Collared Cementless Femoral Components Reduce the Revision Rates in Primary Total Hip Arthroplasty Using the Direct Anterior Approach: An Australian Orthopaedic Association National Joint Replacement Registry Study.

BACKGROUND: An increased risk of periprosthetic fracture and aseptic loosening is reported when the direct anterior approach (DAA) is used for total hip arthroplasty (THA), especially with cementless implants. We assessed the rate of revision comparing collared and collarless femoral stems when using the DAA for THA. METHODS: We used data from the Australian Orthopaedic Association National Joint Replacement Registry for primary THA for osteoarthritis inserted with the DAA between January 2015 and December 2022. There were 48,567 THAs that used the DAA (26,690 collarless cementless, 10,161 collared cementless, and 11,716 cemented). Cumulative percent revision was calculated for all-cause revision, revision for periprosthetic femoral fractures, and aseptic femoral stem loosening. Cox proportional hazard ratios [HRs] were used to compare the revision of collared and collarless cementless stems. We also compared collared cementless stems and cemented stems. RESULTS: A higher rate of all-cause revision within 3 months of surgery was observed with collarless compared to collared cementless implants (HR: 1.99 [95% confidence interval (CI), 1.56 to 2.54]; P < .001). Similarly, collarless cementless implants were associated with a greater rate of revision for fracture in the first 6 months (HR: 2.90 [95% CI, 1.89 to 4.45]; P < .001) and after 6 months (HR 10.04 [95% CI 1.38 to 73.21]; P = .02), as well as an increased rate of revision for aseptic loosening after 2 years (HR: 5.76 [95% CI, 1.81 to 18.28], P = .003). Collared cementless and cemented stems performed similarly. CONCLUSION: Collared stems were associated with a reduced rate of all-cause revision for cementless THA performed via the DAA. The reduction in risk may be due to protection from periprosthetic femoral fracture and aseptic loosening.

A systematic review and meta-analysis of short-stay programmes for total hip and knee replacement, focusing on safety and optimal patient selection.

BACKGROUND: Short-stay joint replacement programmes are used in many countries but there has been little scrutiny of safety outcomes in the literature. We aimed to systematically review evidence on the safety of short-stay programmes versus usual care for total hip (THR) and knee replacement (KR), and optimal patient selection. METHODS: A systematic review and meta-analysis. Randomised controlled trials (RCTs) and quasi-experimental studies including a comparator group reporting on 14 safety outcomes (hospital readmissions, reoperations, blood loss, emergency department visits, infection, mortality, neurovascular injury, other complications, periprosthetic fractures, postoperative falls, venous thromboembolism, wound complications, dislocation, stiffness) within 90 days postoperatively in adults ≥ 18 years undergoing primary THR or KR were included. Secondary outcomes were associations between patient demographics or clinical characteristics and patient outcomes. Four databases were searched between January 2000 and May 2023. Risk of bias and certainty of the evidence were assessed. RESULTS: Forty-nine studies were included. Based upon low certainty RCT evidence, short-stay programmes may not reduce readmission (OR 0.95, 95% CI 0.12-7.43); blood transfusion requirements (OR 1.75, 95% CI 0.27-11.36); neurovascular injury (OR 0.31, 95% CI 0.01-7.92); other complications (OR 0.63, 95% CI 0.26-1.53); or stiffness (OR 1.04, 95% CI 0.53-2.05). For registry studies, there was no difference in readmission, infection, neurovascular injury, other complications, venous thromboembolism, or wound complications but there were reductions in mortality and dislocations. For interrupted time series studies, there was no difference in readmissions, reoperations, blood loss volume, emergency department visits, infection, mortality, or neurovascular injury; reduced odds of blood transfusion and other complications, but increased odds of periprosthetic fracture. For other observational studies, there was an increased risk of readmission, no difference in blood loss volume, infection, other complications, or wound complications, reduced odds of requiring blood transfusion, reduced mortality, and reduced venous thromboembolism. One study examined an outcome relevant to optimal patient selection; it reported comparable blood loss for short-stay male and female participants (p = 0.814). CONCLUSIONS: There is low certainty evidence that short-stay programmes for THR and KR may have non-inferior 90-day safety outcomes. There is little evidence on factors informing optimal patient selection; this remains an important knowledge gap.

Perception of Perioperative Risk for Arthroplasty Patients: A Poll of Australian Orthopedic Surgeons.

BACKGROUND: There is growing interest in the perioperative management of patients who have indications for hip and knee arthroplasty in the setting of modifiable risk factors such as morbid obesity, poorly controlled diabetes, and smoking. A recent survey of the American Association of Hip and Knee Surgeons (AAHKS) found that 95% of respondents address modifiable risk factors prior to surgery. The aim of this study was to poll Australian arthroplasty surgeons regarding their approach to patients who have modifiable risk factors. METHODS: The survey tool used in the AAHKS study was adapted for use in the Australian context and distributed to the membership of the Arthroplasty Society of Australia via SurveyMonkey. There were 77 responses received, representing a response rate of 64%. RESULTS: The majority of respondents were experienced, high volume arthroplasty surgeons. Overall, 91% of respondents restricted access to arthroplasty for patients who have modifiable risk factors. There were 72% restricting access for excessive body mass index, 85% for poor diabetic control, and 46% for smoking. Most respondents made decisions based on personal experience or literature review rather than hospital or departmental pressures. While 49% of surgeons believed that current payment systems did not impair their ability to achieve good outcomes, 58% believed that certain arthroplasty patients would benefit from additional intervention, based on their socioeconomic status. CONCLUSION: Over 90% of surgeons who responded address modifiable risk factors prior to surgery. This finding aligns with the practice patterns of AAHKS members, despite differences in healthcare systems.

