THREE-DIMENSIONAL PREDICTORS OF FAI DISEASE PROGRESSION IN THE CONTRALATERAL HIP

BACKGROUND: Bony morphologies contributing to femoroacetabular impingement (FAI) are relatively common in the general population, but drivers of symptom development are not well understood. HYPOTHESIS/PURPOSE: The purpose of this study was to determine the role of three-dimensional bony morphology in symptom development in the contralateral hip in patients undergoing ipsilateral surgical treatment for FAI. METHODS: The study included a prospective cohort of 161 consecutive patients (101 females, 60 males) who presented for ipsilateral FAI surgical treatment from 2013-2018. The average age was 29.1 years. Minimum follow-up was 1 year (mean, 2.3 years; range, 1-6 years). Low-dose CT scans were obtained prior to surgical treatment. Three-dimensional hip analysis of the contralateral hip was performed relative to normative data and allowed measurements of 15 key parameters. Prior to surgery and at routine follow-up, patients completed standardized questionnaires that included pain in the contralateral hip. Univariate and multivariate analyses were performed to identify independent predictors. RESULTS: There were 133 patients (83%) with follow-up. Significant levels of pain in the contralateral hip were reported in 25 (18.8%) patients at presentation and 50 (35.3%) patients at follow-up. Twenty-six (19.5%) patients progressed to surgery at an average of 1.12 years. Significant predictors of symptom development were alpha angle >55° at 1:00 (p=0.037), femoral version <0° or > 20° (p=0.027), and decreased central acetabular version at 3:00 (p=0.048). Significant predictors of surgery were age <30 years (p=0.023) and alpha angle >55° at 1:00 (p=0.005). CONCLUSION: We found that roughly 1 in 5 patients undergoing surgical treatment for ipsilateral FAI experienced pain in the contralateral hip at presentation, over one third reported pain at follow-up, and 1 in 5 progressed to surgery. Higher alpha angle, abnormal femoral version, and decreased acetabular version were correlated with symptom development, while higher alpha angle and age under 30 were associated with progression to surgery.