Management of the Scapula in Glenohumeral Instability

Abstract

The scapula is a pivotal element in normal scapulohumeral rhythm and glenohumeral stability. It helps to maintain normal glenohumeral angle and acts as a stable base for muscular origins. Scapular dyskinesis, or alterations in scapular position and motion in arm activity, is common in both traumatic and microtraumatic glenohumeral instability. The exact etiology of dyskinesis is not known, but the resulting biomechanical alterations increase glenohumeral angulation, increase tensile strain in the glenohumeral ligaments, and decrease rotator cuff activation. These two actions increase the dysfunction associated with instability and decrease the effectiveness of treatment. Evaluation of scapular motion should be an integral part of the evaluation of the unstable shoulder, and restoration of normal scapulohumeral kinematics should accompany treatment and rehabilitation of the underlying instability. Instability of the glenohumeral joint, either on a macrotraumatic or microtraumatic basis, presents many issues in diagnosis, treatment, and rehabilitation that must be addressed to return the shoulder to maximum function. Alteration in position and function of the scapula is such an issue because the alterations are common in association with instability and may play a large role in determining the extent of the dysfunction and the effectiveness of treatment and rehabilitation. This paper will present information about the roles of the scapula in glenohumeral stability and instability, discuss methods of evaluation of altered scapular position and motion, and provide examples of specific exercises and progressions to help in restoring normal coupled scapulohumeral rhythm.