Reduced leaflet stress in the stentless quadrileaflet mitral valve: a finite element model.

BACKGROUND: Failure of bioprosthetics is usually caused by calcification of the leaflets as a consequence of high tensile stresses. The stentless valve resembles native mitral valve anatomy, has a flexible leaflet attachment and a suspension at the papillary muscles, and preserves annuloventricular continuity. In this study, the effects of the stentless valve design on leaflet stress were investigated with a finite element model. METHODS: Finite element models of the stentless quadrileaflet mitral valve were created in the close and open configurations. The geometry of the stented trileaflet mitral valve was also analyzed for comparative purposes. Under the designated pressures, the regional stresses were evaluated, and the distributions of stresses were assessed. RESULTS: Regardless of whether the valve is in the open or close configuration, the maximum first principal stress was significantly lower in the stentless valve than in the stented valve. For the stentless valves, limited stress concentration was discretely distributed in the papillary flaps under both close and open conditions. In contrast, in the stented valve, increased stress concentration was evident at the central belly under the open condition and at the commissural attachment under close condition. In either configuration, the maximum second principal stress was markedly lower in the stentless valve than in the stented valve. CONCLUSIONS: The stentless valve was associated with a significant reduction in leaflet stress and a more homogeneous stress distribution compared to the stented valve. These findings are consistent with recent reports of the clinical effectiveness of the stentless quadrileaflet mitral valve.

[Three-dimensional finite element model of maxillary protraction of the maxilla in patients with cleft lip and palate].

OBJECTIVE: To determine the effective rule of protraction in different directions,strains, and shifts of maxillary bone,and to supply the scientific data for treatment of the maxilla in patients with cleft lip and palate. METHODS: " Based on the establishment of 3-dimensional finite element model of maxilla with cleft lip and palate,ANSYS 10.0 software was used to simulate protraction,and then we analyzed the change of maxillary stress and shift in the same force of traction in different directions. RESULTS: With 500 g per lateral protraction and the protraction angle from 20 degree to 45 degree,the maxillary shifted upward, forward, and outward, and the shape of maxillary plate bow showed internal shrinkage. There was a close relation between the internal shrinkage and the direction of protraction. The smaller the angle between the direction of protraction and the functional occlusion plane,the larger the internal shrinkage of tooth bow. The larger the angle between the direction of protraction and the functional occlusion plane,the smaller the internal shrinkage of tooth bow. CONCLUSION: With protraction,the maxilla grows upward, forward, and outward, and the maxillary palate shinks internally. There is a close relation between the direction of protraction and the range of internal shrinkage.

Establishment of 3-dimensional finite element model of maxillary in human complete unilateral cleft lip and palate with spiral CT scan.

OBJECTIVE: To explore a faster and more precise method to establish a 3-dimensional (3 D) finite element model of maxillary in human complete unilateral cleft lip and palate. METHODS: The surface of the model was created using Materialists Interactive Medical Image Control System (Mimics) software to deal with Dicom standard files obtained by scanning the cranium of the patient with multi-slice helical CT. The 3D finite element model for complete unilateral cleft lip and plate in maxillary was established by Ansys software. RESULTS: A 3D finite element model of maxillary in human complete unilateral cleft lip and palate was constructed with 27,405 units and 26,876 nodes. CONCLUSION: The combination of Mimics software, Geomagic studio software, Ansys software, and spiral CT is able to create a 3D finite element counter model, which provides a faster and more valid method to study complete unilateral cleft lip and palate.