Shortening of mandibular linear distance with multivector distraction

It was noted that when a multivector distractor is used, there is shortening of the linear distraction distance when the gonial angle is reduced and the transverse distance is increased. The purpose of this study was to measure the distance change at the mandibular corticotomy site when the gonial angle is reduced or the transverse distance is increased. The Synthes multivector distractor was used in this experiment. After initial linear distraction, the distractor was activated by angular and transverse adjustments to achieve an angular, a transverse, and a combined angular and transverse reorientation. The length of the pin from the distractor to the tip of pin was evaluated at 15, 20, and 25 mm. With the pins place at 180 degrees , the distractor arm length was evaluated at 30, 35, 40, 45 and 50 mm apart, respectively. The distance change between the ends of the pins was measured by means of a caliper. For angular activation, one turn shortened the linear distraction distance at the pin end by 1.5 to 2.2 mm. For transverse activation, one turn shortened the linear distraction distance by 1.1 to 2 mm. For combined angular and transverse activation, one turn of angular activation plus one turn of transverse activation shortened the linear distraction distance by 2.2 to 3.2 mm. For angular activation, increasing the pin length did not alter the distance between the pin ends for any of the specific activations. Increase in the distractor arm length in angular reduction resulted in significant increase in the shortening. For transverse increase, alteration in the distractor arm length resulted in the same shortening. Increase in the pin length resulted in increased shortening at the pin ends. When the transverse and angular activation were combined, the shortening was 80% of the combined measurements. The distance between the pin ends will reflect the distance between the bone segment at that site. It will be different at the outer cortex of the bone. These measurements will be valuable in planning the extent of additional linear distraction needed, when the angle is reduced or transverse distance is increased with the use of a multivector distractor. Alteration in the distractor arm length and pin length has a significant effect on the extent of shortening.