Papers by Keyword: Total Knee Replacement

Abstract: The current research presents a novel porous tibia implant design based on porous structure. The implant proximal portion was designed as a porous rhombic dodecahedron structure with 500 μm pore size. Finite element method (FEM) was used to assess the stem behavior under compressive loading compared to a solid stem model. CATIA V5R18 was used for modeling both rhombic dodecahedron and full solid models. Static structural analysis was carried out using ANSYS R18.1 to asses the implant designs. The results indicated enhanced clinical performance of tibial-knee implants compared to the solid titanium implant via increasing the maximum von-Mises stresses by 64% under the tibial tray in porous implant which reduce stress shielding. Also, the maximum shear stress developed in bone/implant interface was reduced by 68% combined with relieving the stress concentration under the stem tip to relieve patients' pain. Finally, porous implants provide cavities for bone ingrowth which improve implant fixation.

Abstract: Nowadays, patients with osteoarthritis in Thailand are likely to increase in number every year. There are approximately 462,000 people and most are females than males. The treatment is surgery knee replacement implants which must be imported from abroad and cost is expensive.Total knee prosthesis used in Thailand would not fit with the body of the Thai women because of the design total knee prosthesis use anatomical data of Europe and designed for both male and female, which is different in the knee structure. This research aims to study the size and shape of knee for Thai women and design total knee replacement. The using of finite elements is to assist in the analysis which focuses on the influence of the force active on and the effects of stress distribution on the part of the knee at different stages of gait cycle. The results of the study can measure the average size of Thai knee women base on analytical data. Anthropometric data on the proximal tibia and distal femur of 55 female knees were obtained using three dimensional computer tomographic measurements. The parametric studies are dimension analysis of the femoral mediolateral (fML) and femoral anteroposterior (fAP) dimension on distal femur surface and tibial mediolateral (tML), tibial anteroposterior (tAP) on proximal tibia surface. The measuring average values are 65, 60, 67 and 45 mm respectively. All parameters were compared to the size of the total knee prosthesis which currently used in Thailand. It is found that values are 70, 62, 68 and 48 mm respectively which is larger than the average Thai woman.The study of finite elements can be made aware of the stress distribution and stress in the area of artificial knee while walking and leading to the design of artificial knee joint to have size and shape suitable for Thai women.

Abstract: The scope of this paper is to explore the input parameters of a Finite Element (FE) model of an active lower limb that are most influential in determining the size and the shape of the performance envelope of the kinematics and peak contact pressure of the knee tibial insert introduced during a Total Knee Replacement (TKR) surgery. The active lower limb FE model simulates the stair ascent and it provides a more complicated setup than the isolated TKR model which includes the femoral component and the tibial insert. It includes bones, TKR implant, soft tissues and applied forces. Two probabilistic methods are used together with the FE model to generate the performance envelopes and to explore the key parameters: the Monte Carlo Simulation Technique (MCST) and the Response Surface Method (RSM). It is investigated how the uncertainties in a reduced set of 22 input variables of the FE model affect the kinematics and peak contact pressure of the knee tibial insert. The kinematics is reported in the Grood and Suntay system, where all motion is relative to the femoral component of the TKR. Reported tibial component kinematics are tibio-femoral flexion angle, anterior-posterior and medial-lateral displacement, internal-external and varus-valgus rotation (i.e. abduction-adduction), while the reported patella kinematics are patella-femoral flexion angle, medial-lateral shift and medial-lateral tilt. Tibio-femoral and patella-femoral contact pressures are also of interest. Following a sensitivity analysis, a reduced set of input variables is derived, which represent the set of key parameters which influence the performance envelopes. The findings of this work are paramount to the orthopedic surgeons who may want to know the key parameters that can influence the performance of the TKR for a given human activity.

Abstract: Aseptic loosening of the femoral component is one cause of failure in total knee replacement (TKR). Inadequate bone stock in the distal femur after TKR, due to the stress shielding, was often found in revision of the femoral component. The pegs in the femoral component are used as an aid to the correct placement of the component but they also help to transfer the load to the diaphyseal part of the bone and improve stability. This paper investigates the influence of femoral component peg design on stress distribution and bone remodelling in the distal femur after TKR. Eight different peg designs were investigated and reported in this paper. The bone remodelling parameters in the distal femur are presented, compared and analysed. Results show that a slender peg is advantageous in TKR.

Abstract: During performing Computer assisted Total Knee surgery, surgeons have difficulties in orientation of cutting block before sawing procedure. The objectives of this study are develop design approach and fabrication of prototype, which able to eliminate stated difficulties. Thus, improve performance and cycle time of total knee surgery. Benchmarking with commercial product had been conducted, two designs of jig system were proposed. Selection of design was conducted using Pugh method. Two designs were compared based on specific requirements, in order to get the most acceptable design. Pugh method analysis shown that the second design give more advantages in handling, easy to operate, least cost in manufacture, and reduction of time in doing the total knee replacement than the first design. Prototype jig assembly consist of arm, base and cutting block were fabricated by rapid protyping for feasibility analysis. Then, simulation of fabrication by machining process was conducted through Mastercam Mill V8. All component were able to fabricated through machining. A prototype of jig system was fabricated using stainless steel typed SS316L, and evaluation of cutting procedure with saw bone confirmed that the second design is fulfill the objectives of this study.

Abstract: Improved cement technique by interposing less than two layers of hydroxyapatite (HA) granules between bone and bone cement at the cementing (Interface Bioactive Bone Cement : IBBC) have been performed in total knee replacement (TKR). Results of TKRs of the rheumatoid arthritis (RA) who used IBBC were evaluated. 54 knees of the RA could be followed up clinically and radiologically. As a control, clinical results of TKR with conventional cementing (Non-IBBC) were used. In IBBC cases, the appearance rate of the radiolucent lines on the tibial components and the periprosthetic osteolysis of the tibial components were significantly low. In IBBC, bone cement bound to HA mechanically immediately after surgery and HA granules bound to the bone physicochemically after bone ingrowth into the spaces around the HA granules. Thus, we believe that IBBC is a method combining the advantage of cementless HA coating and bone cement.