Cumulative revision rates in total hip arthroplasty depending on acetabular cup fixation: an analysis from the German arthroplasty registry.

BACKGROUND: While modern third-generation cementation techniques have optimized outcomes for cemented fixation, cementless acetabular fixation is currently the widely preferred cup option in Germany. In elderly patients, however, international registry data suggest a potential advantage for cemented acetabular fixation strategies. Given the rising volume of total hip arthroplasties (THA) and an ageing population, we performed a registry-based analysis to evaluate revision risk associated with the type of acetabular fixation in elderly patients. METHODS: A registry-based cohort analysis of 330,910 primary THAs was performed. The overall median follow-up was 3.48 years (IQR 1.52-5.82), with a mean follow-up of 3.79 years (SD 2.60) and a maximum follow-up duration of 11.38 years. Statutory health insurance billing data, implant manufacturer product database, and hospital electronic case report forms were evaluated. Longitudinal follow-up was conducted for all-cause revisions and mortality. Estimated risk of revision for any reason at eight years was assessed using Kaplan-Meier, adjusting for age and femoral stem fixation (cemented vs cementless). Furthermore, multivariable Cox proportional hazard regression analyses were performed. RESULTS: Age-stratified analyses showed higher revision rates in patients < 75 years for cemented polyethylene (PE) and highly-cross-linked polyethylene (XPE) cups (both 7.7%) compared to patients ≥ 75 years (5.1% for PE; 4.5% for XPE). In patients ≥ 75 years, the combination of a cemented XPE cup with a cemented stem achieved, together with hybrid THA, the lowest eight-year revision rate (4.1%). Among patients ≥ 80 years (n = 63,278), cemented PE/XPE cups had the highest eight-year revision-free survival (95.5%), compared to hemispherical press-fit cups (94.6%) (p = 0.015), independent of the type of femoral fixation. Within the ≥ 80-year subgroup with cemented stems, no significant differences were observed between cup types (p = 0.100). However, in multivariable Cox regression analyses, cemented XPE cups were associated with revision risks comparable to those of hemispherical cups in patients aged ≥ 75 years with no significant differences (HR 0.98, 95% CI 0.84-1.14; p = 0.80) and ≥ 80 years (HR 0.98, 95% CI 0.81-1.19; p = 0.80). Within the cemented (X)PE cups subgroup, larger head size, ceramic-on-polyethylene, lower comorbidity burden, and a BMI of ≤ 30 were all significantly associated with improved revision-free survival. CONCLUSION: The German arthroplasty registry indicates that, although cementless hemispherical press-fit cups remain the predominant acetabular fixation method used for THA across all age groups, cemented XPE cups have no clinically relevant survivorship differences in selected elderly subgroups (≥ 75-year-old; ≥ 80-year-old patients). For < 75-year-old patients, hemispherical press-fit cups remain the most favorable option. Future studies should focus on prospective analyses of patient-reported outcomes, complication profiles, and long-term cost-effectiveness for acetabular fixation in THA to further define the optimal fixation strategy for different age and risk groups.