Reduction in offset is associated with worse functional outcomes following total hip arthroplasty

Title

Reduction in offset is associated with worse functional outcomes following total hip arthroplasty

Investigators

Michael Bullen, Sina Babazadeh, Dirk van Bavel, Dean McKenzie, Michelle Dowsey, Peter F. Choong

Abstract

Background

Conflicting 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 was to assess the effect of failing to restore global hip offset in comparison to the native contralateral hip.

Methods

A 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 follow-up were included. Post-operative 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 pre-operatively and at 12 months post-operatively.

Results

Regression analyses indicated that a reduction in offset of greater than 20 millimeters resulted in worse WOMAC pain (p = 0.005) and motion (p = 0.015) scores compared to those with maintained offset. WOMAC function (p = 0.063), global (p = 0.025), and VR-12 scores were not affected (physical p = 0.656; mental p = 0.815). Reduction of offset up to 20 millimeters and increased offset were not significantly associated with patient reported outcome measures (p-values ranged from 0.102 to 0.995).

Conclusion

This study demonstrated an association between reduction of offset by more than 20 millimeters and worse WOMAC pain and motion scores following total hip arthroplasty. Surgeons should avoid decreases in offset greater than 20 millimeters in order to optimize functional outcomes