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Total hip replacement with metal-on-polymer hip prostheses is the most common treatment for late-stage osteoarthritis. However, the wear debris generated from the polymer acetabular liner remains a problem. Alternative materials with claimed superior wear properties have been proposed to overcome this problem. In this study, the wear behaviour of carbon fibre reinforced polyether ether ketone (CFR PEEK) was investigated under different contact stresses that are observed in the natural hip joint. A 50-station pin-on-disc machine (SuperCTPOD) was used to investigate the wear behaviour of 50 CFR PEEK pins articulated against cobalt chromium (CoCr) discs under five different contact stresses, namely 1.11, 1.38, 1.61, 2.00 and 5.30 MPa. The results showed that the wear rates of the pins did not differ significantly between groups under different contact stresses. In addition, CFR PEEK produced lower wear rates than ultrahigh molecular weight polyethylene and cross-linked polyethylene. However, the weight of the CoCr discs was found to decrease significantly at the end of the wear test, which was indicative of metallic wear. The findings of this study indicated that, despite having relatively low wear rates, CFR PEEK is not a good alternative to be utilised against orthopaedic metals., (Copyright © 2019. Published by Elsevier Ltd.)

Wear of polyethylene is a current limitation in the long-term survival of reverse shoulder arthroplasties (RSAs). The purpose of this study was to investigate, for the first time, the influence of a combination of clinically relevant activities of daily living (ADLs) as patterns of motion and loading on the wear of ultra-high molecular-weight polyethylene (UHMWPE) in RSA. This physiological combined cycle, termed "repeated-motion-load", was applied on four new samples of a commercially available reverse shoulder prosthesis for five million cycles using the unique Newcastle Shoulder Wear Simulator. This resulted in a mean wear rate of 12.0 ± 3.9 mm 3 /million cycles for the UHMWPE components in combination with metallic glenospheres, while the average articulating UHMWPE surface roughness reduced from 692 ± 132 nm Sa to 42 ± 29 nm Sa., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Ceramic-on-ceramic (CoC) total hip replacements (THR) have a substantially lower wear rate than metal-on-polyethylene (MoP) hips, as shown by hip simulator testing. However, the revision rates of CoC and MoP hips are comparable. To try and explain this discrepancy the wear, at both the bearing surfaces and taper-trunnion interface of 36 mm BIOLOXdelta CoC THRs, mounted on 12/14 titanium (Ti6Al4V) trunnions was investigated using a hip simulator (n = 3) and a dynamically loaded CoC sample in a separate test station. Wear was assessed gravimetrically and surface roughness measurements of the articulating and taper surfaces taken at regular intervals. Scanning electron microscopy, surface roughness, and gravimetric measurements of trunnions was performed. After 5 million cycles, the mean total wear from the ceramic articulating surfaces was 0.25 mm 3 from the hip simulator test, and that from the titanium trunnions was 0.29 mm 3 . This metal wear may provide an explanation for adverse reaction to metal debris found in contemporary CoC hip joints. It is therefore vital to consider taper-trunnion wear in preclinical testing of artificial hip joints. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1199-1209, 2019., (© 2018 Wiley Periodicals, Inc.)

Generation of wear debris and wear particle-induced osteolysis are the main limitations of metal-on-polyethylene artificial joints. Cross-linked polyethylene has been recently used, particularly in hip replacements, as an alternative material to conventional ultrahigh molecular weight polyethylene due to its superior wear resistance. This study focused on the wear behaviour of cross-linked polyethylene under different contact stresses in order to make interpretations of its long-term in-vivo performance. A 50-station SuperCTPOD (pin-on-disc) machine was used to investigate the influence of contact stress on the wear of cross-linked polyethylene pins which were articulated against cobalt chromium discs. It was found that the wear rate of cross-linked polyethylene was lower at higher contact stresses.

