A comparison of survival models for prediction of eight-year revision risk following total knee and hip arthroplasty.

BACKGROUND: There is increasing interest in the development and use of clinical prediction models, but a lack of evidence-supported guidance on the merits of different modelling approaches. This is especially true for time-to-event outcomes, where limited studies have compared the vast number of modelling approaches available. This study compares prediction accuracy and variable importance measures for four modelling approaches in prediction of time-to-revision surgery following total knee arthroplasty (TKA) and total hip arthroplasty (THA). METHODS: The study included 321,945 TKA and 151,113 THA procedures performed between 1 January 2003 and 31 December 2017. Accuracy of the Cox model, Weibull parametric model, flexible parametric model, and random survival forest were compared, with patient age, sex, comorbidities, and prosthesis characteristics considered as predictors. Prediction accuracy was assessed using the Index of Prediction Accuracy (IPA), c-index, and smoothed calibration curves. Variable importance rankings from the Cox model and random survival forest were also compared. RESULTS: Overall, the Cox and flexible parametric survival models performed best for prediction of both TKA (integrated IPA 0.056 (95% CI [0.054, 0.057]) compared to 0.054 (95% CI [0.053, 0.056]) for the Weibull parametric model), and THA revision. (0.029 95% CI [0.027, 0.030] compared to 0.027 (95% CI [0.025, 0.028]) for the random survival forest). The c-index showed broadly similar discrimination between all modelling approaches. Models were generally well calibrated, but random survival forest underfitted the predicted risk of TKA revision compared to regression approaches. The most important predictors of revision were similar in the Cox model and random survival forest for TKA (age, opioid use, and patella resurfacing) and THA (femoral cement, depression, and opioid use). CONCLUSION: The Cox and flexible parametric models had superior overall performance, although all approaches performed similarly. Notably, this study showed no benefit of a tuned random survival forest over regression models in this setting.

Do Dual-mobility Cups Reduce Revision Risk in Femoral Neck Fractures Compared With Conventional THA Designs? An International Meta-analysis of Arthroplasty Registries.

BACKGROUND: Dual-mobility cups in THA were designed to reduce prosthesis instability and the subsequent risk of revision surgery in high-risk patients, such as those with hip fractures. However, there are limited data from clinical studies reporting a revision benefit of dual-mobility over conventional THA. Collaboration between anthroplasty registries provides an opportunity to describe international practice variation and compare between-country, all-cause revision rates for dual-mobility and conventional THA. QUESTIONS/PURPOSES: We summarized observational data from multiple arthroplasty registries for patients receiving either a dual-mobility or conventional THA to ask: (1) Is dual-mobility use associated with a difference in risk of all-cause revision surgery compared with conventional THA? (2) Are there specific patient characteristics associated with dual-mobility use in the hip fracture population? (3) Has the use of dual-mobility constructs changed over time in patients receiving a THA for hip fracture? METHODS: Six member registries of the International Society of Arthroplasty Registries (from Australia, Denmark, Sweden, the Netherlands, the United Kingdom, and the United States) provided custom aggregate data reports stratified by acetabular cup type (dual-mobility or conventional THA) in primary THA for hip fracture between January 1, 2002, and December 31, 2019; surgical approach; and patient demographic data (sex, mean age, American Society of Anesthesiologists class, and BMI). The cumulative percent revision and mortality were calculated for each registry. To determine a global hazard ratio of all-cause revision for dual-mobility compared with conventional THA designs, we used a pseudoindividual patient data approach to pool Kaplan-Meier prosthesis revision data from each registry and perform a meta-analysis. The pseudoindividual patient data approach is a validated technique for meta-analysis of aggregate time-to-event survival data, such as revision surgery, from multiple sources. Data were available for 15,024 dual-mobility THAs and 97,200 conventional THAs performed for hip fractures during the study period. RESULTS: After pooling of complete Kaplan-Meier survival data from all six registries, the cumulative percent revision for conventional THA was 4.3% (95% confidence interval [CI] 4.2% to 4.5%) and 4.7% (95% CI 4.3% to 5.3%) for dual-mobility THA at 5 years. We did not demonstrate a lower risk of all-cause revision for patients receiving dual-mobility over conventional THA designs for hip fracture in the meta-analysis once between-registry differences were adjusted for (HR 0.96 [95% CI 0.86 to 1.06]). A lower proportion of dual-mobility procedures were revised for dislocation than conventional THAs (0.9% versus 1.4%) but a higher proportion were revised for infection (1.2% versus 0.8%). In most registries, a greater proportion of dual-mobility THA patients were older, had more comorbidities, and underwent a posterior approach compared with conventional THA (p < 0.001). The proportion of dual-mobility THA used to treat hip fractures increased in each registry over time and constituted 21% (2438 of 11,874) of all THA procedures in 2019. CONCLUSION: The proportion of dual-mobility THAs in patients with hip fractures increased over time, but there was large variation in use across countries represented here. Dual-mobility cups were not associated with a reduction in the overall risk of revision surgery in patients with hip fractures. A randomized controlled trial powered to detect the incidence of dislocation and subsequent revision surgery is required to clarify the efficacy of dual-mobility cups to treat hip fractures. LEVEL OF EVIDENCE: Level III, therapeutic study.

