2026/05/29 by Chan Hee Cho, John M. Abrahams, Lucian B Solomon +6 · 1 voice
Medicine · #Orthopaedic implants and arthroplasty #Hip disorders and treatments #Orthopedic Infections and Treatments
paper · pdf · doi:10.2340/17453674.2026.45784
openalex publication_date 2026/05/29 · openalex created_date 2026/05/30 · openalex updated_date 2026/07/18
BACKGROUND AND PURPOSE: 2-year proximal migration thresholds for acetabular cups used at primary total hip arthroplasty were first established in 2012 by matching radiostereometric analysis (RSA) measurements of cup migration with long-term survivorship from cohort studies. Subsequently, there have been new RSA studies reporting migration of contemporary cup designs whose survivorships are available from long-term registry data. The primary aim of this study was to re-evaluate the 2-year postoperative RSA migration thresholds and investigate whether thresholds at time points earlier than 2 years were possible. METHODS: The mean 6-month, 1-, and 2-year proximal migration of each RSA cohort was matched to the pooled 10-year proportion of acetabular cup revision due to aseptic loosening in the Australian Orthopaedic Association National Joint Replacement Registry and the Dutch Arthroplasty Registry in 2023. Revision rates were pooled according to these classifications using a random effects model. RESULTS: 164 implant-survival combinations (228,053 cups), involving 27 cup designs, were identified with RSA migration data to 2 years. At 1 year, mean cup migration of ≤ 0.1 mm was considered acceptable, while migration > 0.8 mm was unacceptable. The pooled proportions of acetabular cup revision in the acceptable, at-risk, and unacceptable threshold categories were 0.36% (95% confidence interval [CI] 0.26-0.47), 1.05% (CI 0.80-1.31), and 5.07% (CI 1.41-8.73) respectively. At 2 years, mean cup migration ≤ 0.2 mm was considered acceptable while mean migration > 1.0 mm had unacceptable survivorship. The pooled proportions of acetabular cup revision in the acceptable, at-risk, and unacceptable threshold categories were 0.55% (CI 0.48-0.62), 1.27% (CI 0.87-1.67), and 21.6% (CI 0.0-54.7), respectively, meaning that acetabular cups with high migration can be identified at both 1 and 2 years. CONCLUSION: This study confirmed the existing 2-year migration thresholds and established a new threshold at 1 year. We found no association between continuous migration between 1 and 2 years and 10-year revision rates. The 1-year migration threshold is the earliest surrogate measure for assessing late loosening of the acetabular cup and may identify underperforming implants.