Cross-linked Ultra-high Molecular Weight Polyethylene Research Articles

Characterizing Surface Morphological and Chemical Properties of Commonly Used Orthopedic Implant Materials and Determining Their Clinical Significance.

The goal of the study was to compare the surface characteristics of typical implant materials used in orthopedic surgery and traumatology, as these determine their successful biointegration. The morphological and chemical structure of Vortex plate anodized titanium from commercially pure (CP) Grade 2 Titanium (Ti2) is generally used in the following; non-cemented total hip replacement (THR) stem and cup Ti alloy (Ti6Al4V) with titanium plasma spray (TPS) coating; cemented THR stem Stainless steel (SS); total knee replacement (TKR) femoral component CoCrMo alloy (CoCr); cemented acetabular component from highly cross-linked ultrahigh molecular weight polyethylene (HXL); and cementless acetabular liner from ultrahigh molecular weight polyethylene (UHMWPE) (Sanatmetal, Ltd., Eger, Hungary) discs, all of which were examined. Visualization and elemental analysis were carried out by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Surface roughness was determined by atomic force microscopy (AFM) and profilometry. TPS Ti presented the highest Ra value (25 ± 2 μm), followed by CoCr (535 ± 19 nm), Ti2 (227 ± 15 nm) and SS (170 ± 11 nm). The roughness measured in the HXL and UHMWPE surfaces was in the same range, 147 ± 13 nm and 144 ± 15 nm, respectively. EDS confirmed typical elements regarding the investigated prosthesis materials. XPS results supported the EDS results and revealed a high % of Ti4+ on Ti2 and TPS surfaces. The results indicate that the surfaces of prosthesis materials have significantly different features, and a detailed characterization is needed to successfully apply them in orthopedic surgery and traumatology.

Effect of Component Position and Inward–Outward Rotation on the Wear of Different Ultra-High Molecular Weight Polyethylenes in an Orbital Bearing Type Hip Joint Simulator

The orbital bearing machine is the world’s most widely used hip joint simulator design for wear testing of prosthetic hips. It has been used with inverted and anatomic component position and with and without inward–outward rotation. Still the effect of component position on the wear of the most widely used bearing material, ultrahigh molecular weight polyethylene (UHMWPE), has not been studied directly. With a modified orbital bearing machine, the effects of the component position, anatomic versus inverted, and of the inward–outward rotation, present versus absent, on polyethylene wear were studied for the first time. Acetabular liners made from different ultra-high molecular weight polyethylenes articulated against alumina femoral heads in alpha calf serum. The inverted position resulted in the most realistic, burnished appearance of the polyethylene bearing surfaces. In the inverted position, the wear rate decreased with increasing gamma dose that is known to improve wear resistance by cross-linking. In the anatomic position, the bearing surface was not always entirely burnished. The wear was similar with and without inward–outward rotation. The mean wear rate of vitamin E stabilized highly cross-linked ultra-high molecular weight polyethylene was close to clinical observations. Clinically relevant wear could be produced with the orbital bearing machine for both established and advanced bearing materials. The inverted position appeared preferable in the orbital bearing machine. Inward–outward rotation did not appear important.

Primary stability of a proximally coated and tapered stem.

The aim of this prospective cohort study was to evaluate the early migration of the TriFit cementless proximally coated tapered femoral stem using radiostereometric analysis (RSA). A total of 21 patients (eight men and 13 women) undergoing primary total hip arthroplasty (THA) for osteoarthritis of the hip were recruited in this study and followed up for two years. Two patients were lost to follow-up. All patients received a TriFit stem and Trinity Cup with a vitamin E-infused highly cross-linked ultra-high molecular weight polyethylene liner. Radiographs for RSA were taken postoperatively and then at three, 12, and 24 months. Oxford Hip Score (OHS), EuroQol five-dimension questionnaire (EQ-5D), and adverse events were reported. At two years, the mean subsidence of the head and tip for the TriFit stem was 0.38 mm (SD 0.32) and 0.52 mm (SD 0.36), respectively. The total migration of the head and tip was 0.55 mm (SD 0.32) and 0.71 mm (SD 0.38), respectively. There were no statistically significant differences between the three to 12 months' migration (p = 0.105) and 12 to 24 months' migration (p = 0.694). The OHS and EQ-5D showed significant improvements at two years. The results of this study suggest that the TriFit femoral stem achieves initial stability and is likely to be stable in the mid and long term. A long-term outcome study is required to assess late mechanisms of failure and the effects of bone mineral density (BMD) related changes. Cite this article: Bone Joint J2021;103-B(4):644-649.

