Shoulder Instability

Shoulder Instability-Traumatic New York, Shoulder Instability-Traumatic Specialist Dr Glashow

Overview

Shoulder instability develops in two different ways: traumatic (injury related) onset or atraumatic onset. Understanding the differences is essential in choosing the best course of treatment. Generally speaking, traumatic onset instability begins when an injury causes a shoulder to develop recurrent (repeated) dislocations. The patient with atraumatic instability has general laxity (looseness) in the joint that eventually causes the shoulder to become unstable.

Traumatic shoulder instability is most common in young, athletic people. The younger and more active the patient is when the first dislocation occurs, the more likely it is that recurrent instability will develop. For example, if the first dislocation occurs during the teenage years, there is a 70% chance that recurrent instability will develop. However, people over 40 with a first dislocation have less than a 10% risk of developing chronic instability. Treatment strategies should be designed to suit each patient’s age and lifestyle.

What does the inside of the shoulder look like?

The shoulder is the most mobile joint in the human body, with a complex arrangement of structures working together to provide the movement necessary for daily life. Unfortunately, this great mobility comes at the expense of stability. Several bones and a network of soft tissue structures (ligaments, tendons, and muscles), work together to produce shoulder movement. They interact to keep the joint in place while it moves through extreme ranges of motion. Each of these structures makes an important contribution to shoulder movement and stability. Certain work or sports activities can put great demands upon the shoulder, and injury can occur when the limits of movement are exceeded and/or the individual structures are overloaded.

What is traumatic shoulder instability?

Traumatic shoulder instability begins with a first dislocation that injures the supporting ligaments of the shoulder. The glenoid (the socket of the shoulder) is a relatively flat surface that is deepened slightly by the labrum, a cartilage cup that surrounds part of the head of the humerus. The labrum acts as a bumper to keep the humeral head firmly in place in the glenoid. More importantly, the labrum is the attachment point for ligaments stabilizing the shoulder. When the labrum is torn from the glenoid, the support of these ligaments is lost. The development of recurrent instability depends upon the type and amount of damage that is done to the labrum and the supporting ligaments.

The most common dislocation that leads to traumatic instability is in the anterior(forward) and inferior (downward) direction. A fall on an outstretched arm that is forced overhead, a direct blow on the shoulder, or a forced external rotation of the arm are frequent causes of this type of dislocation. Much less common is a posterior (backward) dislocation, which is usually related to a seizure disorder or electrocution, events in which the muscular forces of the shoulder cause the dislocation.

Symptoms

What are the signs and symptoms of a dislocation?

If the shoulder is dislocated, it is usually very apparent:

• The shoulder is quite painful.
• Motion is severely restricted.
• The shoulder appears to hang down and forward, with a large dimple evident under the acromion (in the area of the collar bone).
• The humeral head may be visible as a bump on the front of the shoulder, or in the armpit.

To return the dislocated arm to its socket (called a reduction) usually requires a visit to the emergency department, where expert assistance can be found. Some individuals with recurrent dislocations eventually become experienced at reducing the arm themselves.

Diagnosis

How is a dislocation and traumatic shoulder instability diagnosed?

As a rule, a sudden dislocation is quite evident. The patient usually holds the arm against the side, since any attempts at motion cause pain. A large crease under the acromion and a bulge in the armpit are cluesto the direction of the dislocation. However, when the shoulder spontaneously relocates into its proper position, the diagnosis can be more difficult. Patients may only report the feeling of having the shoulder “slip” before the spontaneous reduction occurred.

A qualified individual usually can relocate the humerus at the site of the injury occurrence. Once the reduction is performed, there is immediate pain relief. Without medications, some patients may be unable to relax the shoulder muscles enough to allow the reduction to take place. Often, these patients must go to the emergency department to get the reduction accomplished.

• X-rays are usually taken to confirm the dislocation, its direction, and to check for a related fracture. After the reduction, follow up X-rays will confirm proper positioning and assess any other injuries. X-rays may reveal a “bony Bankart“, which is a fracture of the anterior-inferior glenoid (front, lower portion of the glenoid). The presence of this fracture indicates that the labrum and ligaments in the front part of the shoulder are no longer attached to the glenoid.
• If X-rays do not reveal such a fracture, an MRI or arthrogram may be ordered. In this diagnostic test, the status of the labrum and ligaments can be assessed. A Bankart lesion (detachment of the anterior-inferior portion of the labrum from the glenoid) is the most common cause of recurrent instability after an injury.

Treatment

How is a dislocation and traumatic shoulder instability treated?

The initial reduction of a dislocation can be quite difficult. Contractions of the shoulder muscles can trap the humeral head against the glenoid. Gentle traction, and at times, medication may be needed to accomplish the reduction. Once the shoulder is reduced, a sling is used for a few days to protect it, and relieve discomfort. physical therapy may help the patient regain motion in the joint.

Non-Operative Treatment

Initial treatment for recurrent instability of the shoulder centers on physical therapy. Strengthening the rotator cuff muscles and periscapular muscles (those around the scapula) gives stability to the joint. The goal of physical therapy is to help the muscles provide stability to the shoulder that the torn ligaments can no longer supply. The therapy for recurrent instability should be carefully designed for each patient since this condition often causes apprehension about certain arm positions or exercise maneuvers. Very often, physical therapy can help regain lost motion, reduce apprehension, and restore shoulder function.

External Rotation Standing parallel to an elastic resistance cord, the elbow should be bent 90 degrees at the side. The hand should slowly rotate away from the body, using the elbow as a hinge. Rotation should continue until the arm is in a neutral position.

Pendulums While bending at the waist the affected arm should hang relaxed. The arm should be moved in all directions using momentum.

Operative Treatment

Surgery is usually recommended if recurrent instability cannot be controlled with physical therapy and activity modification. The goal of surgery is to return stability to the shoulder with the least loss of motion. All shoulder procedures designed to stabilize the shoulder involve some loss of motion. The current procedures for anterior shoulder instability attempt to restore the normal anatomy without over tightening the ligaments. In certain instances, such as in young persons who have a higher risk of re-dislocation and in contact athletes who plan on continuing to participate in sports that put their shoulders at risk, surgery may be performed after the first dislocation.

Open Labral Repair

Currently, the preferred procedure for anterior instability is an open labral repair with an anterior capsular shift. This procedure is performed through a two to three inch incision on the front of the shoulder. The torn labrum is repaired and the stretched-out anterior shoulder capsule is imbricated (overlapped) to make it smaller. This procedure is successful approximately 95% of the time in eliminating recurrent dislocations.

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Arthroscopic Techniques

Recently, arthroscopic procedures such as Bankart repair have been used to repair the torn labrum and reduce capsular laxity. Arthroscopic techniques are approximately 80% successful. These procedures are performed with visualization through a small fiberoptic scope. Instruments are inserted into the joint through two or three small incisions to repair the labrum. The surgical technique is similar to the one used in an open repair. A loose capsule is more difficult to address arthroscopically. Procedures using thermal energy to shrink the loose capsule have been developed, and are still being evaluated.

What types of complications may occur?

The major complications of anterior stabilization techniques are recurrent instability and/or loss of motion. The rate of recurrent instability depends largely on the technique used for the repair. The loss of motion can be severe, and is a function of over tightening the anterior capsule. In general, the operative shoulder should lose no more than ten degrees of external rotation. Other small risks (less than 1%) include infection, post-operative stiffness, nerve damage, or blood vessel injury.