Construction of a 3D finite element model of temporomandibular joints including the musculoskeletal system / 医用生物力学

Objective To discuss the feasibility of constructing a 3D finite element model of the temporomandibular joint (TMJ) including the musculoskeletal system based on imaging and anatomy, and to provide new ideas of modeling for TMJ biomechanical researches. Methods CT images of the skull, MRI images of masticatory muscles and bilateral TMJ from No.23 Chinese virtual human in the second generation were collected and imported in batches into Mimics in format of DICOM for 3D reconstruction. Then the model was integrated and optimized by Geomagic Studio, and the TMJ capsule and articular cartilage were also constructed. After the material properties of TMJ tissues were defined, a 3D finite element model of TMJ including the musculoskeletal system was finally constructed by ANSYS. Results The 3D finite element model of TMJ with the musculoskeletal system was constructed, including TMJ disc, articular cartilage, TMJ capsule, maxilla (including zygoma and nasal), mandible, sphenoid, temporal bones (including part of parietal), maxillary teeth, mandibular teeth, temporalis muscles, masseter muscles, medial/lateral pterygoid muscles, temporomandibular ligaments, sphenomandibular ligaments and sylomandibular ligaments. Conclusions Based on CT and MRI images and anatomy, the 3D finite element model of TMJ including the musculoskeletal system can be precisely and feasibly constructed by Mimics, Geomagic Studio and ANSYS. This model can restore the biomechanical environment of the TMJ, provide new ideas of modeling for biomechanical researches on the TMJ, and offer the simulation platform for visualization treatment of TMJ disease in clinic.

Biomechanical characteristics analysis on discs with coflex fixation on the different segments of lower lumbar spine / 中国骨伤

<p><b>OBJECTIVE</b>To investigate the biomechanical differences between the surgery and adjacent segments of intervertebral discs in the lower lumbar spine, which were implanted with Coflex into the segments of L4, and L5S1, respectively.</p><p><b>METHODS</b>Three finite-element models (the model of the intact lower lumbar sacrum,the L4.5 and L5S1 segments implanted by Coflex) were developed, respectively. According to the spinal three-column loading theory, three models were forced by the physiological loads of upright standing, flexion and extension. The stress of the different areas of the disc annulus, the changes of intervertebral dorsal height and the degree of nucleus pulposus pressure were compared and analyzed.</p><p><b>RESULTS</b>Coflex implanted into the L4.5 and L5S1 segments in compression and extension could both decrease the stress of the posterior area of intervertebral disc in the surgery segment, resist the changes of the intervertebral disc dorsal height and reduce the perssure of nucleus pulposus. Furthermore, the stress of the L5S1 segment decreased when Coflex fixed the L4.5 segment in extension. However, when Coflex fixed the L5S1 segment, the stress of L4.5 segment had no significant changes.</p><p><b>CONCLUSION</b>Coflex fixing the L4,5 and L5S1 segments can effectively decrease the stress of the surgery segmental discs, respectively. Furthermore, Coflex fixing L4,5 segment may play a biomechanical role in reducing the stress of L5S1 segment.</p>

Finite element model testing on Coflex dynamic fixation for L4/5 and L5/S1 segment of lower lumbar / 医用生物力学

Objective To simulate clinical operation and investigate feasibility of Coflex dynamic device for fixing L5/S1 segment of lower lumbar degenerative diseases. Methods The lower lumbar-sacral digital model was extracted from platform of the second generation of Chinese Digitized Human “Male No.23” data set, and three finite element (FE) models (the model of normal lower lumbar sacrum, L4/5 and L5/S1 segment fixed with Coflex) were developed respectively using a series of CAX software. According to the spinal three-column loading theory and the lower lumbar physiological behaviors, FE model tests were analyzed, validated and compared under the physiological load of upright standing, anteflexion and extension. Results The FE models of normal lower lumbar sacrum (Healthy), Coflex fixed-L4/5 segment (L4/5), Coflex fixed-L5/S1 segment (L5/S1) were developed, respectively. Based on biomechanical indexes (stability and compatibility) of the controlled trial for the FE model, the two Coflex-fixed FE models showed similar biomechanical effects for fixing the lower lumbar. Conclusions The controlled trials of FE models provide biomechanical evidence for the fixation of lower lumbar L5/S1 segment by Coflex dynamic device, which is of significance for application of Coflex in fixing L5/S1 segment in clinic.