Abstract
Purpose: In Le Fort I osteotomy without using an osteotome (LF1-non-COSep), accidental fracture of the pterygoid process may occur in case of pterygomaxillary disjunction (PMD). Pterygoid process fracture is associated occasionally with severe hemorrhage. Therefore, it is important to predict unfavorable pterygoid process fracture. Previously, we reported that three-dimensional finite element analysis (3D-FEA) can fairly accurately predict the PMD pattern of LF1-non-COSep, and that simulation surgery using 3D-FEA could analyze and predict unfavorable pterygoid process fracture.
The aim of this study was to elucidate the technique of PMD to prevent an unfavorable pterygoid process fracture, using simulated surgery with 3D-FEA in LF1-non-COSep.
Materials and Methods: Computed tomography (CT) image data (100 sides) before LF1-non-COPSep were converted to the 3D-FEA analysis model. We simulated the PMD, and examined pterygoid process fracture from various angles of the cutting line in the maxillary lateral wall using 3D-FEA (occlusal plane model, line at 5 degrees to occlusal plane: +5° model, line at 10 degrees to occlusal plane: +10° model). The data were analyzed using Student's t-test, and differences were considered significant at P<0.05.
Results: The rate of pterygoid process fracture using 3D-FEA was 31% in the occlusal plane model, followed by the +10° model (18%) and +5° model (14%).
The incidence of pterygoid process fracture was higher in the occlusal plane model than the +5° model (odds ratio, 2.97; 95% CI, 1.45±6.36; P=0.002) and +10° model (odds ratio, 2.14; 95% CI, 1.09–4.34; P=0.02), respectively.
Conclusions: Simulated surgery using 3D-FEA provides useful information for selecting safer procedures in LF1-non-COPSep. In order to minimize the risk of pterygoid process fracture, a cutting line at 5 to 10 degrees to the occlusal plane in the maxillary lateral wall may be necessary.
