Leg-length discrepancy in revision total hip arthroplasty : computer-assisted navigation improves the discrepancy when compared with manual techniques.

Abstract

Aims: Leg-length discrepancy (LLD) following total hip arthroplasty (THA) is a source of patient dissatisfaction and morbidity. The objectives of this study were to characterize LLD following revision THA (rTHA) and evaluate the difference in LLD between navigated and non-navigated rTHA.

Methods: This retrospective cohort study included 202 patients treated with rTHA performed between 2017 and 2021. An a priori power analysis determined that 101 patients in each group were required. Navigated and non-navigated rTHA were compared with regard to LLD (absolute value), re-revision rate, and patient-reported outcome measures (PROMs).

Results: Mean postoperative LLD was 4.3 mm (SD 4.6) in all patients. In navigated rTHA, mean postoperative LLD of 3.7 mm (SD 4.7) was lower than preoperative LLD (7.5 mm (SD 6.1); p < 0.001). In non-navigated rTHA, postoperative LLD of 4.9 mm (SD 4.3) was lower than preoperative LLD (7.8 mm (SD 6.6); p < 0.001). Postoperative LLD was significantly lower in navigated compared with non-navigated rTHA in all patients and in sub-groups with preoperative LLD < 5 mm (1.7 mm vs 3.5 mm), < 10 mm (2.8 mm vs 3.9 mm), < 15 mm (3.0 mm vs 4.1 mm), and < 20 mm (3.3 mm vs 4.7 mm), respectively (p < 0.05). Based on revision type, postoperative LLD was significantly lower in navigated rTHA compared to non-navigated rTHA in those with both-component and acetabular component-only revisions (p < 0.05). Subsequent re-revision was required in three navigated rTHAs (3%) and eight non-navigated rTHAs (8%, p = 0.121). Changes in patient-reported Hip injury and Osteoarthritis Outcome Score Joint Replacement, Lower Extremity Activity Scale, and pain were not significantly different between navigated and non-navigated patients.

Conclusion: Postoperative LLD was improved relative to preoperative LLD in rTHA with and without the use of navigation. Postoperative LLD was significantly lower in navigated rTHA compared with non-navigated rTHA. There was no significant difference in PROMs between groups. Based on these results, computer-assisted navigation seems to optimize leg-length correction and should be considered for use in rTHA involving the acetabular component, including both-component and acetabular component-only revisions. Of note, the present study was not designed to validate all aspects of all parameters of computer navigation; rather, it was specifically designed to assess LLDs when using navigation. Therefore, the present results only cover the topic of LLD when using navigation in comparison with manual techniques.