Improved Functional Outcome Scores Associated with Greater Reduction in Cam Height Using the Femoroacetabular Impingement Resection Arc During Hip Arthroscopy.

Purpose: We sought to evaluate the association between postoperative cam lesion measured by the femoroacetabular impingement resection (FAIR) arc and show 2-year patient outcomes following hip arthroscopy.

Methods: A retrospective review of prospectively gathered data from 2013-2017 was performed. All patients who underwent hip arthroscopy for femoroacetabular impingement resection (FAI) with ≥2-year follow-up were included. Cam FAIR arc measurements were made preoperatively and postoperatively on a 45° Dunn view radiograph. The clinical effect of postoperative cam maximal radial distance (MRD) was assessed using the modified Harris Hip Score (mHHS) and Non-Arthritic Hip Score (NAHS). Patients were divided into subgroups based on relationship to the mean and standard deviations for cam MRD. One half standard deviation above the mean was found to be 3.15 mm.

Results: Sixty-one hips in 59 consecutive patients (age 38.1 ± 13.1; body mass index [BMI]: 25.5 ± 4.3; 36 females) were included. Mean preoperative and postoperative cam maximal radial distances (MRD) were 4.5 ± 1.7 mm and 2.3 ± 1.7 mm (P < .001), respectively. The interclass correlation coefficient was excellent (>.9) for all measurements. There were no differences in age, sex, BMI or preoperative mHHS/NAHS between <3.15 mm and >3.15 mm cam MRD groups (P > .05). Using linear regression, cam MRD was found to be significantly associated with 2-year outcomes for both mHHS (R = .21, P < .001) and NAHS (R = .004). Subgroup analysis demonstrated that patients in the cam MRD < 3.15 mm group had significantly higher mHHS (89.7 vs 70.0, P < .001) and NAHS scores (90.5 vs 72.9, P < .001) than those in the >3.15 mm group. Additionally, more patients in the <3.15 mm group reached the minimal clinically important difference (95.2% vs 78.9%, P = .048) and were above patient acceptable symptomatic state (95.2% vs 52.6%, P < .001) compared to the >3.15 mm group.

Conclusion: Patients with a lower postoperative cam MRD relative to the FAIR arc demonstrated significantly improved outcomes as compared to those with higher postoperative MRD at two-year follow-up.

Level Of Evidence: Level IV, retrospective case series.