Does acetabular dysplasia affect outcome in arthroscopic treatment of cam femoroacetabular impingement? Case-control study with and without acetabular dysplasia.

BACKGROUND

Arthroscopic management of femoroacetabular impingement (FAI) is classically contraindicated when acetabular dysplasia is associated, although this is controversial in case of moderate dysplasia or isolated cam effect. A case-control study was therefore conducted comparing borderline (center-edgeangle (CEA), 20-24°), moderate (15-19°) and severe dysplasia (<15°) (group D) versus a control group with normal acetabular cover (CEA, 25-30°). The aims were 1) to determine functional results and satisfaction, and 2) to correlate functional results with severity of dysplasia and of cam effect.

HYPOTHESIS

Improvement in functional scores and satisfaction is lower in group D than in controls, due to non-correction of dysplasia.

MATERIAL AND METHOD

A single-center, single-surgeon retrospective comparative case-control study included all patients with isolated cam-effect FAI and dysplasia but without osteoarthritis (group D) or with isolated cam-effect FAI without dysplasia (controls) operated on during the study period. Cases of mixed impingement were excluded. Preoperative and last-follow-up functional variables included McCarthy's modified Harris Hip Score (mHHS) and Christensen's Non-Arthritic Hip Score (NAHS).

RESULTS

Between 2011 and 2014, details of 407 patients operated on by arthroscopy were entered in a data-base. Twenty patients (22 hips) were included in group D, with CEA<25° (mean, 19±3.1; range, 10-23°). The control group comprised 23 patients (25 hips) with CEA>25° (mean, 29±2.1°; range, 25-30°) matched for gender, age and body-mass index. Mean follow-up was 29.6±14.1 months (range, 14-58 months) in group D and 31.4±10.6 months (range, 15-57 months) in the control group (p=0.66). For functional scores, the two groups showed respectively 9.9 (-34 to +47) (p=0.038) and 10.4 (-20 to +48) (p=0.0038) gain in mHHS (non-significant: p=0.943). Mean gain in NAHS was 16.6 (-19 to +33) (p=0.0001) and 13.7 (-11 to +47) (p=0.0002), respectively (non-significant: p=0.56) CONCLUSION: Short-term functional results for cam FAI treatment were equivalent with<25° acetabular cover (mean, 19°; range, 13-24°) or normal cover. Longer-term assessment is indispensable to determine the impact of dysplasia and its severity.

LEVEL OF EVIDENCE

III, case-control study.