BackgroundA number of different femoral anterior cruciate ligament fixation techniques are currently in use. Slippage of the graft caused by excessive early loading or aggressive rehabilitation may negate benefits of surgery and result in... more
BackgroundA number of different femoral anterior cruciate ligament fixation techniques are currently in use. Slippage of the graft caused by excessive early loading or aggressive rehabilitation may negate benefits of surgery and result in a knee with undesirable laxity.HypothesisAnterior cruciate ligament femoral graft slippage varies by fixation technique and amount of cyclic loading.Study DesignControlled laboratory study.MethodsGraft slippage in 5 different soft tissue anterior cruciate ligament femoral fixation techniques (Bio-TransFix cross-pin technique, Stratis ST cross-pin technique, Bilok ST transverse femoral screw, Delta tapered bio-interference screw, and single-loop TensionLok) was compared by cyclic loading of double-bundle grafts in porcine femurs. Graft slippage was measured using a differential variable reluctance transducer.ResultsThe Bio-TransFix had significantly less (P =. 002) total graft slippage (1.14 ± 0.43 mm) compared to the Delta (3.74 ± 3.25 mm), Bilok S...
Research Interests: Mechanical Engineering, Biomedical Engineering, Medicine, Anterior Cruciate Ligament, Femur, and 14 moreAnimals, American, Cyclic Loading, Behavioral Animal Models, Swine, Study design, Soft Tissue, Dynamic Loading, Transplants, Weight Bearing, Orthopedic Procedures, Slippage, Biomechanical Phenomena, and Anterior cruciate ligament reconstruction
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In this study, a grasping motion simulation method based on finite element analysis was developed for the virtual evaluation of gripping comfort while gripping a cylindrical object. The validity of the grasping motion simulation was... more
In this study, a grasping motion simulation method based on finite element analysis was developed for the virtual evaluation of gripping comfort while gripping a cylindrical object. The validity of the grasping motion simulation was verified by comparing the contact pressure distribution generated on the palm of a hand using a finite element model with the measured result obtained via experiments on a human subject. The mean absolute difference between the simulation and experimental results at 23 regions was 7.4 kPa, which was considered to be significantly low and an acceptable value for use in assessment of the gripping comfort score. Furthermore, topology optimization was introduced into the simulation to propose an easy method for obtaining a rough shape of the gripping part of a product that is comfortable to grip. An objective function during the optimization process was defined to minimize the contact pressure concentration level, and this was observed to have a negative cor...
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Research Interests: Biomechanics and Medicine
Mechanical properties of ultra high molecular weight polyethylene (UHMWPE) used as a bearing material in total joint replacements have been investigated under impact compressive load. Cylindrical specimens, 5.3mm in diameter and in... more
Mechanical properties of ultra high molecular weight polyethylene (UHMWPE) used as a bearing material in total joint replacements have been investigated under impact compressive load. Cylindrical specimens, 5.3mm in diameter and in length, were cored from a tibial insert of total knee replacement system. Impact compression tests were performed using the split-Hopkinson pressure-bar (SHPB) method to determine dynamic Young’s modulus and yield stress. Viscoelastic characterization of UHMWPE based on the method developed by the authors showed that the three-element solid model, which consisted of a parallel spring E2 and dashpot η connected with another spring E1 in series, was applicable to UHMWPE. Mean values of dynamic Young’s modulus (0.96GPa), E1 (1.30GPa), E2 (1.72GPa) and η (0.34MPas) were smaller than those of bovine femoral trabecular bone, 2.53GPa for dynamic Young’s modulus, 1.97GPa for E1, 1.73GPa for E2 and 0.94MPas for η.
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Porcine skin was subjected to tensile loading in order to determine its anisotropic tensile properties. Skin specimens were obtained from the dorsal and ventral regions of a pig. From each region, two kinds of specimens (parallel and... more
Porcine skin was subjected to tensile loading in order to determine its anisotropic tensile properties. Skin specimens were obtained from the dorsal and ventral regions of a pig. From each region, two kinds of specimens (parallel and perpendicular to the spine) were tested. Significant difference was detected on the tensile strength between dorsal and ventral regions. Furthermore, anisotropy in tensile properties was also found in both dorsal and ventral regions. Threshold for skin rupture may be different depending on the location and the direction of force.
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Skin laceration injury caused by a penetration of small curvature edge frequently occurs in a domestic accident. An assessment method for this injury is necessary in order to develop a safer manufactured product. To assess the risk of... more
Skin laceration injury caused by a penetration of small curvature edge frequently occurs in a domestic accident. An assessment method for this injury is necessary in order to develop a safer manufactured product. To assess the risk of skin laceration injury in a penetration accident, a skin simulant made from silicone rubber was proposed. However, mechanical responses of this skin simulant under dynamic penetration loading have not yet been investigated. In this study, a drop weight penetration test device was developed in order to simulate penetration accidents under impact velocities of over 1 m/s. The device was then used for investigating the dynamic responses of skin simulant against several blades with different tip curvature radii. Load, penetration depth, impulse and energy at rupture were then determined from the test results. Load and penetration depth at rupture increased with the increase of tip curvature radius of the blades. Furthermore, the drop weight test result sho...
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This chapter deals with the in vitro techniques for the determination of viscoelastic properties and fracture toughness of compact bone. The reliability and feasibility of these techniques have been validated through numerical simulation... more
This chapter deals with the in vitro techniques for the determination of viscoelastic properties and fracture toughness of compact bone. The reliability and feasibility of these techniques have been validated through numerical simulation and experiments on bovine compact bone. The method using the split-Hopkinson pressure bar (SHPB) technique was able to sharply reduce the time required for computation to find viscoelastic parameters, and this could be an alternative method to conventional creep and stress relaxation experiments. Young’s modulus of compact bone was experimentally determined as a function of orientation applying the dynamic mechanical analysis (DMA). Young’s modulus is considered to be dominated by the microstructural arrangement of the mineral phase such as the directions of the c-axes of hydroxyapatite crystals in bone, and the previous model in terms of the unidirectional continuous fibre-reinforced composite theory was unable to obtain a good corresponding prediction to the experimental result. Fracture toughness tests have revealed anisotropic and rate-dependent behaviour in the critical stress intensity factor, K C , of compact bone. The existence of a fracture process zone due to microcrack initiation ahead of the main crack front has been demonstrated. Its contribution to the improvement of the resistance to crack growth or fracture has been discussed also. These findings have helped us to understand the optimum microstructure of compact bone as well as to develop more sophisticated biomaterials such as bone-analogue materials.
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The disuse-related bone loss that results from immobilisation following injury shares characteristics with osteoporosis in post-menopausal women and the aged, with decreases in bone mineral density leading to weakening of the bone and... more
The disuse-related bone loss that results from immobilisation following injury shares characteristics with osteoporosis in post-menopausal women and the aged, with decreases in bone mineral density leading to weakening of the bone and increased risk of fracture. The aim of this study was to use the finite element method to: (i) calculate the mechanical response of the tibia under mechanical load and (ii) estimate of the risk of fracture; comparing between two groups, an able-bodied group and spinal cord injury patients group suffering from varying degrees of bone loss. The tibiae of eight male subjects with chronic spinal cord injury and those of four able-bodied age-matched controls were scanned using multi-slice peripheral quantitative computed tomography. Images were used to develop full three-dimensional models of the tibiae in Mimics (Materialise) and exported into Abaqus (Simulia) for calculation of stress distribution and fracture risk in response to specified loading conditi...