Search

In this study, we address the challenge of surface roughness in CoCrMo alloys, typically used in artificial knee joints, which can initiate a cascade of biological responses causing inflammation, osteolysis, joint instability, and increased susceptibility to infection. We propose the application of a chemical mechanical polishing (CMP) technique, using an ecologically responsible slurry composed of 4 wt% SiO2, 0.3 wt% H2O2, 1.0 wt% glycine, and 0.05 wt% benzotriazole. Our innovative approach demonstrated significant improvements, achieving a material removal rate of 30.9 nm/min and reducing the arithmetic mean roughness from 20.76 nm to 0.25 nm, thereby enhancing the nanoscale surface quality of the artificial knee joint alloy. The smoother surface is attributed to a decrease in corrosion potential to 0.18 V and a reduction in corrosion current density from 9.55 µA/cm2 to 4.49 µA/cm2 with the addition of BTA, evidenced by electrochemical tests. Furthermore, the preservation of the phase structure of the CoCrMo alloy, as confirmed by XRD analysis and elemental mapping, ensures the structural integrity of the treated surfaces. These outcomes and our simulation results demonstrate the effectiveness of our CMP method in engineering surface treatments for artificial knee joints to optimize friction behavior and potentially extend their lifespans. [ABSTRACT FROM AUTHOR]

The titanium alloy artificial knee joint is used extensively in the current medical industry due to its distinct characteristics and properties that are like the real human knee joint, but it does need to be polished to improve its performance and service life before it can be used. Due to the complicated surface profile, the traditional abrasive flow machining technique cannot achieve a good surface finish offering uniformity and quality. Thus, in this paper, a proper constrained flow channel is designed to conduct the abrasive flow machining of the titanium alloy artificial knee joint surface to overcome these issues. A numerical study is first conducted to explore the distribution of abrasive flow velocity and pressure near the target surface in the constrained flow channel by using the COMSOL Multiphysics software, and it is found from the distribution of the dimensionless material removal rate on the target surface that the exchange of the abrasive flow inlet and outlet during the machining process is recommended to improve the surface finish uniformity. Then, the corresponding experiments are conducted to analyze the surface morphology before and after the abrasive flow machining process. It is found that the surface roughness of the target surface decreases from approximately 394 nm to 171 nm with good uniformity as well. Therefore, the proposed abrasive flow machining method with a properly designed constrained flow channel is useful for the rough polishing and fine finishing of the titanium alloy artificial joint. [ABSTRACT FROM AUTHOR]

In this study, we address the challenge of surface roughness in CoCrMo alloys, typically used in artificial knee joints, which can initiate a cascade of biological responses causing inflammation, osteolysis, joint instability, and increased susceptibility to infection. We propose the application of a chemical mechanical polishing (CMP) technique, using an ecologically responsible slurry composed of 4 wt% SiO2, 0.3 wt% H2O2, 1.0 wt% glycine, and 0.05 wt% benzotriazole. Our innovative approach demonstrated significant improvements, achieving a material removal rate of 30.9 nm/min and reducing the arithmetic mean roughness from 20.76 nm to 0.25 nm, thereby enhancing the nanoscale surface quality of the artificial knee joint alloy. The smoother surface is attributed to a decrease in corrosion potential to 0.18 V and a reduction in corrosion current density from 9.55 µA/cm2 to 4.49 µA/cm2 with the addition of BTA, evidenced by electrochemical tests. Furthermore, the preservation of the phase structure of the CoCrMo alloy, as confirmed by XRD analysis and elemental mapping, ensures the structural integrity of the treated surfaces. These outcomes and our simulation results demonstrate the effectiveness of our CMP method in engineering surface treatments for artificial knee joints to optimize friction behavior and potentially extend their lifespans.