Study of wear performance of crosslinking UHMWPE acetabular liner for artificial hip joint made from CNC milling

Crosslinked ultra-high molecular weight polyethylene (UHMWPE) is a preferred material used as a bearing material in the artificial hip joint. The purpose of this study was to analyze the effect of dose cross-linking acetabular liner manufactured by CNC milling on wear depth. The wear test is carried out with a tribometer machine by loading the acetabular liner in a certain cycle. The test results found that specimens given a crosslink dose of 50 kGy with a load of 800 N resulted in a greater wear depth compared to specimens given a crosslink dose of 100 kGy with a load of 800 N. Specimen with crosslink dose 50 kGy yield greater wear depth than specimens given a crosslink dose of 100 kGy. Based on these results it can be concluded that the greater the crosslink dose given to the specimen will increase the wear resistance of the specimen so that the test results in a smaller wear depth.

Computational Wear Simulation on Cross-linked Ultra-high Molecular Weight Polyethylene Artificial Hip Joints

Computational Wear Simulation on Cross-linked Ultra-high Molecular Weight Polyethylene Artificial Hip Joints

Multiwall Carbon Nanotube Composites as Artificial Joint Materials.

Because ultrahigh-molecular-weight polyethylene (UHMWPE) is susceptible to frictional wear when used in sliding members of artificial joints, it is common practice to use cross-linked UHMWPE instead. However, cross-linked UHMWPE has low impact resistance; implant breakage has been reported in some cases. Hence, sliding members of artificial joints pose a major trade-off between wear resistance and impact resistance, which has not been resolved by any UHMWPE. On the other hand, multiwall carbon nanotubes (MWCNTs) are used in industrial products for reinforcement of polymeric materials but not used as biomaterials because of their unclear safety. In the present study, we attempted to solve this trade-off issue by complexing UHMWPE with MWCNTs. In addition, we assessed the safety of these composites for use in sliding members of artificial joints. The results showed the equivalence of MWCNT/UHMWPE composites to cross-linked UHMWPE in terms of wear resistance and to non-cross-linked UHMWPE in terms of impact resistance. In addition, all MWCNT/UHMWPE composites examined complied with the requirements of biosafety testing in accordance with the ISO10993-series specifications for implantable medical devices. Furthermore, because MWCNTs can occur alone in wear dust, MWCNTs in an amount of about 1.5 times that contained in the dust produced from 50 years of wear (in the worst case) were injected into rat knees, which were monitored for 26 weeks. Although mild inflammatory reactions occurred in the joints, the reactions soon became quiescent. In addition, the MWCNTs did not migrate to other organs. Furthermore, MWCNTs did not exhibit carcinogenicity when injected into the knees of mice genetically modified to spontaneously develop cancer. The MWCNT/UHMWPE composite is a new biomaterial expected to be safe for clinical applications in both total hip arthroplasty and total knee arthroplasty as the first sliding member of artificial joints to have both high wear resistance and high impact resistance.

