EP1.57 Lateral Center Edge Angle Influences Translational and Rotational Hip Kinematics During Walking

Abstract Introduction Acetabular dysplasia (AD) is a non-arthritic hip disorder characterized by insufficient coverage of the femoral head, causing instability of the hip joint. Over time, this instability causes damage to the labrum and cartilage, which can cause pain and lead to early hip osteoarthritis. Periacetabular osteotomy (PAO) is the gold standard surgical procedure to treat symptomatic AD. Although hip joint kinematics during activities of daily living have been investigated in asymptomatic young adults, the kinematics of the pre-operative dysplastic hip remain elusive. The present study is an interim analysis of an ongoing study comparing hip kinematics prior to an after PAO to hip kinematics in a healthy asymptomatic cohort. Methods Ten patients (10F, age 20.2 years) scheduled to undergo a PAO to treat symptomatic AD were included in this IRB-approved study. Synchronized biplane radiographic images were collected during treadmill walking. CT-derived 3D bone models were generated and matched to the biplane radiographs by a validated model-based tracking technique to quantify 6-DOF kinematics of the hip joint. A dataset of healthy control participants (13F,11M; age 21.9 years) was also used for this analysis. Lateral center edge angle (LCEA) was measured for each hip, and the spearman correlation coefficient was used to evaluate the association between LCEA and 6DOF kinematics. Results Across all hips (n=65), there was an average LCEA of 27.5±7.6°, while within the pre-operative cohort, there was an average LCEA of 15.5±2.5°. Lower LCEA was associated with greater hip translation during gait, including average AP translation (rho=-0.35, p<0.01) and both average and maximum ML translation (rho=-0.26, p=0.03; rho=-0.20, p=0.02). Conversely, LCEA was positively associated with rotational kinematics, including maximum and range of flexion (rho=0.40 and rho=0.35, both p<0.01), average and maximum internal rotation (rho=0.32, p<0.01; rho=0.29, p=0.02, respectively), and average, maximum, and range values of abduction (rho=0.33, 0.40, 0.29, all p≤0.02). Discussion Hips with increased joint translation demonstrated significant correlations with lower LCEA measurements. Additionally, LCEA influenced rotational hip motion across all kinematic variables, suggesting a fear-avoidance motion pattern in individuals with symptomatic AD.