Recurrent shoulder instability: current concepts for evaluation and management of glenoid bone loss.

Introduction Recurrent instability of the glenohumeral joint is usually associated with a Bankart tear—a soft-tissue injury of the glenoid labrum attachment. However, patients with recurrent shoulder instability often present with osseous injury to the glenoid and humeral head as well. Understanding and appropriately addressing irregularities in the osseous architecture of the glenohumeral joint are critical to the overall success of surgical repair for the treatment of glenohumeral instability. The integrity of the osseous architecture of the glenoid has recently been highlighted as one of the most important factors related to the success of surgical repair. After the initial traumatic shoulder dislocation, an associated glenoid rim fracture or attritional bone injury may compromise the static restraints of the glenohumeral joint, making further instability more likely. With recurrent instability, there can be further attritional glenoid bone loss. Glenoid bone deficiency with recurrent shoulder instability is an increasingly recognized cause of failed shoulder stabilization surgery. It is critical to evaluate all patients with recurrent shoulder instability for the presence of osseous injuries to the glenoid. Specific findings in the history and the physical examination provide important clues to the presence of glenoid bone loss, and a careful preoperative evaluation to diagnose and quantify anterior glenoid deficiency is crucial for the success of surgical treatment. Appropriate preoperative imaging is essential for detection and quantification of osseous abnormalities in patients with recurrent shoulder instability. The apical oblique view described by Garth et al., the West Point view, and the Didiée view are recognized as being the most sensitive radiographs for detecting osseous abnormalities of the glenoid. Magnetic resonance imaging and magnetic resonance arthrography may be used, but they are primarily employed to assess the surrounding soft tissues. If any osseous lesion is discovered on radiographs, or with magnetic resonance imaging, a computed tomography scan can provide valuable information about the extent of the bone loss. Furthermore, a three-dimensionalreconstruction computed tomography scan allows digital subtraction of the humeral head from images of the glenohumeral complex, providing an en face sagittal oblique view of the glenoid. Precise measurements of the percentage of glenoid bone loss can be calculated by modeling the inferior aspect of the intact glenoid as a true circle. It is preferable to accurately assess glenoid bone loss prior to surgical intervention, as this permits informed consent and shared clinical decision-making with the patient regarding optimal treatment strategies. Once a precise estimation of bone loss is made, decisions regarding the surgical approach to be used, particularly those related to the risk of the recurrence of shoulder instability, can be discussed with the patient. Although the exact treatment for each percentage of glenoid bone loss has yet to be fully defined, the published literature supports the idea that, in patients with less than 15% to 20% glenoid bone loss (usually less than 5 to 7 mm of bone), recurrent instability can be successfully treated with soft-tissue stabilization alone. However, when bone loss is 25% to 30% of the glenoid sphere (more than 6 to 8 mm of bone loss), open repair or bone augmentation procedures should be considered. Osseous reconstruction techniques include the Bristow procedure, the Latarjet procedure, use of iliac crest bone graft, and allografting with use of the femoral head or the distal part of the tibia. The principles of surgical management are guided by the extent of osseous deficiency, consideration of combined glenoid and humeral bone defects, the surgeon’s personal experience with specific reconstructive techniques, and patient-specific