Shoulder Dislocation & Instability (Labrum Tear)
Shoulder Anatomy and the Labrum
The shoulder joint is a ball (humeral head) and socket (glenoid) joint. Unlike the hip joint where the socket is deep and naturally keeps the ball in place, the shoulder joint has a very shallow socket. This is more like a golf ball on a golf tee situation where the size of the socket is small relative to the size of the ball. This creates a situation where the ball can easily fall off the socket.
In order to improve the stability of this situation but still allow for range of motion of the joint, the body has placed a structure call the labrum around the rim of the socket. The labrum is a soft tissue structure that increases the effective size of the socket and is attached to the surrounding capsule.
What happens during a shoulder dislocation or subluxation?
If the humeral head (ball) completely leaves the glenoid (socket), it is considered a dislocation. If the humeral head moves out of the glenoid but not completely, it is considered a subluxation event. In the both cases, the humeral head has moved beyond the normal range of the shoulder and this can cause injury to the labrum, cartilage or bone within the shoulder.
What injuries happen in the joint during a dislocation?
The injury that almost always happens during a shoulder dislocation is a tear of the labrum and its attached capsule away from the glenoid bony rim. This is also referred to as a Bankart tear. The direction of the dislocation will determine which section of the labrum is torn.
The cartilage on the surface of the glenoid is often frayed or torn during the dislocation event. Sometimes, there is loose fragment torn loose.
The humeral head can also suffer and injury while it is dislocated. The upper back side of the humeral head can be indented by the edge of the socket. This is called a Hill-Sachs lesion. Most of these are small and are not treated surgically but every once in a while, there is an extremely large lesion that needs to be addressed.
How is a shoulder dislocation diagnosed?
If acute, the diagnosis is typically made with clinical exam and x-rays. X-rays are necessary to evaluate for concomitant fracture.
Is any other workup required?
Often, the orthopedic surgeon will order an MRI of the shoulder to define the extent of tear of the labrum (which cannot be seen on an x-ray).
If there is a fracture or concern for one, a CT scan may be ordered.
How are shoulder dislocations treated?
If acutely dislocated, then the initial treatment should be to reduce or relocate the joint as soon as possible.
Sometimes this can be done immediately (on the field).
Many times, the muscle spasm is too great and the patient will need sedation to reduced the joint. This is often performed in the Emergency Room.
Assessment of nerve and vascular function in the upper extremity is performed.
Once the shoulder is back in place (reduced), then the patient can usually go home in a sling
Further evaluation as detailed above will be coordinated by an orthopedic surgeon at his/her office
Once the details of the labrum tear are known, then a discussion of treatment options for the patient is initiated.
Treatment of shoulder dislocations can often be treated without surgery. This treatment path will include a short period of time in a shoulder sling. Usually, there is also a short course of physical therapy. Pain can be managed with anti-inflammatories.
Surgical management is reasonable for patients that have failed non-surgical management and continue to have instability symptoms or episodes.
Surgical management can also be considered after first dislocation for a young individual. For patients less than 20-25 years of age, the recurrence rate for shoulder dislocation is extremely high (greater than 90%). Because of this, sometimes surgery is considered.
Surgery is typically arthroscopic if only soft tissue work is needed. Sometimes there is significant bony injury and these may require larger open surgery. Surgery is designed to achieve several goals including:
Repairing the shoulder labrum back to the glenoid bone while tightening the capsule that is attached to it (called capsulorrhaphy).
Addressing any cartilage damage that has occurred.
Addressing any bony defect on the humeral side (i.e. Hill-Sachs lesion) if needed
Addressing any bony defect on the glenoid side. This may sometimes require a larger surgery called Laterjet.