PURPOSE: The purpose of this study was to assess accurately the three-dimensional movements of the scapula and humerus relative to the thorax during internal/external rotation motion with abduction of the shoulder joint. METHODS: Ten right shoulders of ten healthy volunteers were examined using a wide-gantry open magnetic resonance imaging (MRI) system. MRI was performed every 30° from 90° external rotation to 90° internal rotation of the shoulder joint. RESULTS: The contribution ratio of the scapulothoracic joint was 12.5% about the long axis of the humerus during internal/external rotation motion. With arm position changes from 90° external rotation to 60° internal rotation, most movement was performed by the glenohumeral joint. Conversely, at internal rotation of ≥60°, the scapula began to markedly tilt in the anterior direction. At 90° internal rotation, the scapula was significantly tilted anteriorly (p < 0.05) when compared with the other positions. CONCLUSIONS: We clarified the existence of a specific scapulohumeral motion pattern, whereby the glenohumeral joint moves with internal rotation and the scapulothoracic joint moves with anterior tilt together with internal rotation motion of the shoulder joint.
PURPOSE: The purpose of this study was to assess accurately the three-dimensional movements of the scapula and humerus relative to the thorax during internal/external rotation motion with abduction of the shoulder joint. METHODS: Ten right shoulders of ten healthy volunteers were examined using a wide-gantry open magnetic resonance imaging (MRI) system. MRI was performed every 30° from 90° external rotation to 90° internal rotation of the shoulder joint. RESULTS: The contribution ratio of the scapulothoracic joint was 12.5% about the long axis of the humerus during internal/external rotation motion. With arm position changes from 90° external rotation to 60° internal rotation, most movement was performed by the glenohumeral joint. Conversely, at internal rotation of ≥60°, the scapula began to markedly tilt in the anterior direction. At 90° internal rotation, the scapula was significantly tilted anteriorly (p < 0.05) when compared with the other positions. CONCLUSIONS: We clarified the existence of a specific scapulohumeral motion pattern, whereby the glenohumeral joint moves with internal rotation and the scapulothoracic joint moves with anterior tilt together with internal rotation motion of the shoulder joint.
Authors: Paula M Ludewig; Vandana Phadke; Jonathan P Braman; Daniel R Hassett; Cort J Cieminski; Robert F LaPrade Journal: J Bone Joint Surg Am Date: 2009-02 Impact factor: 5.284