Short term outcomes of hip arthroscopy on hip joint mechanics and cartilage health in patients with femoroacetabular impingement syndrome

Background: Femoroacetabular acetabular impingement syndrome consists of abnormal hip joint morphology resulting in painful hip joint impingement. Hip arthroscopy corrects the abnormal morphology and reduces clinical symptoms associated with femoroacetabular impingement syndrome yet the effects of hip arthroscopy on gait mechanics and cartilage health are not well understood. Methods: Ten femoroacetabular impingement syndrome patients and 10 matched asymptomatic controls underwent gait analysis consisting of three-dimensional hip joint kinematics and kinetics. Femoroacetabular impingement syndrome patients underwent gait analysis and quantitative magnetic resonance imaging of the surgical hip joint before and seven months post-surgery. Patient reported outcomes were obtained from all study participants and were used to quantify hip joint pain, function and quality of life. Findings: Prior to surgery, femoroacetabular impingement syndrome patients demonstrated hip joint kinematics or kinetics as the control group. After surgery, femoroacetabular impingement syndrome patients exhibited improved patient reported outcomes, similar hip joint kinematic patterns, increased hip flexion and decreased hip extension moment impulses within the surgical limb. The femoroacetabular impingement syndrome patients that ambulated with increased HFMI post-surgery demonstrated a decrease in femoral cartilage T1ρ and T2 values. Interpretation: Femoroacetabular impingement syndrome patients exhibited improved clinical symptoms yet ambulated with altered sagittal plane hip joint loading after hip arthroscopy. Increased hip flexion moment impulse post-surgery was associated with improved cartilage health within the surgical limb. These study findings suggest that sagittal plane hip joint loading at short-term follow-up after hip arthroscopy is associated with cartilage health and may be an important biomechanical parameter in post-operative rehabilitation programs.