RESUMO
[Objective]To evaluate the effect of fibula shortening on biomechanical characters of tibiotalar joint and prescribe the most acceptable extent of fibula shortening.[Method]Six fresh cadaveric specimens were disarticulated though the knee,and the soft tissues were removed from the knee to the level of the ankle joint.The position of the ankle joint during testing simulated the single leg stance phase of gait.Every group of specimen carried out a biomechanical test in the turn of intact,fibula 2mm shortening,4mm shortening,6mm shortening.The biomechanical change of the tibiotalar joint after fibular shortening was found.[Result]The total contact area of the tibiotalar joint tended to decrease in the fibular shortening model.The contact area and contact pressure in anteromedial and posteromedial quadrant tended to decrease,while,the contact area and contact pressure in anterolateral and posterolateral quadrant tended to increase.[Conclusion]The 2 mm fibular shortening(including 2 mm) significantly alter the biomechanical characters in tibiotalar joint.
RESUMO
Objective To explore the biomechanical mechanism of long-term complication of cervical spinal operations by measuring pressure changes of zygapophysial joints using pressure sensitive film (PSF) after cervical spine anterior operations. Methods C4,5 anterior discectomy and C4,5 anterior plate fixation were done on 10 fresh adult cervical spine specimens (C2～T1). PSF was put into zygapophysial joints and pressure changes were measured in positions of extension, left/right lateral bending and axial rotation on a universal testing machine. Results After cervical spine anterior operations, pressure of the adjacent facet joints increased. The differences were significant in extension and axial rotation (P
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Objective To evaluate factors which maintain the stability of the ankle, and discuss indications for trans-syndesmotic fixation. Methods 12 freshly-frozen cadaver legs amputated below the knee were collected and divided into 2 groups. An ankle fracture model of unconstrained pronation-external rotation was then designed. Group A simulated the injury combined with medial malleolus fracture, and Group B the injury combined with deltoid tear. Ligaments were cut off sequentially to simulate the increasing severity of the injury. Fuji super low-pressure sensitive films and displacement transducers were used to measure the contact area of the tibiotalar articular surface and the width of the syndesmosis. The data were analyzed with SPSS to analyze the relationship of ligament injury and ankle stability. Results In Group A, the articular contact area and the syndesmotic width after section of the deltoid were significantly different from those before the section (P
RESUMO
The wear or deformation of UHMWPE contact surfaces, one of the major causes of the failure in total knee replacement arthroplasty (TKRA), results from the stress concentration. Thus the kinematics of knee implant should be considered. The objective of this study was to investigate the stress distribution and kinematics of UHMWPE in TKRA. Geometry analysis of UHMWPE was performed using FEM program(ABAQUS 5.8, 1998). 3D auto meshing preprocessor, which made it possible to perform rapid geometry modeling, was developed for the generation of computer model including the effect of the nonlinear soft tissue. For the linear analysis, 2 steps of loading conditions (i) 550N axial compression, (ii) 550N axial compression with 150N shear in AP direction were applied. The compression test using Fuji pressure sensitive film was utilized to validate this finite element analysis. Increasing the femoral frontal radius and closing the frontal clearance reduced the maximum contact stress in inverse proportion to the contact area. Increasing the tibial sagittal radius increased the AP laxity but little affected the conformity.