Background. Stress shielding and wear induced aseptic loosening cause failure in arthroplasty surgery. To improve survivorship, the use of a low modulus, low wearing biomaterial may be a suitable alternative to hard bearing prostheses, such as cobalt chromium (CoCr). There has been considerable research interest in the use of polyetheretherketone (PEEK) based on observed clinical success especially in spinal surgery. This study investigated the wear performance of PEEK, carbon reinforced PEEK (CFR-PEEK) and acetal as bearing materials in an all polymer total knee arthroplasty (TKA) using a unidirectional pin on plate test. Methods. The following material combinations were tested: PEEK vs. UHMWPE, CFR-PEEK vs. UHMWPE, PEEK vs. PEEK, CFR-PEEK vs. PEEK, CoCr vs. UHMWPE, PEEK vs. XLPE, CFR-PEEK vs. CFR-PEEK, PEEK vs. Acetal, Acetal vs. XLPE and CoCr vs. XLPE.Tribological couples tested (Pin vs. Plate) Using a previously validated modification of ASTM F732, 20mm diameter spherically ended pins with a radius of 25mm were articulated against 40mm diameter plates. A load of 1000N was applied to generate a contact stress of about 70MPa similar to contact stresses previously reported in the knee. The lubricant used was 25% newborn calf serum containing 0.3% sodium azide to retard bacteria growth and 20mM EDTA to prevent calcium deposition. Three repeats of pin on plate combinations (including 2 passive soak controls) were tested for 2 million cycles at a cycle frequency of 1Hz and a stroke length of 10 mm. Gravimetric wear was analysed every 250,000 cycles and results converted to volumetric wear using material density. Results. All CFR-PEEK articulations were stopped due to excessive wear of the counter-surfaces. Results showed a linear wear rate of UHMWPE and XLPE plates over the test period. PEEK vs. XLPE showed similar wear rate to metal on polyethylene (MoP) bearings. Conclusion. At stresses representative of the knee, PEEK pins when articulated against XLPE plates generated volumetric wear similar to that noted in MoP bearings

The purpose of the study was to compare the mechanical properties, oxidation and wear resistance of a vitamin E blended and moderately crosslinked polyethylene for total knee arthroplasty (MXE) in comparison with clinically established polyethylene materials. The following polyethylene materials were tested: CPE (30 kGy e-beam sterilized), XLPE (75 kGy gamma crosslinked @ 100°C), ViXLPE (0.1 % vitamin E blended, 80 kGy e-beam crosslinked @ 100°C), and MXE (0.1 % vitamin E blended polyethylene, 30 kGy gamma sterilized). For the different tests, the polyethylene materials were either unaged or artificially aged for two or six weeks according to ASTM F2003-02. The oxidation index was measured based on ASTM F2102 at a 1 mm depth. Small punch testing was performed based on ASTM F2977. Mechanical properties were measured on unaged materials according to ASTM D638. Wear simulation was performed on a load controlled 3 + 1 station knee wear simulator (EndoLab GmbH, Thansau, Germany) capable of reproducing loads and movement of highly demanding activities (HDA) as well as ISO 14243-1 load profiles. The load profiles were applied for 5 million cycles (mc) or delamination of the polyethylene components. Medium size AS e.motion. ®. PS Pro (Aesculap AG, Tuttlingen, Germany) femoral and tibial components with a ZrN-multilayer surface, as well as Columbus. ®. CR cobalt-chrome alloy femoral and tibial components were tested. Particle analysis was performed on the serum samples of the ISO 14243-1 wear simulations based on ISO 17853:2011 and ASTM F1877. The analysis of the mechanical properties show that moderately crosslinked polyethylene (MXE) might be a superior material for total knee arthroplasty applications [Schwiesau et al. 2021]. The addition of vitamin E in a moderately crosslinked polyethylene prevented its oxidation, kept its mechanical characteristics, and maintained a low wear, even under a HDA knee wear simulation

Background. The R3 cementless acetabular system (Smith & Nephew, Memphis, Tennessee, United States) is a modular titanium shell with an asymmetric porous titanium powder coating. It supports cross-linked polyethylene, metal and ceramic liners with several options for the femoral head component. The R3 cup was first marketed in Australia and Europe in 2007. Two recent papers have shown high failure rates of the MoM R3 system with up to 24% (Dramis et al 2014, Hothi et al 2015). There are currently no medium term clinical papers on the R3 acetabular cup. Objectives. The aim of the study is to review our results of the R3 acetabular cup with a minimum of 5 year follow up. Study Design & Methods. Patients who were implanted with the R3 acetabular cup were identified from our centre”s arthroplasty database. Our centre started implanting the R3 acetabular cup in August 2009. For this study, we only included patients with a minimum of 5 year follow up (until June 2011). Over this time period, 293 consecutive THAs were performed in 286 patients, of which 7 were bilateral staged total hip arthroplasties. The primary outcome was revision. The secondary outcomes were the Oxford hip scores and radiographic evaluation. Results. The mean age of the patients was 69.4 years (range 20–100 years). There were 117 males and 169 females in our series. The majority of the total hip arthroplasties in our series were cementless (n=283, 97%) and the rest were hybrid (n=10, 3%). The articulation bearings were as follows: ceramic on ceramic (n=167; 57%), Ceramic on Poly XLPE (n=97; 33%), Oxinium-Poly XLPE (n=19; 6.5%), stainless steel- Poly XLXE (n=10; 3.5%). The mean pre-operative Oxford Hip Score was 23 (range 10–34) and the mean Oxford Hip Score was 40 (range 33–48) at the final follow-up. Radiological evaluation showed an excellent ARA-score in all patients at five years. None of the R3 cups showed osteolysis at final follow up. There were 3 revisions in our series, of which two R3 cup were revised. The risk of revision was 0.28% at 5 years. Using Weibull analysis, it gives a 10-year estimate of 98.8% survival for the R3 cup (95%CI 95.0 to 99.6). Conclusions. Our experience at a district general hospital using the R3 acetabular system with conventional bearings showed high survivorship and is consistent with the allocated Orthopaedic Data Evaluation Panel (ODEP) rating of 5A* as rated in 2015 in the United Kingdom

In 2011, approximately 1.6 million total hip arthroplasties (THAs) were conducted in 27 of the 34 member countries in the Organization for Economic Cooperation and Development (OECD) However, approximately 10–15% of patients still require revision surgery every year. Therefore, new technologies are required to increase the life-spam of the prosthesis from the current 10–15 years to at least 20–30 years. Our strategy focuses on surface modification of the bearing materials with a hydrophilic coating to improve their wear behaviour. These coatings are biocompatible, with high swelling capacity and antifouling properties, mimicking the properties of natural cartilage, i.e. wear resistance with permanent hydrated layer that prevents prosthesis damage. Clear beneficial advantages of this coating have been demonstrated in different conditions and different materials, such as UHMWPE, PEEK, CrCo, Stainless steel, ZTA and Alumina. Using routine tribological experiments, the wear for UHMWPE substrate was decreased by 75% against alumina, ZTA and stainless steel. For PEEK-CFR substrate coated, the amount of material lost against ZTA and CrCo was at least 40% lower. Further experiments on hip simulator adding abrasive particles (1-micron sized aluminium particles) during 3 million cycles, on a total of 6 million, showed a wear decreased of around 55% compared to uncoated UHMWPE and XLPE. In conclusion, CIDETEC‘s coating technology is versatile and can be adapted to protect and improve the tribological properties of different types of surfaces used for prosthesis, even in abrasive conditions