External Rotation of the Shoulder against Resistance as a Clinical Sign to Aid in the Diagnosis of Acromioclavicular Injury.

Introduction: Acromioclavicular joint (ACJ) injuries account for more than 40% of all sports-related shoulder injuries. Early and effective diagnosis is crucial with surgical intervention favored over non-operative management in high-grade injury. At present diagnosis is primarily by plain radiography with a clear lack of good clinical examination techniques. This study aims to describe external rotation against resistance (ERAR) as a means of ACJ injury assessment. Case Report: This case report describes three patients who presented to a local tertiary hospital with sporting injuries. In all cases, plain radiography demonstrated ACJ injury. Patients performed ERAR with the elbow by the side and flexed to 90° to assess for increase in ACJ deformity and coracoclavicular (CC) distance. The cases reported include two acute and one chronic ACJ injury. In all cases, this physical examination technique resulted in increased ACJ deformity and CC distance. This examination technique was well tolerated in all patients. All three patients underwent operative fixation and achieved excellent clinical outcomes. Conclusion: In our experience, external rotation of the shoulder against resistance is a well-tolerated examination technique which has demonstrated good clinical utility, aiding in the diagnosis of moderate to high-grade ACJ injury. While this clinical examination technique may aid in the diagnosis of high-grade ACJ injury, the authors strongly recommend further clinical and radiological confirmation before the diagnosis of acute traumatic shoulder injuries.