Gradual ulnar lengthening by an Ilizarov ring fixator for correction of Masada IIb forearm deformity without tumor excision in hereditary multiple exostosis: preliminary results

Abstract

Bony exostoses are benign osteocartilaginous growths that start close to growth plates. Approximately 30-60% of patients have forearm deformities. The commonly encountered forearm deformities in these patients are bowing of the radius, with or without ulnar drift of the carpus, radial head dislocation, shortening of the ulna, and radial head dislocation. The current study reported on the results of management of radial head dislocation for type IIb Masada and Oho classification of forearm deformities by Ilizarov ulnar lengthening and without tumor excision. A series of 12 patients with Masada type IIb deformity were treated by Ilizarov lengthening at AlHadra University Hospital, Alexandria, Egypt, during the period from January 2008 to June 2014. There were eight males and four females; the right forearm was affected in seven patients. The mean age of the patients was 8.7 years (range: 7.5-10 years). All cases showed ulnar shortening with distal ulnar exostosis and radial head dislocation (Masada type IIb). All patients were operated on under general anesthesia, with application of the Ilizarov frame to the forearm. The frame used was assembled of two complete rings; the proximal one was fixed to the proximal ulna and the distal ring was fixed to both radius and ulna. Ulnar osteotomy was performed between the two rings, followed by ulnar lengthening 10 days postoperatively to lengthen the ulna and pull down the radius. Over a follow-up period of 33.2 months (24-48 months), all patients showed spontaneous reduction of the radial head and correction of the forearm deformity. The range of motion improved: flexion increased from 117.5° (110-130°) to 145° (130-160°) and extension increased to 4.6° (0-10°), whereas it was 13.8° (10-20°) preoperatively and the supination increased from 46.3° (40-50°) preoperatively to 73.6° (65-80°) postoperatively. Pronation improved from a preoperative average of 37.9° (30-40°) to 70.8° (60-80°) at the end of follow-up. The average amount of ulnar length was 27.9 mm (25-35) and the duration of external fixation was 103.3 days on average, with a range of 90-130. Thus, the average external fixation index was 3.7 days/mm (range: 3.6-4.0). Gradual lengthening of the ulna and pulling down the radius with an Ilizarov frame is an excellent method for correction of forearm deformity in patients with multiple hereditary exostosis (Masada IIb). Early intervention is the key to achieving spontaneous reduction of the radial head in all patients without the need for corrective osteotomy or tumor excision. Level of evidence: level IV.