A Study on the Development and Application of Patellofemoral Joint Radiography Auxiliary Device for Tangential Axial Radiography of the Patellar and Patellofemoral Joints

Abstract This study evaluated the accuracy of tangential axial radiography of the patellofemoral joints using an auxiliary device, which we named patellofemoral joint radiography (PJR). To compare the PJR and conventional radiography methods such as the Laurin, Merchant, and Settegast, the images taken by three methods were evaluated using a whole body phantom (PBU-31). Settegast was the radiographic method that had the smallest inclination of the patella and showed the best half lateral image of the patella, with a difference of 5.76% when compared with PJR (p = 0.001). PJR was the method that had the largest distance between the patellar and femoral joint spaces, with a difference of 14.54% when compared with the Merchant method (p = 0.001). PJR was the method in which the two bones were well overlapped (i.e., measured by the distance between the femoral trochlear groove and the tibial tuberosity), with a difference of 109.41% when compared with the Merchant method (p = 0.001). The Settegast method has the image with the smallest inclination of the patella, but the PJR has the image that best describes the patellofemoral joint and the least distortion of the image. when using PJR, bending the knee by 40° degree and setting a 140° angle between the long axis of the femur and the long axis of the lower leg were considered to be the most beneficial conditions. We propose the use of PJR for tangential axial radiography of the patellar and patellofemoral joints.