Anterior shoulder dislocation is a common injury, and one that I see frequently in athletes of all ages. Risks of repeat dislocation depends on many factors, including particularly the injured person’s age, whether the dislocation caused any bony defects, and the size of those defects. Decision making regarding surgery/no surgery can be difficult in some cases. When there is bone injury, however, the decision is usually surgery. The most common bone injury, called the bony Bankart lesion, is a defect in the front of the shoulder socket, (glenoid), that occurs due to the impact of the dislocation/relocation event. Having this bony injury with a dislocation increases the likelihood of repeat dislocation. Most of these injuries can be treated with a simple arthroscopic surgery to repair the soft tissue along with the small piece of attached bone.
Larger bone pieces have a higher risk of repeat dislocations, and the larger the defect, the bigger the risk. For defects that comprise 20-25% of the glenoid socket or more, we would classically perform a reconstruction of the bone defect, which is a more involved procedure and involves larger incisions. When I was in training, I studied at UC Irvine and the Long Beach VA biomechanics lab, which created an anatomic laboratory model to study shoulder motion and dislocation, I used this excellent model to study the forces involved in dislocating an uninjured versus a repaired shoulder in order to to evaluate repair quality. The lab continues to do cutting edge work in dynamic modeling of joint motion in the laboratory. This recent study from my alma matter now suggests that we look at repairing glenoid defects at lower thresholds of around 15% bone loss.