The sternoclavicular joint (SCJ) is a pivotal articulation in the linked system of the upper limb girdle, providing load-bearing in compression while resisting displacement in tension or distraction at the manubrium sterni. The SCJ and acromioclavicular joint (ACJ) each have a small surface area of contact protected by an intra-articular fibrocartilaginous disc and are reinforced by strong extrinsic and intrinsic capsular ligaments. The function of load-sharing in the upper limb by bulky periscapular and thoracobrachial muscles is extremely important to the durability of both joints. Ligamentous and capsular laxity changes with age, subjecting both joints to increased strain, which could explain the rising incidence of arthritis in both with age. The incidence of arthritis in the SCJ is less than that in the ACJ, suggesting that the extrinsic ligaments of the SCJ provide more stability than the coracoclavicular ligaments of the ACJ. Instability of the SCJ is not common and can be difficult to distinguish from medial clavicular physeal or metaphyseal fracture-separation: cross-sectional imaging is often required. The distinction is significant because the treatment options and outcomes of treatment are dissimilar, whereas the treatment and outcomes of ACJ separation and fracture of the lateral clavicle can be similar. Proper recognition and treatment of traumatic instability is vital as these injuries may be life-threatening. Instability of the SCJ does not always call for surgical intervention. An accurate diagnosis is required before surgery can be considered, and the authors’ recommend the use of the Stanmore instability triangle. Most poor outcomes result from a failure to recognise the underlying pathology. There is a natural hesitance for orthopaedic surgeons to operate in this area due to unfamiliarity with, and the close proximity of, the related vascular structures, but the interposed sternohyoid and sternothyroid muscles are rarely injured and provide a clear boundary to the medial retroclavicular space, as well as an anatomical barrier to unsafe intervention.
This review presents current concepts of instability of the SCJ, describes the relevant surgical anatomy, provides a framework for diagnosis and management, including physiotherapy, and examines the technical challenges of operative intervention.