Glenohumeral and scapulohumeral kinematic analysis of patients with traumatic anterior instability wearing a shoulder brace: a prospective laboratory study

Purpose: To assess the effectiveness of a novel glenohumeral joint immobilizer, the S2 Shoulder Stabilizer®, by evaluating shoulder kinematics with a stereophotogrammetry system. Methods: Participants in this prospective laboratory study were recruited from patients with anterior traumatic instability awaiting arthroscopic glenohumeral stabilization. Glenohumeral and scapulohumeral kinematic data (arm abduction–adduction and internal–external rotation, and scapular pronation–retraction and mediolateral rotation) were collected twice, without and with the brace, using a VICON™ motion capture system, and processed with MATLAB®software. Results: The tests showed a significantly lower joint angle during abduction–adduction (p = 0.0022) and external rotation (p = 0.0076) and a significantly lower (p = 0.0022) mediolateral scapular rotation angle in the limbs wearing the immobilizer. Humeral head translation during abduction–adduction and internal–external rotation was also lower in the patients wearing the brace. Conclusions: The immobilizer significantly limited joint excursion in all planes of movement except internal rotation. The narrower humeral head translation with respect to the trunk, measured in the tests with the brace, demonstrates that the immobilizer achieves the goal of preserving joint stability in the movements that are at risk of dislocation.