Background: There is currently no consensus regarding the amount of posterior glenoid bone loss that is considered critical. Critical bone loss is defined as the amount of bone loss that occurs in which an isolated labral repair will not sufficiently restore stability Purpose: The purpose of this study was to identify the critical size of the posterior defect. Methods: 11 cadaver shoulders were tested. With the use of a custom robot device, a 50-N compressive force was applied to the glenohumeral joint and the peak force that required to translate the humeral head posteriorly and the lateral displacement that occurred with translation were measured. The defect size was measured as a percentage of the glenoid width. Testing was performed in 11 conditions: (1) intact glenoid and labrum, (2) simulated reverse Bankart lesion, (3) the reverse Bankart lesion repaired, (4) a 10% defect, (5) the reverse Bankart lesion repaired, (6) a 20% defect, (7) the reverse Bankart lesion repaired (8) a 30% defect, (9) the reverse Bankart lesion repaired, (10) a 40% defect, and (11) the reverse Bankart repaired. Results: Force and displacement decreased as the size of the osseous defect increased. The mean peak force that occurred with posterior displacement in specimens with a glenoid defect ≥ 20% and a reverse Bankart repair (13 ± 9 N) was significantly lower than the peak force that occurred in specimens with an isolated reverse Bankart repair (22 ± 10N) (p=0.0451). Additionally, the mean lateral displacement was significantly lower in the specimens with a 20% glenoid defect and a reverse Bankart repair (0.61 ± 0. 57 mm) compared with the lateral displacement that occurred in specimens with an isolated reverse Bankart repair (1.6 mm ± 0.78 mm) (p=0.0058). Conclusions: An osseous defect that is ≥ 20% of the posterior glenoid width remains unstable after isolated reverse Bankart repair.

BackgroundPosterior shoulder instability is common in young athletes. Although the posterior shoulder instability literature is less robust than its anterior counterpart, many surgical procedures have been developed and refined over the past several centuries to address this condition.Materials and methodsThis article represents a retrospective historical analysis of the most common procedures used to treat posterior shoulder instability after sports injuries. A systematic approach to obtain published information on posterior shoulder instability was performed using the PubMed/MEDLINE database, manual searches of high–impact factor journals, and conference proceedings and books.ResultsA wide array of both soft tissue–based and bone-based procedures have been developed for the treatment of posterior shoulder instability, ranging from procedures addressing the soft tissue alone (capsular shift, labral repair, reverse Putti-Platt) or bone-based procedures (glenoid and/or humeral osteotomy, glenoid bone block) to a combination of both bone and soft-tissue procedures (modified McLaughlin procedure).DiscussionOver the past several centuries, a number of procedures have been developed to address posterior shoulder instability, particularly as this pathology has become better understood. Future work is required not only to continue to advance these procedures but also to assess their outcomes. An understanding of the historical perspective of posterior shoulder instability procedures is essential as surgeons continue to modify these procedures in an effort to best help their patients.

Skiing and snowboarding have increased in popularity since the 1960s. Both sports are responsible for a substantial number of musculoskeletal injuries treated annually by orthopaedic surgeons. Specific injury patterns and mechanisms associated with skiing and snowboarding have been identified. No anatomic location is exempt from injury, including the head, spine, pelvis, and upper and lower extremities. In these sports, characteristic injury mechanisms often are related to the position of the limbs during injury, the athlete's expertise level, and equipment design. Controversy exists about the effectiveness of knee bracing and wrist guards in reducing the incidence of these injuries. Understanding these injury patterns, proper training, and the use of injury prevention measures, such as protective equipment, may reduce the overall incidence of these potentially debilitating injuries.