Shoulder reconstruction in children with obstetric brachial plexus injury



Doctors at Mayo Clinic offer a new approach for shoulder reconstruction and tendon transfer in infants and children with obstetric brachial injury. Bassem T. Elhassan, MD, Mayo Clinic, Rochester, Minnesota, USA describes the procedure.

Shoulder deformity, pain and limited range of motion are common in patients with obstetric brachial plexus injury. Depending on the level and extent of nerve injury, and the age at presentation, children may have variable dysfunction of the shoulders and upper extremities. Injury to the nerves that power the muscles of the shoulder, elbow and hand leads to imbalance in muscle function around the shoulder, in addition to progressive bony deformity and posterior dislocation of the glenohumeral joint (ball and socket joint of the shoulder) (Figure 1). Furthermore, the acromial bone, which forms the roof of the glenohumeral joint, becomes progressively deformed and starts to hook downward. This eliminates the space on top of the glenohumeral joint and the rotator cuff, and may lead to worsening range of motion and progressive pain secondary to impingement of the hooked bone on the rotator cuff.

The muscle imbalance, weakness and bony deformity around the shoulder lead to progressive internal rotation contracture of the shoulder. This is manifested by the arm being rotated inward and the hand becoming more bound to the belly because patients cannot move their hand outward.

This pattern of shoulder contracture leads to significant limitation of shoulder function because the patients become limited in using their hand in the horizontal plane in front of their body. In addition, it is very common for patients to have elbow-flexion contracture (inability to straighten the elbow) and variable limitation of shoulder abduction (moving the arm sideway away from the body) or flexion (moving the arm forward towards the ceiling).

Early intervention in patients born with brachial plexus injury is directed toward dedicated physical therapy with motion and stretching exercises, performed mainly by the parents under the direction of the therapist. Nerve surgery is recommended if the patient does not recover elbow flexion (bending) between 3 and 9 months after delivery. The outcome of nerve surgery has been variable. While restoration of elbow function has a high success rate, restoration of shoulder function is more variable. With patients who start to develop bony deformity of the shoulder, nerve surgery will not correct the bony deformity by itself, and shoulder surgery becomes more necessary to correct the deformity.

In children and adolescents who present with shoulder and arm deformity years after delivery, surgical correction becomes more challenging and less predictable. In patients with lesser bony deformity, surgical release of the internal-rotation contracture with transfer of the latissimus dorsi is the most recommended surgical procedure, which leads to variable result depending on the extent of the injury, bony deformity and age at presentation. In patients with worse bony deformity, associated weakness of the muscle around the shoulder (i.e. rotator cuff and deltoid muscles) external-rotation osteotomy, has been reported as the main salvage procedure. Although this procedure may potentially correct the hand position, it does not do anything to the shoulder deformity; in fact, it may potentially worsen the shoulder deformity and the dislocation of the shoulder. Once the shoulder deformity is fixed, the only possible procedure for the child in the future is fusion of the shoulder.

In an effort to correct the shoulder deformity in the latter category of patients, the Mayo Clinic instituted a new surgical approach that addresses the bony deformity of the shoulder as well as the weakness of the muscles around the shoulder. Our goal was to try to restore the normal anatomy of the bony shoulder as well as to replace the weak muscles around the shoulder with more developed muscles through tendon transfer. The bony deformity varies among patients, but in most patients there is significant loss of the posterior aspect of the glenoid, which leads to the humeral head that is dislocated from the posterior. This is associated with significant internal contracture of the shoulder. This means that all soft tissues anterior to the glenohumeral joint, including the subscapularis muscle (the main muscle that internally rotates the shoulder), are shortened.

In order to replace the humeral head on the glenoid, the anterior contracted structures need to be released, and the subscapularis tendon needs to be lengthened (only if necessary). The releasing of the subscapularis muscle is not recommended because it may lead to imbalance of the muscles around the glenohumeral joint, in addition to loss of the internal rotation function of the shoulder (i.e. limited ability to bring the hand to the abdominal level). Once this is done, the humeral head could be placed on the glenoid; however, it will not stay in place because of the major deficiency in the glenoid bone.

The best way to understand this problem is to imagine the ball-and-socket of the shoulder like a golf ball on a tee. If the cup part of the tee is half-broken, the ball will not stay on the tee no matter what. It will only remain on the tee if the tee has a full cup that can hold the ball. The same idea applies to the shoulder glenohumeral joint. Without attempting restoration of the deficient glenoid, the humeral head will not stay centred over the glenoid, and it will redislocate. The best way to restore the bony anatomy of the glenoid is to try to reconstruct the bony deficiency. This could be done by harvesting a piece of bone from the pelvis that matches the size of the defective bone on the glenoid and fixing this bone to the glenoid (Figure 2 A, B).

The same concept of correction of bony deformity is applied to the deformed acromion. The spine of the scapula, which connects to the acromion, is cut, lengthened and corrected with the use of a bone graft from the pelvis (iliac crest) and fixed with a plate and screws. This corrects the downsloping of the acromion and recreates the space between this bone and the glenohumeral joint and rotator cuff muscles and tendons.

Once the bony anatomy is restored, attention should be directed toward replacing the weak muscles with normal muscles through tendon transfer. Since the most common function lost is shoulder external rotation, this should be the first function restored, followed by restoration of other shoulder function as needed. Previously, we described the use of the lower trapezius as a tendon transfer to restore shoulder external rotation. The shape of the muscle, the line of pull and its strength are a good match to the infraspinatus muscle, which is the main muscle that externally rotates the shoulder. Additional muscles, if available, could be used for transfer in an attempt to restore more shoulder function. These muscles include teres major to restore shoulder external rotation, levator scapulae and upper trapezius to restore shoulder abduction and free (pedicled) local muscle transfers of the latissimus or pectoralis major muscles for shoulder flexion.

Some children may require release of the elbow-flexion contracture, which can be done. However, once the major shoulder reconstruction is performed and the arm is immobilized, any attempt at releasing the elbow contracture may fail. For this reason, we prefer to wait for the patient to recover from shoulder surgery before performing the elbow release.

The patient is in a shoulder spica cast for eight weeks, which allows enough time for bone and soft tissue to heal. After that, a CT scan is obtained to confirm the bony healing of the glenoid and the improved position of the humeral head on the glenoid. Then physical therapy begins slowly and gently over a six week period to allow the shoulder to regain motion. During this time, exercises in the pool are highly encouraged. After the first six weeks of therapy, gentle strengthening begins. Children are allowed unrestricted activities six months after surgery.

The results of this reconstruction of bony and soft tissue of the shoulder have been very promising. The bony anatomy and centralisation of the humeral head on the glenoid have been successful in all children thus far. All patients were very satisfied with the outcome in terms of look, function and pain levels after surgery.

In summary, our new approach for shoulder reconstruction and tendon transfer in infants and children with obstetric brachial injury may offer new hope to those with no other available options.

ate of upload: 26th Jul 2012


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