In Search of the Spherical Femoroplasty: Cam Over-Resection Leads to Inferior Functional Scores before and after Revision Hip Arthroscopy

Purpose: To examine the effect of accuracy of previous femoroplasty on hips presenting for revision hip arthroscopy.

Methods: Data were prospectively collected for patients presenting for revision hip arthroscopy between June 2010 and August 2014. Based on measurements on Dunn view x-rays, cases were divided into three groups: over-resection (OR) where over-resection measured over 5% of the diameter of the femoral head, under-resection (UR) where there was a residual cam lesion (alpha angle >60°, and neutral. Data collection included modified Harris Hip Score (mHHS), Non-Arthritic Hip Score (NAHS), Hip Outcome Score – Sports Specific Subscale (HOS-SSS), and visual analog scale (VAS)at presentation and at minimum two-year follow-up after revision hip arthroscopy, and rates of conversion to THA.

Results: 130 hips (120 patients) were included. Twenty hips (15.4%) were classified as OR, 16 (12.3%) were classified as UR, and 94 (72.3%) were classified as neutral.

Mean follow-up was 39.6±15.9 months. mHHS and NAHS at presentation were lower in the OR compared to the UR group (50.2±15.5 vs 64.7±19.4, p=0.033 and 48.5±18.6 vs 63±19.1, p=0.044 respectively). mHHS at minimum two-year follow-up after revision was lower for the OR (66.7±19.8) than for the UR group (81±14.5, p=0.031). Conversion to THR was more common in the OR than in the UR group (30% vs. 0%, p=0.024).

Conclusions: Over-resection was a more common problem than under-resection in this cohort of patients presenting for revision hip arthroscopy. Cam over-resection of more than 5% of the diameter of the femoral head predicts inferior clinical measures compared to cam under-resection in this population. Furthermore, over-resection predicts inferior outcomes after revision hip arthroscopy and higher rates of conversion to THA.