Posterior shoulder instability

Purpose of review: Posterior instability of the glenohumeral joint is a relatively rare diagnosis that can be debilitating for the active patient. Practicing orthopaedic surgeons should be attentive when evaluating patients with shoulder instability to reduce misdiagnosis and treatment delay. This review will include recent reports on the evaluation, treatment, and basic science of posterior shoulder instability. Recent findings: Laxity testing during physical examination of the shoulder is critical in obtaining a correct diagnosis: positive results correlate to the reproduction of instability symptoms and not necessarily to pain or side-to-side differences. Arthroscopic and open surgical techniques are effective for posterior instability with average success rates of 89%. Thermal capsulorrhaphy techniques result in inferior outcomes compared to other techniques and their efficacy has been questioned. Biomechanical studies show decreased posterior glenohumeral translation with rotator interval closure and suggest including this as a part of stabilization procedures. Electromyographic studies support the importance of periscapular muscle strengthening in treatment of shoulder instability. Summary: Appropriate treatment of posterior shoulder instability begins with accurate diagnosis. Surgery is appropriate for instability if conservative treatment fails and both open and arthroscopic techniques are effective. Surgical procedures are evolving as the understanding of glenohumeral biomechanics improves.