years. Changes (pre- vs post-THA) in generic quality of life (QoL) and joint-specific disability were evaluated. Propensity score matching controlled for baseline differences between patients with and without THA dislocation. RESULTS: Among 13,044 patients (mean age 69.2 years (SD 11.4), 60.9% female), 191 (1.5%) had THA dislocation. Two-year median direct medical costs were £15,333 (interquartile range (IQR) 14,437 to 16,156) higher for patients with THA dislocation. Patients underwent revision surgery after a mean of 1.5 dislocations (1 to 5). Two-year costs increased to £54,088 (IQR 34,126 to 59,117) for patients with multiple closed reductions and a revision procedure. On average, patients with dislocation had greater healthcare resource use and less improvement in EuroQol five-dimension index (mean 0.24 (SD 0.35) vs 0.44 (SD 0.35); p < 0.001) and visual analogue scale (0.95 vs 8.85; p = 0.038) scores, and Oxford Hip Scores (12.93 vs 21.19; p < 0.001). CONCLUSION: The cost, resource use, and QoL burden of THA dislocation in England are substantial. Further research is required to understand optimal timing of revision after dislocation, with regard to cost-effectiveness and impact on QoL. Cite this article: Bone Joint J 2022;104-B(7):811-819.

Cost-effectiveness of dual-mobility components in patients with displaced femoral neck fractures.

AIMS: Total hip arthroplasty (THA) with dual-mobility components (DM-THA) has been shown to decrease the risk of dislocation in the setting of a displaced neck of femur fracture compared to conventional single-bearing THA (SB-THA). This study assesses if the clinical benefit of a reduced dislocation rate can justify the incremental cost increase of DM-THA compared to SB-THA. METHODS: Costs and benefits were established for patients aged 75 to 79 years over a five-year time period in the base case from the Canadian Health Payer's perspective. One-way and probabilistic sensitivity analysis assessed the robustness of the base case model conclusions. RESULTS: DM-THA was found to be cost-effective, with an estimated incremental cost-effectiveness ratio (ICER) of CAD $46,556 (£27,074) per quality-adjusted life year (QALY). Sensitivity analysis revealed DM-THA was not cost-effective across all age groups in the first two years. DM-THA becomes cost-effective for those aged under 80 years at time periods from five to 15 years, but was not cost-effective for those aged 80 years and over at any timepoint. To be cost-effective at ten years in the base case, DM-THA must reduce the risk of dislocation compared to SB-THA by at least 62%. Probabilistic sensitivity analysis showed DM-THA was 58% likely to be cost-effective in the base case. CONCLUSION: Treating patients with a displaced femoral neck fracture using DM-THA components may be cost-effective compared to SB-THA in patients aged under 80 years. However, future research will help determine if the modelled rates of adverse events hold true. Surgeons should continue to use clinical judgement and consider individual patients' physiological age and risk factors for dislocation. Cite this article: Bone Joint J 2021;103-B(12):1783-1790.

Can dual mobility cups prevent dislocation without increasing revision rates in primary total hip arthroplasty? A systematic review.