Selective laser melting (SLM) is an enabling additive manufacturing technology to fabricate complex parts such as metallic orthopedic implants. The rapid heating melting and cooling thermal cycle during SLM often induce high residual stress which leads to part distortion or even cracks. To predict residual stress with accuracy and efficiency, this work has developed an innovative modeling approach by incorporating the scanning strategy. The results have shown that residual stress can be predicted with improved accuracy using the modeling approach with scanning strategy accounted in the simulations. [ABSTRACT FROM AUTHOR]

The combination of ultrahigh-molecular-weight polyethylene (UHMWPE) pads and zirconia joints has been used extensively in all artificial knee joints. The wear of UHMWPE is the leading cause of artificial joint failure. However, it is unlikely to detect UHMWPE damage until the patient feels pain. Therefore, developing a sensor to detect the wear of UHMWPE outside the human body is crucial. In this study, the surface of UHMWPE and zirconia was treated with low-temperature atmospheric plasma to increase the surface energy so that the lubricating fluid can be effectively adsorbed on the surface of the material. Furthermore, adding the appropriate proportion of hydroxypropyl methylcellulose with collagen produces good self-assembly behavior, which can reduce the UHMWPE wear and coefficient of friction (COF) by 50%. Therefore, the wear consumption of UHMWPE can be observed simply by sensing the changes in COF, which can be used as a life sensor for joint damage. At a distance of 9500 m continuous use, the COF increases by 17%, which means that the use of UHMWPE can be predicted by detecting the changes in COF. Finally, we proposed that the artificial knee joint's service life can be detected by monitoring the variation in COF. [ABSTRACT FROM AUTHOR]

The titanium alloy artificial knee joint is used extensively in the current medical industry due to its distinct characteristics and properties that are like the real human knee joint, but it does need to be polished to improve its performance and service life before it can be used. Due to the complicated surface profile, the traditional abrasive flow machining technique cannot achieve a good surface finish offering uniformity and quality. Thus, in this paper, a proper constrained flow channel is designed to conduct the abrasive flow machining of the titanium alloy artificial knee joint surface to overcome these issues. A numerical study is first conducted to explore the distribution of abrasive flow velocity and pressure near the target surface in the constrained flow channel by using the COMSOL Multiphysics software, and it is found from the distribution of the dimensionless material removal rate on the target surface that the exchange of the abrasive flow inlet and outlet during the machining process is recommended to improve the surface finish uniformity. Then, the corresponding experiments are conducted to analyze the surface morphology before and after the abrasive flow machining process. It is found that the surface roughness of the target surface decreases from approximately 394 nm to 171 nm with good uniformity as well. Therefore, the proposed abrasive flow machining method with a properly designed constrained flow channel is useful for the rough polishing and fine finishing of the titanium alloy artificial joint.

In this study, we address the challenge of surface roughness in CoCrMo alloys, typically used in artificial knee joints, which can initiate a cascade of biological responses causing inflammation, osteolysis, joint instability, and increased susceptibility to infection. We propose the application of a chemical mechanical polishing (CMP) technique, using an ecologically responsible slurry composed of 4 wt% SiO 2 , 0.3 wt% H 2 O 2 , 1.0 wt% glycine, and 0.05 wt% benzotriazole. Our innovative approach demonstrated significant improvements, achieving a material removal rate of 30.9 nm/min and reducing the arithmetic mean roughness from 20.76 nm to 0.25 nm, thereby enhancing the nanoscale surface quality of the artificial knee joint alloy. The smoother surface is attributed to a decrease in corrosion potential to 0.18 V and a reduction in corrosion current density from 9.55 µA/cm 2 to 4.49 µA/cm 2 with the addition of BTA, evidenced by electrochemical tests. Furthermore, the preservation of the phase structure of the CoCrMo alloy, as confirmed by XRD analysis and elemental mapping, ensures the structural integrity of the treated surfaces. These outcomes and our simulation results demonstrate the effectiveness of our CMP method in engineering surface treatments for artificial knee joints to optimize friction behavior and potentially extend their lifespans.

