BackgroundPrevious studies regarding modular head-neck taper corrosion were largely based on cobalt chrome (CoCr) alloy femoral heads. Less is known about head-neck taper corrosion with ceramic femoral heads.Questions/purposesWe asked (1) whether ceramic heads resulted in less taper corrosion than CoCr heads; (2) what device and patient factors influence taper fretting corrosion; and (3) whether the mechanism of taper fretting corrosion in ceramic heads differs from that in CoCr heads.MethodsOne hundred femoral head-stem pairs were analyzed for evidence of fretting and corrosion using a visual scoring technique based on the severity and extent of fretting and corrosion damage observed at the taper. A matched cohort design was used in which 50 ceramic head-stem pairs were matched with 50 CoCr head-stem pairs based on implantation time, lateral offset, stem design, and flexural rigidity.ResultsFretting and corrosion scores were lower for the stems in the ceramic head cohort (p = 0.03). Stem alloy (p = 0.004) and lower stem flexural rigidity (Spearman’s rho = −0.32, p = 0.02) predicted stem fretting and corrosion damage in the ceramic head cohort but not in the metal head cohort. The mechanism of mechanically assisted crevice corrosion was similar in both cohorts although in the case of ceramic femoral heads, only one of the two surfaces (the male metal taper) engaged in the oxide abrasion and repassivation process.ConclusionsThe results suggest that by using a ceramic femoral head, CoCr fretting and corrosion from the modular head-neck taper may be mitigated but not eliminated.Clinical RelevanceThe findings of this study support further study of the role of ceramic heads in potentially reducing femoral taper corrosion.

Cobalt-chromium-molybdenum alloy, used for over four decades in orthopedic implants, may corrode and release wear debris into the body during use. These degradation products may stimulate immune and inflammatory responses in vivo. We report here on evidence of direct inflammatory cell-induced corrosion of human implanted and retrieved CoCrMo implant surfaces. Corrosion morphology on CoCrMo implant surfaces, in unique and characteristic patterns, and the presence of cellular remnants and biological materials intimately entwined with the corrosion indicates direct cellular attack under the cell membrane region of adhered and/or migrating inflammatory cells. Evidence supports a Fenton-like reaction mechanism driving corrosion in which reactive oxygen species are the major driver of corrosion. Using in vitro tests, large increases in corrosion susceptibility of CoCrMo were seen (40 to 100 fold) when immersed in phosphate buffered saline solutions modified with hydrogen peroxide and HCl to represent the chemistry under inflammatory cells. This discovery raises significant new questions about the clinical consequences of such corrosion interactions, the role of patient inflammatory reactions, and the detailed mechanisms at play.

The objective of this article is to provide an up-to-date overview of zirconia-toughened alumina (ZTA) components used in total hip arthroplasties. The structure, mechanical properties, and available data regarding the clinical performance of ZTA are summarized. The advancements that have been made in understanding the in vivo performance of ZTA are investigated. This article concludes with a discussion of gaps in the literature related to ceramic biomaterials and avenues for future research.

BackgroundMetal release resulting from taper fretting and corrosion is a clinical concern, because wear and corrosion products may stimulate adverse local tissue reactions. Unimodular hip arthroplasties have a conical taper between the femoral head (head bore taper) and the femoral stem (stem cone taper). The use of ceramic heads has been suggested as a way of reducing the generation of wear and corrosion products from the head bore/stem cone taper junction. A previous semiquantitative study found that ceramic heads had less visual evidence of fretting-corrosion damage compared with CoCr heads; but, to our knowledge, no studies have quantified the volumetric material loss from the head bore and stem cone tapers of a matched cohort of ceramic and metal heads.Questions/purposesWe asked: (1) Do ceramic heads result in less volume of material loss at the head-stem junction compared with CoCr heads; (2) do stem cone tapers have less volumetric material loss compared with CoCr head bore tapers; (3) do visual fretting-corrosion scores correlate with volumetric material loss; and (4) are device, patient, or intraoperative factors associated with volumetric material loss?MethodsA quantitative method was developed to estimate volumetric material loss from the head and stem taper in previously matched cohorts of 50 ceramic and 50 CoCr head-stem pairs retrieved during revision surgery for causes not related to adverse reactions to metal particles. The cohorts were matched according to (1) implantation time, (2) stem flexural rigidity, and (3) lateral offset. Fretting corrosion was assessed visually using a previously published four-point, semiquantitative scoring system. The volumetric loss was measured using a precision roundness machine. Using 24 equally spaced axial traces, the volumetric loss was estimated using a linear least squares fit to interpolate the as-manufactured surfaces. The results of this analysis were considered in the context of device (taper angle clearance, head size, head offset, lateral offset, stem material, and stem surface finish) and patient factors that were obtained from the patients’ operative records (implantation time, age at insertion, activity level, and BMI).ResultsThe cumulative volumetric material losses estimated for the ceramic cohort had a median of 0.0 mm3 per year (range, 0.0–0.4 mm3). The cumulative volumetric material losses estimated for the CoCr cohort had a median of 0.1 mm3 per year (range, 0.0–8.8 mm3). An order of magnitude reduction in volumetric material loss was found when a ceramic head was used instead of a CoCr head (p < 0.0001). In the CoCr cohort, the femoral head bore tapers had a median material loss of 0.02 mm3 (range, 0.0–8.7 mm3) and the stem cone tapers had a median material loss of 0.0 mm3 (range, 0.0–0.32 mm3/year). There was greater material loss from femoral head bore tapers compared with stem cone tapers in the CoCr cohort (p < 0.001). There was a positive correlation between visual scoring and volumetric material loss (Spearman’s ρ = 0.67, p < 0.01). Alth...