BACKGROUND: Dislocation is one of the leading causes for early revision surgery after total hip arthroplasty (THA). To address this problem, the dual mobility (DM) cup was developed in the 1970s by the French. Despite the increased and, in some countries, broad use of DM cups, high quality evidence of their effectiveness compared to traditional unipolar (UP) cups is lacking. There are a few well-conducted literature reviews, but the level of evidence of the included studies was moderate to low and the rates of revision were not specifically investigated. Therefore, we did a systematic review to investigate whether there is a difference in the rate of dislocations and revisions after primary THA with a DM cup or a UP cup. METHODS: We conducted a systematic literature search in PubMed, Embase and Cochrane databases in July 2019. The articles were selected based upon their quality, relevance and measurement of the predictive factor. We used the MINORS criteria to determine the methodological quality of all studies. RESULTS: The initial search resulted in 702 citations. After application of the inclusion and exclusion criteria, eight articles met our eligibility criteria and were graded. Included studies were of medium to low methodological quality with a mean score of 14/24 (11-16) points following the MINORS criteria. In the case-control studies, a total of 549 DM cups and 649 UP cups were included. In the registry studies, a total of 5.935 DM cups and 217.362 UP cups were included. In the case-control studies, one (0.2%) dislocation was reported for the DM cups and 46 (7.1%) for the UP cup (p=0.009, IQR=0.00-7.00). Nine (1.6%) revisions, of which zero due to dislocation, were reported for the DM cup and 39 (6.0%), of which 30 due to dislocation, for the UP cup (p=0.046, CI=-16.93-5.73). In the registry studies 161 (2.7%) revisions were reported for the DM cup, of which 14 (8.7%) due to dislocation. For the UP cup, 3.332 (1.5%) revisions were reported (p=0.275, IQR=41.00-866.25), of which 1.093 (32.8%) due to dislocation (p=0.050, IQR=3.50-293.25). CONCLUSION: This review suggests lower rates of dislocation and lower rates of revision for dislocation in favor of the DM cups. Concluding, DM cups might be an effective solution to reduce dislocation in primary THA. To evaluate the efficacy of DM cups compared to UP cups, an economic evaluation alongside a randomized controlled trial is needed focusing on patient important endpoints. LEVEL OF EVIDENCE: III, systematic review of level III studies.

Cost-effectiveness analysis of a surveillance program to prevent hip dislocation in children with cerebral palsy.

OBJECTIVE: In this study we conducted an economic evaluation of a surveillance programme to prevent hip dislocation in children with cerebral palsy. METHOD: We developed a model that compared costs and health outcomes of children with cerebral palsy with and without a surveillance programme. Information from a number of sources was combined into a decision analytical model, primarily based on data from a comparative study with a 20-year follow-up. Effectiveness was measured using Quality-Adjusted Life Years (QALYs). The analysis took the perspective of the Spanish National Health Service. We undertook extensive sensitivity analyses including a probabilistic sensitivity analysis. RESULTS: The surveillance programme led to higher QALYs and higher health care costs, with an estimated incremental cost per QALY gained of 12,282€. The results were robust to model assumptions. The probability that the programme was cost-effective was estimated to be over 80% at the threshold of 25.000€/QALY recommended in Spain. CONCLUSION: This study indicates that surveillance programmes to prevent hip dislocation in children with cerebral palsy are likely to be cost-effective.

Hip dysplasia among children with spastic cerebral palsy in rural Bangladesh.

BACKGROUND: Hip dysplasia is common among children with cerebral palsy (CP), particularly in spastic CP. It can result in pain, reduced function and quality of life. However, the burden of hip dysplasia among children with CP in llow-and middle-income countries (LMICs) like Bangladesh is unknown. We aimed to define the burden of hip dysplasia among children with spastic CP in Bangladesh. METHODS: This study includes a subset of the Bangladesh CP Register (BCPR) study cohort who were registered between January and March 2015. The BCPR is a population-based surveillance of children with CP (aged < 18 years) operating in a northern sub-district (Shahjadpur; child population ~ 226,114) of Bangladesh. Community-based key informant's method (KIM) survey conducted to identify children with CP in the surveillance area. A diagnosis of CP was made based on clinical history and examination by the study physicians and physiotherapist. Study participants had an antero-posterior (AP) X-ray of their pelvis. The degree of subluxation was assessed by calculating the migration percentage (MP). RESULTS: During the study period, 196 children with CP were registered, 144 had spastic CP. 40 children with spastic CP (80 hips) had pelvic X-Rays (mean age 9.4 years, range 4.0-18.0 years) and 32.5% were female. Gross Motor Function Classification System (GMFCS) showed 37.5% (n = 15) with GMFCS level I-II and 62.5% (n = 25) with GMFCS level III-V. Twenty percent (n = 8) of the children had hip subluxation (MP: 33-80%). Osteopenic changes were found in 42.5% (n = 17) children. CONCLUSIONS: To the best of our knowledge this is one of the first studies exploring hip dysplasia among children with spastic CP in Bangladesh. Our findings reflect that hip dysplasia is common among children with spastic CP. Introduction of hip surveillance programmes is imperative for prevention of secondary complications, reduced function and poor quality of life among these children.

