Examination of the Direction and Quantity of Extension following Distraction Osteogenesis in Apert Syndrome

We conducted maxillary distraction utilizing internal distraction devices in three patients with Apert syndrome. For these cases, we examined maxillary bone displacement, the relapse of bone distraction length and inclination changes. For this study, we chose three female patients between nine years two months and fifteen years eight months of age at the time of operation. After receiving a Le Fort III osteotomy, each patient received maxillary advancement utilizing internal distraction devices. The device was activated 1.0mm per day. After the lengthening devices were removed, the maxilla was reconstructed using poly L-lactic acid (PLLA) plates. Corresponding to pre-operation, post-operation, 1-year and 2-year post-operative periods, lateral cephalogram tracings were made. By standardizing the superimposition lateral cephalogram for the cranial base, each measurement point reflected it on the FH plane. Based on these observations, we studied the displacement in the horizontal and vertical directions of the maxilla which were indicated by point A, and we examined the inclination changes of the palatal plane based on the FH plane. As a result, the distraction lengths at point A were from 10.0mm to 14.8mm. In the two younger age groups, large differences between setting and real quantities of bone distraction lengths have not been found. Yet for the other case, actual distraction length was less than the setting length. As for the bone distraction length relapse, an average rate of 4.0% was recognized in the horizontal direction, but was not found in the vertical direction. To explain such a small relapse rate, the following reasons were discussed: longer than three months of retention period had been taken for the studies; mini-plate fixation had been applied as well as retention with the maxillary protractor; and anterior and downward growth of maxilla had taken place. The changes of the palatal plane angle had rotated counter-clockwise from 1.5° to 3.0° in the pre- and post-operative stages, and had rotated clockwise from 0.5° to 3.0° in the immediately-post and 1-year post-operative period. For the 1-year and 2-year post-operative period, a clockwise rotation rate from 1.0° to 1.5° was recognized. The palatal plane had rotated counter-clockwise after the operation, but we succeeded in achieving a relapse rate almost the same as the preoperative length.