Gradual lengthening of the ulna in patients with multiple hereditary exostoses with a dislocated radial head

Abstract

Purpose: Multiple hereditary exostoses of the forearm typically form in the distal ulna, causing disturbances in the growth of the ulna and functional disability. Multiple hereditary exostoses inhibit the growth of the ulna, leading to an acquisition of a varus deformity in the radius, which sometimes leads to dislocation of the radial head, the development of limitations in the pronation-supination of the forearm, and cosmetic problems.

Materials and methods: We retrospectively reviewed the cases of four patients who had deformities of the forearm with radial head dislocation associated with multiple hereditary exostoses, and evaluated the radiologic and clinical results of excision of the osteochondromas from the distal ulna and gradual ulnar lengthening with an Ilizarov external fixator.

Results: Good clinical and radiological results were obtained after a mean follow-up of 25 months. At the most recent follow-up, radial bowing, ulnar shortening, carpal slip, and the pronation/supination arch of the forearm had improved. There was little change in terms of preoperative radial articular angle and the flexion/extension arch of the elbow by the most recent follow-up.

Conclusion: Treatment of four forearms from four patients by excision of osteochondromas and gradual lengthening of the ulna with an Ilizarov external fixator spontaneously reduced dislocations of the radial heads without the need for any additional operative intervention. All patients were satisfied with the final results.

Keywords: Ilizarov external fixator; Multiple hereditary exostosis; gradual lengthening.

Fig. 1

This patient was 7 years and 10 months old. (A) The preoperative X-ray shows dislocated radial head (arrow) and distal ulnar osteochondroma (arrow). (B) Immediate postoperative X-ray shows a temporary reduction pin for the dislocated radial head. (C) 33 mm lengthening was done and we removed the temporary reduction pin six weeks after the operation. The arrow indicates the reduced radial head. (D) At the most recent follow-up X-ray, we found a reduced radial head.

Fig. 2

Classification of MHE forearm deformities. Type 1: the main osteochondroma formation is in the distal portion of the ulna, but the radial head is not dislocated. Type IIA: the radial head is dislocated because of an osteochondroma at the proximal metaphysic of the radius. Type IIB: in addition to ulnar shortening the radial head is dislocated. Type III: the main osteochondroma formation is in the metaphysic of the distal radius, and there is relative shortening of the radius. MHE, multiple hereditary exostosis.

Fig. 3

Radiologic assessment. (A) Ulnar shortening: measured by a line drawn from the distal end of the ulna to the linear axis. Radial bowing: the distance that the radial diaphysis deviates from the linear axis of the forearm divided by the length of the linear axis. (B) The ulna tilt of the distal radial articular surface was recorded as the radial articular angle. The ulna drift of the carpus was assessed by the carpal slip. RL, radial length; RB, radial bowing; CS, carpal slip; RAA, radial articular angle; US, ulna shortening.

Fig. 4

Preoperative and postoperative radial length, radial bowing, percentage of radial bowing, radial articular angle. (A) Average preoperative radial length was 170.5 mm, and 174.2 mm at the last follow up. (B) Average preoperative radial bowing was 16.0 mm, and 13.2 mm at the last follow up. (C) Average preoperative percentage of radial bowing was 9.9%, and 7.8% at the last follow up. (D) The average preoperative radial articular angle was 40.7 degree, and 37.5 degree at the last follow up. Testing for statistical significance was performed using the Wilcoxon signed rank test, but we found no statistical significance.

Fig. 5

Preoperative and postoperative ulnar length, ulnar shortening, percentage of ulnar shortening, carpal slip. (A) Average preoperative ulnar length was 168.0 mm, and 202.7 mm at the last follow up. (B) Average preoperative ulnar shortening was 29.7 mm, and -1.0 mm at the last follow up. (C) Average preoperative percentage of ulnar shortening was 17.5%, and -0.3% at the last follow up. (D) The average preoperative carpal slip was improved, preoperatively 69.5%, and most recent follow up 43.9%. Testing for statistical significance was performed using the Wilcoxon signed rank test, but we found no statistical significance.