In Search of the Spherical Femoroplasty: Cam Overresection Leads to Inferior Functional Scores Before and After Revision Hip Arthroscopic Surgery
Background: Femoroplasty performed for the treatment of cam-type femoroacetabular impingement (FAI) has become a common procedure. Underresection may result in residual FAI. Conversely, overresection may disrupt the labral seal, which is responsible for chondroprotective fluid dynamics of the hip. Hypothesis/Purpose: It was hypothesized that cam overresection negatively affects hip function. The purpose was to examine the effect of the accuracy of previous femoroplasty on hips presenting for revision hip arthroscopic surgery.
Study design: Cohort study; Level of evidence, 3.
Methods: Data were prospectively collected for patients presenting for revision hip arthroscopic surgery between June 2010 and August 2014. On the basis of measurements on Dunn view radiographs, cases were divided into 3 groups: overresection (OR group) in which overresection measured over 5% of the diameter of the femoral head, underresection (UR group) in which there was a residual cam lesion (alpha angle >60°), and neutral resection (neutral group). Data collection included the modified Harris Hip Score (mHHS), Nonarthritic Hip Score (NAHS), Hip Outcome Score-Sports-Specific Subscale, and visual analog scale at presentation and at a minimum 2-year follow-up after revision hip arthroscopic surgery and rates of conversion to total hip arthroplasty (THA).
Results: One hundred thirty hips (120 patients) were included. Twenty hips (15.4%) were classified as the OR group, 16 (12.3%) as the UR group, and 94 (72.3%) as the neutral group. The mean follow-up was 39.6 ± 15.9 months. The mHHS and NAHS values at presentation were lower in the OR group compared with the UR group (50.2 ± 15.5 vs 64.7 ± 19.4 [ P = .033] and 48.5 ± 18.6 vs 63.0 ± 19.1 [ P = .044], respectively). The mHHS value at a minimum 2-year follow-up after revision was lower for the OR group (66.7 ± 19.8) than for the UR group (81.0 ± 14.5) ( P = .031). Conversion to THA was more common in the OR group than in the UR group (30% vs 0%, respectively; P = .024). Fifty percent of cases in the OR group, 69.9% in the neutral group, and 75% in the UR group met the minimal clinically important difference for the mHHS (Δ). The latest mHHS value reached the patient acceptable symptomatic state (PASS) in 35% of the cases in the OR group, 53.2% in the neutral group, and 75% in the UR group. Hips in the OR group had a significantly lower chance of reaching the PASS than the UR group (odds ratio, 0.1795 [95% CI, 0.0418-0.7711]; P = .0209).
Conclusion: Cam overresection of more than 5% of the diameter of the femoral head on the Dunn view predicts inferior clinical outcomes compared with cam underresection in this population. Furthermore, overresection predicts inferior outcomes after revision hip arthroscopic surgery and higher rates of conversion to THA.