Spinopelvic fixation surgery in relation to the femoroacetabular impingement syndrome under the ultrasound.

Purpose: Spinopelvic fixation surgery is widely used for adult spinal deformity, but its impact on hip joint pathology remains unclear. This study investigates its association with femoroacetabular impingement syndrome (FAIS) using ultrasonography.

Methods: This retrospective study included 80 patients (160 hips) who underwent spinal fusion for adult spinal deformity. Patients were categorized based on sacroiliac joint fixation into fixation (group F) and non-fixation (group N). Ultrasonography was performed to assess hip morphology, including labral degeneration, cam lesions, and acetabular osteophytes. The Kellgren-Lawrence (KL) grade, and alpha angle were measured on standing radiographs. The anterior impingement test was conducted to evaluate clinical symptoms, and prevalence was statistically compared.

Results: We analyzed 151 hips (26 males, 125 females) with a mean follow-up of 52.7 ± 39.6 months. After excluding 27 hips with advanced hip osteoarthritis (KL grade ≥ 2), labral degeneration (69.5% vs. 37.9%, p = 0.0076) and cam lesions (30.5% vs. 6.9%, p = 0.01) were significantly more prevalent in group F than group N. The mean alpha angle did not significantly differ between two groups at the time of surgery, but significantly greater in group F compared to group N (48.7 ± 3.9° vs. 46.7 ± 4.7°, p = 0.01) at final follow-up.

Conclusion: Spinopelvic fixation may contribute to FAIS-related hip abnormalities by increasing mechanical stress. Ultrasonography may aid in early detection of hip joint changes after adult spinal deformity surgery.