Management of Recurrent Anterior Shoulder Instability With Large Bone Defect

Abstract

The shoulder joint is a multiaxial joint possessing a wide range of freedom of motion between the roughly hemispherical humeral head and the shallow scapular glenoid cavity.(1) Stability of the shoulder comes from a complex interaction of various factors. Dynamic and static components are provided by soft tissue and bony structures creating joint stability (3). Anterior shoulder instability occurs with the combination of many factors, Glenoid and humeral head bone deficiency is a common reason for recurrent anterior shoulder instability, Glenoid bone loss has been found in 49% to 86% of patients with recurrent instability. Humeral head impression defects have been found in 70% of shoulders sustaining a first-time dislocation and 93% to 100% with recurrent instability (5). Biomechanical studies showed that glenoid and humeral bone defects can affect normal shoulder kinematics by changing glenohumeral contact forces and reducing resistance to dislocation, clinical studies reported a significant incidence of bony Bankart lesion and Hill-Sachs lesion after first dislocation, a high percentage of glenoid bone loss in chronic instability, and a significant correlation between the amount of gleno-humeral bone loss and recurrence rate of instability after surgical treatment.(32) In recurrent glenohumeral instability, advanced imaging techniques are strongly recommended before proceeding to surgery in order to quantify glenohumeral bone loss, including defect size and location (6). Imaging options include plain radiographs, computed tomography (CT) scan has a golden role, and arthroscopy. Although magnetic resonance imaging is valuable in assessing the location and degree of soft tissue injury, it often underestimates the degree of bone loss (8). While nonoperative treatment options are available, surgical treatment is often the gold-standard of the therapeutic options for both glenoid and humeral head bone loss when significant bony defects exist (7). In recurrent anterior instability cases, the aim of surgical treatment is to have anatomical reconstruction of the pathological lesion. Open or arthroscopic techniques could be preferred according to the underlying pathology in recurrent instabilities, several different reconstructive solutions have been proposed for dealing with large Hill-Sachs lesions including soft tissue transfers to bony reconstructions, and others advocate hemi arthroplasty as a definitive treatment.