Image processing for rear foot image evaluating leg and foot angles

The subtalar joint is in a neutral position when it is neither pronated nor supinated and the posterior midline of the calcaneus is vertically aligned with the calf and perpendicular to the forefoot. An incorrect foot position that causes excessive and prolonged pronation during the standing phase, as well as biomechanical abnormalities, is believed to increase the risk of overuse injuries. The leg and foot angles form key information in the assessment for, and fabrication of, foot orthoses. In this study, a foot evaluating system were proposed for the measurement of the foot and leg angles. The digital image processing was able to provide an objective and automatic method of calculating the midlines of the tibia and calcaneus. To achieve a high contrast image of the rearfoot, various screen and light positions were investigated. With the black box screen, the effect of shadow resulting from the light position in the image completely disappeared. The Sobel operator demonstrated that clearer characteristic edges of the lower leg and Achilles tendon can be achieved through image processing. The leg and foot angles were determined through the midline of the leg and the calcaneus. By having doctor place markers on the lower leg and calcaneus, the feasibility of the image processing method for determining leg and foot angles was verified.