Evaluation of post-surgical relapse in maxillary surgery using resorbable plate

Background: This study was carried out to evaluate the vertical and horizontal changes after maxillary surgery using resorbable plates made of an L-lactic acid and D-lactic acid copolymer of PLA (P(L/DL)LA), and to analyze factors of skeletal pattern and surgical movement affecting the post-surgical change. Materials and methods: The subjects consisted of 20 patients who underwent bimaxillary surgery using P(L/DL)LA resorbable plate Onion CPS, Inion Ltd., Tampere, Finland). Lateral cephalograms were taken at 1 month before (T0), 1 month after (T1) and 6 months after surgery (T2). They were divided into two groups, one showing less relapse (LR) and one more relapse (MR) using K-means clustering analysis of post-surgical relapse (T2 T1). In terms of linear and angular variables of maxillary relapse, the two groups were compared with measurements at the pre-surgical stage (TO), the surgical change obtained (T1 TO) and post-surgical relapse (T2 T1) using Mann-Whitney test. Results: Because Frankfort horizontal (FH) to anterior nasal spine (ANS) showed the largest variance in post-surgical relapse of the maxilla, it was used for clustering analysis to define the MR and LR groups. Comparison between the MR and LR groups showed that a short preoperative anterior facial height (AFH) was a significant factor in maxillary relapse. The AFH of the MR group was significantly shorter pre-surgically (p < 0.01) and was significantly increased postoperatively (p < 0.05) when compared to the LR group. In post-surgical relapse, AFH, FH to A, FH to ANS and the palatal plane angle of the MR group were significantly decreased. Conclusions: In the case of a short AFH, P(L/DL)LA resorbable plates may not provide enough vertical stability in the maxillary position due to the muscle force. Facial height might be an important factor when deciding to use P(L/DL)LA resorbable plates for maxillary surgery. (C) 2011 European Association for Cranio-Maxillo-Facial Surgery.