PURPOSE: To determine long-term mandibular growth / stability following unilateral mandibular distraction in growing children. METHODS: Twelve consecutive mandibular distraction patients (N= 9 Males, N= 3 Females) with unilateral craniofacial microsomia and a minimum of 5 years follow up (range 5 to 10 years) were retrospectively analyzed. Records included clinical examination, photographs, dental study models, lateral and posteroanterior cephalograms, and panoramic radiographs. Data were obtained at the following time points: pre-distraction, device removal, and 1, 5 and 10 years post-distraction. The mean age of patients at the time of distraction was 4.8 years (range 2 to 11 years old). The device was activated 1 mm per day for an average total of 21 mm (recorded on device). The mean latency period was 6 days and the mean consolidation period was 60 days. Twenty-six cephalometric parameters were examined at each of the five time intervals. RESULTS: On average the ramal height ratio (Co'-Go'/Co-Go) increased from 70% preoperatively to 93% post-distraction. One year after distraction the ratio was 81%. At 5 and 10 years following distraction, the average ratio was 79% and 89% respectively. The average increase in ramal length with distraction was 13 mm. However, 22% of the increase in length was lost after 1 year. CONCLUSIONS: Mandibular distraction osteogenesis in growing children with unilateral craniofacial microsomia significantly increased ramal height. While the ramus increased in length by 13 mm on average with distraction, 22% of that increase was lost in the first postoperative year. While the average ramal height decreased in the first postoperative year, it then remained stable. The rami grew between postoperative years 1, 5, and 10, although at a lower rate than the contralateral “normal” rami or when compared to normal controls (Moyers Co-Go). These data suggest that mandibular distraction in the growing child should be directed toward "overcorrection."
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