Frozen shoulder or missed posterior dislocation?

Abstract

The clinical presentation of a missed posterior shoulder dislocation has similarities with an idiopathic frozen shoulder masking proper diagnosis at the time of injury. We report a case of a 48-year-old woman with shoulder pain which demonstrates the importance of correct initial diagnosis and management. The glenohumeral (GH) joint consists of the humeral head that articulates in the glenoid fossa of the scapula, surrounded by several static and dynamic structures. It is the most mobile joint of the human body which makes it vulnerable to dislocation in all directions. Posterior shoulder dislocation (PSD) is less common than anterior. The rarity of this pathology together with the restrictions of standard view X-rays often leads to the diagnosis being missed. Case reportA 48-year-old woman presented with 4 months of spontaneous progressive pain and limited range of motion of the right shoulder. Her pain was aggravated by movement and impacts, particularly those activities associated with daily living. She was unable to lie on her right side but did not complain of any pain at night. She had no history of trauma although she recently started experiencing episodes of syncope. Further to this, her medical history consisted of hypertension, hypercholesterolaemia, asthma and previous left frozen shoulder.Upon clinical examination she held the right upper limb in internal rotation with the elbow in flexed position. There was diffuse, mild tenderness over the anterolateral side of the shoulder. Range of motion was limited to 5 degrees of passive and active abduction. External rotation was not possible. Other shoulder tests were impossible to implement. X-rays showed normal proportions of the GH joint with the humeral head articulating in the glenoid. On the anterior side of the humeral head a medium sized dent was visible, suggestive of a reverse Hill-Sachs lesion. The differential diagnosis was an overlooked posterior shoulder dislocation or adhesive capsulitis.