The Role of Crosslinked Polyethylene in Reducing Aggregated Costs of Total Hip Arthroplasty in the United States.

BACKGROUND: Widespread adoption of crosslinked polyethylene for the acetabular articular surface for total hip arthroplasty has substantially reduced revision rates and dislocation rates. We aim to provide estimates of the resulting magnitude of the annual reduction in aggregated costs of total hip arthroplasty surgery in the United States. METHODS: After we obtained, from the literature, the contrasting mid-term rates of revisions and dislocations of total hip arthroplasty using conventional polyethylene vs those using crosslinked polyethylene, specifically from only registry studies and prospective, randomized controlled studies, we multiplied these incidence figures by the cost estimates of these failures to generate approximations of the cost savings in the United States from the use of crosslinked polyethylene. RESULTS: The estimates suggest that in the United States these savings might be one billion dollars per annual cohort over a 15-year duration. CONCLUSION: The use of crosslinked polyethylene has reduced substantially the overall costs of total hip arthroplasty surgery in the United States.

Does Timing of Primary Total Hip Arthroplasty Prior to or After Lumbar Spine Fusion Have an Effect on Dislocation and Revision Rates?

BACKGROUND: Patients undergoing primary total hip arthroplasty (THA) following lumbar spine fusion have an increased incidence of dislocation compared to those without prior lumbar fusion. The purpose of this study is to determine if timing of THA prior to or after lumbar fusion would have an effect on dislocation and revision incidence in patients with both hip and lumbar spine pathology. METHODS: One hundred percent Medicare inpatient claims data from 2005 to 2015 were used to compare dislocation and revision risks in patients with primary THA with pre-existing lumbar spine fusion vs THA with subsequent lumbar spine fusion within 1, 2, and 5 years after the index THA. A total of 42,300 patients met inclusion criteria, 28,668 patients of which underwent THA with pre-existing lumbar spinal fusion (LSF) and 13,632 patients who had prior THA and subsequent LSF. Patients who had THA first followed by LSF were further stratified based on the interval between index THA and subsequent LSF (1, 2, and 5 years), making 4 total groups for comparison. Multivariate cox regression analysis was performed adjusting for age, socioeconomic status, race, census region, gender, Charlson score, pre-existing conditions, discharge status, length of stay, and hospital characteristics. RESULTS: Patients with prior LSF undergoing THA had a 106% increased risk of dislocation compared to those with LSF done 5 years after THA (P < .001). Risk of revision THA was greater in the pre-existing LSF group by 43%, 41%, and 49% at 1, 2, and 5 years post THA compared to the groups with THA done first with subsequent LSF. Dislocation was the most common etiology for revision THA in all groups, but significantly higher in the prior LSF group (26.6%). CONCLUSION: Results of this study demonstrate that sequence of surgical intervention for concomitant lumbar and hip pathology requiring LSF and THA respectively significantly impacts the fate of the THA performed. Patients with prior LSF undergoing THA are at significantly higher risk of dislocation and subsequent revision compared to those with THA first followed by delayed LSF. LEVEL OF EVIDENCE: 3.

Cost Analysis of Dual-Mobility Versus Large Femoral Head Constructs in Revision Total Hip Arthroplasty.

BACKGROUND: The purpose of this study is to report healthcare payer costs of dual-mobility (DM) and large femoral head (LFH) constructs in revision total hip arthroplasties (THAs). METHODS: A Markov model was constructed to analyze costs of re-interventions incurred by Medicare and private payers over a 3-year time horizon in patients who underwent unilateral revision THA with DM (n = 126) or LFH (n = 176) implants. Model states and probabilities were derived from prospectively collected registry data. Medicare costs were estimated as the weighted-average national Medicare payment for revision THA. Private payer costs were estimated by using a multiplier of Medicare costs. RESULTS: Over a 3-year period following revision THA, re-interventions were performed in 11 (9%) DM patients and 34 (19%) LFH patients, costing $263-$1898 in DM THAs and $1285-$3946 in LFH THAs for Medicare. When compared to LFH implants, DM constructs were less costly to Medicare and private payers, resulting in cost differentials of $1536 and $2611, respectively. CONCLUSIONS: At mid-term follow-up, DM constructs utilized in revision THAs were associated with 11% lower absolute risk of re-intervention and payer savings of $1500-$2500 per case when compared to LFH constructs. LEVEL OF EVIDENCE: Economic and decision analysis, Level III.

