Elsevier

The Journal of Arthroplasty

Volume 38, Issue 2, February 2023, Pages 329-334
The Journal of Arthroplasty

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

https://doi.org/10.1016/j.arth.2022.09.001Get rights and content

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 is 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 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.

Results

Regression 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).

Conclusion

This 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.

Section snippets

Study Population

The St Vincent’s Melbourne Arthroplasty Outcomes Registry is an institutional, prospective database which includes all elective hip arthroplasty patients undertaken at the hospital since 1998 [5]. Twelve-month follow-up of patient-reported outcomes is >98% [5]. The study population included all registry participants presenting between January 1, 2012 and December 31, 2016 for elective, unilateral primary THA for any diagnosis, with minimal osteoarthritis of the contralateral hip

Radiological Measurements

The mean postoperative offset for the study population was reduced by 3.38 mm (range −43.50 to 92.53) compared to the native contralateral side, with a similar median of 3.77 mm (25th percentile = −12.70, 75th percentile = 5.58). Offset was within 10 mm of the contralateral side in 224 patients (54.1%), with 126 patients (30.4%) having offset decreased by >10 mm, and 64 patients (15.5%) having offset increased by >10 mm (Fig. 3).

Clinical and Functional Outcomes

The results of the WOMAC and VR-12 functional scores at the

Discussion

Accurate restoration of offset continues to be a cause of controversy for surgeons, despite being studied for well over 40 years [14]. This study evaluated the effects of offset following THA on pain and functional outcomes from prospectively collected registry data with 12-month follow-up, and found that patients who had offset decreased by 20 mm or more had worse pain, motion, and global WOMAC scores, and those with offset decreased between −10.00 and −0.01 mm had worse motion WOMAC scores.

Conclusion

This study demonstrated an association between reduction in offset by >20 mm and worse WOMAC pain and motion scores following THA. Surgeons should avoid decreases in offset >20 mm in order to optimize functional outcomes.

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  • One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to https://doi.org/10.1016/j.arth.2022.09.001.

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