Hip Arthroplasty Outcomes in the Presence of Kidney Failure: A National Data Linkage Study.

BACKGROUND: Patients who have kidney failure are at higher risk of requiring total hip arthroplasty (THA) and are at higher risk of complications. This study compared the rate of revision surgery and mortality following THA between patients who have kidney failure receiving long term dialysis or who had a kidney transplant and those who did not have kidney failure. METHODS: A data linkage study was performed using data from 2 national registries: a registry of dialysis and kidney transplant patients and a registry of THA procedures. Both registries had coverage of almost all procedures or treatments in Australia. Data from September 1999 to December 2016 were used. Mortality and revision surgery were compared between patients receiving dialysis, those who had a functioning kidney transplant, and patients who did not have kidney failure using Cox and Fine-Gray (competing risk) regression models. A total of 383,478 primary THA procedures were identified as people receiving dialysis (n = 490), who had a functioning kidney transplant (n = 459), or who did not have kidney failure (n = 382,529). RESULTS: There was no significant difference in the overall rate of revision surgery between the groups (dialysis versus no kidney failure HR = 1.20; 95% CI 0.76, 1.88, transplant versus no kidney failure (hazard ratio) HR = 1.01; 95% (confidence interval) CI 0.66, 1.53). The risk for death after surgery was significantly higher in the dialysis group compared to both the functioning transplant group (HR = 3.44; 95%CI 1.58, 7.5), and in those without kidney failure (HR = 4.13; 95%CI 3.25, 5.25). CONCLUSION: The rate of mortality after THA in patients on dialysis is higher than in patients who have a functioning transplant or those who do not have kidney failure, but there is no early excess mortality to suggest a difference in this metric due to the surgery.

Short-stem hip arthroplasty in Australia and the Netherlands: a comparison of 12,680 cases between the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) and the Dutch Arthroplasty Register (LROI).

BACKGROUND AND PURPOSE: We compared the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) and the Dutch Arthroplasty Register (LROI) regarding patient, prosthesis, and procedure characteristics as well as revision rates for uncemented short-stem total hip arthroplasties (THAs). PATIENTS AND METHODS: All THAs with an uncemented short-stemmed femoral component performed between 2009 and 2021 were included from the AOANJRR (n = 9,328) and the LROI (n = 3,352). Kaplan-Meier survival analyses and multivariable Schemper's weighted Cox regression analyses with data from 2009-2021 and 2015-2021 were performed with overall revision as endpoint. RESULTS: In Australia, the proportion of male patients (51% vs. 40%), patients with ASA III-IV score (30% vs. 3.7%), BMI ≥ 30.0 (39% vs. 19%), and femoral heads of 36 mm (58% vs. 20%) were higher than in the Netherlands. Short-stem THAs in Australia and the Netherlands had comparable 10-year revision rates (3.4%, 95% confidence interval [CI] 2.9-4.0 vs. 4.8%, CI 3.7-6.3). Multivariable Cox regression analyses with data from 2009-2021 showed a higher risk for revision of short-stem THAs performed in the Netherlands (HR 1.8, CI 1.1-2.8), whereas the risk for revision was comparable (HR 0.9, CI 0.5-1.7) when adjusted for more potential confounders using data from 2015-2021. CONCLUSION: Short-stem THAs in Australia and the Netherlands have similar crude and adjusted revision rates, which are acceptable at 10 years of follow-up.

What Is the Outcome of the First Revision Procedure of Primary THA for Osteoarthritis? A Study From the Australian Orthopaedic Association National Joint Replacement Registry.

