A diagnosis of shoulder separation describes a specific condition in which the ligaments connecting the acromioclavicular (AC) joint – where the upper portion of the scapula (acromion) meets the collarbone or clavicle – separate and move away from the clavicle.
The shoulder comprises four different joints: the AC joint; the glenohumeral (GH) joint, where the large bone in the upper arm (humerus) joins the cup-like structure on the scapula (the glenoid); the sternoclavicular joint, where the clavicle meets the sternum; and the scapulothoracic articulation where the scapula meets the thoracic (chest) wall. Together, these create the "shoulder girdle." A network of supportive ligaments, muscles and soft tissue maintains proper alignment and a wide range of motion. The most common injuries to the shoulder involve the AC joint or GH joint and are usually a result of either a single trauma or a series of smaller traumas which accumulate over time.
"Movement of the shoulder is more complex than other large joints," explains Frank Cordasco, M.D., orthopedic surgeon in the Sports Medicine and Shoulder Service at Hospital for Special Surgery (HSS) in New York. "Each time the arm is raised, the ball of the humerus must move in the socket of the glenoid, the clavicle and the acromion must rotate 40 degrees in relation to one another, and the scapula must move on the chest wall."
Because shoulder separation is a disruption of the mechanism that keeps the arm suspended from the clavicle and close to the chest, it can be very disabling. Ranging from a sprain or partial tear of the ligaments – the least severe injury – to a severe condition resulting from a complete tear of the major supporting ligaments, shoulder separation is a common athletic injury. Athletes participating in sports heavily based in throwing, including baseball, football and lacrosse, among others, are most at risk.
"Treatment of shoulder separation depends on a number of variables," explains Dr. Cordasco. "We factor in the severity of the injury, age of the athlete, and the ability to modify activity. We also take into consideration proximity to the playing season – with different standards of care for pre-, during, or post-season injuries." For example, athletes who are mid-season may be treated non-operatively (depending upon their sport and position) so that they may continue participation, then opt for surgical treatment in the off-season.
Lower grade shoulder separations with only partial separation of ligaments are usually treated non-surgically, with rest and physical therapy to maintain flexibility and range of motion. When a full tear occurs, however, treatment can take a variety of courses.
"Traditionally, patients may have undergone non-surgical treatment, but today we tend to recommend surgical repair for a complete AC separation," says Dr. Cordasco. "Though patients with a full separation may feel better in six or eight weeks after the injury, long-term effects of these injuries can be problematic. A full separation alters the mechanics of the muscles that move the arm. After ten or 15 years of repetitive motion, we see wear of the rotator cuff muscles and often, the development of secondary impingement and loss of motion."
Surgical treatment to repair ligament injury can be performed either with open incision or arthroscopic surgery. In each, repair of the ligaments requires a graft from another location, either obtained from the patient or a cadaver donor.
"Completely torn ligaments will not heal on their own," Dr. Cordasco explains," so the goal of surgery is to restore the anatomy by reconstructing the ligaments."
Surgical treatment of shoulder separation has a high success rate, with positive long-term results. Interestingly, patients with less severe forms of AC separation may be at greater risk for developing the long-term complication of AC arthritis, due to a disruption of the joint surfaces that occurs with the injury. This can, over time, erode the joint cushion and cause "wear and tear" arthritis.
"Arthroscopic techniques are well established and are the standard of care for shoulder dislocation at Hospital for Special Surgery (HSS)," Dr. Cordasco notes. "We think it's the best available treatment because it restores the anatomy with a minimally invasive procedure. Results are overall 85-90% good to excellent."