Global perspective of Innovation in Hip and Knee Replacement in 2020

The knowledge of new technologies and current concepts are primordial in orthopaedic surgery. That is necessary to progress and improve our current practice continuously. This special issue of SICOT-J about hip and knee arthroplasty consists of 12 original articles on orthopaedic advances or controversial subjects, such as robotic-assisted surgeries, alignment of total knee arthroplasty (TKA), cementless tibial implants, polyethylene or ceramic in total hip arthroplasty, return to sport and arthroplasty… Kouyoumdjian et al. reported the current concepts in robotic-assisted total hip arthroplasty. The advantages and the impact of robotic-assisted surgery in knee arthroplasty has been often described in recent literature. Nevertheless, the impact of robotic-assisted system for hip arthroplasty is less known. This paper brings a clear state of knowledge about this new technology [1]. The materials used in total hip arthroplasty remain a relevant issue. In a comparative study on highly cross-linked polyethylene (XLPE) and ultra-high molecular weight polyethylene (UHMWPE), Carli et al. showed that annual linear wear rates were significantly higher with UHMWPE (0.21 mm/year) compared to XLPE (0.05 mm/year) in a simple mobility in total hip arthroplasty [2]. XLPE coupled with oxidized zirconium femoral heads had minimal wear and no osteolysis at 10-year follow-up. In a relevant update, Langlois and Hamadouche reported the major and recent knowledges on crosslinked polyethylene in total hip arthroplasty [3]. While Bauwens et al. reported the earlier results of ceramic-on-ceramic bearing in total hip arthroplasty by direct anterior approach [4]. Neri et al., described with a pragmatic way the tips and tricks of the dual mobility in total hip arthroplasty [5]. This article brings interesting and relevant advices and concepts to improve the right use of dual mobility. The surgical approach in total hip arthroplasty can also evolve, but this evolution can become difficult according to the complexity of surgical techniques. Foissey et al. have described the learning curve of the anterior approach in total hip arthroplasty according to the surgeon experience [6]. Five published articles reported interesting results about knee arthroplasty. Pacoret et al. described the survival rate of the tibial component in cementless TKA at a mean follow-up of 8 years, with a minimal follow-up of 5 years [7]. Indeed, it is now accepted that cementless implantation of the femoral component provides equivalent results to cemented one, however, the optimal fixation method of the tibial component remains controversial. This comparative study reports a very satisfying survival rate in both groups cemented and cementless TKA. In addition to implants fixation, two articles introduce the impact of alignment in TKA. In a systematic review, Sappey-Marinier et al. assessed five prospective randomized controlled trials comparing clinical and radiological outcomes, and complications in TKA with kinematic alignment and mechanical alignment [8]. Kinematic alignment in TKA achieved clinical and radiological results similar to those of mechanical alignment. The complication rate was not increased. Assi et al. were warning that the intra-medullary guide can yield sub-optimal corrections, particularly for severe tibial varus in TKA [9]. The osteotomies around the knee can impact the surgical strategy of TKA and their outcomes. In a relevant systematic review, Luceri et al. reported the results of five useful studies on TKA after distal femoral osteotomy [10]. They concluded on the complexity of this surgery and the need of specific technical tips and tricks to obtain an accurate knee balancing. But future prospective studies and comparative trials are yet necessary to address the impact of distal femoral osteotomy in knee replacement surgery. In the last study, Plassard et al. described the return to sport after TKA and assessed its predictive factors in a large cohort of TKA [11]. Preoperative condition and activity are the two most significant predictive factors for return to sport. The current concepts and innovations can also settle in the treatment of prosthetic-joint infection. In a didactic article, Ferry et al. described the medical innovations to maintain the function in patients with chronic prosthetic-joint infection for whom explantation is not desirable: phage therapy and phage lysins [12]. There is no doubt that these technologies and current concepts are here to stay and as they improve, they will change the operating theatre of the future and the outcomes for our patients. We hope that you will enjoy reading this special issue of SICOT-J about hip and knee arthroplasty. Good reading.

VitaminE-blended versus conventional polyethylene liners in prostheses : Prospective, randomized trial with 3-year follow-up.

