Background:: Although advances in joint-replacement technology have made total ankle arthroplasty a viable treatment for end-stage arthritis, revision rates for ankle replacements are higher than in hip or knee replacements. The questions asked in this study were what can retrieved ankle devices demonstrate about ankle arthroplasty failures and how can understanding the causes of these failures inform clinical decisions for current and future ankle arthroplasty patients?
Methods:: An IRB-approved retrieval laboratory received retrieved components and surgeon-supplied reason for revision from 70 total-ankles (7 designs, including 5 currently marketed designs) from 2002 to 2018. These retrievals were rated for clinical wear and damage. Metal components were rated by method and effectiveness of fixation. Polyethylene inserts received by the laboratory 6 months or less after retrieval (n = 45) were analyzed for oxidation using Fourier transform infrared spectroscopy. Statistical analysis was performed using IBM SPSS, version 22.
Results:: The ankle implants were retrieved most commonly for loosening and polyethylene fracture. Loosening occurred more frequently in fixed-bearing designs (n = 18) than in the mobile-bearing designs (n = 4) and after shorter in vivo time (mean in vivo time to retrieval for loosening: fixed bearing 3.2 ± 2.1 years, mobile bearing 9.7 ± 4.5 years). Gamma-sterilized ankle inserts oxidized at a higher rate than non-gamma (EtO or gas-plasma) sterilized ankle inserts (gamma 0.29 ± 0.22/y, non-gamma 0.07 ± 0.05/y, mean difference=0.215, 95% CI 0.128-0.303, P < .001). The presence of clinical fatigue (cracking and/or delamination) of the polyethylene insert correlated with measured oxidation (Spearman rho = 0.685, P < .001). Nine inserts, all gamma-sterilized, fractured in vivo.
Conclusions:: This study suggests that loosening could be more of a problem in fixed-bearing devices than in mobile bearing devices. Gamma-sterilized polyethylene inserts were found to suffer fatigue damage or fracture in vivo, resulting in the need for revision. Retrieval analysis can provide insight into implant-related reasons for revision, with the goal of understanding the implant-related causes of these failures, informing future ankle design and clinical decisions for current and future ankle arthroplasty patients.
Level of evidence:: Level III, comparative series.
Keywords: polyethylene oxidation; retrieval analysis; total ankle prostheses.