IDENTIFICATION OF FACTORS ASSOCIATED WITH DISEASE PROGRESSION IN THE CONTRALATERAL HIP OF PATIENTS WITH SYMPTOMATIC FEMOROACETABULAR IMPINGEMENT

Abstract

Introduction:Femoroacetabular Impingement (FAI) is one of the most common causes of hip osteoarthritis. Nevertheless, the factors contributing to symptom development and FAI disease progression are poorly understood.Hypothesis/Purpose:The purpose of this study was to (1) investigate rates of initial and subsequent symptom development in the contralateral hip of patients with FAI, and (2) identify predictors of disease progression (symptom development) in the contralateral hip.Methods:This prospective study included a minimum 5 year follow-up of the contralateral hip in 179 patients undergoing FAI surgery. Symptoms (moderate pain) were monitored over the study course. Univariate analysis compared patient and FAI imaging characteristics of patients developing symptoms to those who remained asymptomatic.Results:146 patients (146 hips, 81.5%) were included (min 5 year, mean 6.7 years). Thirty-nine (26%) presented with symptoms in the contralateral hip while 34 (23%) developed symptoms. Head-neck offset ratio (HNOR) on AP pelvis radiographs was significantly lower among hips that developed symptoms (0.164 vs. 0.153 p=0.025). Maximum alpha angle (p=0.413), lateral center edge angle (p=0.704), and crossover sign (p=0.115) were not predictive of symptoms. Patients with a UCLA activity score greater than 9 were less likely to develop symptoms (14% vs. 46%, p=0.081), but this was not statistically significant. The total arc of rotation in extension (35.740 vs 45.140, p=0.012) and 900 of flexion (40.00 vs 50.800, p=0.009) as well as external rotation at 900 of flexion (28.940 vs 36.590, p=0.020) were decreased in hips developing symptoms. Internal Rotation in flexion was not significantly decreased in symptomatic patients (11.060 vs 14.20, p=0.113).Conclusions:We identified unique radiographic and physical exam findings that are associated with symptom development in patients with FAI. Specifically, decreased hip rotation arc and decreased HNOR were strongly associated with disease progression and may represent important factors for future risk modeling in FAI patients.