Despite continuous technical improvements, polyethylene wear debris induced periprosthetic osteolysis remains the main cause for failure of hip arthroplasty. Progressive oxidation of polyethylene was identified as another risk factor for material failure. To overcome this problem, antioxidants such as vitamin E (alpha-tocopherol) were supplemented by diffusion into the latest generation of polyethylene liners. The purpose of the present study was to investigate the clinical outcome of patients treated with vitaminE blended highly cross-linked ultra-high molecular weight polyethylene liners (UHMWPE-XE) in comparison with conventional UHMWPE‑X liners by evaluating patient-reported outcome measures (PROM's) at 3‑year follow-up. Atotal of 143patients were recruited into this prospective, randomized trial in our academic center. Three years after implantation, 101 patients were examined in the outpatient clinic for follow-up. Of these, 51 (50.5%) received UHMWPE-XE and 50 (49.5%) UHMWPE‑X liners. Clinical outcome was evaluated using Harris-Hip-Score (HHS) UCLA-Score and Hip Disability and Osteoarthritis Outcome Score (HOOS). There was asignificant improvement in all PROM's at one- and three-year follow-up compared to the status before implantation. PROM's did not differ significantly between the first and third year follow-up. Both liner groups showed an equal clinical outcome. The present study demonstrates that the supplementation of vitaminE to polyethylene liners is reliable and safe without showing higher complication rates compared with conventional polyethylene liners. The shortterm clinical outcome of vitamin E-blended (UHMWPE‑XE) is equivalent to those of conventional highly cross-linked polyethylene liners.

Effects of vitamin E incorporation in polyethylene on oxidative degradation, wear rates, immune response, and infections in total joint arthroplasty: a review of the current literature.

Highly cross-linked ultrahigh molecular weight polyethylene (UHMWPE) was introduced to decrease wear debris and osteolysis. During cross-linking, free radicals are formed, making highly cross-linked polyethylene vulnerable to oxidative degradation. In order to reduce this process, anti-oxidant vitamin E can be incorporated in polyethylene. This review provides an overview of the effects of vitamin E incorporation on major complications in total joint arthroplasty: material failure due to oxidative degradation, wear debris and subsequent periprosthetic osteolysis, and prosthetic joint infections. Secondly, this review summarizes the first clinical results of total hip and knee arthroplasties with vitamin E incorporated highly cross-linked polyethylene. Based on in vitro studies, incorporation of vitamin E in polyethylene provides good oxidative protection and preserves low wear rates. Incorporation of vitamin E may have the beneficial effect of reduced inflammatory response to its wear particles. Some microorganisms showed reduced adherence to vitamin E-incorporated UHMWPE; however, clinical relevance is doubtful. Short-term clinical studies of total hip and knee arthroplasties with vitamin E-incorporated highly cross-linked UHMWPE reported good clinical results and wear rates similar to highly cross-linked UHMWPE without vitamin E.

Enhanced oxidation stability of highly cross-linked ultrahigh molecular weight polyethylene by tea polyphenols for total joint implants

Despite being currently state-of-the-art to prevent the oxidation of irradiated ultrahigh molecular weight polyethylene (UHMWPE) bearings, vitamin E (VE) poses concerns in the loss of cross-linking efficiency and is limited to be used at very low concentrations. It thus emphasizes the urgent demand for more efficient stabilizers. In this study, oxidation stability of highly cross-linked UHMWPE was demonstrated to be enhanced by tea polyphenols, such as lipid-soluble tea polyphenols (lsPPT), epigallocatechin gallate (EGCG), and lipid-soluble epigallocatechin gallate (lsEGCG). These antioxidants were blended with UHMWPE granules and consolidated by compression molding prior to E-beam irradiation. The presence of tea polyphenols substantially prolonged oxidation induction time of the irradiated UHMWPE before and after accelerated aging. Especially, lsEGCG was significantly superior to VE in terms of stabilizing capacity. Explained by the hydrogen donation mechanism, tea polyphenols with multiple phenolic hydroxyls could scavenge more radiation-induced free radicals than VE with only one phenolic hydroxyl, which was verified by the electron spin resonance spectra. Intriguingly, tea polyphenols showed less inhibitive effect on the cross-link density of irradiated UHMWPE than VE. Besides, there is no significant difference in crystallinity, mechanical performance as well as in vitro biocompatibility between the irradiated UHMWPE stabilized by tea polyphenols and VE. These findings highlight tea polyphenols, especially lsEGCG, are promising alternatives to extend the life span of UHMWPE implants.

