Quantitative study of new bone formation in distraction osteogenesis of craniofacial bones by bone scintigraphy.

Although distraction osteogenesis is widely accepted as a technique to augment the craniofacial skeleton, timing to start distraction after an osteotomy or to remove distractors is basically based on studies on long bones. Because bone scintigraphy is well known to be the gold standard for quantitative measurement of bone formation, we conducted this pilot study to evaluate its feasibility as a tool for assessing new bone formation by distraction osteogenesis. Five patients with midface hypoplasia and four with mandibular hypoplasia were studied. Each patient had five bone scans: before surgery, 3 and 30 days after stopping distraction, and 3 days before and 3 months after distractor removal. Radiotracer uptake values at distraction sites were measured at I and 3 hours. Each uptake value was compared with preoperative study as uptake ratio. A typical pattern of radiotracer uptake ratio was observed in all cases with successful distraction. Uptake rose to the maximum during the consolidation period and remained at or above the preoperative level until the study end point. In one patient who had mandibular distraction and nonunion of the right ramus, there was no uptake peak during early consolidation as seen in the successfully distracted body and in the other cases. Bone scintigraphy was found to be a useful investigation in craniofacial distraction. It showed the dynamic of new bone formation by demonstrating the osteoblastic activity, which is important objective information for determining distraction rate and consolidation duration in each case. It may also be a tool that can predict the outcome of distraction osteogenesis.