Shoulder Instability

The shoulder is the most frequently dislocated joint in the body. The ball and “flat” socket configuration of the joint allows the largest range of motion of any joint in the body but sacrifices stability. A shoulder dislocation occurs for 2 reasons: 1) from a traumatic injury that forces the ball out of its socket 2) from an inherent baseline laxity of the ligaments. On occasion, the shoulder slides back into place on its own. Most of the time the shoulder needs to be put back into place in the hospital with medication to help relax the muscles. Once the shoulder is back in place, patients are usually put into a sling for a couple of weeks to allow the shoulder to heal. At this point a physical therapy program can begin to restore range of motion and strength. Unfortunately, the torn tissue with the joint does not always heal enough to restore stability to the joint. Therefore, if someone dislocates their shoulder once, there is a good chance that it will happen again. This depends somewhat on age and activity. If a person less than 20 dislocates twice there is a >90% chance it will continue to dislocate. In these settings frequently surgery is chosen to restore stability.

Surgical treatment of a shoulder dislocation depends on what is injured in the shoulder. X-rays and an MRI are done to look for what is injured inside the joint. Surgery to fix the shoulder can be done arthroscopically through small incisions most of the time. Surgery is aimed at repairing the small bumper of tissue, called the labrum that tears off of the socket. The labrum is the structure that attaches the ligaments to the socket (glenoid). On occasion, an open surgery may need to be done to repair the labrum or to fix bone fragments that have broken off the socket to improve stability. If the bone on the socket wears away from repeated shoulder dislocations, bone from another part of the body may be needed to reconstruct the socket to make the shoulder stable again.

For patients with baseline loose ligaments due to stretchy collagen surgery may not be the first line of treatment. Due to their loose ligaments they are prone to stretch out surgical reconstructions so a long period of therapy is tried first before resorting to surgery.

After surgery, patients are placed in a sling to protect the shoulder for 4 weeks. Patients then begin a controlled physical therapy program and return to sports often takes 5-6 months. Arthroscopic surgery outcomes are usually successful 90% of the time with no further instability. Here at Washington University we are involved with a multi-center instability study as part of the MOON Shoulder Study Group to analyze predictors of successful shoulder stabilization surgery. Future blogs will look at additional issues regarding shoulder instability.