The shoulder is the most mobile in the body and at the same time is susceptible to increased risk of injury. To fully appreciate the types of injuries and mechanisms involved, you must first be able to understand the underlying anatomy of the shoulder. The scapula, clavicle, and humerus bones are joined by tendons, ligaments, and muscle to make up the shoulder. The three joints of the shoulder include the glenohumeral joint, acromioclaviclar joint, and the sternoclavicular joint.
Traumatic injuries to the shoulder can be classified into three groups: fractures, dislocations, and soft tissue injuries. A fracture (or broken bone) of the clavicle or proximal humerus commonly results from a direct blow to the area as a result of a motor vehicle accident, fall, or sports related event. Scapular fractures occur less frequently but are often associated high energy type injuries and often occurs with other internal injuries. The chest and surrounding muscles protect the scapula from injury.
An anterior shoulder dislocation (glenohumeral dislocation) can occur from a fall or direct trauma to the shoulder in which the arm is forcefully externally rotated while above the level of the shoulder. Posterior dislocations have a much lower incidence. Timely medical evaluation and management including reduction is vital to reduce risk of neurovascular compromise and long-term sequelae. Similarly, a dislocation of the sternoclavicular joint and can lead to pulmonary compromise if displaced posteriorly.
A fall directly onto the anterior shoulder or an outstretched arm can result in disruption of the acromioclavicular joint. Some refer to this as an AC separation. This injury can result in the ligament being sprained, disrupted or torn. A visible injury may be seen with more severe cases. Simple disruption of the joint can usually be treated without surgery, while complete disruption of the joint often requires surgical repair.
Soft-tissue injuries can occur to the shoulder either as an isolated condition or in conjunction with a fracture or dislocation. Common soft tissue injuries include traumatic rotator cuff tears, labral tears, and instability. Treatment for these types of injuries are dependent upon the nature and severity of the injury(s) and underlying medical co-morbidities.