Papers by Keyword: Knee

Abstract: In the present paper, a review of some of the common orthoses designed for osteoarthritis of the knee is performed. The functional and constructive characteristics and the main advantages that recommend them for use are presented.

Abstract: Knee malalignment is considered one of the key biomechanical factors that influence the progression of knee osteoarthritis. In this context, a three-dimensional Finite Element model of the knee joint is developed and used to investigate the effect of the frontal plane femoro-tibial angle as well as the body weight load on the stress distribution in the knee cartilage and menisci. Therefore, the knee joint model is obtained through CAD software. Bones, articular cartilage and menisci are considered linear, elastic and isotropic materials. Ligaments were modelled using connectors. Consequently, contact pressures and equivalent stress (von-Mises) are calculated in Abaqus software. This model was validated using experimental and numerical results obtained by other authors. Results of this work demonstrated that; compressive stress and contact pressure on the medial compartment of the knee joint were found to be larger compared to those in the lateral compartment when the femoro-tibial angle and the body weight load increased from 0° to 12° varus and 500 N to 1250 N, respectively, suggesting that these two parameters might be risk factors for developing medial compartment knee osteoarthritis.

Abstract: Some theoretical and experimental considerations upon the biomechanics of oscillatory flexion-extension movements developed at knee level of human subjects, without previous detected pathologies are presented in this paper. Thus, the first part of the paper is referring to the analysis of aspects related to the locomotion system biomechanics concerning the flexion-extension movement at knee level and also to the setting of various samples of subjects out of which the examples for the proposed methodology application will be selected. In the second part of the paper, the analysis structures required for the recording and assessment of oscillatory movements biomechanics at knee level are developed and presented. In the third part, the results and conclusions regarding the behavior and performance limits of movements at knee level are presented and processed.

Abstract: Orthoses are common devices to correct or prevent gait abnormalities in children. In this paper we present a new design for knee orthoses with a modular structure used for childrens locomotion recovery through kinetotherapeutic procedures, after some bone fractures or surgical interventions at the lower limb level. This research consists of an experimental analysis on children walking, a complete human lower limb dynamic analysis, modeling and simulation of a new knee orthosis. A new modular knee orthosis validated by analytical results and computer simulation using MSC Adams software was developed and is presented here.

Abstract: Abstract Objective To analyze the relationship between knee and ankle, and provide the design of the intelligent prostheses with the theory foundation. Method The gait of 30 healthy young people walking at fast, normal, and low speeds separately were detected by 3D gait analysis sysytem, and the gait data were investigated through BP Network. Result The kinematic information of the ankle could get from the knee through BP Network which could study the relationship well. Conclusion The control strategy could be used on the intelligent prostheses according that the kinematic information of the ankle could be forecasted from the knee.

Abstract: Complications in total knee arthroplasty (TKA), which may include the inaccuracy of the implantation and the poor component design, can cause major failures in the TKA. Therefore, the present investigation studies the onlay knee implants commonly used clinically to find the major causes of the damage to artificial patella by the computer aided analysis of the three-dimensional finite element model of the artificial patello-femoral joint built through reverse engineering. Results showed that although a significant difference is found in the condition and the state of the stress distribution generated as the patello-femoral joint changes with the flexion of the knees, this variation is still within the tolerable range; but the patellar lateral tilt is something that caught our attention. Furthermore, through the comparison between the study and the clinical results, this investigation concludes that the bone cement on the implant interface is the major cause for the breaking of the pegs, and is not related to the original design of the patella. This study also discovers that slight design modification on the parts of commonly used artificial joints may effectively reduce surgical failure rate; therefore, a more robust design configuration for patellar pegs is proposed.

Abstract: The development of artificial joints is now considered quite mature, and the main treatment for osteoarthritis. However, in recent unicompartmental knee arthroplasty (UKA) clinical follow-ups, complications due to wear of polyethylene (PE) tibial components still exist. Therefore, this study focused on the possibility of avoiding and minimizing damage to the PE tibial component. Currently, the most common problem in the application of UKA is the malresection of the tibial plateau, often resulting in malpositioning of the tibial implant. This positioning problem may be the main reason for advanced wear and dislocation of a PE tibial component. In this study, finite element analysis (FEA) was used to study the stress change of malpositioned PE tibial components in order to better understand the damaging mechanism on PE tibial components. It was found that anatomically designed unicompartmental knee prostheses (UKP) allowed more positioning error in varus tilt than symmetrically designed ones. And both should avoid any positional error greater than 10° valgus tilt. Otherwise, increased wear of PE tibial components would result in shortened lifetime of the artificial joint.

Abstract: We studied the long-term wear behaviour of alumina-doped zirconia femoral condyles against ultra-high molecular weight polyethylene (UHMWPE) tibial inserts. The simulator kinematics included 20 degrees of flexion/extension, ± 5 degrees of internal/external rotation, and 6 mm of anterior/posterior translation. All knee components were subjected to 10 million cycles of normal walking (2.6 KN max, freq. 1.8 Hz). Lubricant was 50% alpha-calf serum (20 mg/ml protein) with EDTA. The tibial inserts were from one lot of ram-extruded UHMWPE and sterilized with 3.5-Mrad or 7-Mrad radiation dose. Soak controls were stored unloaded in deionised water for 60 days prior to testing. Implants were studied with high-resolution confocal Raman spectroscopy after 10-Mc duration. The wear of control knees (CoCr/3.5-Mrad) averaged 4.5mm3/Mc while the wear with the ZrO2/7-Mrad combination was unmeasurably low even after 10 million cycle duration. Raman Spectroscopy at 10-Mc duration showed only the presence of the desired tetragonal phase. Thus, the ZrO2/7-Mrad bearing combination should prove excellent for active patients who may otherwise risk high wear rates over many years of use.

Abstract: The design of knee prostheses can be improved by computer aided design and structural analysis based on the finite element simulation. Our assumption is that by knowing the stress patterns between the knee prosthesis components and between this implant and its surroundings, we can better evaluate the wear performances and improve its design. The geometry of mobile bearing knee prosthesis with a polyethylene insert was used to predict peak and average contact pressures in several explicit dynamics finite elements analyses. The contact pressure, shear stress distribution and shear movements at the interface implant-cement and bone-cement are important for prostheses life and were computed. Rigid body dynamics analysis was used to predict body positions and orientations. Numerical modeling and simulations are used to predict contact pressures between three-dimensional surfaces. Our computational results showed a positive matching with experimental data from literature. This modeling approach is sufficiently fast and accurate to be used in design sensitivity and optimization studies of knee implant mechanics.