BACKGROUND: After artificial knee joint replacement, some patients have low postoperative satisfaction because of the failure of the prosthesis. The early failure of the knee prosthesis is caused by the early wear of the polyethylene component, the loosening and the instability of the prosthesis, which are affected by the contact pressure of the prosthesis. OBJECTIVE: To study the effect of load offset angle on contact pressure, contact area and contact pressure distribution on the polyethylene insert during gait circle. METHODS: The model of the knee prosthesis was introduced into the Abaqus three-dimensional finite element software. The axial force of gait load was offset by 0°, 1°, 2°, 3°, 4°, 5° and 6° to form seven working conditions. The contact pressure, contact area and contact pressure distribution of the polyethylene insert were studied under different working conditions. RESULTS AND CONCLUSION: (1) The contact pressure of the polyethylene insert increases with the augment of the axial load deviation angle during the gait circle. (2) As the axial load shifting to the outside, the contact area between the polyethylene insert and the medial condyle decreases, and the contact area with the lateral condyle increases. (3) Through the contact pressure distribution cloud map, it is found that the contact position gradually moves toward the edge of the tibial tray, and stress concentration occurs at the contact position between the tibial tray and the lateral condyle. (4) The load deviation caused by the poor malalignment will cause the contact pressure on the polyethylene component to increase significantly, and will change the original contact area and contact position. If the knee prosthesis is in the above-mentioned poor mechanical environment for a long time, it will lead to the failure of the knee prosthesis. [ABSTRACT FROM AUTHOR]

BACKGROUND: Total knee arthroplasty has been gradually applied in the treatment of knee joint diseases. However, there is still a controversy about whether synovectomy in surgery, even affecting joint function recovery. OBJECTIVE: To explore the effect of synovectomy in total knee arthroplasty on the functional recovery of knee joint, so as to provide reference for choosing appropriate surgical method in total knee arthroplasty. METHODS: One hundred and twenty patients with osteoarthritis undergoing unilateral total knee arthroplasty admitted at No.152 Hospital of Chinese PLA between September 2009 and September 2014 were included. The patients were randomized into two groups (n=60/group), undergoing retaining synovial membrane and synovectomy in total knee arthroplasty, respectively. Intraoperative tourniquet and postoperative drainage tube were used in all patients. Sex, age, body mass index, hemoglobin, preoperative Hospital Special Surgery knee score and Visual Analogue Scale score were compared between two groups. The operation time, drainage volume at postoperative 6, 24 and 48 hours and the hemoglobin level at postoperative 1 and 7 days, and 1 day before leaving hospital were recorded. Visual Analogue Scale score and Hospital Special Surgery knee score at postoperative 2 weeks, 3 months, 1, 2 and 4 years were detected. RESULTS AND CONCLUSION: (1) There was no significant difference in baseline data between two groups. (2) The operation time and drainage volume at postoperative 6 and 24 hours in the retaining synovial membrane group were significantly lower than those in the synovectomy group (P < 0.05). (3) The hemoglobin levels at postoperative 1 and 7 days, and 1 day before leaving hospital in the retaining synovial membrane group were significantly higher than those in the synovectomy group (P < 0.05). (4) The Visual Analogue Scale score and Hospital Special Surgery knee score at postoperative 2 weeks, 3 months and 1 year showed no significant differences between two groups. The scores at postoperative 2 and 4 years in the synovectomy group were superior to the retaining synovial membrane group (P < 0.05). (5) These findings imply that synovectomy in total knee arthroplasty for osteoarthritis increases postoperative blood loss, with risk for complications. Its short-term efficacy is similar with the retaining synovial membrane, but long-term efficacy is pertinent. [ABSTRACT FROM AUTHOR]

