Finite element study of maxillary Le Fort-I osteotomy with rigid internal fixation / 中华整形外科杂志

<p><b>OBJECTIVE</b>To study the biomechanical characteristic of maxillary Le fort- I osteotomy with rigid internal fixation (RIF) , so as to choose best fixation method.</p><p><b>METHODS</b>The 3-dimensional finite element models of maxillary Le Fort-I osteotomy with 9 kinds of RIF methods were established. Then the models were divided into three groups to calculate the stress distribution of the maxilla and the displacement of bone segment under 3 kinds of occlusion condition. The fixation stability of the different RIF methods was evaluated.</p><p><b>RESULTS</b>Under the incisor occlusion condition, the stress of the cranio maxillary complex transmits mainly along the nasal-maxillary buttress. Under the premolar and molar occlusion condition, the stress transmits along the alveolar process first, then turns to the nasal-maxillary and zygomatic-maxillary buttress. The focused stress position of the internal fixation system is at the connection between the screws and the plate and at the plate near the osteotomy line. Under the premolar occlusion condition, the displacement of bone segment with different RIF methods was (in a decreasing order) 0.396509 mm (with bio-absorbable plate), 0.148393 mm (with micro-plate ), 0.078436 mm (with mini-plate) in group 1; 0.188791 mm (fixing at the nasal-maxillary buttress), 0.121718 mm (fixing at the zygomatic-maxillary buttress), 0.078436 mm (fixing at the both buttress) in group 2; 0.091023 mm (with straight plate), 0.078436 mm (with L shape plate), 0.072450 mm (with Y shape plate), 0.065617 mm (with T shape plate) in group 3.</p><p><b>CONCLUSIONS</b>The fixation stability of using the bio-absorbable plate in Le Fort-I osteotomy is less stable than using the titanium plate. Fixing at the zygomatic-maxillary buttress is more stable than at the naso-maxillary buttress. The fixation stability is different by using different shapes of plates.</p>

Establishment and primary analysis of the three-dimensional finite element model of mandibular bilateral sagittal split ramus osteotomy with rigid internal fixation / 中华整形外科杂志

<p><b>OBJECTIVE</b>Establish the three-dimensional finite element models of mandibular bilateral sagittal split ramus osteotomy (BSSRO) with rigid internal fixation (RIF), for further study of BSSRO.</p><p><b>METHODS</b>CT scanned technology and the finite element software (ANSYS) were used to establish the original three-dimensional model of mandible, modify the model to animate the BSSRO, then establish the model of RIF, last mesh the model to establish the finite element model of BSSRO with RIF. Apply 100 N occlusion force at the central incisor; calculate the stress distribution of the mandible and the RIF.</p><p><b>RESULTS</b>Three-dimensional finite element models of BSSRO with RIF were established, such as miniplate model, bicortical fixation screw model. When biting with the incisor and fixed with upper plate, the stress of the medial screw position of the distal and medial segment of mandible is high. When fixed with bicortical fixation screw, the highest stress position located at the internal surface of the medial screw' s position of the distal segment of mandible.</p><p><b>CONCLUSIONS</b>The mentioned methods proved feasible in establishing the finite element models of BSSRO with RIF . The models can be applied to the study of BSSRO with RIF.</p>