Periprosthetic fracture as a late mode of failure of the Anatomique Benoist Girard II femoral prosthesis.

AIM: The Anatomique Benoist Girard (ABG) II femoral implant was a commonly used stem for primary total hip replacement (THR) at our institution (Launceston, Tasmania Australia). We identified peri-prosthetic fracture as the main cause of late failure. METHODS: The late periprosthetic fracture rate for ABG II implants was reviewed with national statistics, using Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) data. National revision rates for periprosthetic fracture were used to compare ABG II with all other cementless femoral stems. RESULT: ABG II stems accounted for 1% (2719 implants) of all femoral stem implants in Australia during the 12-year review period, compared to 23% (587 implants) in Launceston Hospitals. Although the Launceston cumulative percent revision rate for the ABG II stem was lower than the National rate at all time points, the reasons for revision were similar. The most common reason for revision of ABG II was fracture (56.8%), followed by loosening (15.3%). This differs from the reasons for revision in other cementless prostheses (loosening 23.9%, fracture 20.8%, dislocation 18.7%). Cumulative percent revision rates from late periprosthetic fracture, were higher for the ABG II stem than other cementless femoral prostheses. CONCLUSION: This review of the AOANJRR has confirmed a local and national higher revision rate of the ABG II stem due to late periprosthetic fracture compared with other cementless stems. Stem design must be considered to reduce the risk of late periprosthetic fracture.

Bipolar Hemiarthroplasty Does Not Result in a Higher Risk of Revision Compared with Total Hip Arthroplasty for Displaced Femoral Neck Fractures: An Instrumental Variable Analysis of 36,118 Procedures from the Australian Orthopaedic Association National Joint Replacement Registry.

BACKGROUND: Previous randomized studies have suggested that there is no short-term difference between the risk of revision following total hip arthroplasty (THA) and hemiarthroplasty (HA) for hip fracture in elderly patients. The aim of the present study was to compare the long-term revision rates of primary THA and HA for femoral neck fracture in order to determine whether unipolar or bipolar HA increases the all-cause risk of revision in patients 50 to 79 years old. METHODS: Data for 36,188 patients who underwent primary arthroplasty, including 13,035 unipolar and 8,220 bipolar HAs and 14,863 THAs, from September 1, 1999, to December 31, 2019, were obtained from the Australian Orthopaedic Association National Joint Replacement Registry. Unadjusted analyses were performed, as well as analyses adjusted for age, sex, femoral cement, and procedure year. The primary outcome was time to first revision for any cause. Secondary analyses were performed for the reason for revision (i.e., infection, dislocation, and periprosthetic fracture). Instrumental variable analysis of hospital preference (for either HA or THA) was performed in order to mitigate the effect of any unmeasured confounding. All analyses were restricted to hospitals performing at least 10 procedures in the prior year. RESULTS: A total of 18,955 procedures were available for the comparison of modular unipolar HA to THA. Both the adjusted analysis performed with use of Cox proportional hazards (hazard ratio [HR], 1.94; 95% confidence interval [CI], 1.64 to 2.31; p < 0.001) and the instrumental variable analysis (HR, 2.82; 95% CI, 1.89 to 4.22; p < 0.001) demonstrated a higher risk of revision following modular unipolar HA compared with THA from 3 months postoperatively. A total of 13,168 procedures were available for the comparison of bipolar HA to THA. The adjusted analysis performed with use of Cox proportional hazards showed a significantly higher risk of revision for bipolar HA (HR, 1.29; 95% CI, 1.08 to 1.54; p = 0.01). The instrumental variable analysis showed a similar effect size that was not significant (HR, 1.27; 95% CI, 0.91 to 1.78; p = 0.16). CONCLUSIONS: Bipolar HA and THA demonstrated no significant difference in revision risk at long-term follow-up. Unipolar HA demonstrated higher risk of revision from 3 months postoperatively compared to THA. The higher risk of revision for dislocation observed following THA may be offset by the higher risk of revision for acetabular erosion or pain following bipolar HA, resulting in more equivalent revision risk. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Acetabular screws do not improve early revision rates in primary total hip arthroplasty. An instrumented registry analysis.