Finite Element Analysis to Probe the Influence of Acetabular Shell Design, Liner Material, and Subject Parameters on Biomechanical Response in Periprosthetic Bone.

The implant stability and biomechanical response of periprosthetic bone in acetabulum around total hip joint replacement (THR) devices depend on a host of parameters, including design of articulating materials, gait cycle and subject parameters. In this study, the impact of shell design (conventional, finned, spiked, and combined design) and liner material on the biomechanical response of periprosthetic bone has been analyzed using finite element (FE) method. Two different liner materials: high density polyethylene-20% hydroxyapatite-20% alumina (HDPE-20%HA-20%Al2O3) and highly cross-linked ultrahigh molecular weight polyethylene (HC-UHMWPE) were used. The subject parameters included bone condition and bodyweight. Physiologically relevant load cases of a gait cycle were considered. The deviation of mechanical condition of the periprosthetic bone due to implantation was least for the finned shell design. No significant deviation was observed at the bone region adjacent to the spikes and the fins. This study recommends the use of the finned design, particularly for weaker bone conditions. For stronger bones, the combined design may also be recommended for higher stability. The use of HC-UHMWPE liner was found to be better for convensional shell design. However, similar biomechanical response was captured in our FE analysis for both the liner materials in case of other shell designs. Overall, the study establishes the biomechanical response of periprosthetic bone in the acetabular with preclinically tested liner materials together with new shell design for different subject conditions.

Mechanical wear and oxidative degradation analysis of retrieved ultra high molecular weight polyethylene acetabular cups.

The number of revision joint replacements has been increasing substantially over the last few years. Understanding their failure mechanism is extremely important for improving the design and material selection of current implants. This study includes ten retrieved and four new mildly cross-linked ultra-high molecular weight polyethylene (UHMWPE) acetabular liners. Among them, most of the prostheses (n = 5) were reported to be revised and replaced due to aseptic loosening, followed by painful joint (n = 2), dislocation (n = 1), intra articular ossification (n = 1), combination of wear (liner) and osteolysis (stem) (n=1). Surface deviations (wear, material inflation and roughness), oxidative degradation and change of material properties were measured using micro-computed tomography (micro-CT) scan, 3D laser scanning microscopy, raman spectroscopy and nanoindentation, respectively. Prostheses having eccentric worn areas had much higher linear wear rates (228.01 ± 35.51µm/year) compared to that of centrically worn prostheses (96.71 ± 10.83µm/year). Oxidation index (OI) showed similar trends to the surface penetration depth. Among them, sample 10 exhibited the highest OI across the contact area and the rim of the cup liner. It also had the lowest hardness/elasticity ratio. Overall, wear and creep, oxidative degradation and reduced hardness/elasticity ratio all contributed to the premature failure of the UHMWPE acetabular cup liners.

A comprehensive combined experimental and computational framework for pre-clinical wear simulation of total knee replacements.