BACKGROUND: Joint arthroplasty registries traditionally report survivorship outcomes mainly on primary joint arthroplasty. The outcome of first revision procedures is less commonly reported, because large numbers of primary procedures are required to analyze a sufficient number of first revision procedures. Additionally, adequate linkage of primary procedures to revisions and mortality is required. When undertaking revision hip surgery, it is important for surgeons to understand the outcomes of these procedures to better inform patients. QUESTIONS/PURPOSES: Using data from a large national joint registry, we asked: (1) What is the overall rate of revision of the first aseptic revision procedure for a primary THA? (2) Does the rate of revision of the first revision vary by the diagnosis for the first revision? (3) What is the mortality after the first revision, and does it vary by the reason for first revision? METHODS: The Australian Orthopaedic Association National Joint Replacement Registry longitudinally maintains data on all primary and revision joint arthroplasties, with nearly 100% capture. The analyses for this study were performed on primary THA procedures in patients with a diagnosis of osteoarthritis up to December 31, 2020, who had undergone subsequent revision. We excluded all primary THAs involving metal-on-metal and ceramic-on-metal bearing surfaces and prostheses with exchangeable necks because these designs may have particular issues associated with revisions, such as extensive soft tissue destruction, that are not seen with conventional bearings, making a comparative analysis of the first revision involving these bearing surfaces more complicated. Metal-on-metal bearing surfaces have not been used in Australia since 2017. We identified 17,046 first revision procedures from the above study population and after exclusions, included 13,713 first revision procedures in the analyses. The mean age at the first revision was 71 ± 11 years, and 55% (7496 of 13,713) of the patients were women. The median (IQR) time from the primary procedure to the first revision was 3 years (0.3 to 7.3), ranging from 0.8 years for the diagnosis of dislocation and instability to 10 years for osteolysis. There was some variation depending on the reason for the first revision. For example, patients undergoing revision for fracture were slightly older (mean age 76 ± 11 years) and patients undergoing revision for dislocation were more likely to be women (61% [2213 of 3620]). The registry has endeavored to standardize the sequence of revisions and uses a numerical approach to describe revision procedures. The first revision is the revision of a primary procedure, the second revision is the revision of the first revision, and so on. We therefore described the outcome of the first revision as the cumulative percent second revision. The outcome measure was the cumulative percent revision, which was defined using Kaplan-Meier estimates of survivorship to describe the time to the second revision. Hazard ratios from Cox proportional hazards models, adjusting for age and gender, were performed to compare the revision rates among groups. When possible, the cumulative percent second revision at the longest follow-up timepoint was determined with the available data, and when there were insufficient numbers, we used appropriate earlier time periods. RESULTS: The cumulative percent second revision at 18 years was 26% (95% confidence interval [CI] 24% to 28%). When comparing the outcome of the first revision by reason, prosthesis dislocation or instability had the highest rate of second revision compared with the other reasons for first revision. Dual-mobility prostheses had a lower rate of second revision for dislocation or instability than head sizes 32 mm or smaller and when compared to constrained prostheses after 3 months. There was no difference between dual-mobility prostheses and head sizes larger than 32 mm. There were no differences in the rate of second revision when first revisions for loosening, periprosthetic fracture, and osteolysis were compared. If cemented femoral fixation was performed at the time of the first revision, there was a higher cumulative percent second revision for loosening than cementless fixation from 6 months to 6 years, and after this time, there was no difference. The overall mortality after a first revision of primary conventional THA was 1% at 30 days, 2% at 90 days, 5% at 1 year, and 40% at 10 years. A first revision for periprosthetic fracture had the highest mortality at all timepoints compared with other reasons for the first revision. CONCLUSION: Larger head sizes and dual-mobility cups may help reduce further revisions for dislocation, and the use of cementless stems for a first revision for loosening seems advantageous. Surgeons may counsel patients about the higher risk of death after first revision procedures, particularly if the first revision is performed for periprosthetic fracture.Level of Evidence Level III, therapeutic study.

Low percentage of surgeons meet the minimum recommended unicompartmental knee arthroplasty usage thresholds: Analysis of 3037 Surgeons from Three National Joint Registries.

PURPOSE: The reported usage of UKA is around 10% in the UK, Australian and New Zealand joint registries. However, some authors recommend that a higher UKA usage of 20%, or a minimum 12 UKA cases per year, would reduce revision rates. The purpose of this study was to analyze the percentage of surgeons performing the recommended thresholds in these 3 registries. METHODS: Data from the UK, Australian and New Zealand registry databases was utilized from the time period since their respective introduction until 2017. All primary TKA and UKA performed for the diagnosis of osteoarthritis by surgeons with more than 100 recorded knee arthroplasties in their respective registry were included. The results between the registries were compared and a pooled analysis was performed. The number of surgeons meeting the recommended caseload of > 20% UKA yearly or 12 UKA cases yearly was calculated. RESULTS: We identified 3037 knee surgeons performing 1,556,440 knee arthroplasties, of which 131,575 were UKA (8.45%). Over 50% of knee surgeons in each registry had a proportion of less than 5% UKA of their knee replacement procedures. After pooling of data, median surgeon UKA usage was 2.0% (IQR 0-9.1%). The percentage of surgeons meeting the proposed caseload criteria was highest in New Zealand, 16.3%, followed by the UK at 12.4% and Australia 11.3% (p = 0.28). CONCLUSION: More than 50% of knee surgeons in UK, Australian and New Zealand joint registries perform less than 5% of UKA yearly. The majority of experienced knee surgeons are not meeting the recommended minimum thresholds, which might indicate that the recommended thresholds are not feasible for the vast majority of knee surgeons. The reasons behind this require further research. LEVEL OF EVIDENCE: Level III retrospective registry study.

Survivorship Comparisons of Ultracongruent, Cruciate-Retaining and Posterior-Stabilized Tibial Inserts Using a Single Knee System Design: Results From the Australian Orthopedic Association National Joint Replacement Registry.

BACKGROUND: Ultracongruent (UC) tibial inserts can increase knee replacement stability, but how survivorship compares to cruciate retaining (CR) or posterior stabilized (PS) inserts is unclear. METHODS: Data from a large joint registry were used to calculate the cumulative percent revision of a single popular knee design used with different inserts. There were 67,523 procedures, of which 12,434 were UC, 21,635 CR, and 33,454 PS. Revision rates and reasons for revision were analyzed. RESULTS: The cumulative percent revision at 18 years was 8.3% for UC, 9.2% for CR, and 8.9% for PS. There was no difference when UC was compared to CR, but PS had a higher risk of revision. Revision reasons were similar. CONCLUSION: Compared to the CR, an UC insert did not increase revision rates and was actually lower than a PS insert. An UC insert does not compromise long-term total knee arthroplasty survivorship in the Genesis II prosthesis.

No Difference in Revision Rate Between Low Viscosity and High Viscosity Cement Used in Primary Total Knee Arthroplasty.