Abstract The wear rate of five types of cruciate-retaining artificial knee joint ultrahigh-molecular-weight polyethylene (UHMWPE) inserts was examined using two custom-made knee joint simulators satisfying ISO 14243–1 (load control) and ISO 14243–3 (displacement control). The wear rate of knee joints composed of a UHMWPE insert and a Co-Cr-Mo alloy or oxidized zirconium femoral component linearly increased with increasing number of wear cycles, and the volumetric wear rate per million cycles was approximately 6–18 mm3/Mc. The wear rate was the lowest in the highly crosslinked knee joint irradiated at 90 kGy (Scorpio) among the five UHMWPE inserts. The extent of oxidation in UHMWPE after a knee simulator test of up to 5 × 106 cycles was small. The load-controlled wear rates measured in this work were close to the displacement-controlled wear rates reported in the literature. The effect of the control method on the wear rate was small for Nexgen and Scorpio knee joints. However, it was larger for the PFC Sigma knee joint having a high curvature of the surface. The wear rate of various knee joints made of highly crosslinked UHMWPE (XLPE) markedly decreased when they were subjected to a radiation dose of 40 kGy or more. The 10-year cumulative percentage revision rate since the primary operation slightly decreased with decreasing volumetric knee simulator wear rate for conventional UHMWPE (CPE) and XLPE knee joint inserts. The XLPE knee joint was shown to exhibit reduced in vivo wear and lower rates of revision for total knee replacement. On the other hand, Nexgen and PFC Sigma (both CPE) knee joints showed the lowest revision rate in the AOA and NJR national joint replacement registries. The volumetric wear rates of 3 mm3/Mc for XLPE and 15 mm3/Mc for CPE knee joint inserts are recommended as a goal for the development of new knee joints. Highlights • Effect of the control method (load or displacement control) on the knee simulator wear rate of UHMWPE was small. • Wear rate of highly crosslinked UHMWPE markedly decreased when they were subjected to a radiation dose of 40 kGy or more. • Clinical revision rate decreased with decreasing knee simulator wear rate for conventional or highly crosslinked UHMWPE. [ABSTRACT FROM AUTHOR]

The torsional friction behavior of the materials (CoCrMo alloy and ultra-high-molecular-weight polyethylene (UHMWPE)) that are used in artificial knee joint replacement (AKJR) were investigated under dynamic loading. The torsional friction torque, wear loss and scars and stress distribution were analyzed and compared. The results show the following: (1) the friction torque declines rapidly at the beginning of the experiments, and meanwhile, the maximum normal load and the torsional angle amplitude show very little effect on the steady value; (2) the wear loss decreases with the increased torsional angle amplitude but increases with the increased maximum normal load; additionally, as the cycle times increase, the wear rate decreases, and the wear is minimal; (3) unloading and secondary loading significantly reduce the friction and wear of the materials, and thus, patients should rest after prolonged exercise to reduce wear; (4) the margins of UHMWPE and CoCrMo are worn, and the wear mechanism is abrasive wear; (5) around the center of the UHMWPE, the surface is peeled off, and the wear mechanism is fatigue wear; and (6) in terms of the compressive stress and shear stress, the calculated results from a finite element model match the experimental results well. [ABSTRACT FROM AUTHOR]

