Construction Of A Finite Element Model Of CLP Cranio-maxillary Complex With Sutures And Relative Biomechanical Research

PURPOSE (1) To develop an effective method of constructing a finite element model of UCLP Cranio-maxillary complex with sutures;(2) To investigate the biomechanical influence of circum-maxillary sutures on the reaction of orthopedic forces;(3) To explore the biomechanical effect of maxillary protraction with or without maxillary expansion on the UCLP patient.METHODS (1) One male patient aged9with left complete lip and palate cleft was selected and CT scan was taken at0.75mm intervals on the skull. Two FEM models-one with sutures while the other with no sutures except the mid-palatal suture-were constructed from the CT scan data with the following softwares:Mimics10.0, Geomagic studiol2.0, Solidworks(version2011) and E-fearure Biomedical Modeler;(2) Both models were loaded by a maxillary protraction force (500g per side,20degrees downward and forward from the occlusal plane) with the mid-palatal suture opened6mm by maxillary expansion. Displacement of some important craniofacial structures was measured;(3) Anther two UCLP cranio-maxillary complex FEM models with circum-maxillary sutures were constructed. The mid-palatal suture of one model was opened6mm by maxillary expansion force and then the model was loaded with a maxillary protraction force (500g per side,20degrees downward and forward from the occlusal plane) while the other model was loaded only with the maxillary protraction force. Displacement of some important craniofacial structures was measured and stress distribution of some important sutures was analyzed;RESULTS (1) A three-dimensional finite element model of UCLP cranio-maxillary complex with12sutures was established from the CT scan data. This simulation model was consisted of206753individual elements and260662nodes;(2) The displacement of cranio-maxillary structures of the UCLP cranio-maxillary complex with sutures was more than that of the UCLP cranio-maxillary complex without sutures when they were loaded with the same maxillary protraction force in the combination with maxillary expansion;(3) Either loaded with maxillary protraction and maxillary expansion, or loaded with maxillary protraction force only, the UCLP cranio-maxillary complex moved forwards and downwards obviously, and the displacement of cranio-maxillary structures decreased gradually from downwards to upwards. The amount of displacement of cranio-maxillary structures on the cleft side was larger than that on the non-cleft side;(4) The amount of displacement of cranio-maxillary structures of the model with maxillary expansion was larger than that of the model without maxillary expansion;(5) The tissues on the two sides of the cleft moved towards the cleft and the palatal plane rotated counterclockwise under maxillary protraction force. By contrast, the tissues on the two sides of the cleft move laterally and the palatal plane rotated clockwise under maxillary protraction force in the combination with maxillary expansion;(6) Either loaded with maxillary protraction and maxillary expansion, or loaded with maxillary protraction force only, the sutures of UCLP Cranio-maxillary complex were presented with tensile stress as well as compressive stress, and the stress distribution of the sutures on the cleft side and on the non-cleft side had similar regular pattern. However, the former is larger than the latter;(7) The maximum stress of sutures on the model with maxillary expansion was much more than that on the model without maxillary expansion, and the distribution of the maximum stress was obviously different in the two models.CONCLUSION (1) It is an effective way to establish the three-dimensional finite element model of UCLP cranio-maxillary complex with sutures from CT images with the help of the following techniques:Mimics10.0, Geomagic Studio12.0, Solidworks and E-feature Biomedical Modeler;(2) From the respective of biomechanics, this research hints that circum-maxillary sutures play an important role in the process of growth modification;(3) The biomechanical research suggests that maxillary protraction with maxillary expansion is much better than simply maxillary protraction to treat UCLP patients with maxillary deficiency.