The shoulder joint is a ball and socket joint that connects the bone of the upper arm (humerus) with the shoulder blade (scapula). The shallow socket in the scapula is the glenoid cavity. The capsule is a broad ligament that surrounds and stabilizes the joint. The glenoid labrum is a rim of cartilage attached to the glenoid rim. If the arm is pulled out of its socket, the capsule and labrum tear, usually from the rim of the glenoid cavity. A dislocation occurs when the humerus comes completely out of the socket and stays out. A subluxation occurs when the humerus comes partly out of the socket and then slips back in.
When the capsule tears from the glenoid rim, the shoulder can become unstable
and dislocate or subluxate repeatedly. The most common direction for the
humeral head to dislocate is
toward the front of the body (anteriorly); this typically occurs if the arm goes too far behind the body when the arm is in an overhead position (such as when throwing a ball). The humeral head can also dislocate toward the back of the body (posteriorly) when force is directed toward the back of the shoulder; this can occur when falling forward on an outstretched arm, seizures, electrical shocks or blocking with the arm straight ahead in football It is possible for the shoulder to be unstable in more than one direction. Multidirectional instability is more common in loose-jointed (double jointed) individuals.
To help confirm the diagnosis of instability several different tests are helpful and may be employed:
- Magnetic resonance imaging (MRI) or computed tomography (CT)
- MRI or CT scan with dye is injected into the shoulder joint (MRI arthrogram or CT arthrogram)
- Examination under anesthesia followed by arthroscopy
- Some patients who dislocate their shoulder do well after the injury and do not have recurrent instability. They tend to be older in age and not active in sports. Young people, especially athletes, are prone to have recurrent dislocations and subluxations and usually need surgery to correct the shoulder problem.
- Often, anterior shoulder dislocations can be fixed using arthroscopic, or minimally invasive, surgery to fix the ligaments around the shoulder. However, when the socket (glenoid) is missing a significant amount of bone – over 20% – a minimally invasive surgery is often not successful at maintaining the shoulder in its socket and a reconstruction using your own bone gives the best results. The two most common sites of bone are from your coracoid bone (a knuckle of bone near your shoulder) or your iliac crest (hip bone). Depending on the nature of your injury, Dr. Price will discuss which of these options is more desirable.
- In the Latarjet procedure, an incision is made over the front part of your shoulder and the coracoid bone is exposed. About 2cm of the bone is cut and moved to the front part of the shoulder to make a new shoulder socket.
The risks of the surgery include but are not limited to:
- Nerve injury
- Failure of the repair/recurrent instability
- Non-union of the bone graft, with subsequent resorption
- Stiffness in the shoulder
- Pain, postoperative and/or persistent
- Blood clots