The cost-effectiveness of dual mobility in a spinal deformity population with high risk of dislocation: a computer-based model.

AIMS: The routine use of dual-mobility (DM) acetabular components in total hip arthroplasty (THA) may not be cost-effective, but an increasing number of patients undergoing THA have a coexisting spinal disorder, which increases the risk of postoperative instability, and these patients may benefit from DM articulations. This study seeks to examine the cost-effectiveness of DM components as an alternative to standard articulations in these patients. PATIENTS AND METHODS: A decision analysis model was used to evaluate the cost-effectiveness of using DM components in patients who would be at high risk for dislocation within one year of THA. Direct and indirect costs of dislocation, incremental costs of using DM components, quality-adjusted life-year (QALY) values, and the probabilities of dislocation were derived from published data. The incremental cost-effectiveness ratio (ICER) was established with a willingness-to-pay threshold of $100 000/QALY. Sensitivity analysis was used to examine the impact of variation. RESULTS: In the base case, patients with a spinal deformity were modelled to have an 8% probability of dislocation following primary THA based on published clinical ranges. Sensitivity analysis revealed that, at its current average price ($1000), DM is cost-effective if it reduces the probability of dislocation to 0.9%. The threshold cost at which DM ceased being cost-effective was $1180, while the ICER associated with a DM THA was $71 000 per QALY. CONCLUSION: These results indicate that under specific clinical and economic thresholds, DM components are a cost-effective form of treatment for patients with spinal deformity who are at high risk of dislocation after THA. Cite this article: Bone Joint J 2018;100-B:1297-1302.

Body mass index, hip function and surgeon volume are independent predictors of dislocation: an analysis of 4334 total hip replacements.

The aim of this study was to identify pre-operative and intra-operative factors that are predictive of dislocation following primary total hip replacement (THR). Data were prospectively collected for a consecutive series of 4334 THRs undertaken over a 14-year period. Ninety-eight (2.3%) of the 4334 patients had one or more dislocation post-operatively. A body mass index (BMI) of ≥ 35 (p < 0.001), a Harris Hip Score (HHS) of ≤ 41 (p < 0.001) and a low-volume surgeon (p < 0.001), which was defined as performing fewer than 43 THRs per annum, were identified as independent predictors of dislocation using logistic regression analysis. Using these three variables in differing combinations the risk of dislocation varied from 0.5 to 10.4%. Patients at high risk of dislocation, with a BMI of ≥ 35 and a pre-operative HHS of ≤ 41, undergoing surgery by a low-volume surgeon had a dislocation rate of 10.5%, but this decreased to 2.3% when operated on by a high-volume surgeon. These risk factors could be used to identify patients at high risk of dislocation, and modification of these factors, such as weight loss to achieve a BMI of ≤ 35 or referral to a high-volume surgeon, may decrease the risk of dislocation and the resulting secondary morbidity.

The Cost-Effectiveness of Dual Mobility Implants for Primary Total Hip Arthroplasty: A Computer-Based Cost-Utility Model.