The response to loading of human articular cartilage as assessed by magnetic resonance imaging (MRI) remains to be defined in relation to histology and biomechanics. Therefore, an MRI-compatible whole-knee joint loading device for the functional in situ assessment of cartilage was developed and validated in this study. A formalin-fixed human knee was scanned by computed tomography in its native configuration and digitally processed to create femoral and tibial bone models. The bone models were covered by artificial femoral and tibial articular cartilage layers in their native configuration using cartilage-mimicking polyvinyl siloxane. A standardized defect of 8 mm diameter was created within the artificial cartilage layer at the central medial femoral condyle, into which native cartilage samples of similar dimensions were placed. After describing its design and specifications, the comprehensive validation of the device was performed using a hydraulic force gauge and digital electronic pressure-sensitive sensors. Displacement-controlled quasi-static uniaxial loading to 2.5 mm $$(\delta _{2.5})$$ and 5.0 mm $$(\delta _{5.0})$$ of the mobile tibia versus the immobile femur resulted in forces of $$141 \pm 8$$ N $$(\delta _{2.5})$$ and $$906 \pm 38$$ N $$(\delta _{5.0})$$ (on the entire joint) and local pressures of $$0.680 \pm 0.088$$ MPa $$(\delta _{2.5})$$ and $$1.050 \pm 0.100$$ MPa $$(\delta _{5.0})$$ (at the site of the cartilage sample). Upon confirming the MRI compatibility of the set-up, the response to loading of macroscopically intact human articular cartilage samples ( $$n=5$$ ) was assessed on a clinical 3.0-T MR imaging system using clinical standard proton-density turbo-spin echo sequences and T2-weighted multi-spin echo sequences. Serial imaging was performed at the unloaded state $$(\delta _{0})$$ and at consecutive loading positions (i.e. at $$\delta _{2.5}$$ and $$\delta _{5.0})$$ . Biomechanical unconfined compression testing (Young's modulus) and histological assessment (Mankin score) served as the standards of reference. All samples were histologically intact (Mankin score, $$1.8 \pm 1.3$$ ) and biomechanically reasonably homogeneous (Young's modulus, $$0.42 \pm 0.14$$ MPa). They could be visualized in their entirety by MRI and significant decreases in sample height [ $$\delta _{0}$$ : $$2.86 \pm 0.25$$ mm; $$\delta _{2.5}$$ : $$2.56 \pm 0.25$$ mm; $$\delta _{5.0}$$ : $$2.02 \pm 0.16$$ mm; $$p<0.001$$ (repeated-measures ANOVA)] as well as pronounced T2 signal decay indicative of tissue pressurization were found as a function of compressive loading. In conclusion, our compression device has been validated for the noninvasive response-to-loading assessment of human articular cartilage by MRI in a close-to-physiological experimental setting. Thus, in a basic research context cartilage may be functionally evaluated beyond mere static analysis and in reference to histology and biomechanics. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Purpose:The purpose of this study was to clinically evaluate the automatic stance-phase lock (ASPL) knee mechanism against participants’ existing weight-activated braking (WAB) prosthetic knee joint. Method:This prospective crossover study involved 10 young adults with an above-knee amputation. Primary measurements consisted of tests of walking speeds and capacity. Heart rate was measured during the six-minute walk test and the Physiological Cost Index (PCI) which was calculated from heart rate estimated energy expenditure. Activity was measured with a pedometer. User function and quality of life were assessed using the Lower Limb Function Questionnaire (LLFQ) and Prosthetic Evaluation Questionnaire (PEQ). Long-term follow-up over 12 months were completed. Results:Walking speeds were the same for WAB and APSL knees. Energy expenditure (PCI) was lower for the ASPL knees (p = 0.007). Step counts were the same for both knees, and questionnaires indicated ASPL knee preference attributed primarily to knee stability and improved walking, while limitations included terminal impact noise. Nine of 10 participants chose to keep using the ASPL knee as part of the long-term follow-up. Conclusions:Potential benefits of the ASPL knee were identified in this study by functional measures, questionnaires and user feedback, but not changes in activity or the PEQ. Keywords:Amputee; artificial knee joint; energy expenditure; prosthesis; stance-phase control; transfemoral amputation, stance-phase control [ABSTRACT FROM PUBLISHER]

The objective of this study was to set forth guidelines for designing such an artificial knee joint that can make deep flexion. To this respect, we performed 2D model simulation for deep squatting in which the conventional posterior stabilized knee prosthesis was fitted. In the simulation we introduced a newly defined slip ratio in order to describe an over slipping phenomenon; the slipping and the rolling directions were mutually reversing. Then, the results demonstrated that the slip ratio was over 1 at high and deep flexion, indicating that the femoral rollback did not occur even though the post and the cam contacted. The relation also indicated that the conventional post-cam mechanism would not work appropriately at high/deep flexion. To overcome the above, and to promote femoral rollback even at high/deep flexion, we proposed a new design of the post-cam mechanism, which we called as a ball-ditch mechanism.

The load-dependent frictional performance of vitamin E-blended ultrahigh molecular weight polyethylene (UHMWPE) in serum lubricant was examined. The UHMWPE specimens were slid against the surface of Co-28Cr-6Mo alloy by using a pin-on-disk friction test apparatus. The frictional performance of vitamin E-blended UHMWPE differed from that of virgin UHMWPE under 30 MPa loading, while little difference was observed under 3 MPa loading. The friction force of vitamin E-blended UHMWPE showed a lower value in initial friction and a higher value in steady state friction, and the variability of friction force in the transition process was relatively small. Frictional performance similar to that of the vitamin E-blended UHMWPE was observed as a result of applying vitamin E to the sliding surface of virgin UHMWPE. These results suggest that the frictional performance of vitamin E-blended UHMWPE in serum lubricant is affected by the presence of vitamin E on the sliding surface under high compressive load.

