Patellofemoral joint study via image processing.

Plain Merchant-view X-rays of patellofemoral joints are used to study the geometry and kinematics of the patellofemoral joint. A method for calculating the kinematic parameters: sulcus angle (SA), patellofemoral congruence angle (PFC), lateral patellar angle (LPA), patellar rotation angle (PR) and lateral patellar displacement (LPD) is presented. Using digitized X-ray images of patellofemoral joints, contours of the patella and the femur can be acquired by boundary detection and morphological thinning. A radiograph is converted to a line drawing and the data points required for calculation of the parameters are chosen automatically without human intervention. Parameter measurements were demonstrated for 5 X-rays of 3 patients. Comparisons between computer calculated and hand calculated parameters were made. This technique is inexpensive but will provide the necessary information, and is practical, especially during the evaluation of patients with patellofemoral abnormalities.