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Adverse reaction to metal debris released from the taper‐trunnion junction of modular metal‐on‐polyethylene (MoP) total hip replacements (THRs) is an issue of contemporary concern. Therefore, a hip simulator was used to investigate material loss, if any, at both the articulating and taper‐trunnion surfaces of five 32‐mm metal‐on‐cross‐linked‐polyethylene THRs for 5 million cycles (Mc) with a sixth joint serving as a dynamically loaded soak control. Commercially available cobalt–chromium–molybdenum femoral heads articulating against cross‐linked polyethylene (XLPE) acetabular liners were mounted on 12/14 titanium (Ti6Al4V) trunnions. Weight loss (mg) was measured gravimetrically and converted into volume loss (mm3) for heads, liners, and trunnions at regular intervals. Additionally, posttest volumetric wear measurements of the femoral tapers were obtained using a coordinate measuring machine (CMM). The surface roughness (Sa) of femoral tapers was measured posttest. After 5 Mc, the mean volumetric wear rate for XLPE liners was 2.74 ± 0.74 mm3/Mc. The CMM measurements confirmed material loss from the femoral taper with the mean volumetric wear rate of 0.045 ± 0.024 mm3/Mc. The Sa on the worn area of the femoral taper showed a significant increase (p < 0.001) compared with the unworn area. No other long‐term hip simulator tests have investigated wear from the taper‐trunnion junction of contemporary MoP THRs. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:156–166, 2020. [ABSTRACT FROM AUTHOR]

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 mm3 from the hip simulator test, and that from the titanium trunnions was 0.29 mm3. 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. [ABSTRACT FROM AUTHOR]

The articulating surfaces of four different sizes of unused pyrolytic carbon proximal interphalangeal prostheses (PIP) were evaluated though measuring several topographical parameters using a white light interferometer: average roughness (Sa); root mean-square roughness (Sq); skewness (Ssk); and kurtosis (Sku). The radii of the articulating surfaces were measured using a coordinate measuring machine, and were found to be: 2.5, 3.3, 4.2 and 4.7 mm for proximal, and 4.0, 5.1, 5.6 and 6.3 mm for medial components. ANOVA was used to assess the relationship between the component radii and each roughness parameter. Sa, Sq and Ssk correlated negatively with radius (p = 0.001, 0.001, 0.023), whilst Sku correlated positively with radius (p = 0.03). Ergo, the surfaces with the largest radii possessed the better topographical characteristics: low roughness, negative skewness, high kurtosis. Conversely, the surfaces with the smallest radii had poorer topographical characteristics. [ABSTRACT FROM AUTHOR]

A recognized issue related to metal-on-metal hip resurfacings is early fracture of the femur. Most theories regarding the cause of fracture relate to clinical factors but an engineering analysis of failed hip resurfacings has not previously been reported. The objective of this work was to determine the wear volumes and surface roughness values of a cohort of retrieved hip resurfacings which were removed due to early femoral fracture, infection and avascular necrosis (AVN). Nine resurfacing femoral heads were obtained following early fracture of the femur, a further five were retrieved due to infection and AVN. All fourteen were measured for volumetric wear using a co-ordinate measuring machine. Wear rates were then calculated and regions of the articulating surface were divided into "worn" and "unworn". Roughness values in these regions were measured using a non-contacting profilometer. The mean time to fracture was 3.7 months compared with 44.4 months for retrieval due to infection and AVN. Average wear rates in the early fracture heads were 64 times greater than those in the infection and AVN retrievals. Given the high wear rates of the early fracture components, such wear may be linked to an increased risk of femoral neck fracture. [ABSTRACT FROM AUTHOR]

Total wrist arthroplasty (TWA) aims to restore pain-free motion to diseased joints. One such TWA, the Motec, has demonstrated good results with acceptable complication rates. It has recently been suggested that the metal-on-carbon fibre reinforced poly ether ether ketone (Mo-CFR-PEEK) version of the Motec TWA be implanted instead of the metal-on-metal version. An explant analysis was undertaken on seven Motec Mo-CFR-PEEK TWAs, revised for a variety of reasons, after a mean time of 2 years in vivo. Compared to a new Motec implant, five of the explanted metal heads and three of the CFR-PEEK cups became smoother in vivo, suggesting self-polishing and negative skewness, indicating some material loss in vivo. Two explanted cups showed indentation marks on their rims and one of these was from component impingement with embedded metallic debris. In the short-term, the articulating surfaces of Motec Mo-CFR-PEEK TWAs did not show major damage. Level of evidence: IV., Competing Interests: Declaration of conflicting interestsThe authors disclosed the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: DJB has a paid consultancy role with Swemac. He receives no royalties for the use of any wrist replacements.

The ReMotion wrist replacement has good short- to medium-term survival with an acceptable complication profile as we previously reported in a cohort of patients with rheumatoid arthritis. We now report the long-term results of the same cohort and details of explant analysis of revisions undertaken for aseptic loosening. A total of 16 wrists were reviewed. Seven prostheses remain in situ with no obvious signs of wear or radiological loosening at a mean follow-up of 15.5 years. Three wrists had been revised: one for infection and two for aseptic loosening. Five patients (six wrists) died 2-9 years after operation from unrelated causes. Explant analysis demonstrated relatively minor wear compared with the published results of the Universal-2 prosthesis. We hypothesize that this may be explained by differences in polyethylene sterilization and prosthetic design. The ReMotion wrist replacement has favourable long-term results in patients with rheumatoid arthritis with a 16-year survival rate of 78%-86%. Level of evidence: IV., Competing Interests: Declaration of conflicting interestsThe authors disclosed the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: The senior clinical author (DJB) has a paid consultancy role with Swemac, a manufacturer of an alternative wrist replacement. He receives no royalties for the use of any wrist replacements.

Single-piece silicone implants dominate metacarpophalangeal joint arthroplasty. The NeuFlex® implant was introduced to improve on the clinical performance of other silicone implants by having a pre-flexed hinge. By visually examining a cohort of 30 explanted NeuFlex® metacarpophalangeal joint prostheses we sought to identify the failure modes of these implants. Seven were not fractured, 11 had fractured across the hinge, nine had fractured at the junction of the distal stem and the hinge, and three showed fractures at both the hinge and at the junction of the distal stem and the hinge. These data may prove helpful in identifying how the performance of single-piece silicone implant designs can be improved.

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.)