Summary

Patients with hip dysplasia or acetabular overcoverage achieved poor long-term survivorship compared to those with normal coverage.

Abstract

PURPOSE/HYPOTHESIS: The purpose of the present study was to investigate if patients with hip dysplasia or acetabular overcoverage had significantly different femoroacetabular joint space width (JSW) and 15-year THA-free survivorship compared to patients with normal acetabular coverage. We hypothesized that 1) patients with dysplasia or overcoverage would have worse long-term survivorship and 2) lateral center edge angle (LCEa) has a linear relationship with a reduced JSW.

Methods

This study queried patients who underwent arthroscopic repair of symptomatic acetabular labral tears secondary to femoroacetabular impingement (FAI). Patients were stratified into cohorts according to LCEa: dysplasia (<25o), overcoverage (≥40o), and normal coverage (25o-39.9o). Femoroacetabular joint space width (JSW) of the ipsilateral hip was collected using a computer-assisted, semi-automated method of assessing anteroposterior (AP) radiographs. JSW was collected at 3 fixed locations per hip at 10° [lateral], 30° [central], and 50° [medial] with respect to a polar coordinate system. Patients with minimum 5-year follow-up, Tönnis grade 0 or 1, and JSW >2 mm were included. A multivariate linear regression assessed the correlation between LCEa and lateral, central, and medial JSW. 15-year THA-free survivorship was assessed using a Kaplan-Meier survival curves analyzed by log-rank test. A weighted Cox regression adjusting for baseline demographics and intraoperative findings was performed to identify independent risk factors for converting to THA.

Results

Overall, 256 patients (age, 38.1 ± 11.5 years; BMI, 25.8 ± 4.2 kg/m2; sex, 51.6% female) with a mean 8.5 ± 3.4 years follow-up met inclusion criteria. By multivariate linear regression, each 1o increase in LCEa was correlated with a -0.038mm (P<.001) and -0.028mm (P<.001) decrease in medial and central JSW, respectively. There were significant differences in 15-year THA-free survivorship among LCEa cohorts: dysplasia (n=15; 24.0%), overcoverage (n=65; 44.0%), and normal coverage (n=176; 89.66%) (P<.001). Patients with dysplasia or overcoverage had a 121% greater risk of converting to THA compared to normal coverage patients (P=.029). When further stratifying the normal coverage cohort, each 5o decrease in LCEa (e.g. 35o to 39.9o vs. 30o to 34.9o) increased the risk of THA by 112% (P=.046).

Discussion

AND CONCLUSIONS: Patients with hip dysplasia or acetabular overcoverage achieved poor long-term survivorship compared to those with normal coverage. Furthermore, Acetabular coverage was significantly associated with femoroacetabular JSW. Proper surgical management of dysplasia or FAI in younger patients may be an important consideration for improving hip arthroscopy outcomes.