Incidence, risk factors, and prognostic consequences of femoroacetabular cup impingement following hip resurfacing arthroplasty.

Purpose: Hip resurfacing arthroplasty (HRA) is recommended for younger patients seeking higher levels of activity. However, femoroacetabular cup impingement (FACI) between the femoral neck and acetabular prosthesis remains a concern. This study aimed to determine the incidence, risk factors, and prognostic consequences of FACI after HRA.

Methods: This study included 242 HRAs performed at a single institution. Three types of implants with different cup articular arc angle (CAAA) values were used. FACI was defined as indentation or spur formation at the femoral neck corresponding to the ridge of the acetabular cup. Multivariate regression analyses were conducted to identify risk factors for FACI. Clinical outcomes were compared between groups with and without impingement. The mean follow-up duration was 12 years (range, 2‒19).

Results: FACI was identified in 87 out of 242 HRAs (36%). Multivariate regression analysis showed that FACI was associated with the use of implants with a greater CAAA (P < 0.001). At the latest evaluation, the mean Harris Hip Score (94 vs. 93; P = 0.405) and the incidence of groin pain (16.1% vs. 14.8%; P = 0.795) were similar between the groups with and without FACI. Implant survivorship free of any revision was 94.5% in the FACI group and 89.8% in the non-FACI group at 12 years (log-rank, P = 0.165).

Conclusion: This study identified that the incidence of FACI after HRA was 36%. Implants with greater CAAA were associated with a higher risk of impingement. However, radiographic FACI was not associated with adverse clinical outcomes of HRA after a mean follow-up of 12 years.