BACKGROUND: Loosening remains one of the most common reasons for revision total knee arthroplasty (TKA). Cement viscosity has a potential role in reducing revision rates for loosening. The aim of this study was to assess the outcome for loosening of the 5 most used cemented knee prostheses by constraint type, based on the cement viscosity type used. METHODS: There were 214,708 TKA procedures performed between 1999 and 2020 for a diagnosis of osteoarthritis using the 5 most commonly used minimally stabilized, posterior stabilized, and medial pivot design cemented tibial components. Only procedures with a cemented tibial component were included. Outcomes for two different cement viscosities, 140,060 high viscosity and 74,648 low viscosity cement, were compared for each fixation type within each of the three stability groups. RESULTS: There was no difference in a risk of all-cause revision when high viscosity cement was used compared to low viscosity cement for minimally stabilized prostheses (hazards ratio [HR] 1.07 [95% CI 0.99-1.15], P = .09), posterior stabilized prostheses (HR 1.03 [95% CI 0.95-1.11], P = .53), and medial pivot design prostheses (HR 1.06 [95% CI 0.80-1.41], P = .67). No difference was observed between cement viscosity types for any of the prosthesis constraint types when aseptic loosening was assessed. CONCLUSIONS: We found no difference in the risk of revision for any reason, or for loosening, with cement viscosity for the most commonly used minimally stabilized, posterior stabilized, and medial pivot TKA. The role of cement viscosity in the risk of TKA revision remains unclear and further research is required. LEVEL OF EVIDENCE: Level III Retrospective comparative study.

Primary Total Knee Arthroplasty Revised for Instability: A Detailed Registry Analysis.

BACKGROUND: Instability after total knee arthroplasty is a common but poorly understood complication. METHODS: Data from a large national registry was used to study patient and prosthesis characteristics of 2605 total knee arthroplasty revisions for instability. The cumulative percent revision was calculated using Kaplan-Meier estimates, and Cox proportional models used to compare revision rates. The rate of further revision was analyzed with regard to prostheses used in the first revision. RESULTS: Instability increased from 6% of all first revision procedures in 2003 to 13% in 2019. The revision risk was lower for minimally stabilized prostheses, males, and patients aged ≥65 years. Polyethylene insert exchange was used for 55% of revision procedures, using a thicker insert in 93% and a change in insert conformity in 24% of cruciate-retaining knees. The increase in either thickness or conformity had no effect on the rate of further revision. After a revision for instability, 24% had a second revision by 14 years. Recurrent instability accounted for 32% of further revisions. A lower second revision rate was seen after revision of both femoral and tibial components, and where constrained components were used. CONCLUSION: Revision for instability is increasing. Revising both femoral and tibial components led to a lower rate of second revision compared to a change in insert alone. Recurrent instability was common.

Impact of patient and prosthesis characteristics on common reasons for total knee replacement revision: a registry study of 36,626 revision cases from Australia, Sweden, and USA.

BACKGROUND AND PURPOSE: Total knee replacement (TKR) studies usually analyze all-cause revision when considering relationships with patient and prosthesis factors. We studied how these factors impact different revision diagnoses. PATIENTS AND METHODS: We used data from 2003 to 2019 of TKR for osteoarthritis from the arthroplasty registries of Sweden, Australia, and Kaiser Permanente, USA to study patient and prosthesis characteristics for specific revision diagnoses. There were 1,072,924 primary TKR included and 36,626 were revised. Factors studied included age, sex, prosthesis constraint, fixation method, bearing mobility, polyethylene type, and patellar component use. Revision diagnoses were arthrofibrosis, fracture, infection, instability, loosening, pain, patellar reasons, and wear. Odds ratios (ORs) for revision were estimated and summary effects were calculated using a meta-analytic approach. RESULTS: We found between-registry consistency in 15 factor/reason analyses. Risk factors for revision for arthrofibrosis were age < 65 years (OR 2.0; 95% CI 1.4-2.7) and mobile bearing designs (MB) (OR 1.7; CI 1.1-2.5), for fracture were female sex (OR 3.2; CI 2.2-4.8), age ≥ 65 years (OR 2.8; CI 1.9-4) and posterior stabilized prostheses (PS) (OR 2.1; CI 1.3-3.5), for infection were male sex (OR 1.9; CI 1.7-2.0) and PS (OR 1.5; CI 1.2-1.8), for instability were age < 65 years (OR 1.5; CI 1.3-1.8) and MB (OR 1.5; CI 1.1-2.2), for loosening were PS (OR 1.5; CI 1.4-1.6), MB (OR 2.2; CI 1.6-3.0) and use of ultra-high molecular weight polyethylene (OR 2.3; CI 1.8-2.9), for patellar reasons were not resurfacing the patella (OR 13.6; CI 2.1-87.2) and MB (OR 2.0; CI 1.2-3.3) and for wear was cementless fixation (OR 4.9; CI 4.3-5.5). INTERPRETATION: Patients could be counselled regarding specific age and sex risks. Use of minimally stabilized, fixed bearing, cemented prostheses, and patellar components is encouraged to minimize revision risk.

The effect of patient and prosthesis factors on revision rates after total knee replacement using a multi-registry meta-analytic approach.

