投球フォームが野球肘の要因となったサイドスロー投手の一症例

抄録

We report a case of baseball elbow that developed in a sidearm pitcher. The pitcher alternatively bowled over arm and sidearm in a practice session, which led to baseball elbow. He experienced pain at the inside of his right elbow and visited a hospital when the pain persisted. The pain was reproduced by the valgus test in the right elbow. Accordingly, motion analysis of his pitching form was performed to investigate the cause of the stress at the inside of the elbow. A lateral tilt towards the ball-throwing side of the torso was observed in the late cocking phase of pitching. This characteristic motion of the torso caused excessive abduction of the shoulder joint, because the right upper limb horizontally moved to the left while throwing a ball sidearm. Furthermore, on moving the left lower limb forward, the knee joint became positioned at an angle more acute than that of the ankle joint. Therefore, the axis of rotation of the torso shifted proximally and anteriorly. We considered that his pitching form employed centrifugal force, which would easily cause stress in the elbow joint. To improve his pitching form, rehabilitation programs, including facilitation of the righting reflex and range of motion (ROM) of lower limbs, were initiated. In addition, the pitcher studied the problems in his pitching form by comparing it with those of other professional players. His elbow pain disappeared in two weeks, and his pitching form improved. We believe that using professional pitching form as a reference helped our patient to understand the factors contributing to the appropriate form. This method can also be used for similar evaluation of other such patients in the future.