Prevalence and preoperative demographic and radiographic predictors of bilateral femoroacetabular impingement.

Background: Patients with symptomatic femoroacetabular impingement (FAI) frequently have bilateral deformity and inquire about the prognosis of their contralateral, asymptomatic hip. Idiopathic coxarthrosis has been established as an independent risk factor for joint failure on the other side. Purpose: To determine the prevalence of bilateral arthroscopic treatment for FAI and to identify predictive patient demographics and radiographic findings for bilateral, symptomatic disease. Study Design: Case control study; Level of evidence, 3. Methods: Over a 2-year period, patients receiving single-sided FAI surgery for pain and radiographic deformity were identified as unilateral. In the same period, patients undergoing their second side were labeled bilateral, regardless of when the first surgery was performed. Proximal femoral alpha angle; lateral center edge angle; sagittal center edge angle; acetabular version at 1, 2, and 3 o'clock; and femoral torsion were measured on preoperative computed tomography scans. Results: The unilateral group included 514 patients, and the bilateral group included 132 patients. Women composed 48% of the unilateral group but only 35% of the bilateral group (P=.006). The mean age of unilateral patients was 30.3 (+/- 10.7) years and 27.6 (+/- 9.7) years for the first side of bilateral patients (P=.010). The bilateral hips had higher alpha angles (63.8 degrees vs 59.8 degrees, P=.004), less acetabular anteversion at the 3-o'clock position (13.0 degrees vs 15.9 degrees, P<.001), and similar femoral torsion (15.1 degrees vs 15.5 degrees, P=.793) compared with unilateral hips. A multivariable logistic regression model found that for every 5 years of younger age, 5 degrees higher alpha angle, and 5 degrees decrease in 3-o'clock acetabular version, patients were more likely to undergo bilateral treatment for FAI, by 13.5%, 14.5%, and 25.5%, respectively. In a side-to-side comparison of both hips in bilateral patients, alpha angle (r = 0.72) and acetabular version at 1 o'clock (r = 0.73) showed high correlation. Conclusion: Male sex, younger age, higher alpha angles, and reduced acetabular anteversion at initial presentation are significant risk factors for identifying patients who may ultimately require bilateral surgery for symptomatic FAI. Among bilaterally treated patients, no radiographic parameters were predictive of which side would require treatment first. Patients with FAI requiring surgery should be closely monitored for contralateral hip disease.