A more robust pre-clinical wear simulation framework is required in order to simulate wider and higher ranges of activities, observed in different patient populations such as younger more active patients. Such a framework will help to understand and address the reported higher failure rates for younger and more active patients (National_Joint_Registry, 2016). The current study has developed and validated a comprehensive combined experimental and computational framework for pre-clinical wear simulation of total knee replacements (TKR).The input mechanical (elastic modulus and Poisson’s ratio) and wear parameters of the moderately cross-linked ultra-high molecular weight polyethylene (UHMWPE) bearing material were independently measured from experimental studies under realistic test conditions, similar to the loading conditions found in the total knee replacements. The wear predictions from the computational wear simulation were validated against the direct experimental wear measurements for size 3 Sigma curved total knee replacements (DePuy, UK) in an independent experimental wear simulation study under three different daily activities; walking, deep squat, and stairs ascending kinematic conditions.The measured compressive mechanical properties of the moderately cross-linked UHMWPE material were more than 20% lower than that reported in the literature under tensile test conditions. The pin-on-plate wear coefficient of moderately cross-linked UHMWPE was significantly dependant of the contact stress and the degree of cross-shear at the articulating surfaces.The computational wear predictions for the TKR from the current framework were consistent and in a good agreement with the independent full TKR experimental wear simulation measurements, with 0.94 coefficient of determination of the framework. In addition, the comprehensive combined experimental and computational framework was able to explain the complex experimental wear trends from the three different daily activities investigated. Therefore, such a framework can be adopted as a pre-clinical simulation approach to optimise different designs, materials, as well as patient’s specific total knee replacements for a range of activities.

Hip and Knee Arthroplasty in Osteoarthritis

Osteoarthritis (OA) of the hip and knee continues to increase in prevalence with the increasing age of our population. This condition is characterized by joint pain, stiffness, and limitations in activities of daily living. Management options are initially aimed at preventing the progression of disease and delaying the need for total joint arthroplasty (TJA). This includes nonoperative measures, as well as surgical interventions, including arthroscopy, osteotomy, and arthrodesis. However, once patients fail alternative therapy, TJA is indicated. Total knee arthroplasty (TKA) and total hip arthroplasty (THA) are highly effective procedures at reducing pain and improving functional status. Patients report high satisfaction rates after TJA and experience minimal complications. Moreover, these procedures are cost effective. Significant research into patient-specific implants (PSI) and computer-navigation-assisted surgery shows improved component positioning; however, further research is needed to determine the clinical effect of this innovation. Wear rates in both TKA and THA have improved significantly over the past decade, with highly cross-linked ultra-high molecular-weight polyethylene showing promising results. New minimally invasive surgical techniques are also showing excellent short-term results, but long-term data is still lacking. Overall, hip and knee OA is a debilitating condition that can be effectively managed with TKA or THA. Indications continue to expand for these procedures and innovation continues to aim for improved outcomes.

Graphene oxide enhanced, radiation cross-linked, vitamin E stabilized oxidation resistant UHMWPE with high hardness and tensile properties

A method for enhancing the micro-hardness and tensile properties of cross-linked ultrahigh molecular weight polyethylene (UHMWPE) by radiation cross-linking after adding vitamin-E (VE) and graphene oxide (GO) was reported.

High temperature homogenization improves impact toughness of vitamin E-diffused, irradiated UHMWPE

Diffusion of vitamin E into radiation cross-linked ultrahigh molecular weight polyethylene (UHMWPE) is used to increase stability against oxidation of total joint implant components. The dispersion of vitamin E throughout implant preforms has been optimized by a two-step process of doping and homogenization. Both of these steps are performed below the peak melting point of the cross-linked polymer (<140°C) to avoid loss of crystallinity and strength. Recently, it was discovered that the exposure of UHMWPE to elevated temperatures, around 300°C, for a limited amount of time in nitrogen, could improve the toughness without sacrificing wear resistance. We hypothesized that high temperature homogenization of antioxidant-doped, radiation cross-linked UHMWPE could improve its toughness. We found that homogenization at 300°C for 8 h resulted in an increase in the impact toughness (74 kJ/m2 compared to 67 kJ/m2 ), the ultimate tensile strength (50 MPa compared to 43 MPa) and elongation at break (271% compared to 236%). The high temperature treatment did not compromise the wear resistance or the oxidative stability as measured by oxidation induction time. In addition, the desired homogeneity was achieved at a much shorter duration (8 h compared to >240 h) by using high temperature homogenization. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1343-1347, 2017.

