Scapular Kinematics During Late Cocking of a Simulated Throwing Activity in Baseball Players With Shoulder Injury: A Cross-Sectional Study Using a 3D-to-2D Registration Technique
Context:Abnormal scapular kinematics during throwing motion in baseball players with shoulder disorders has not yet been clarified, although altered scapular position has been suggested to be associated with shoulder disorder.Objective:To determine if the shoulders of baseball players with throwing disorders demonstrate abnormal scapular kinematics during the simulated arm-cocking phase of throwing activity.Design:Cross sectional study.Setting:Laboratory.Participants:Eleven baseball players (age 21.1 ± 1.2 y) with a unilateral shoulder disorder volunteered to participate, including 9 players at the college level and 2 at the adult level. The mean playing experience was 12.1 ± 2.7 y.Main Outcome Measures:Scapular upward/downward rotation, anteroposterior tilting, and external/internal rotation during simulated arm-cocking motion were analyzed using a 3-to-2-dimensional registration technique.Results:Scapular external rotation in the throwing shoulder was significantly smaller by 2.0–6.0° than that of the contralateral shoulder. There were no detectable differences in scapular upward/downward rotation or anteroposterior tilting between the throwing and contralateral shoulders.Conclusions:Compared with that in the contralateral shoulder, scapular external rotation was smaller in the throwing shoulder, which would increase glenohumeral horizontal abduction during the arm-cocking phase and be related to the throwing-shoulder disorder.