This article is a retrospective review of four patients treated with metacarpal distraction lengthening for symbrachydactyly. Three patients underwent lengthening of the 4th and 5th metacarpal and one underwent lengthening of only the 5th metacarpal. All patients had well-developed thumbs with the goal to develop improved pinch between the thumb and the ulnar side of the hand. The operations occurred between the ages of 5 and 11 years, and the osteotomy was placed in the mid-portion of the metacarpal with two half pins placed both proximal and distal to the osteotomy site. A 1mm intramedullary K wire was used in each metacarpal to maintain longitudinal alignment. Distraction commenced on the first post-operative day at a planned rate of 1mm per day. The actual calculated rate of distraction based on serial radiographs was 0.6mm per day. The mean duration of distraction was 37 days, and the distracter was maintained at a mean of 84 days after surgery. The metacarpals were lengthened by a mean of 22mm (81.6% of the original length). Only one complication occurred which was a fracture through the regenerate site during distraction. No patient exhibited evidence of growth disturbance with a mean follow-up of 3.9 years (range 2-12 years) post-operatively. Pinch power between the thumb and elongated fingertip improved in all patients to a mean of 1.3 kg on the involved side vs. 1.7 kg on the contralateral side.
This study confirms the feasibility of callus distraction lengthening of the ring and small finger for symbrachydactyly in patients with an adequate thumb for opposition. The authors used a standard distraction lengthening technique except they did not delay the usual 5-7 days before initiating distraction following the osteotomy. Although the review included a low sample size, they had a low complication rate, which may be related to early removal of the external fixator device. The mean duration of distraction was 37 days and the mean duration of consolidation was only 46 days. Standard Ilizarov technique calls for doubling the duration of distraction to calculate the time for consolidation. Despite the authors minimal assessment of outcome (pinch strength only), callus distraction lengthening is a reasonable option in older patients with symbrachydactyly who are no longer candidates for free toe phalangeal transfers.
J Bone Joint Surg