Evaluating joint space width and hip morphology in symptomatic female hips with femoroacetabular impingement and instability.

Abstract

Purpose: This study aims to determine differences in joint space width (JSW) between hips with femoroacetabular syndrome (FAIS) and instability, and to investigate the influence of several hip morphological measures on JSW.

Methods: A retrospective review of symptomatic female hips, which used standing anterior-posterior x-rays to measure JSW at the medial, superior, and lateral acetabular sourcil, was conducted. Hips were grouped by radiographic indices, collected from 3D-reconstructed models, into cam-femoroacetabular impingement (FAI), pincer-FAI, mixed-FAI, mild instability, instability, and combined FAIS-instability. Associations between JSW and hip morphology measures, including lateral centre edge angle (LCEA), acetabular coverage, Tönnis angle, and femoral neck shaft angle (FNSA), were analysed.

Results: In 493 symptomatic female hips, JSW at all locations was significantly lower in pincer hips compared to all other pathology groups (P < .05), with the exception of mixed-FAI hips (P > .4). Hips with isolated instability and combined instability-FAI morphology had significantly greater JSW than pincer- and mixed-FAI groups (P < .05). There were no significant JSW differences between instability and combined FAI-instability groups at any location (P > .1). Acetabular coverage, LCEA, Tönnis angle, and FNSA were significantly associated with JSW (P < .001). No significant associations were observed for acetabular version (P > .05) or femoral torsion (P > .05).

Conclusion: Differences in JSW across groups highlight the influence of femoroacetabular morphology and orientation in pre-arthritic hips. In patients with naturally decreased JSW and no other findings of osteoarthritis, attention should be given to evaluation for pincer-FAI. In contrast, in patients with naturally increased JSW, instability findings should be thoroughly evaluated.