The possibility of pressure-induced leaching of vitamin E from inside of vitamin E-blended ultrahigh molecular weight polyethylene (UHMWPE) was investigated. UHMWPE specimens were pressed against a base plate, and leached vitamin E was dissolved in ethanol. The quantification of vitamin E in ethanol was carried out by fluorescence spectrophotometry. Vitamin E was confirmed to leach from inside of the vitamin E-blended UHMWPE specimens under compressive load, and the amount of leached vitamin E was positively correlated with the applied load.

The objective of this study is to analyze kinetics and kinematics of artificial knee joint at deep flexion, using a 2D geometric model. Our knee model was composed of the tibio-femoral and patello-femoral joints, including the patella tendon and the quadriceps muscles. Since the model was 2D, it neglected the rotation and the varus/valgus motion. In the model, such assumption was made that articulation surfaces were rigid and a point contact was made. Also it was assumed that the force and moment equilibrium conditions were always satisfied. The motion to be studied was decided as the motion from standing to deep squatting with heel-rising. From the simulation we found such results that the femur did not make a rollback and contact force at post-cam became pretty large in high and deep flexion, indicating the post-cam mechanism did not function well. Also patello-femoral contact forces reached larger than tibio-femoral contact forces. Our results demonstrated that how to design the post-cam and patello-femoral joint should be critical issues for developing a new prosthesis which can make deep flexion.

The effect of polyvinylpyrrolidone (PVP) on tribological properties of joint prostheses is still unclear despite its good lubricity and biocompatibility. PVP solutions with five concentrations were prepared with two different solvents. The viscosity, surface tension, and static contact angle of the solutions were measured as well as the friction coefficient and wear volume of artificial joint pairs. With PVP concentration increasing, the friction coefficient firstly decreased significantly but subsequently tapered off after a high level. The inclusion of PVP also improved the wear resistance of the pair. It implies that PVP could be a promising lubrication additive for artificial joints. [ABSTRACT FROM AUTHOR]

This paper describes how three different unique design solutions for artificial knee joints each provide extremely low wear and the potential for a 50-year osteolysis-free lifetime in high-demand patients. Each of the three low-wearing prosthetic design solutions provides a different and distinctive functional solution for the patient and surgeon. [ABSTRACT FROM AUTHOR]

Summary: Objective: Aseptic loosening of artificial knee joints induced by wear particles from a tibial polyethylene (PE) insert is a serious problem limiting their longevity. This study investigated the effects of grafting with our original biocompatible phospholipid polymer 2-methacryloyloxyethyl phosphorylcholine (MPC) on the insert surface. Methods: The hydrophilicity of the PE surface was determined by the contact angle of a water droplet, and the friction torque was measured against a cobalt–chromium alloy component. The wear amount was compared among PE inserts with or without cross-linking and MPC grafting during 5×106 cycles of loading in a knee joint simulator. The surfaces of the insert and the wear particles in the lubricant were subjected to electron and laser microscopic analyses. The mechanical properties of the inserts were evaluated by the small punch test. Results: The MPC grafting increased hydrophilicity and decreased friction torque. In the simulator experiment, the wear of the tibial insert was significantly suppressed in the cross-linked PE (CLPE) insert, and even more dramatically decreased in the MPC-grafted CLPE insert, as compared to that in the non-cross-linked PE insert. Surface analyses confirmed the wear resistance by the cross-linking, and further by the MPC grafting. The particle size distribution was not affected by cross-linking or MPC grafting. The mechanical properties of the insert material remained unchanged during the loading regardless of the cross-linking or grafting. Conclusion: Surface grafting with MPC polymer furnished the PE insert with wear resistance in an artificial knee joint through increased hydrophilicity and decreased friction torque. [Copyright &y& Elsevier]

