Failure of a “Screw-in” Acetabular Component: Ten-year Results, Survivorship Analysis, and the Prediction of Failure

The Rotalok screw-in threaded acetabular component was prospectively reviewed with 10-year clinical and radiological follow-up for 60 patients. Nine patients died and 5 were lost to follow-up. Clinically, 28 patients were pain-free, 13 had mild pain, and 3 had moderate pain. Thirteen patients underwent revision for loosening and 3 required revision but were unfit. Superior migration, angular migration, and zone lucency were measured radiologically. Cumulative survival was 70.75% with revision surgery as the end point and 60% with combined clinical failure and revision as the end point. Angular migration of 3° or more was a significant predictor of clinical failure and revision (P < .0001), with 5° being very highly predictive with a sensitivity of 0.72 and a specificity of 1.00. Revision was associated with younger patients (P = .03) and autograft use without screw stabilization (P = .024). The high failure rate of the Rotalok necessitates careful clinical and radiological follow-up, with asymptomatic radiological angular migration often the first predictor of failure.