Outcomes of Surgical Treatment for Masada Type lVa Forearm Deformity in Children with Multiple Hereditary Exostosis: A Case Series.

Introduction: Multiple hereditary exostosis (MHE) is a rare autosomal dominant skeletal disorder widely known as multiple osteochondromatosis that frequently affects the growing ends of long bones. It causes multiple progressive deformities, especially in the wrist, elbow, knee and ankle. The spectrum of features in the forearm includes deformities due to growth arrest of the distal ulnar physis, an increase in the negative ulnar variance, excess radial bowing, an increased radial articular angle, with or without radial head dislocation and restricted pronosupination. Masada's classification applies to forearm deformity in MHE, where Type IVa deformity includes distal osteochondromas of both radius and ulna with ulnar shortening without radial head subluxation or dislocation. It warrants timely surgical intervention to prevent progressive deformity, radial head dislocation and irreversible articular damage. Aim: The aim of the study was to report the clinical and radiological outcomes of single-stage surgical intervention for Masada Type IVa forearm deformity in children with MHE. Materials and Methods: Retrospective study of three children with Masada 4 A forearm deformity due to MHE was included in the study. Their mean age was 12.7 years, and they all underwent single stage Ulnar osteochondroma resection, proximal ulnar corticotomy, and gradual ulnar lengthening by distraction osteogenesis using an LRS (Limb reconstruction system) external fixator. All three cases had periodic follow-up with a mean of 27.5 months. Results: All patients showed high negative ulnar variance needing ulnar distraction lengthening in addition to ulnar osteochondroma excision. Mean ulnar lengthening achieved was 3.6 cm (range: 2.3-4.3 cm). The bowed radius with a mean magnitude of 1.5 in all these cases had a normal range of bow percentage, but with a high radio-capitular articulation inclination angle. High Radio-articular angle of 36° with open physis warranted radial growth modulation in one of the cases, in addition to redo distraction lengthening of the ulna. Conclusion: Single-stage surgical correction combining distal ulnar osteochondroma excision with Ulnar lengthening by distraction osteogenesis is safe and reproducible for Masada Type IVa deformity in growing children that prevents radial head dislocation. Early intervention confers the greatest benefit of a normal elbow joint in addition to deformity correction that is consistent in radiological and its functional gains.