Biotribological behaviour of Vitamin E-blended highly cross-linked UHMWPE in a hip joint simulator

Purpose The purposes of this paper are to investigate the biotribological behaviour of Vitamin E-blended highly cross-linked ultra-high molecular weight polyethylene (HXL-UHMWPE) under multi-directional motion by using a CUMT II artificial joint hip simulator and compare it with HXL-UHMWPE and conventional UHMWPE. Design/methodology/approach The biotribological behaviour of conventional, highly cross-linked and Vitamin E-blended highly cross-linked UHMWPE acetabular cups counterfaced with CoCrMo alloy femoral head under multi-directional motion were investigated by using CUMT-II artificial hip joint simulator for one-million walking cycles. The test environment was at 36.5 ± 0.5°C and 25 per cent bovine serum was used as lubricant. A Paul cycle load with a peak of 784 N was applied; the motion and loading were synchronized at 1 Hz. Findings The wear resistance of Vitamin E-blended highly cross-linked UHMWPE was significantly higher than that of highly cross-linked and conventional UHMWPE. The wear marks observed from the worn surface of UHMWPE were multi-directional, with no dominant wear direction. Only abrasion occurred on the surface of Vitamin E-blended highly cross-linked UHMWPE, while yielding and accumulated plastic flow processes occurred on the surface of conventional UHMWPE and flaking-like facture and abrasion occurred on the surface of highly cross-linked UHMWPE. Originality/value Besides the prevention of oxidative degradation, blending with Vitamin E can also reduce the incidence of fatigue crack occurred in the surface layer of HXL-UHMWPE samples. Therefore, the wear resistance of HXL-UHMWPE under multi-directional motion can be further enhanced by blending with Vitamin E.

Effect of high temperature melting on radiation cross-linked UHMWPE

Effect of high temperature melting on radiation cross-linked UHMWPE

Early Fracture of a Vitamin-E-Infused, Highly Cross-Linked Polyethylene Liner After Total Hip Arthroplasty: A Case Report.

A vitamin-E-infused, highly cross-linked ultra-high molecular weight polyethylene (HXLPE) acetabular liner fractured without trauma less than twelve months after its implantation in a seventy-one-year-old woman. The remelting process utilized in the production of many commercially available HXLPE acetabular liners causes an immediate reduction in the fracture toughness of the material; however, it provides the benefit of oxidative stability, which prevents the loss of beneficial mechanical properties over time. Vitamin-E-infused HXLPE avoids the immediate decrease in fracture toughness by avoiding the remelting process. The case of our patient demonstrates that this material still can experience catastrophic failure despite acceptable component positioning.

Study on the Wettability and Tribological Behavior of Different Polymers as Bearing Materials for Cervical Prosthesis

Tribological behaviors of four polymers (conventional and cross-linked UHMWPE, conventional and glass fiber-reinforced PEEK) articulated with Ti6Al4V ball were studied under both dry sliding and 25% bovine serum lubrication. The hardness, static contact angle, surface damage topography, and wear parameter of wear scar were tested. Both cross-linked process of UHMWPE and glass fiber-reinforced treatment of PEEK improved wettability while they did not increase hardness. PEEK revealed higher surface hardness and better wettability than UHMWPE. The dominant wear mechanisms for UHMWPE were plastic deformation and fatigue wear while the failure mechanisms were severe adhesive and abrasive wear for PEEK. Cross-linked process of UHMWPE could form multi-molecular arrangement and reduce stratification, also decreasing friction coefficient and wear rate in both dry sliding and lubrication conditions. However, glass fiber-reinforced treatment of PEEK only decreased its friction coefficient and wear rate in dry condition, which was closely related to the function and wear mechanism of glass fiber. Cross-linked UHMWPE revealed the lowest friction coefficient and wear rate under lubrication condition, which was attributed to the cross-linked treatment and the formation of both protein adsorption film and lubrication film. Hence, cross-linked UHMWPE may be an alternative polymer for use as artificial cervical disc bearing material when it articulated with Ti6Al4V.