BACKGROUND AND PURPOSE: Characteristics of patients receiving total knee arthroplasty (TKA) and prostheses used vary between regions and change with time. How these practice variations influence revision remains unclear. We combined registry data for better understanding of the impact of variation, which could potentially improve revision rates. PATIENTS AND METHODS: We used data from 2003 to 2019 for primary TKA from arthroplasty registries of Sweden (SKAR), Australia (AOANJRR), and Kaiser Permanente (KPJRR). We included 1,072,924 TKA procedures for osteoarthritis. Factors studied included age, sex, ASA class, BMI category, prosthesis constraint, fixation, bearing mobility, patellar resurfacing, and polyethylene type. Cumulative percentage revision (CPR) was calculated using Kaplan-Meier estimates, and unadjusted Cox hazard ratios were used for comparisons. Random-effects generic inverse-variance meta-analytic methods were used to determine summary effects. RESULTS: We found similarities in age and sex, but between-registry differences occurred in the other 7 factors studied. Patients from Sweden had lower BMI and ASA scores compared with other registries. Use of cement fixation was similar in the SKAR and KPJRR, but there were marked differences in patellar resurfacing and posterior stabilized component use. Meta-analysis results regarding survivorship favored patients aged ≥ 65 years and minimally stabilized components. There were inconsistent results with time for sex, fixation, and bearing mobility, and no differences for the patellar resurfacing or polyethylene type comparisons. INTERPRETATION: Marked practice variation was found. Use of minimally stabilized and possibly also cemented and fixed bearing prostheses is supported.

Do Fixed or Mobile Bearing Implants Have Better Survivorship in Medial Unicompartmental Knee Arthroplasty? A Study From the Australian Orthopaedic Association National Joint Replacement Registry.

BACKGROUND: During the last 5 years, there has been an increase in the use of unicompartmental knee arthroplasty (UKA) to treat knee osteoarthritis in Australia, and these account for almost 6% of annual knee replacement procedures. However, there is debate as to whether a fixed bearing or a mobile bearing design is best for decreasing revision for loosening and disease progression as well as improving survivorship. Small sample sizes and possible confounding in the studies on the topic may have masked differences between fixed and mobile bearing designs. QUESTIONS/PURPOSES: Using data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR), we selected the four contemporary designs of medial compartment UKA: mobile bearing, fixed modular, all-polyethylene, and fixed molded metal-backed used for the treatment of osteoarthritis to ask: (1) How do the different designs of unicompartmental knees compare with survivorship as measured by cumulative percentage revision (CPR)? (2) Is there a difference in the revision rate between designs as a function of patient sex or age? (3) Do the reasons for revision differ, and what types of revision procedures are performed when these UKA are revised? METHODS: The AOANJRR longitudinally maintains data on all primary and revision joint arthroplasties, with nearly 100% capture. The study population included all UKA procedures undertaken for osteoarthritis between September 1999 and December 2018. Of 56,628 unicompartmental knees recorded during the study period, 50,380 medial UKA procedures undertaken for osteoarthritis were included in the analysis after exclusion of procedures with unknown bearing types (31 of 56,628), lateral or patellofemoral compartment UKA procedures (5657 of 56,628), and those performed for a primary diagnosis other than osteoarthritis (560 of 56,628). There were 50,380 UKA procedures available for analysis. The study group consisted of 40% (20,208 of 50,380) mobile bearing UKA, 35% (17,822 of 50,380) fixed modular UKA, 23% (11,461 of 50,380) all-polyethylene UKA, and 2% (889 of 50,380) fixed molded metal-backed UKA. There were similar sex proportions and age distributions for each bearing group. The overall mean age of patients was 65 ± 9.4 years, and 55% (27,496 of 50,380) of patients were males. The outcome measure was the CPR, which was defined using Kaplan-Meier estimates of survivorship to describe the time to the first revision. Hazard ratios from Cox proportional hazards models, adjusted for sex and age, were performed to compare the revision rates among groups. The cohort was stratified into age groups of younger than 65 years and 65 years and older to compare revision rates as a function of age. Differences among bearing groups for the major causes and modes of revision were assessed using hazard ratios. RESULTS: At 15 years, fixed modular UKA had a CPR of 16% (95% CI 15% to 17%). In comparison, the CPR was 23% (95% CI 22% to 24%) for mobile bearing UKA, 26% (95% CI 24% to 27%) for all-polyethylene UKA, and 20% (95% CI 16% to 24%) for fixed molded metal-backed UKA. The lower revision rate for fixed modular UKA was seen through the entire period compared with mobile bearing UKA (hazard ratio 1.5 [95% CI 1.4 to 1.6]; p < 0.001) and fixed molded metal-backed UKA (HR 1.3 [95% CI 1.1 to 1.6]; p = 0.003), but it varied with time compared with all-polyethylene UKA. The findings were consistent when stratified by sex or age. Although all-polyethylene UKA had the highest revision rate overall and for patients younger than 65 years, for patients aged 65 years and older, there was no difference between all-polyethylene and mobile bearing UKA. When compared with fixed modular UKA, a higher revision risk for loosening was shown in both mobile bearing UKA (HR 1.7 [95% CI 1.5 to 1.9]; p < 0.001) and all-polyethylene UKA (HR 2.4 [95% CI 2.1 to 2.7]; p < 0.001). The revision risk for disease progression was higher for all-polyethylene UKA at all time points (HR 1.4 [95% CI 1.3 to 1.6]; p < 0.001) and for mobile bearing UKA after 8 years when each were compared with fixed modular UKA (8 to 12 years: HR 1.4 [95% CI 1.2 to 1.7]; p < 0.001; 12 or more years: HR 1.9 [95% CI 1.5 to 2.3]; p < 0.001). The risk of revision to TKA was higher for mobile bearing UKA compared with fixed modular UKA (HR 1.4 [95% CI 1.3 to 1.5]; p < 0.001). CONCLUSION: If UKA is to be considered for the treatment of isolated medial compartment osteoarthritis, the fixed modular UKA bearing has the best survivorship of the current UKA designs. LEVEL OF EVIDENCE: Level III, therapeutic study.

