- WHY IS THE SHOULDER THE MOST FREQUENTLY DISLOCATED LARGEJOINT?
- WHAT STRUCTURES ARE INJURED WITH SHOULDER DISLOCATIONS?
- WHAT IS THE MECHANISM OF SHOULDER DISLOCATIONS?
- HOW CAN THE SHOULDER BE RELOCATED?
- WILL MY SHOULDER DISLOCATE AGAIN?
- IS SURGERY NECESSARY?
- HOW IS SURGERY PERFORMED?
WHY IS THE SHOULDER THE MOST FREQUENTLY DISLOCATED LARGE JOINT?
The shoulder is actually several joints, the main joint, the glenohumeral joint (which is most frequently dislocated) has the greatest range of motion of all joints in the body. There is a large ball (humeral head) and a small shallow socket (glenoid). The glenoid is made deeper by a rim of fibrocartilage called the labrum. There are several loose ligaments that form the shoulder capsule. These ligaments are attached to both the humeral head and glenoid. Each ligament tightens in different arm positions, thus keeping the humeral head attached to the glenoid. These ligaments are responsible for “static stability”. Rotator cuff muscles that originate on the scapula (wing bone) form a cuff of tendons that surround the humeral head. These rotator cuff muscles and tendons provide for “dynamic stability” of the glenohumeral joint.
WHAT STRUCTURES ARE INJURED WITH SHOULDER DISLOCATIONS?
When the shoulder dislocates (the humeral head becomes dissociated from the glenoid) usually the ligamentous structures are stretched and/or torn. The fibrocartilage (labrum) that surrounds the glenoid can be torn away from the labrum. Occasionally the front of the glenoid will actually fracture. At other times, the humeral head, once it slips forward, will become impacted on the glenoid and will develop an impaction fracture called a “Hill-Sachs lesion”.
WHAT IS THE MECHANISM OF SHOULDER DISLOCATIONS?
Usually the shoulder dislocates anteriorally when the arm is caught above and behind the patient, such as a football player reaching out to his side to tackle a runner. It is common for athletes to dislocate their shoulders while playing football, hockey or sliding into a base head first with arms stretched out ahead of them. Occasionally the humeral head can be pushed posteriorly out of the glenoid, which can happen from a direct blow to the front of the shoulder.
HOW CAN THE SHOULDER BE RELOCATED?
For the first true dislocation, the patient must usually be taken to an emergency room facility where medication is given to relieve pain and muscle spasm. Once this is done, a physician can apply gentle traction and relocate the humeral head back into the glenoid. With a recurrent dislocating shoulder, sometimes a patient can use their own muscles to pull the humeral head back into the socket; however, if it is dislocated for more than a minute or so, the muscles around the shoulder will go into spasm and the patient will need medication to help reduce the shoulder.
WILL MY SHOULDER DISLOCATE AGAIN?
There are various reports in the medical literature stating that a patient under 20 years old will have a high recurrence rate for dislocating the shoulder (various studies report re-dislocation rates from 30- 90%). There are newer studies showing when an acute dislocation is treated with arthroscopic stabilization, this will greatly reduce the re-dislocation rate.
Currently, the typical treatment involves rehabilitation programs that start with a short period of immobilization, isometric exercises, and progress to exercises involving motion of the shoulder. These exercises are aimed at strengthening the rotator cuff muscles. Over time, the exercises are to increase coordination of the shoulder and help return the patient to sports.
IS SURGERY NECESSARY?
Surgery for acute shoulder dislocations seems to prevent recurrent dislocations. However, the need for surgery depends on the functional demands of the patient and degree of instability and disability. If the patient does not wish to return to sports or it is their non-dominant arm, the need for surgery is less than if it is the dominant arm of an athlete who participates in collision or contact sports.
HOW IS SURGERY PERFORMED?
Surgery for recurrent dislocations of the shoulder can be performed by the traditional open approach or via arthroscopy. The repair is focused on tightening the stretched ligaments and/or repairing the labrum if it was torn at the time of injury. Generally, if the patient is going to return to a collision sport, such as hockey or football, an open repair is favored over an arthroscopic repair. The goal of surgery is to restore stability while maintaining motion of the glenohumeral joint. The success rate of open surgery vary from 90-95% and success rate for arthroscopic surgery vary from 85-90%.