Surgical correction of unsuccessful derotational humeral osteotomy in obstetric brachial plexus palsy: evidence of the significance of scapular deformity in the pathophysiology of the medial rotation contracture

Abstract

Background: The current method of treatment for persistent internal rotation due to the medial rotation contracture in patients with obstetric brachial plexus injury is humeral derotational osteotomy. While this procedure places the arm in a more functional position, it does not attend to the abnormal glenohumeral joint. Poor positioning of the humeral head secondary to elevation and rotation of the scapula and elongated acromion impingement causes functional limitations which are not addressed by derotation of the humerus. Progressive dislocation, caused by the abnormal positioning and shape of the scapula and clavicle, needs to be treated more directly.

Methods: Four patients with Scapular Hypoplasia, Elevation And Rotation (SHEAR) deformity who had undergone unsuccessful humeral osteotomies to treat internal rotation underwent acromion and clavicular osteotomy, ostectomy of the superomedial border of the scapula and posterior capsulorrhaphy in order to relieve the torsion developed in the acromio-clavicular triangle by persistent asymmetric muscle action and medial rotation contracture.

Results: Clinical examination shows significant improvement in the functional movement possible for these four children as assessed by the modified Mallet scoring, definitely improving on what was achieved by humeral osteotomy.

Conclusion: These results reveal the importance of recognizing the presence of scapular hypoplasia, elevation and rotation deformity before deciding on a treatment plan. The Triangle Tilt procedure aims to relieve the forces acting on the shoulder joint and improve the situation of the humeral head in the glenoid. Improvement in glenohumeral positioning should allow for better functional movements of the shoulder, which was seen in all four patients. These dramatic improvements were only possible once the glenohumeral deformity was directly addressed surgically.

Figure 1

CT images showing SHEAR deformity present after humeral osteotomy. Ten year old boy after unsuccessful humeral osteotomy with right-sided SHEAR deformity demonstrated in 3D CT anterior view (above) and posterior subluxation demonstrated in axial view (below).

Figure 2

Functional Improvement with Triangle Tilt surgery. Pictures of 10 year old girl who had previously undergone an unsuccessful humeral osteotomy, pre (a through c) and 6 months post (d through f) Triangle Tilt surgery. Panels a and d show decreased trumpet sign during the hand to mouth movement. Panels b and e show improved supination. Panels c and f show the improvement in resting arm position.