BACKGROUND: Dislocation remains a clinically important problem following primary total hip arthroplasty, and it is a common reason for revision total hip arthroplasty. Dual mobility (DM) implants decrease the risk of dislocation but can be more expensive than conventional implants and have idiosyncratic failure mechanisms. The purpose of this study was to investigate the cost-effectiveness of DM implants compared with conventional bearings for primary total hip arthroplasty. METHODS: Markov model analysis was conducted from the societal perspective with use of direct and indirect costs. Costs, expressed in 2013 U.S. dollars, were derived from the literature, the National Inpatient Sample, and the Centers for Medicare & Medicaid Services. Effectiveness was expressed in quality-adjusted life years (QALYs). The model was populated with health state utilities and state transition probabilities derived from previously published literature. The analysis was performed for a patient's lifetime, and costs and effectiveness were discounted at 3% annually. The principal outcome was the incremental cost-effectiveness ratio (ICER), with a willingness-to-pay threshold of $100,000/QALY. Sensitivity analyses were performed to explore relevant uncertainty. RESULTS: In the base case, DM total hip arthroplasty showed absolute dominance over conventional total hip arthroplasty, with lower accrued costs ($39,008 versus $40,031 U.S. dollars) and higher accrued utility (13.18 versus 13.13 QALYs) indicating cost-savings. DM total hip arthroplasty ceased being cost-saving when its implant costs exceeded those of conventional total hip arthroplasty by $1,023, and the cost-effectiveness threshold for DM implants was $5,287 greater than that for conventional implants. DM was not cost-effective when the annualized incremental probability of revision from any unforeseen failure mechanism or mechanisms exceeded 0.29%. The probability of intraprosthetic dislocation exerted the most influence on model results. CONCLUSIONS: This model determined that, compared with conventional bearings, DM implants can be cost-saving for routine primary total hip arthroplasty, from the societal perspective, if newer-generation DM implants meet specific economic and clinical benchmarks. The differences between these thresholds and the performance of other contemporary bearings were frequently quite narrow. The results have potential application to the postmarket surveillance of newer-generation DM components. LEVEL OF EVIDENCE: Economic and decision analysis Level III. See Instructions for Authors for a complete description of levels of evidence.

Complication Rates for Hip Arthroscopy Are Underestimated: A Population-Based Study.

PURPOSE: To identify major and minor complication rates associated with hip arthroscopy from a payer-based national database and compare with the rates reported in the existing literature. METHODS: Patients who underwent hip arthroscopy between 2007 and 2014 were identified using PearlDiver, a publicly available database. Rates of major and minor complications, as well as conversion to total hip arthroscopy (THA), were determined by using Current Procedural Terminology (CPT) and International Classification of Diseases, Ninth Revision (ICD-9), codes. Incidence rates of select major complications across the entire database were used as a comparison group. Statistical significance was set at P < .05. RESULTS: Of 18 million patients screened from 2007 to 2014, a total of 2,581 hip arthroscopies were identified. The rates of major and minor complications within a 1-year postoperative period were 1.74% and 4.22%, respectively. Complications included heterotopic ossification (2.85%), bursitis (1.23%), proximal femur fracture (1.08%), deep vein thrombosis (0.79%), and hip dislocation (0.58%). The rate of conversion to THA within 1 year was 2.85%. When compared to rates in the general population, the relative risks [RRs] of requiring a THA (age <50 years, RR = 57.66, P < .001; age >50 years, RR = 22.05, P < .001), sustaining a proximal femur fracture (age <50 years, RR = 18.02, P < .001; age >50 years, RR = 2.23, P < .001), or experiencing a hip dislocation (RR 19.60, P < .001) at 1 year after hip arthroscopy were significantly higher in all age groups. CONCLUSIONS: Higher major complication rates after hip arthroscopy were observed using a national payer-based database than previously reported in the literature, especially in regard to hip dislocations and proximal femur fractures. Rates of total hip arthroplasty were similar to prior studies, whereas the rates of revision hip arthroscopy were higher. LEVEL OF EVIDENCE: Level IV, case series.

Health Utility of Early Hemiarthroplasty vs Delayed Total Hip Arthroplasty for Displaced Femoral Neck Fracture in Elderly Patients: A Markov Model.

BACKGROUND: Treatment for femoral neck fracture among patients aged 65 years or older varies, with many surgeons preferring hemiarthroplasty (HA) over total hip arthroplasty (THA). There is evidence that THA may lead to better functional outcomes, although it also carries greater risk of mortality and dislocation rates. METHODS: We created a Markov decision model to examine the expected health utility for older patients with femoral neck fracture treated with early HA (performed within 48 hours) vs delayed THA (performed after 48 hours). Model inputs were derived from the literature. Health utilities were derived from previously fit patients aged more than 60 years. Sensitivity analyses on mortality and dislocation rates were conducted to examine the effect of uncertainty in the model parameters. RESULTS: In the base case, the average cumulative utility over 2 years was 0.895 for HA and 0.994 for THA. In sensitivity analyses, THA was preferred over HA until THA 30-day and 1-year mortality rates were increased to 1.3× the base case rates. THA was preferred over HA until the health utility for HA reached 98% that of THA. THA remained the preferred strategy when increasing the cumulative incidence of dislocation among THA patients from a base case of 4.4% up to 26.1%. CONCLUSION: We found that delayed THA provides greater health utility than early HA for older patients with femoral neck fracture, despite the increased 30-day and 1-year mortality associated with delayed surgery. Future studies should examine the cost-effectiveness of THA for femoral neck fracture.

