HOW DOES HIP ARTHROSCOPY INFLUENCE SPINOPELVIC CHARACTERISTICS AMONG PATIENTS WITH FEMOROACETABULAR IMPINGEMENT COMPARED TO ASYMPTOMATIC CONTROLS?

The hip-spine relationship may influence hip pathomechanics. Cam morphology is associated with pain and arthritis, but not all individuals with such morphology are symptomatic. This study aimed to (1) Compare spinopelvic characteristics between symptomatic patients with CAM-FAI and a matched cohort of asymptomatic volunteers; (2) assess whether spinopelvic characteristics change following femoral osteochondroplasty (FOCP), and (3) test whether spinopelvic characteristics are associated with patient-reported outcome. This is a prospective, case-control, study at a tertiary referral hospital. From a cohort of 112 patients treated with hip arthroscopy and 44 asymptomatic volunteers (Oxford Hip Score≥45) without osteoarthritis (Tonnis≤1), 50 patients (25 each group) were matched for age (mean: 39±8 years-old; p=0.5), acetabular- (LCEA: 30±6°; p=0.6; AI 4±5°; p=0.7; AWI 0.48±0.13; p=0.2; PWI: 0.91±0.43; p=0.1) and CAM- (alpha-angle: 56±9°; p=0.9) morphology. All underwent standing and deep-seated spinopelvic radiographs pre-operatively and 1-year post-operatively, to measure lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT) and pelvic-femoral angle (PFA). Difference between standing and flexed-seated measurements allowed to uncouple lumbar- (∆LL), pelvic- (∆PT) and hip- (∆PFA) mobility. The Hip User index quantifies the relative contribution of the hip to overall sagittal movement and was calculated as [∆PFA/(∆PFA+∆LL)]*100. Outcome was assessed using the international Hip Outcome Tool (iHOT). Pre-operatively, patients had less standing PT compared to controls (11±5° vs. 15±8°; p=0.009) and a lower PFA (190±6° vs. 194±6°; p=0.04). There were no other differences between groups. Post-operatively, patients continued to have lower standing PT (12±7° vs. 15±8°; p=0.02) but had similar similar PFA to controls (194±9° vs. 194±6°; p=0.9). Hip flexion improved by 4±12° (p=0.015), allowing patients to have greater hip flexion than controls (∆PFA 110±16° vs. 101±16°; p=0.013). Hip user index increased following hip arthroscopy (69±7% vs. 63%; p=0.002). In a multi-variate model, pre-operative iHOT was associated with alpha angle (p Decreased pelvic tilt is associated with less acetabular anteversion, which reduces impingement-free flexion arc, predisposing to FAI symptoms. iHOT was associated with spinopevic characteristics; the stiffer the segments, the worse the function. Post-surgery, PFA increased (hip more extended when standing) and flexion improved, both of which were associated with patient-reported outcome.