Measurement of Traction Force in Distraction Osteogenesis for CLP

Objectives: Distraction osteogenesis (DOG) using rigid external distraction (RED) system has been popular in the treatment of patients with severe maxillary hypoplasia. Substantial maxillary advancement can be achieved by tooth-born distraction with RED system, while occasionally it requires long term to attain desired advancement. In this paper, we established a real-time monitoring system of traction force for Le Fort I maxillary DOG using RED system to investigate the reaction of soft and hard tissue in dento-maxillary region, as well as mechanical property of distraction device. Methods: Micro tension gauges were integrated into the both sides of traction wires of the RED system. Tension of traction wires, estimated to be equal to the loading force applied to anchor teeth, was measured in 8 cleft lip and palate (CLP) patients aged 22.3±6.0 (mean, SD); 3 males and 5 females; 6 UCLP, 1 BCLP and 1 CP. At daily measurement of traction force for each side, the tension gauges were connected to an amplifier and the data was monitored and recorded using a personal computer, and statistically analyzed by linear regression between force and amount of activation (p<0.05). Lateral cephalograms were taken to estimate maxillary advancement before and after activation stages. Results: The amount of maxillary advancement ranged 4.0-9.5 mm. The force increased with daily activation (positive correlation, p<0.05) on both sides in all cases. The increasing rate of force to the amount of activation ranged 0.45-1.61 N/mm. Total force of the both sides measured after final activation in each case showed positive correlation with the amount of activation among 8 cases (p<0.05). Conclusions: The force might increase in proportion to the amount of activation of the RED device. Moreover, the assessment of the traction force at early stage of activation period might predict the further process of DOG.