Three-dimensional finite element analysis of medial patellofemoral ligament reconstruction with transosseous and wire anchor fixation / 中国组织工程研究

BACKGROUND:Reconstruction of the medial patellofemoral ligament is the primary and basic treatment for patellofemoral dislocation.Generally,autologous or allogeneic tendons are used to fix the patellofemoral podogram area and the femoral insertion,respectively.There are various fixation methods.Patellar lateral insertion fixation methods are relatively diverse,mainly traditional transosseous fixation and recent anchoring methods,including single tunnel,double-tunnel transosseous fixation,and two-wire anchor fixation.However,which fixation method is more effective in reducing patellofemoral joint stress and is more biomechanical has not been determined. OBJECTIVE:To observe the mechanical effects of patellofemoral joint and medial patellofemoral ligament reconstruction with transosseous and wire anchor fixation. METHODS:A three-dimensional finite element model of the knee joint was constructed.The medial patellofemoral ligament was reconstructed by a single tunnel through the bony canal or two wire anchors at the medial edge of the patella.The femoral side was fixed by extrusion nails to the medial epicondyle of the femur and the midpoint of the adductor tubercle.We observed the effects of the two fixation methods on patellofemoral joint and medial patellofemoral ligament loading during knee flexion at 0°,30°,60°,90°,and 120°. RESULTS AND CONCLUSION:(1)The stress on the patellofemoral joint was large when the knee was at flexion of 0-60°,peaked at 30°,and gradually decreased at 90° and 120°.The two fixation methods had little difference in the stress on the patellofemoral joint.(2)The stress on the medial patellofemoral ligament peaked at 30° and decreased significantly at 60°,and the load on the medial patellofemoral ligament was significantly greater at all angles with anchor fixation than with bony canal fixation.(3)The results showed that there was no significant difference in patellofemoral joint loading between the two fixation methods,but the stress on the medial patellofemoral ligament in anchoring was significantly greater than that in transosseous fixation.

Finite element analysis of the stability of Mason type Ⅲ radial head fracture fixed with three cross-bridge headless compression screw and locking plate / 中国骨伤

OBJECTIVE@#To compare the biomechanical stability of three cross-bridge headless compression screws and locking plates in the fixation of Mason type Ⅲ radial head fractures by finite element method.@*METHODS@#Using reverse modeling technology, the radial CT data and internal fixation data of a healthy 25-year-old male were imported into the relevant software. Three-dimensional finite element model of 3 cross-bridge headless compression screws and locking plates for MasonⅢ radial head fractures were established, and the radial head was loaded with 100 N axial loading. The maximum displacement, maximum Von Mises stress and stress distribution of the two groups were compared.@*RESULTS@#The maximum displacements of the three cross-bridge screws group and locking plate group were 0.069 mm and 0.087 mm respectively, and the Von Mises stress peaks were 18.59 MPa and 31.85 MPa respectively. The stress distribution of the three screws group was more uniform.@*CONCLUSION@#Both internal fixation methods can provide good fixation effect. CoMPared with the locking plate fixation method, the 3 cross-bridge headless compression screws fixation is more stable and the stress distribution is more uniform.

The SACT Template: A Human Brain Diffusion Tensor Template for School-age Children / 神经科学通报·英文版

School-age children are in a specific development stage corresponding to juvenility, when the white matter of the brain experiences ongoing maturation. Diffusion-weighted magnetic resonance imaging (DWI), especially diffusion tensor imaging (DTI), is extensively used to characterize the maturation by assessing white matter properties in vivo. In the analysis of DWI data, spatial normalization is crucial for conducting inter-subject analyses or linking the individual space with the reference space. Using tensor-based registration with an appropriate diffusion tensor template presents high accuracy regarding spatial normalization. However, there is a lack of a standardized diffusion tensor template dedicated to school-age children with ongoing brain development. Here, we established the school-age children diffusion tensor (SACT) template by optimizing tensor reorientation on high-quality DTI data from a large sample of cognitively normal participants aged 6-12 years. With an age-balanced design, the SACT template represented the entire age range well by showing high similarity to the age-specific templates. Compared with the tensor template of adults, the SACT template revealed significantly higher spatial normalization accuracy and inter-subject coherence upon evaluation of subjects in two different datasets of school-age children. A practical application regarding the age associations with the normalized DTI-derived data was conducted to further compare the SACT template and the adult template. Although similar spatial patterns were found, the SACT template showed significant effects on the distributions of the statistical results, which may be related to the performance of spatial normalization. Looking forward, the SACT template could contribute to future studies of white matter development in both healthy and clinical populations. The SACT template is publicly available now ( https://figshare.com/articles/dataset/SACT_template/14071283 ).