Decreased Hip Labral Width Measured via Preoperative Magnetic Resonance Imaging Is Associated With Inferior Outcomes for Arthroscopic Labral Repair for Femoroacetabular Impingement

Purpose: To determine the association between labral width as measured on preoperative magnetic resonance imaging (MRI) and hip-specific validated patient self-reported outcomes at a minimum of 2 years' follow-up. Methods: We performed an institutional review board-approved retrospective review of prospectively gathered hip arthroscopy patients from 2010 to 2017. The inclusion criteria were defined as patients aged 18 to 65 years with radiographic evidence of femoroacetabular impingement who underwent a primary labral repair and had a minimum of 2 years' clinical follow-up. The exclusion criteria were defined as inadequate preoperative imaging, prior hip surgery, Tonnis grade 1 or higher, or lateral center-edge angle lower than 25 degrees. An a priori power analysis was performed. MRI measurements of labral width were conducted by 2 blinded, musculoskeletal fellowship-trained radiologists at standardized "clock-face" locations using a previously validated technique. Outcomes were assessed using the Harris Hip Score (HHS), modified Harris Hip Score (mHHS), and Non-arthritic Hip Score (NAHS). For the mHHS, scores of 8 and 74 were used to define the minimal clinically important difference and patient acceptable symptomatic state, respectively. Patients were divided into groups by a labral width less than 1 SD below the mean (hypoplastic) orwidths above 1 SD below the mean. Statistical analysis was performed using linear and polynomial regression; the Mann-Whitney U, chi(2), and Fisher exact tests; and intraclass correlation coefficient testing. Results: A total of 103 patients (107 hips) met the inclusion criteria (mean age, 39.4 +/- 17 years; body mass index, 25.0 +/- 4; 51% right sided; 68% female patients; mean follow-up, 76.5 +/- 19.1months [range, 30.0-113.0 months]). Mean labral width at the 11:30 clock-face position (indirect rectus), 3-o'clock position (psoas U), and 1:30 clock-face position (point halfway between the 2 aforementioned positions) was 7.1 +/- 2.2 mm, 7.0 +/- 2.0mm, and 5.5 +/- 1.9 mm, respectively. Intraclass correlation coefficient agreements were good to excellent between readers at all positions (0.83-0.91, P<.001). The preoperative HHS, mHHS, and NAHS were not statistically significantly different (P>.05) between the 2 groups. Sex, laterality, and body mass index were not predictive of outcomes (P>.05). The postoperative HHS, mHHS, and NAHS were found to be significantly lower in the hypoplastic group at each location tested (P<.01), including them HHS at the 11:30 clock-face position (69 vs 87), 3-o'clock position (70 vs 87), and 1:30 clock-face position (71 vs 87). The proportion of patients with hypoplastic labra who reached the minimal clinically important difference was significantly lower (P<.001) at the 11:30 clock-face position (50% vs 91%), 3-o'clock position (56% vs 90%), and 1:30 clock-face position (58% vs 91%) in comparison to the non-hypoplastic labrum group. The proportion of patients with hypoplastic labra above the patient acceptable symptomatic state was significantly lower (P<.001) at the 11:30 clock-face position (44% vs 83%), 3-o'clock position (37.5% vs 84%), and 1:30 clock-face position (42% vs 85%) in comparison to the non-hypoplastic labrum group. Linear regression modeling was not significant at any position (P>.05). Polynomial regression was significant at the 11:30 clock-face position (R-2 = 0.23, P<.001), 3-o'clock position (R-2 = 0.17, P<.001), and 1:30 clock-face position (R-2 = 0.26, P<.004). Conclusions: Hip labral width less than 1 SD below the mean measured via preoperative MRI was associated with significantly worse functional outcomes after arthroscopic labral repair and treatment of femoroacetabular impingement. The negative relation between labral width and outcomes may be nonlinear.