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.

Variation and trends in reasons for knee replacement revision: a multi-registry study of revision burden.

Background and purpose - Studies describing time-related change in reasons for knee replacement revision have been limited to single regions or institutions, commonly analyze only 1st revisions, and may not reflect true caseloads or findings from other areas. We used revision procedure data from 3 arthroplasty registries to determine trends and differences in knee replacement revision diagnoses.Patients and methods - We obtained aggregated data for 78,151 revision knee replacement procedures recorded by the Swedish Knee Arthroplasty Register (SKAR), the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR), and the Kaiser Permanente Joint Replacement Registry (KPJRR) for the period 2003-2017. Equivalent diagnosis groups were created. We calculated the annual proportions of the most common reasons for revision.Results - Infection, loosening, and instability were among the 5 most common reasons for revision but magnitude and ranking varied between registries. Over time there were increases in proportions of revisions for infection and decreases in revisions for wear. There were inconsistent proportions and trends for the other reasons for revision. The incidence of revision for infection showed a uniform increase.Interpretation - Despite some differences in terminology, comparison of registry-recorded revision diagnoses is possible, but defining a single reason for revision is not always clear-cut. There were common increases in revision for infection and decreases in revision for wear, but variable changes in other categories. This may reflect regional practice differences and therefore generalizability of studies regarding reasons for revision is unwise.

Does Knee Prosthesis Survivorship Improve When Implant Designs Change? Findings from the Australian Orthopaedic Association National Joint Replacement Registry.

BACKGROUND: TKA generally has excellent long-term survivorship. When a new knee system supersedes a previous model, increased survivorship, improved functional performance, or both may be expected, because key areas of design modification are often targeted to address wear, stability, and the patellofemoral articulation. However, not all design changes are beneficial, and to our knowledge, knee arthroplasty has not been systematically evaluated in the context of design changes that occur during the development of new knee arthroplasty systems. QUESTIONS/PURPOSES: Using the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) we performed multiple old-to-new comparisons of frequently used contemporary knee implants to ask: (1) does overall prosthesis survivorship free from revision increase when a new knee prosthesis system is introduced to replace a prior prosthesis system? (2) Has survivorship free from revision improved for the revision indications of wear, instability, and patellofemoral articulation issues, where development efforts have been concentrated? METHODS: Data from the AOANJRR from September 1999 to December 2017 were used to compare the survivorship of prostheses free from revision at a maximum of 17 years in procedures where a new design model was introduced to replace a prior knee system from the same manufacturer. Only prosthesis systems used in a minimum of 2000 primary TKA procedures for osteoarthritis that had a minimum of 5 years of follow-up were included. Varus-valgus constrained and hinge TKA designs were excluded. Cruciate-retaining, posterior-stabilized, and medial pivot-design knees were considered separately. The new and old prosthesis systems were paired for analysis. Survivorship was calculated with Kaplan Meier estimates and comparisons were performed using the Cox proportional hazards method. Subanalyses according to the three main revision indications were performed, and where possible, analyses were performed based on polyethylene types (highly cross-linked polyethylene and ultra-high-molecular-weight polyethylene), combined and separated. Revision was defined as a reoperation of a previous knee arthroplasty in which one or more of the components was removed, replaced, or added. There were 323,955 TKA procedures and 11 new prosthesis system designs that were introduced to replace an earlier knee system from the same manufacturer. Of these prosthesis system pairs, six were cruciate-retaining prostheses, four were posterior-stabilized designs, and one was a medial pivot design. RESULTS: Six of the 11 knee system pairs showed improved survivorship with the new design, three were no different, and in two, the newer prosthesis systems had a higher rate of revision than the old one did. When revision for wear was analyzed, five prosthesis systems showed improvement, five were no different, and one had a higher rate of revision than the previous system did. There was no improvement in the rate of revision for instability; seven new prosthesis systems showed no difference from the previous system and four new prosthesis systems had a higher rate of revision than the previous system did. A subanalysis of revision for patellofemoral complications showed improvement in two comparisons, no difference in six, and a higher revision rate in two; one could not be calculated because of an insufficient number of revisions for this reason. CONCLUSIONS: It is difficult to predict whether a new system will demonstrate better survival than a previous one, and widespread uptake of a new design before a benefit is shown in robust clinical studies is unwise. Similarly, adoption of a new system for which there is no difference in survivorship from a previous model may be premature because a new device may have associated unknown and unintended consequences. Healthcare policy makers and therapeutic device regulators should similarly be guided by results and seek out peer-reviewed evidence before accepting change to established practice. Surgeons must be aware that implant changes may not translate into better survivorship and must seek compelling evidence of improvement in survival and/or function before changing systems. LEVEL OF EVIDENCE: Level III, therapeutic study.

Decreased Survival of Medial Pivot Designs Compared with Cruciate-retaining Designs in TKA Without Patellar Resurfacing.