BACKGROUND: Initial stability of uncemented acetabular components in total hip arthroplasty (THA) is important for osseointegration and potentially enhanced by screw fixation. We used Australian Orthopaedic Association National Joint Replacement Registry data to determine whether screw usage influences uncemented acetabular component survival. METHODS: Primary THA with uncemented acetabular components performed for osteoarthritis from 1999 to 2018 was included. Survivorship was calculated using Kaplan-Meier estimates of cumulative percent revision (CPR). Comparisons used Cox proportional hazards method. An instrumental variable analysis adjusted for surgeon preference for screws as a confounding factor was used. RESULTS: Three hundred thirty thousand one hundred ninety-two THAs were included (31.8% with screws, 68.2% without). Two hundred twenty thousand six hundred seven were included in the instrumental variable analysis. Revision rate of acetabular components (all causes) was higher with screws during the first six years (hazard ratio (HR) = 1.45 (95% CI 1.34, 1.57), p < 0.001) and lower thereafter (HR = 0.81 (95% CI 0.67, 0.98), p = 0.027). Revision rate of acetabular components for loosening was higher with screws over the entire study period (HR = 1.73 (95% CI 1.51, 1.98), p < 0.001). Overall THA revision rate was higher with screws during the first six years (HR = 1.20 (95% CI 1.15, 1.26), p < 0.001) but lower thereafter (HR = 0.89 (95% CI 0.81, 0.98), p = 0.020). Revision rate for dislocation was higher with screws over the entire period (HR = 1.16 (95% CI 1.06, 1.26), p < 0.001). Instrumental variable analysis revealed higher revision rates with acetabular screws in the first six years. (HR = 1.18 (95% CI 1.09-1.29), p < 0.001). CONCLUSION: Screws did not confer a protective effect against acetabular loosening and were not associated with long-term negative consequences.

Revision Risk After Unipolar or Bipolar Hemiarthroplasty for Femoral Neck Fractures: An Instrumental Variable Analysis of 62,875 Procedures from the Australian Orthopaedic Association National Joint Replacement Registry.

BACKGROUND: There remains much international practice variation regarding the choice of a unipolar or bipolar prosthesis design for displaced femoral neck fractures that are treated with hemiarthroplasty. The purpose of the present study was to compare revision rates following primary hemiarthroplasty for femoral neck fracture to determine if the unipolar hemiarthroplasty design increases the risk of revision arthroplasty for all causes. METHODS: Instrumental variable analysis was performed with use of data that had been entered into the Australian Orthopaedic Association National Joint Replacement Registry from September 1, 1999, to December 31, 2018. Sixty-two thousand, eight hundred and seventy-five patients with femoral neck fractures that were treated with primary modular unipolar or bipolar hemiarthroplasty procedure were analyzed. Hospital preference for prosthesis design in the 12 months prior to the index procedure was used as an instrument to adjust for unmeasured confounding. The primary outcome was time to first revision for any cause. Secondary analyses were performed on the reason for revision (infection, dislocation, periprosthetic fracture, or acetabular erosion), the use of cement femoral stem fixation, and the type of stem (polished or matte). RESULTS: Modular unipolar hemiarthroplasty was associated with a higher rate of revision at >2.5 years (hazard ratio [HR], 1.86; 95% confidence interval [CI], 1.46 to 2.36; p < 0.001), but there was no difference between the groups before 2.5 years (HR, 0.98; 95% CI, 0.85 to 1.13; p = 0.79). Protective factors for revision included female sex (HR, 0.82; 95% CI, 0.74 to 0.9), use of cemented fixation (HR, 0.69; 95% CI, 0.62 to 0.77), and surgery performed in a public hospital setting (HR 0.79; 95% CI, 0.70 to 0.89). Modular unipolar prostheses had a greater risk of revision for acetabular erosion, particularly in later time periods (HR at ≥5.5 years, 5.10; 95% CI, 2.40 to 10.83; p < 0.001), while being protective against periprosthetic fractures (HR, 0.72; 95% CI, 0.59 to 0.87; p < 0.001) at all time points. There was no difference in terms of the risk of revision for infection, dislocation, or stem type. CONCLUSIONS: Bipolar hemiarthroplasty designs resulted in a lower risk of revision than unipolar designs. Unipolar hemiarthroplasties are justified for patients with femoral neck fracture and a shorter life expectancy (≤2.5 years). LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