It has been proposed that an increased surface roughness of the femoral components of Total Knee Replacements (TKRs) may be a contributing factor to the accelerated wear of the polyethylene (PE) bearing and ultimately prosthesis failure. Oxidised Zirconium was introduced to the orthopaedic market in an attempt to reduce PE wear associated failures and increase the longevity of the prosthesis. In this study, non-contacting profilometry was used to measure the surface roughness of the femoral components of 6 retrieved TKRs (3 Oxidised Zirconium (OxZr) and 3 Cobalt Chromium alloy (CoCr) femoral components) and 2 as-manufactured femoral components (1 OxZr and 1 CoCr). A semi-quantitative method was used to analyse the damage on the retrieved PE components. The S a values for the retrieved OxZr femoral components (S a = 0.093 µm ± 0.014) and for the retrieved CoCr femoral components (S a = 0.065 µm ± 0.005) were significantly greater (p < .05) than the roughness values for the as-manufactured femoral components (OxZr S a = 0.061 µm ± 0.004 and CoCr S a = 0.042 µm ± 0.003). No significant difference was seen between the surface roughness parameters of the retrieved OxZr and retrieved CoCr femoral components. There was no difference between the PE component damage scores for the retrieved OxZr TKRs compared to the retrieved CoCr TKRs. These results agree with other studies that both OxZr and CoCr femoral components roughen during time in vivo but the lack of difference between the surface roughness measurements of the two materials is in contrast to previous topographical reports. Further analysis of retrieved OxZr TKRs is recommended so that a fuller appreciation of their benefits and limitations be obtained., (Copyright © 2017 IPEM. All rights reserved.)

Clinical results of the PyroCarbon proximal interphalangeal joint replacement are inconsistent with various complications reported. To address this, in vitro testing was conducted using finger joint simulators. Two PyroCarbon proximal interphalangeal prostheses were tested in a lubricant of dilute bovine serum to 5 × 10(6) cycles of flexion-extension (90°-30°) with dynamic forces of 10 N applied. At intervals of 3000 cycles testing ceased and a static load of 100 N was applied to simulate gripping. In addition, two 'control' prostheses were immersed alongside the test prostheses to account for lubricant absorption. Wear and roughness averages (Ra) were measured every 1 × 10(6) cycles. Minimal wear for all of the components was measured with a negligible increase in Ra for most of the components. One condyle of one component increased in Ra over the 5 × 10(6) cycles with a value above the recommended 50 nm. Unidirectional marks were visible on the condyle from micrographs, consistent with an abrasive wear mode., (© IMechE 2015.)

In the present study, numerical and experimental wear investigations on reverse total shoulder arthroplasties (RTSAs) were combined in order to estimate specific wear coefficients, currently not available in the literature. A wear model previously developed by the authors for metal-on-plastic hip implants was adapted to RTSAs and applied in a double direction: firstly, to evaluate specific wear coefficients for RTSAs from experimental results and secondly, to predict wear distribution. In both cases, the Archard wear law (AR) and the wear law of UHMWPE (PE) were considered, assuming four different k functions. The results indicated that both the wear laws predict higher wear coefficients for RTSA with respect to hip implants, particularly the AR law, with k values higher than twofold the hip ones. Such differences can significantly affect predictive wear model results for RTSA, when non-specific wear coefficients are used. Moreover, the wear maps simulated with the two laws are markedly different, although providing the same wear volume. A higher wear depth (+51%) is obtained with the AR law, located at the dome of the cup, while with the PE law the most worn region is close to the edge. Taking advantage of the linear trend of experimental volume losses, the wear coefficients obtained with the AR law should be valid despite having neglected the geometry update in the model., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Although the market for replacement of diseased metacarpophalangeal (MCP) joints is dominated by single-piece silicone prostheses, several two-piece designs have been implanted. One such is the Digital Joint Operative Arthroplasty (DJOA) which consists of a part-spherical stainless steel metacarpal component which articulates within a matching concave phalangeal component made of ultra high molecular weight polyethylene (UHMWPE). A DJOA MCP prosthesis was tested using a clinically-validated finger simulator while a second DJOA prosthesis acted as a statically-loaded soak-control. Testing ran to 7.1 million cycles of flexion-extension. It was found that the UHMWPE components, both test and control, gained in weight by a similar amount. Therefore apparently there was no wear of the test components. However, the initial and final surface finish values of the test stainless steel metacarpal head were relatively high. Calculations based on this roughness data, plus recent dynamically-loaded soak data, may explain the apparent lack of wear.