![]() consider the inflammasome to be a key element in the intracellular response to metals and they examined the effect of cobalt-chromium particle size and surface irregularity in the stimulation of this response in human primary monocytes ( 11). This is in contrast to malpositioned hips which produced larger particles with higher concentrations of cobalt ( 10). In well-functioning metal-on-metal hips with low wear rates, only small volumes of particles are produced and these generally consist of oxidized chromium nanoparticles with minimal to no cobalt content ( 9). The size, concentration and shape of particles, regardless of material ( 7, 8) appear to affect the type of response elicited by the cells in the tissues surrounding arthroplasty components. ![]() The local reaction of cells to wear particles This review will survey some of the key findings from those studies in terms of the local and systemic consequences of hip resurfacing. This has resulted in a large body of literature based on multifaceted retrieval analysis and histopathology. The opportunity to evaluate HRA components revised for early failure due to femoral neck fracture or mid-term loosening provided a contrasting set of data with which to compare with cases that failed for reasons related to implant wear. The degree of component wear has been found to be similar ( 6). With the exception of femoral neck fracture and revisions for complications of modular taper corrosion, the modes of failure experienced by metal-on-metal hip resurfacings and standard, stemmed metal-on-metal total hips are similar, i.e., aseptic loosening, infection and metal hypersensitivity. The aim of this review is to examine the local and systemic consequences of metal-on-metal hip resurfacing implants. When present in excessive amounts, both the particles and the ions have the potential to cause adverse local and systemic biological responses. However, the metal particles are predominantly nanometer-sized and these can potentially corrode into metal ions. The observation that the local tissue response to well-functioning, early generation, metal-on-metal bearings was markedly less inflammatory than the typically macrophage-dominated tissues around metal-on-polyethylene bearings encouraged the reintroduction of metal-on-metal bearings in the late 1990’s. Metal-on-metal articulations typically produce significantly less volumetric wear compared with early generation metal-on-polyethylene bearings that were associated with osteolysis. The clinical use of metal-on-metal HRA expanded from the early 2000’s and, during the peak period, 13 different designs were available worldwide ( 5). Contemporary metal-on-metal HRA can be attributed to the early procedures by Wagner ( 2) which inspired later designs by McMinn ( 3) and also by Amstutz ( 4). Hip resurfacing arthroplasty (HRA) is a potentially bone-conserving operation that has a long history and mixed clinical success ( 1). Received: 26 August 2019 Accepted: 30 September 2019 Published: 15 January 2020. Keywords: Hip resurfacing arthroplasty (HRA) metal-on-metal tissue ions toxicity Systemic toxicity from chronic exposure to the ions from metal-on-metal implants is still extremely rare although studies into potential cardiac or neurologic effects have suggested that subtle changes may be present that warrant continued and larger follow-up studies of longer-term cohorts. ![]() The number of patients with a sensitivity to the cobalt or chromium constituents of metal-on-metal implants is thought to be low and the cause and effect between patient sensitivity and implant failure is considered to be uncertain. ![]() Surgical placement, particularly of the acetabular component, is important to the generation of wear debris. Metal particle size, shape and volume are important to the response around metal-on-metal implants. Factors affecting the local tissue response to any implant include surgical, implant and patient factors. Local tissue reactions cover a spectrum from no clinically adverse effects to adverse complications leading to revision associated with pain, osteolysis, or pseudotumor formation. This paper reviews the local and systemic consequences of metal-on-metal hip resurfacing implants. Policy of Dealing with Allegations of Research MisconductĪbstract: Hip resurfacing arthroplasty (HRA) has a long clinical history and has utilized a variety of bearing material combinations with mixed clinical success.Policy of Screening for Plagiarism Process.
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