Assessment of bone defects in anterior shoulder instability.

Glenohumeral bone defects are a common finding in shoulder instability and they are strongly correlated with recurrence of dislocation and failure following arthroscopic Bankart repair. Most authors agree that open surgery should be considered in the presence of certain conditions: glenoid bone loss > 25%, a lesion involving > 30% of the humeral head, an engaging Hill-Sachs lesion, bipolar bone lesions even without engagement. A careful imaging evaluation must therefore be performed in order to identify, quantify and characterize the bone defects. Even though magnetic resonance has important additional value in the assessment of the glenoid labrum and rotator cuff, computed tomography scan is the examination of choice for studying bone defects. Several methods have been proposed to quantify the extent of the glenoid bone defect; the most accurate ones utilize two-dimensional computed tomography images with multiplanar reconstructions (PICO method) or more sophisticated three-dimensional reconstruction software. Conversely, the literature lacks studies that accurately quantify humeral bone defects and, above all, that demonstrate definitively the clinical and prognostic significance of the lesion location and size.