Previous studies have speculated that modular taper design may have an effect on the corrosion and material loss at the taper surfaces. We present a novel method to measure taper angle for retrieved head taper and stem trunnions using a roundness machine (Talyrond 585, Taylor Hobson, UK). We also investigated the relationship between taper angle clearance and visual fretting-corrosion score at the taper-trunnion junction using a matched cohort study of 50 ceramic and 50 metal head-stem pairs. In this study, no correlation was observed between the taper angle clearance and the visual fretting-corrosion scores in either the ceramic or the metal cohorts.

Background Metal debris and ion release has raised concerns in joint arthroplasty. The purpose of this study was to characterize the sources of metallic ions and particulate debris released from long-term (in vivo > 15y) TKA femoral components. Methods A total of 52 CoCr femoral condyles were identified as having been implanted for more than 15 years. The femoral components were examined for incidence of five types of damage (metal-on-metal wear due to historical polyethylene insert failure, MACC at taper interfaces, cement interface corrosion, third-body abrasive wear, and ICIC). Third-body abrasive wear was evaluated using the Hood method for polyethylene components and a similar method quantifying surface damage of the femoral condyle was used. The total area damaged by ICIC was quantified using digital photogrammetry. Results Surface damage associated with corrosion and/or CoCr debris release was identified in 98% (n=51) of the CoCr femoral components. Five types of damage were identified: 98% of femoral components exhibited 3rd body abrasive wear (mostly observed as scratching, n=51/52), 29% of femoral components exhibited ICIC damage (n=15/52), 41% exhibited cement interface damage (n=11/27), 17% exhibited metal-on-metal wear following wear-through of the polyethylene insert (n=9/52), and 50% of the modular femoral components exhibited MACC taper damage (n=2/4). The total ICIC damaged area was an average of 0.11 ± 0.12 mm2 (Range: 0.01–0.46mm2). Conclusion Although implant damage in TKA is typically reported with regard to the polyethylene insert, the results of this study demonstrate that abrasive and corrosive damage occurs on the CoCr femoral condyle in vivo.

Porous hydrogels of poly(ethylene glycol) (PEG) have been shown to facilitate vascularized tissue formation. However, PEG hydrogels exhibit limited degradation under physiological conditions which hinders their ultimate applicability for tissue engineering therapies. Introduction of poly(L-lactic acid) (PLLA) chains into the PEG backbone results in copolymers that exhibit degradation via hydrolysis that can be controlled, in part, by the copolymer conditions. In this study, porous, PEG-PLLA hydrogels were generated by solvent casting/particulate leaching and photopolymerization. The influence of polymer conditions on hydrogel architecture, degradation and mechanical properties was investigated. Autofluorescence exhibited by the hydrogels allowed for three-dimensional, non-destructive monitoring of hydrogel structure under fully swelled conditions. The initial pore size depended on particulate size but not polymer concentration, while degradation time was dependent on polymer concentration. Compressive modulus was a function of polymer concentration and decreased as the hydrogels degraded. Interestingly, pore size did not vary during degradation contrary to what has been observed in other polymer systems. These results provide a technique for generating porous, degradable PEG-PLLA hydrogels and insight into how the degradation, structure, and mechanical properties depend on synthesis conditions.

This study identifies the acetabular liner/shell interface in modular metal-on-metal devices as a potential source of metal wear or corrosion products. The relation between metal debris and clinical performance, regardless of the type of bearing couple, is a concern for clinicians. Therefore, it is important to characterize every type of modular junction to understand the quantity, location, and mechanism(s) of material loss.