Is There a Difference in Revision Risk Between Metal and Ceramic Heads on Highly Crosslinked Polyethylene Liners?

BACKGROUND: The most common bearing surface used among primary THAs worldwide is a metal or ceramic femoral head that articulates against a highly crosslinked ultrahigh-molecular-weight polyethylene (HXLPE) acetabular liner. Despite their widespread use, relatively little is known about the comparative effectiveness of ceramic versus metal femoral heads with respect to risk of revision and dislocation as well as the role of head size in this relationship. QUESTIONS/PURPOSES: The purpose of this study was to evaluate the risk of (1) all-cause revision in metal versus ceramic femoral heads when used with an HXLPE liner, including an evaluation of the effect of head size; and (2) dislocation in metal versus ceramic femoral heads when used with an HXLPE liner as well as an assessment of the effect of head size. METHODS: Data were collected as part of the Kaiser Permanente Total Joint Replacement Registry between 2001 and 2013. Patients in this study were on average overweight (body mass index = 29 kg/m2), 67 years old, mostly female (57%), and had osteoarthritis (93%) as the primary indication for surgery. The material of the femoral head (metal, ceramic) was crossed with head size (< 32, 32, 36, > 36 mm), yielding eight device groupings. Only uncemented devices were evaluated. The primary outcome was all-cause revision (n = 28,772) and the secondary outcome was dislocation within 1 year (n = 19,623). Propensity scores were used to adjust for potential confounding at the implant/patient level using between-within semiparametric survival models that control for surgeon and hospital confounding and adjust estimates for the within-cluster correlation among observations on the response. RESULTS: For all-cause revision, there was no difference between ceramic versus metal (reference) heads in combination with an HXLPE liner (hazard ratio [HR] = 0.82 [0.65-1.04], p = 0.099). Smaller metal head sizes of < 32 mm were associated with increased risk of revision relative to 36 mm (HR = 1.66 [1.20-2.31], p = 0.002, adjusted p = 0.025). For dislocation, ceramic heads increased risk relative to metal at < 32 mm only (HR = 4.39 [1.72-11.19], p = 0.002, adjusted p = 0.020). Head sizes < 32 mm were associated with increased risk of dislocation relative to 36 mm for metal (HR = 2.99 [1.40-6.39], p = 0.005, adjusted p = 0.047) and ceramic heads (HR = 15.69 [6.07-40.55], p < 0.001, adjusted p < 0.001). CONCLUSIONS: The results did not provide evidence for use of one femoral head material over another when used with HXLPE liners for the outcome of revision, but for dislocation, metal performed better than ceramic with < 32-mm heads. Overall, the findings suggest increased risk of revision/dislocation with head sizes < 32 mm. LEVEL OF EVIDENCE: Level III, therapeutic study.

Custom-made triflanged acetabular components in the treatment of major acetabular defects. Short-term results and clinical experience.

We report on the Belgian experience with the aMace® custom-made triflange acetabular component in revision total hip arthroplasty between September 2009 and November 2014. We focused on (1) the complexity of the preoperative planning and reimbursement procedure; (2) the surgical problems and operative experience; and (3) the early outcome. We collected 20 patients' reviews and 22 surgeons' reviews, with a mean follow-up of 25 months. The preoperative planning and reimbursement procedures were rated as time-consuming and cumbersome. In 6/22 cases, the operation was difficult or very difficult. Technical problems occurred in 8/22 cases, including problematic fitting in four. However, all aMace® components could be implanted successfully. The mean postoperative Harris Hip Score (HHS) was 68/100; patients' satisfaction was high and most patients experienced no or mild pain. Complications occurred in 8/22 cases, half of them dislocations. The aMace® implant can provide a solution for complex acetabular revisions. As dislocations were common, the use of dual-mobility cups should be considered. Because of the high cost and the lack of bone stock restoration, we suggest using custom-made triflange acetabular implants only in cases with large cavitational and segmental defects, which would be difficult to reconstruct with alternative methods.