Most total knee replacement joints consist of a metal femoral component made from a cobalt‐chromium‐ molybdenum (CoCrMo)‐alloy and a tibial component with an ultrahigh molecular weight polyethylene (UHMWPE) bearing surface. Wear of the UHMWPE remains the primary disadvantage of these implants. The allergic potential ascribed to CoCrMo‐alloys is a further concern. Other metallic alloys with and without ceramic coatings are clinically used to avoid these problems. This study compared the mechanical surface properties of an oxidized zirconium alloy with those of cast and wrought CoCrMo and TiAlV6‐4. Additionally, the influence of a titanium nitride (TiN)‐plasma coating on the surface properties was investigated. The composition of the oxidized zirconium layer was analyzed. Micro‐ and macrohardness tests as well as adhesion tests were used to reveal material differences in terms of their abrasive wear potential in artificial joints. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010 [ABSTRACT FROM AUTHOR]

The effects of vitamin E addition on the strain-induced crystallization and molecular chain orientation of ultrahigh molecular weight polyethylene (UHMWPE) were examined in order to clarify the wear mechanism of vitamin E-blended UHMWPE in knee prostheses. The structure changes of vitamin E-blended UHMWPE before and after tensile strain were analyzed by X-ray diffraction, Raman spectroscopy and image correlation method. The vitamin E-blended UHMWPE exhibited lower strain-induced crystallization than virgin UHMWPE but a higher Ic value in Raman spectroscopic analysis. The vitamin E-blended UHMWPE also exhibited a larger percentage of negative areal dilatation under tensile strain. These results suggest that the addition of vitamin E to UHMWPE decreases the strain-induced crystallization and increases the strain-induced orientation of the molecular chains present in the amorphous phase. [ABSTRACT FROM AUTHOR]

Abstract: A passive above knee prosthesis being currently in use does not respond adequately to the needs of daily living activities of an amputee due to its limited functions. Therefore, this study deals with design and testing of an active above knee prosthesis. The essential part of this prosthesis is the knee joint actuator based on active control of basic flexion and extension functions of the knee joint with the motor. The imitation of walking gait pattern by the proposed prosthesis was provided with a trajectory control scheme for the knee joint angle in accordance with the necessity of rule-based control approach. [Copyright &y& Elsevier]

Charcot arthropathy is a type of destructive osteoarthropathy characterized by neurotrophic and sensory disorders. The condition is relatively rare, with an insidious onset, and it is easily misdiagnosed. Total knee arthroplasty (TKA) can cause excessive joint wear, continuous inflammatory stimulation of the prosthesis, postoperative residual cavity, prosthesis loosening and subsidence, peripheral fracture, infection, and other complications. Furthermore, these complications are more likely to occur in patients with Charcot arthropathy because of disease-specific pathological characteristics, when TKA is performed. Therefore, Charcot arthropathy was once a contraindication to TKA. Recently, with the optimization of joint prostheses and the maturity of surgical techniques, more studies have reported successful cases of TKA in patients with Charcot arthropathy. We report a case of Charcot arthropathy in our hospital, and describe the patient's medical history, clinical symptoms, signs, imaging findings, diagnosis, and the entire TKA process, to explore the TKA strategy and prosthesis selection in a patient with Charcot arthropathy.

For the longevity of total knee joint prostheses, we have developed an artificial lubricant using polyethylene glycol (PEG) for the prevention of wear of ultra-high-molecular-weight polyethylene (UHMWPE). In the present study, the lubricative function of this PEG lubricant was evaluated by a wear test using Co-Cr alloy and UHMWPE counter surface samples. As a result, human synovial fluid including the PEG lubricant showed good result regarding the wear volume and a worn surface of UHMWPE. Considering its lubrication mechanism, it is suspected that interaction between the PEG molecules and the proteins in synovial fluid was involved. Since PE molecules are also organic compounds having a hydroxyl group at one or both ends, the albumin and PEG molecule complex would have bound more strongly to the metal oxide surface and UHMWPE surfaces might enhance and stabilize the lubricating film between the contact surfaces under the boundary lubrication. This study suggests that PEG lubricant as an intra-articular viscous supplement has the potential to prevent wear of UHMWPE by mixing with synovial fluid and to contribute to the longevity of knee joint prostheses., (Copyright © 2014 Elsevier Ltd. All rights reserved.)