The Effect of Surgeon Preference for Selective Patellar Resurfacing on Revision Risk in Total Knee Replacement: An Instrumental Variable Analysis of 136,116 Procedures from the Australian Orthopaedic Association National Joint Replacement Registry.

BACKGROUND: The optimum strategy regarding resurfacing the patella in total knee replacement (TKR) remains debated, with wide national and international variability. To minimize the confounders of a direct comparison of cases with or without resurfacing, we performed an instrumental variable analysis examining revision risk on the basis of surgeon preference for patellar resurfacing in TKR, specifically examining the subsequent patellar revision risk and all-cause revision risk among cases of surgeons preferring to perform resurfacing on a selective basis compared with those whose preference is to routinely resurface or who infrequently perform resurfacing. METHODS: Data from the Australian Orthopaedic Association National Joint Replacement Registry from 1999 to 2016 were obtained to assess the cumulative percent revision, hazard ratio, and revision diagnoses for 3 cohorts, grouped according the surgeons' patellar-resurfacing preferences: infrequently (<10% of the time), selectively (10% to <90% of the time), or routinely (≥90% of the time). To avoid confounding from implant design or surgeon performance, only minimally stabilized TKRs using hybrid or cemented fixation and performed by surgeons performing ≥50 TKR procedures per year were included. RESULTS: A total of 136,116 procedures were included, with patients in all 3 cohorts having similar demographics. The selectively resurfaced cohort had a higher patellar revision risk compared with the routinely resurfaced cohort, with this risk being greatest in the first 4.5 years following the primary procedure, including 306% higher in the first 1.5 years, and remaining 50% higher after 4.5 years. In a subgroup analysis, increased revision risk was observed among males, females, those <65 years of age, and those ≥65 years of age. The infrequently resurfaced cohort had the highest risk of subsequent patellar revision, up to 482% higher, as seen in the first 1.5 years after the primary procedure, compared with the routinely resurfaced cohort. Additionally, the risk of all-cause revision was 20% higher for the selectively resurfaced cohort compared with routinely resurfaced. CONCLUSIONS: Surgeons who preferred selective resurfacing of the patella had a higher risk of patellar revision than those who had preference for routine resurfacing of the patella. Overall, a greater preference for resurfacing resulted in a lower risk of patellar revision. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Impact of Image-Derived Instrumentation on Total Knee Arthroplasty Revision Rates: An Analysis of 83,823 Procedures from the Australian Orthopaedic Association National Joint Replacement Registry.

BACKGROUND: Computer navigation and image-derived instrumentation (IDI) are technology-based methods developed to improve outcomes and potentially reduce revision total knee arthroplasty (TKA). IDI refers to the use of manufactured, patient-specific surgical jigs. Conflicting reports exist on IDI-associated improvements in outcomes. The primary aim of the current study was to compare the rates of revision among TKA cases in which components were initially implanted with use of IDI, computer navigation, or neither of these methods ("other" TKA). The secondary aim was to determine whether the outcomes of IDI differed for specific subgroups. METHODS: Data were obtained from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) for the 3 TKA groups: IDI, computer-navigated, and other TKA. The study period was from the first IDI procedure recorded by the AOANJRR (April 2010) to December 31, 2016. The analysis was restricted to primary TKA cases undertaken for osteoarthritis and involving patellar resurfacing and the use of a cross-linked polyethylene insert. Subanalyses were performed to evaluate the effects of age, sex, implantation method, IDI manufacturer, prosthetic design, and prosthesis type on the rates of revision. Kaplan-Meier estimates of survivorship described the time to first revision. Hazard ratios (HRs, Cox proportional hazards models) with adjustment for age and sex were used to compare revision rates. RESULTS: IDI was used in 5,486 primary TKA procedures. There was no significant difference among the groups in the cumulative percent revision (CPR) at 5 years: 3.3% (95% confidence interval [CI], 2.4% to 4.6%) for IDI, 2.4% (95% CI, 2.2% to 2.7%) for the computer-navigated group, and 2.5% (95% CI, 2.3% to 2.7%) for other TKA. Posterior-stabilized TKA with use of the IDI method had a significantly higher rate of revision at >3 months (HR, 1.45 [95% CI, 1.02 to 2.04]; p = 0.036), as did IDI TKA in the ≤65-year-old patient cohort (HR, 1.52 [95% CI, 1.10 to 2.09]; p = 0.010), compared with computer-navigated TKA. Patellar revision was significantly more likely in the IDI group. CONCLUSIONS: IDI TKA demonstrated no overall difference in early to mid-term revision rates compared with standard implantation methods. However, elevated rates of revision were seen with posterior-stabilized TKA, in patients ≤65 years of age, and for patellar revision, meaning that this method should be used with some caution and requires further study. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Constrained Acetabular Components Used in Revision Total Hip Arthroplasty: A Registry Analysis.