Inpatient Dislocation After Primary Total Hip Arthroplasty.

BACKGROUND: Inpatient dislocation after total hip arthroplasty (THA) is considered a nonreimbursable "never event" by the Centers for Medicare and Medicaid Services. There is extensive evidence that technical procedural factors affect dislocation risk, but less is known about the influence of nontechnical factors. We evaluated inpatient dislocation trends after elective primary THA and identified patient and hospital characteristics associated with the occurrence of dislocation. METHODS: We used discharge records from the Nationwide Inpatient Sample (2002-2011). Temporal trends were assessed, and multivariable logistic regression modeling was used to identify factors associated with dislocation. RESULTS: The in-hospital dislocation rate increased from 0.025% in 2002 to 0.15% in 2011, despite a downward trend in length of stay (P < .001). Patient characteristics associated with the occurrence of dislocation were black or Hispanic race/ethnicity, lower household income, and Medicaid insurance. Comorbidities associated with dislocation included hemiparesis/hemiplegia, drug use disorder, chronic renal failure, psychosis, and obesity. Dislocations were less likely to occur at teaching hospitals and in the South. CONCLUSION: The in-hospital dislocation rate after elective primary THA is increasing, in spite of shorter stays and surgical advances over time. Given the sociodemographic disparities in dislocation risk documented herein, interventions to address social determinants of health might do as much or more to reduce the occurrence of dislocation than technical improvements.

Assessment of lateral subluxation in Legg-Calvé-Perthes disease: a time-sequential study of magnetic resonance imaging and plain radiography.

Lateral subluxation of the femoral head is one of the poor prognostic factors of Legg-Calvé-Perthes disease. The aim of this study was to investigate the cause of lateral subluxation of the femoral head on the basis of the changes over time on MRI. Twenty-four patients with unilateral Legg-Calvé-Perthes disease were analyzed retrospectively. Lateral subluxation was measured as the tear drop distance on radiographs. We focused on joint fluid, medial articular cartilage thickening, and abnormal lesion on MRI. Lateral subluxation continued significantly in patients with poor results. Among the MRI findings, the presence of an abnormal lesion was associated significantly with the continuous lateral subluxation.

How Critical is Patient Positioning in Radiographic Assessment of the Hip in Cerebral Palsy When Measuring Migration Percentage?

BACKGROUND: Migration percentage (MP) is an accepted method of assessing lateral displacement of the femoral head in children with cerebral palsy (CP). Difficulty in positioning of patients for pelvic radiography remains a concern for the reliability of the MP. METHODS: This 2-part quantitative study examined 100 anteroposterior pelvic radiographs for children with CP. Fifty were from a region that had a positioning protocol for hip surveillance of children with CP and 50 images were from a region without. Images were assessed for acceptability of position in relation to hip abduction/adduction and/or pelvic rotation.Ten images deemed Acceptable or Borderline from the region with no protocol were then randomly selected. MP was measured on 2 separate occasions by 5 children's orthopaedic surgeons and statistically analyzed for intrarater and interrater reliability. RESULTS: There was no statistically significant difference in the acceptability of images between the 2 regions with 60% to 66% of the images meeting the criteria outright. When allowances were made for slight variation of abduction/adduction within 5 degrees, 74% to 80% of the images were acceptable.Reliability was variable with limits of agreement between 4.96% and 15.15%. Observers more familiar with the software measuring package had higher reliability within and between occasions. Variability within and between observers decreased as MP increased. CONCLUSIONS: Poor positioning did not appear to be the main reason for the variation in reliability of MP. Repeat measurements were reliable although standardized technique, training, and familiarity with software measuring programmes did influence outcomes.