BACKGROUND: The medial pivot TKA design was introduced in the 1990s. These are fixed-bearing, medial-conforming implants with virtually no translation in the medial part of the knee, in contrast to the flat lateral part of the insert allowing for translation similar to the native knee during flexion and extension. Most primary TKAs performed in Norway and Australia are cruciate-retaining. All of the medial pivot implants in our study are cruciate-sacrificing but without a post-cam mechanism. The medial pivot implant design was developed to more closely mimic native knee motion, in the hope of improving function, and not primarily as a more constrained knee for difficult cases. In the past 10 to 12 years, a second-generation medial-pivot design has emerged, but there are no larger registry studies on the survival of these implants. Both cruciate-retaining and medial pivot designs are reported in the Australian and Norwegian registries, allowing for large-scale, comparative survivorship studies. QUESTIONS/PURPOSES: (1) Is there any difference in survival between the medial pivot design and the three most commonly used cruciate-retaining TKA designs? (2) Is there any difference in survival among the different medial pivot implant designs? (3) What are the main indications for revision of medial pivot TKAs? METHODS: Registry data from the Australian Orthopaedic Association National Joint Replacement Registry and Norwegian Arthroplasty Register from 2005 until the end of 2017 were used to compare the five different brands of medial pivot TKA designs (total primary TKAs assessed: 6310). In Australia, the study group of medial pivot implants represented 9% (6012 of 72,477) of the total number of cemented/hybrid TKAs without patellar resurfacing; 345 had cementless femoral components. In Norway, the study group represented 1% (298 of 47,820) of the total number of TKAs with cemented tibias without patellar resurfacing; all had cemented femoral components. The control group consisted of the three most commonly used cruciate-retaining TKA designs (n = 70,870; Australia n = 54,554; Norway n = 16,316). All TKAs used a fixed-bearing, cemented tibial component and did not involve patella resurfacing. Kaplan-Meier survival analysis was assessed to estimate survivorship. We compared the groups by calculating the hazard ratios (HR) using Cox regression adjusted for age, gender and preoperative diagnosis with 95% CI. To answer our third question, we calculated the percentage of each revision indication from the total number of revisions in each group, and used a Cox regression analysis to compare revision causes and HRs. Analyses were performed separately by each registry. Accounting for competing risks (Fine and Gray) did not alter our findings []. RESULTS: After controlling for potential confounding variables such as gender, age and preoperative diagnosis, we found an increased revision risk for the medial pivot compared with cruciate-retaining TKA designs in Australia (HR 1.4 [95% CI 1.2 to 1.7]; p < 0.001), but not in Norway (HR 1.5 [95% CI 0.9 to 2.4]; p = 0.1). Two brands of the medial pivot design reported to the AOANJRR showed an increased risk of revision compared with cruciate-retaining designs: the Advance® II MP (HR 1.7 [95% CI 1.2 to 2.6]; p = 0.004) and the GMK® Sphere (HR 2.0 [95% CI 1.5 to 2.6]; p < 0.001), whereas the MRK (HR 0.7 [95% CI 0.4 to 1.5]; p = 0.4), the Evolution® MP (HR 1.4 [95% CI 1.0 to 1.9]; p = 0.06) and the SAIPH® (HR 0.9 [95% CI 0.5 to 1.5]; p = 0.7) showed no difference. The most common reasons for revision of medial pivot implants in Australia were infection (27%), pain alone (19%), patellar erosion (13%), loosening/lysis (12%); in Norway the primary indications were loosening/lysis (28%), instability (28%), malalignment (11%) and pain alone (11%). CONCLUSIONS: The medial pivot TKA design as a group had a higher revision rate than cruciate-retaining fixed-bearing controls in TKA performed without patellar component resurfacing. By brand, the Advance II MP and the GMK Sphere had inferior survivorship, whereas the MRK, the SAIPH and the Evolution MP had no differences in survivorship compared with cruciate-retaining controls. In Australia, TKAs with the medial pivot design without patella resurfacing had a higher rate of revisions for instability, malalignment, and patella erosion. In Norway, there was an increased risk of revision for lysis and loosening compared with the cruciate-retaining design. Several of these implants had short follow-up in this study. Further registry studies with longer follow up are therefore necessary. LEVEL OF EVIDENCE: Level III, therapeutic study.

Short-term Revision Risk of Patellofemoral Arthroplasty Is High: An Analysis from Eight Large Arthroplasty Registries.

BACKGROUND: Patellofemoral arthroplasty (PFA) is one option for the treatment of isolated patellofemoral osteoarthritis, but there are limited data regarding the procedure and results. Because isolated patellofemoral arthritis is relatively uncommon, available case series generally are small, and even within national registries, sample sizes are limited. Combining data from multiple registries may aid in assessing worldwide PFA usage and survivorship. QUESTIONS/PURPOSES: We combined and compared data from multiple large arthroplasty registries worldwide to ask: (1) What proportion of patients undergoing primary knee arthroplasty have PFA? (2) What are the patient and prosthesis characteristics associated with PFA in common practice, as reflected in registries? (3) What is the survivorship free from revision of PFA and what are the reasons for and types of revisions? METHODS: Data were provided by eight registries that are members of the International Society of Arthroplasty Registries (ISAR) who agreed to share aggregate data: Australia, New Zealand, Canada, Sweden, Finland, Norway, the Netherlands, and the United States. De-identified data were obtained for PFA performed from either the beginning of year 2000, or the earliest recorded implantation date after that in each individual registry when PFA data collection commenced, up to December 31, 2016. This included patient demographics, implant use, all-cause revision rate (determined by cumulative percent revision [CPR]), and reasons for and type of revision. RESULTS: During the data collection period, 6784 PFAs were performed in the eight countries. PFAs comprised less than 1% of primary knee replacements in all registries. Patient demographics were comparable in all countries. Patients were generally more likely to be women than men, and the mean age ranged from 50 years to 60 years. All registries showed a high rate of revision for PFA. The 5-year CPR for any reason ranged from 8.0% (95% CI 4.5 to 11.5) in Norway to 18.1% (95% CI 15.5 to 20.7) in the Netherlands. The most common reason for revision across all countries was disease progression (42%, 434 of 1034). Most PFAs (83%, 810 of 980) were revised to a TKA. CONCLUSIONS: The revision risk of PFA in all registries surveyed was more than three times higher than the reported revision risk of TKA at the same times. The survivorship of PFA is similar to that of the no-longer-used procedure of metal-on-metal conventional hip replacement. Although there may be potential functional benefits from PFA, these findings of consistent and alarmingly high rates of revision should create concern, particularly as this procedure is often used in younger patients. LEVEL OF EVIDENCE: Level III, therapeutic study.

