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.
Arthroplasty* ; Arthroplasty, Replacement, Knee* ; Biomechanical Phenomena ; Computer Simulation ; Finite Element Analysis ; Knee ; Radius

Mechanical properties of trabecular bone were major particulars to understand a bone's quality and a information of osteoporotic patients. In a measurement of trabecular bone's properties, however, it was very difficult to extract and prepare it's specimen. Thus the goal of this study was to estimate the validity for indentation test which widely used as a non-destructive test of porous materials such as a trabecular bone using a FE analysis. We composed the FE model based on uniaxial compression test and clinical observation. It was able to extend for the simulation of indentation test. In addition to that, this FE model well imitated a behavior of a trabecular bone. We obtained a load-displacement curve by the indentation simulation and calculated the elastic modulus using Pharr's hypothesis. We estimated the validity of the indentation test by comparing compression simulation and indentation simulation. When indenter diameter was five times of pore size, the result of indentation simulation converged on compression simulation. If indentation depth was insufficient, the result of indentation simulation made serious errors. Therefore, to obtain the appropriate result of the indentation test, indenter diameter have to be five times of pore size and indentation depth should be about 8% of indenter diameter at least.
Elastic Modulus ; Humans

OBJECTIVE: Development of telemedicine for an elder has been an important research area in an aging society, and effective Personal Emergency Response System(PERS) can provide exact medical decision and prompt treatment under emergency conditions. Previous studies have been focused on adapting troublesome sensors or passive calling system to monitor the old in their house. However, these previous systems might have limited applications due to its difficulties in usage and restraints in their daily activities, especially in the emergency. METHODS: In this study, the real time algorithms using surveillance camera was developed to monitor their pose change, such as emergency and falling motion. To estimate the motion of elder people, this research use a ratio of eigenvectors of the Principal Component Analysis (PCA) technique. RESULTS: In this system, no additional motion sensors or devices were applied to the object and it can be automatically controlled and monitor the old from a distance. It was found that this system can successfully monitor the old in living room regardless of surveillance camera angles and a silhouette size depending camera distance as using image processing and PCA. CONCLUSION: This algorithm was validated by experiments in a living room and this technique can be applicable to home monitoring and further applications.
Aging ; Emergencies ; Humans ; Passive Cutaneous Anaphylaxis ; Principal Component Analysis* ; Telemedicine

PURPOSE: To compare the fixation power of the newly devised RSP (rigid stepped plate) with the L-plate by mechanical study and to prove the efficacy of the RSP. MATERIALS AND METHODS: Lateral closing wedge proximal tibial osteotomy was performed on the 10-monthsold porcine tibiae, which were fixed by 15 L-plates and 15 RSP's. Each group of 5 pairs of the specimen were applied to the Instron apparatus and loaded by compression, valgus, and varus bending. The fixation power was compared by the stiffness of each construct. RESULTS: Specimen fixed by the RSP's showed larger stiffness than those fixed by the L-plate. Even though the difference was not statistically significant in compression (p=0.465), it was statistically significant in valgus (p=0.047) and varus (p=0.009) bending. CONCLUSION: The RSP can be applied with minimal skin incision, will provide firm initial fixation to the osteotomy site, and seems to enable early range of motion exercise. It will improve the outcome of proximal tibial osteotomy by preventing excessive soft tissue dissection and complications resulting from long-term immobilization of the knee joint.
Immobilization ; Knee Joint ; Osteotomy* ; Range of Motion, Articular ; Skin ; Tibia