Shoulder Dislocation Anatomy | Shoulder Biomechanics | Sports Injury

Grant Norte, ATC discusses the pathoanatomy of a shoulder dislocation. The shoulder is a complex with many parts, "Intricate complex with a fragile system of checks and balances." The shoulder biomechanics have 3 axes of motion. The shoulder has low intrinsic stability. The static restraints of the shoulder - the "anterior capsular mechanism" plays a roll in limiting a shoulder dislocation. The rotator cuff is the primary dynamic restraint. These mechanisms provide stability through mid-ranges.

The mechanism of injury includes an indirect force to abducted and externally rotated arm (30%). A force directed posteriorly on distal segment or anteriorly on proximal humerus (29%). Forced elvation and external rotation (24%) and a fall onto an outstretched hand (17%).

The subcoracoid anterior shoulder dislocation is the most prevalent. Fractures can be commonly seen with shoulder dislocations. Bony Bankart accounts for 50% of all fractures in a shoulder dislocation. When assessing the athlete on the field - are xrays necessary? Majority of fractures have not precluded, prevented, or complicated closed reduction. Notion that all patients require pre-reduction and post-reduction radiographs has been challenged.

Neurovascular injuries are rare, but can occur with a shoulder dislocation. Premanent axillary nerve damage is uncommon following shoulder dislocation and rarely a result of the reduction method. Age, delayed reduction and the degree of trauma complicate any neurovascular injury.

The soft tissue structures - the Bankart lesion occurs in 97% of the time. Occasionally, the anterior labrum periosteal sleeve avulsion and humeral avulsion of the glenohumeral ligaments can occur with a shoulder dislocation. Rotator cuff tears are uncommon in younger patients, but they can occur.

For the acute management of the shoulder dislocation the athletic trainer should follow a systematic approach. Brief history, inspect, palpation, nurovascular clearance and functionally assess the motor capacity.