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.