Reduction in Offset Is Associated With Worse Functional Outcomes Following Total Hip Arthroplasty

Abstract

BackgroundConflicting reports exist about the effect of offset variation on functional outcomes following total hip arthroplasty. Reproducing native hip offset is thought to optimize function by restoring biomechanics and appropriately tensioning the hip abductor muscles. The aim of this study is to assess the effect of failing to restore global hip offset in comparison to the native contralateral hip. MethodsA retrospective analysis of a prospective patient cohort was performed on patients undergoing an elective primary total hip arthroplasty. A total of 414 patients who had a minimum of 12 months of follow-up were included. Postoperative plain radiographs were analyzed for offset and compared to the contralateral native hip. Western Ontario and McMaster Universities Arthritis Index (WOMAC) and Veterans RAND 12 (VR-12) scores were assessed preoperatively and at 12 months postoperatively. ResultsRegression analyses indicated that a reduction in offset of >20 mm resulted in worse WOMAC pain (P = .005) and motion (P = .015) scores compared to those with maintained offset. WOMAC function (P = .063), global (P = .025), and VR-12 scores were not affected (physical P = .656; mental P = .815). Reduction in offset up to 20 mm and increased offset were not significantly associated with patient-reported outcome measures (P-values ranged from .102 to .995). ConclusionThis study demonstrated an association between reduction in offset by >20 mm and worse WOMAC pain and motion scores following total hip arthroplasty. Surgeons should avoid decreases in offset >20 mm in order to optimize functional outcomes.