BACKGROUND: Constrained acetabular components have a mechanism to lock in the femoral head. They have been developed to control postoperative dislocation, particularly in revision total hip arthroplasty (THA). Although these components may reduce dislocation, there are durability concerns: with reports of locking mechanism failures and loosening. We wanted to determine the outcome of constrained components in controlling dislocation, and if these components had a higher rate of second revision when compared with standard nonconstrained components. METHODS: Revision THA procedures from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) with a recorded primary procedure and initial diagnosis of osteoarthritis were used to compare constrained and standard nonconstrained components. Kaplan-Meier estimates of survivorship were calculated, and hazard ratios using Cox proportional hazard models were used to compare groups. RESULTS: There were 9509 THA first-revision procedures and 700 constrained components. Constrained components had a significantly higher revision rate after 3 months when large-head metal-on-metal components were included (hazard ratio = 1.37; P = .005). When large-head metal-on-metal components were excluded, there was no difference in the rate of second revision between the 2 groups. When the analysis was limited to first revision for dislocation, constrained components had a higher second revision rate for further dislocation after 9 months. CONCLUSION: Constrained acetabular components had similar second-revision rates when compared with standard nonconstrained components, both for all first-revision reasons and when used to treat dislocation. Although possibly used for the more difficult unstable hips, constrained components had a higher rate of second revision for further dislocation.

Lower prosthesis-specific 10-year revision rate with crosslinked than with non-crosslinked polyethylene in primary total knee arthroplasty.

BACKGROUND AND PURPOSE: While highly crosslinked polyethylene has shown reduced in vivo wear and lower rates of revision for total hip arthroplasty, there have been few long-term studies on its use in total knee arthroplasty (TKA). We compared the rate of revision of non-crosslinked polyethylene to that of crosslinked polyethylene in patients who underwent TKA for osteoarthritis. PATIENTS AND METHODS: We examined data from the Australian Orthopaedic Association National Joint Replacement Registry on 302,214 primary TKA procedures with non-crosslinked polyethylene and 83,890 procedures with crosslinked polyethylene, all of which were performed for osteoarthritis. The survivorship of the different polyethylenes was estimated using the Kaplan-Meier method and was compared using proportional hazard models. RESULTS: The 10-year cumulative revision rate for non-crosslinked polyethylene was 5.8% (95% CI: 5.7-6.0) and for crosslinked polyethylene it was 3.5% (95% CI: 3.2-3.8) (> 6.5-year HR = 2.2 (1.5-3.1); p < 0.001). There was no effect of surgical volume or method of prosthesis fixation on outcome. There were 4 different TKA designs that had a minimum of 2,500 procedures in at least 1 of the polyethylene groups and a follow-up of ≥ 5 years. 2 of these, the NexGen and the Natural Knee II, had a lower rate of revision for crosslinked polyethylene. The Scorpio NRG/Series 7000 and the Triathlon Knee did not show a lower rate of revision for crosslinked polyethylene. INTERPRETATION: There is a lower rate of revision for crosslinked polyethylene in TKA, and this appears to be prosthesis-specific and when it occurs is most evident in patients < 65 years of age. The difference in revision rates was mainly due to revisions because of lysis and loosening.