The shoulder is perhaps the most complicated joint in the body.  It is really a set of four joints, including the articulation of the collar bone with the breast bone (sternoclavicular joints), ACJ, GHJ, and scapulothoracic joint, where the shoulder blade glides on the chest wall.  The purpose of the shoulder is to allow a great deal of range of motion to facilitate positioning of the arm and hand.  Stability is a subservient concern, hence, the predilection of instability problems in the shoulder joint complex.  This is especially evident in the GHJ.

The GHJ is a “ball and socket” type joint, very much like a golf ball on a tee.  The socket is very shallow deepened slightly by the addition of a thin rubbery  lining called the labrum.  There are some thickenings in the lining of the shoulder joint that resemble ligaments, but these are not always robust.  The critical factor for stability is the rotator cuff, a set of four muscles and tendons attached to the margin of the humeral head.

Instability of the GHJ:

Instability of the GHJ can be classified as either traumatic or atraumatic or anterior, posterior or multidirectional.

In general, traumatic instability results from an injury, usually resulting in the humeral head or ball, shifting forward relative to the socket.  This often will occur with the arm over the head.

Posterior instability:

Can occur with either a traumatic or congenital problem, and multidirectional instability is similar to posterior instability.

Contact and collision sports such as football, hockey lacrosse, and wrestling have an increased risk of traumatic instability.  The shoulder may slide partly out on a temporary basis called a “subluxation” or may come completely out and remain so, producing a “dislocation”.

One need not have an outright injury to suffer instability.  Gradual attenuation or stretching of ligaments may occur in such sports as baseball, particularly in the throwing arm, racket sports, and swimming.  Instability may come on gradually and manifest initially as pain without the sensation of the shoulder actually coming out of the socket.

In congenital multidirectional instability, the ball and socket joint may be painfully loose due to loose ligaments and capsule, and poor musculature control of the joint.

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Although all of these problems basically have in common a sloppy ball and socket joint, treatment and outcomes can be vastly different.

GHJ Instability Evaluation:

A shoulder dislocation is obvious.  An anterior dislocation is at least 20 times more common than a posterior dislocation. In other words, the shoulder is 20 times more likely to come out the front than the back.

Initial findings include:  loss of the normal rounded contour of the edge of the shoulder, inability to move the arm, and significant pain. If the shoulder goes back in by itself  (“spontaneous reduction”), relief of pain is dramatic.  However, a medical reduction may be necessary.   Under light sedation and after relaxation of the patient is obtained, appropriate manipulative maneuvers may be required to pop the ball back into the socket.

Unfortunately, once a shoulder dislocates once, recurrent dislocation is the rule in the young person.  Studies have shown redislocation rates of 70 to 95%, in young contact and collision athletes.

Management of the Acute Injury:

Initial management of the recent shoulder dislocation or subluxation includes:  rest with a sling, ice, and prevention of reinjury.  Return to sports and activity generally can occur with several weeks or months as pain subsides and motion and muscle function is recovered, however, A SIGNIFICANT RISK OF RECURRENT DISLOCATION IS THE RULE.

Rehabilitation is useful for all types of GHJ instability, although it cannot be expected to cure the root of the problem, which is a stretched out or torn capsule ligament complex.  In cases of multidirectional or posterior instability, rehabilitation may provide enough control of the ball and socket joint to allow satisfactory function, at least on an intermittent basis.

GHJ Instability:  Surgical Treatment

For cases of recurrent instability, which interfere with desired level of function and activity, surgery may be considered.  The basic goal is to restore the ligamentous attachment points, or to tighten the lining of the shoulder to control ball and socket joint instability.

When a shoulder dislocates, the most common resulting abnormality is loss of the ligamentous attachment point to the edge of the socket.  In other words, the ligaments tear from their attachment to the bone on the very lip of the socket.  This area is particularly resistant to healing, and thus the separation remains, allowing the ball to slip out of the socket during provocative activities.  Although control of this situation can sometimes be gained by enhancing the strength of the rotator cuff muscles, many shoulders will remain symptomatic with the ball sliding free from the socket with resultant subluxation or dislocation.

In cases of atraumatic instability, muscle control can be overcome and the shoulder may sublux intermittently.

Arthroscopic view of “subluxated” humeral ahead, sliding out of the glenoid socket.

In both cases, surgery is designed to tighten these ligaments. It can be done either arthroscopically (see below) or via a formal open approach.  In either case, it is an outpatient one-day surgical procedure.

Although the goal can be accomplished via an arthroscopic approach, using smaller incisions, the success rate of open surgery significantly exceeds that of arthroscopic approaches, to the tune of 70 and 95% respectively, according to the bulk of orthopedic literature.


Arthroscopic Instability Repair:

Below is a specific example of a “Bankart Repair”, i.e.- that of a torn labrum from the front edge of the glenoid shoulder socket.  This is the most common type of instability repair.

The torn labrum is noted behind the metal shaver.  Normally, this labrum should be firmly attached to the edge of the glenoid (socket) below and in the foreground:

In preparation for repair, the edge of the glenoid is debrided, or roughened with a motorized burr, as seen below:

…and the labrum with a rasp:

A screw is inserted into the edge of the glenoid.  The screw has a permanent braided suture through its eyelet, much like a tent-stake:

The screw is countersunk below the surface of the glenoid, leaving only the sutures protruding:

The sutures must then be passed through the labrum, using a special tool:

…and a knot is then tied behind the labrum, pushing the labrum up to the prepared bony glenoid, optimally as below:

The same general steps can be done via an open incision, or with a variety of anchor types.

Newer procedures such as shrinking the lining ligaments and capsule using an arthroscopic approach are currently unproved, but may offer some promise.

After tightening the ligaments, the shoulder is protected in a sling or immobilizer for several weeks while therapy is undertaken.  Healing takes time and therefore return to vigorous sports must be delayed.  Range of motion and strength is gradually restored while protecting the repair site, and return to unlimited activities can be expected between 4 and 6 months.

Surgical risks include:  potential permanent loss of motion, failure of the procedure to restore stability, nerve injury, and infection, among others.

GHJ Instability Late Sequelae:

Long term problems of shoulder instability are relatively rare, though recurrent instability is very common in an active athletic person who continues with contact, collision, or overhead sports.  As the shoulder is  a non-weight bearing joint, arthritis related to instability is relative unusual.  In general, the untreated shoulder can be expected to become progressive looser, thereby limiting activities.  Suffice it to say that the better the muscular control, the less frequent and severe the instability episodes, though potential for instability can never be completely eliminated by strengthening alone.  The best surgical repairs, done by an open technique, for a traumatic anterior dislocation, can be expected to have a 95% success rate with recurrent dislocation rates averaging 3 to 5%.  Arthroscopic repairs are less successful, averaging about 75% success at long-term (several year) follow-up, presumably due to less robust scar formation.  Arthroscopic repairs may have a place in the relatively sedentary patient, with instability in low level activity.  However, an arthroscopic repair may not be the best option for the high level contact collision athlete.  They may have a role in the throwing athlete.

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