Increases in the rates of primary and revision knee replacement are reducing: a 15-year registry study across 3 continents.

Background and purpose - Rates of knee replacement (KR) are increasing worldwide. Based on population and practice changes, there are forecasts of a further exponential increase in primary knee replacement through to 2030, and a corresponding increase in revision knee replacement. We used registry data to document changes in KR over the past 15 years, comparing practice changes across Sweden, Australia, and the United States. This may improve accuracy of future predictions.Patients and methods - Aggregated data from the Swedish Knee Arthroplasty Register (SKAR), the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR), and the Kaiser Permanente Joint Replacement Registry (KPJRR) were used to compare surgical volume of primary and revision KR from 2003 to 2017. Incidence was calculated using population census statistics from Statistics Sweden and the Australian Bureau of Statistics, as well as the yearly active membership numbers from Kaiser Permanente. Further analysis of KR by age < 65 and ≥ 65 years was carried out.Results - All registries recorded an increase in primary and revision KR, with a greater increase seen in the KPJRR. The rate of increase slowed during the study period. In Sweden and Australia, there was a smaller increase in revision surgery compared with primary procedures. There was consistency in the mean age at surgery, with a steady small decrease in the proportion of women having primary KR. The incidence of KR in the younger age group remained low in all 3 registries, but the proportional increases were greater than those seen in the ≥ 65 years of age group.Interpretation - There has been a generalized deceleration in the rate of increase of primary and revision KR. While there are regional differences in KR incidence, and rates of change, the rate of increase does not seem to be as great as previously predicted.

What Is the Risk of Repeat Revision When Patellofemoral Replacement Is Revised to TKA? An Analysis of 482 Cases From a Large National Arthroplasty Registry.

BACKGROUND: Patellofemoral replacements (PFRs) have a higher rate of revision than unicompartmental knee arthroplasty or TKA. However, there is little information regarding why PFRs are revised, the components used for these revisions, or the outcome of the revision procedure. Some contend that PFR is a bridging procedure that can easily be revised to a TKA with similar results as a primary TKA; however, others dispute this suggestion. QUESTIONS/PURPOSES: (1) In the setting of a large national registry, what were the reasons for revision of PFR to TKA and was the level of TKA constraint used in the revision associated with a subsequent risk of rerevision? (2) Is the risk of revision of the TKA used to revise a PFR greater than the risk of revision after a primary TKA and greater than the risk of rerevision after revision TKA? METHODS: Data were obtained from the Australian Orthopaedic Association Joint Replacement Registry through December 31, 2016, for TKA revision procedures after PFR. Because revisions for infection may be staged procedures resulting in further planned operations, for the revision analyses, these were excluded. There were 3251 PFRs, 482 of which were revised to TKA during the 17-year study period. The risk of second revision was calculated using Kaplan-Meier estimates of survivorship for PFRs revised to TKAs, and that risk was compared with the risk of first revision after TKA and also with the risk of a second revision after revision TKA. Hazard ratios (HRs) from Cox proportional hazards models were used to compare second revision rates among the different levels of prosthesis constraint used in the index revision after PFR (specifically, cruciate-retaining versus cruciate-substituting). RESULTS: The main reasons for revising a PFR to TKA were progression of disease (56%), loosening (17%), and pain (12%). With the numbers available for analysis, there was no difference in the risk of a second revision when a PFR was revised to a cruciate-retaining TKA than when it was revised to a cruciate-substituting TKA (HR, 1.24 [0.65-2.36]; p = 0.512). A total of 204 (42%) of the PFR revisions had the patella component revised when the PFR was converted to a TKA. There difference in rates of second revision when the patella component was revised or not revised (HR, 1.01 [0.55-1.85]; p = 0.964). When we eliminated the devices that ceased to be used before 2005 (older devices), we found no change in the overall risk of repeat revision. The risk of a PFR that was revised to a TKA undergoing a second revision was greater than the risk of TKA undergoing a first revision (HR, 2.39 [1.77-3.24]; p < 0.001), but it was less than the risk of a revision TKA undergoing a second revision (HR, 0.60 [0.43-0.81]; p = 0.001). CONCLUSIONS: The risk of second revision when a PFR is revised is not altered if cruciate-retaining or posterior-stabilized TKA is used for the revision nor if the patella component is revised or not revised. The risk of repeat revision after revision of a PFR to a TKA was much higher than the risk of revision after a primary TKA, and these findings did not change when we analyzed only devices in use since 2005. When PFR is used for the management of isolated patellofemoral osteoarthritis, patients should be counselled not only about the high revision rate of the primary procedure, but also the revision rate after TKA. Further studies regarding the functional outcomes of these procedures may help clarify the value of PFRs and subsequent revisions. LEVEL OF EVIDENCE: Level III, therapeutic study.