A review of the biologic effects of spine implant debris: Fact from fiction

Abstract

BackgroundBiologic-reactivity to implant-debris is the primary determinant of long-term clinical performance. The following reviews: 1) the physical aspects of spinal-implant debris and 2) the local and systemic biologic responses to implant debris.MethodsMethods included are: 1) gravimetric wear analysis; 2) SEM and LALLS; 3) metal-ion analysis; 4) ELISA, toxicity testing, patch testing; and 5) metal-lymphocyte transformation testing (metal-LTT).ResultsWear and corrosion of spine-implants produce particles and ions. Particles (0.01–1000 μm) are generally submicron ( <1 µm). Wear rates of metal-on-polymer and metal-on-metal disc arthroplasties are approximately 2–20 and 1 mm3/yr, respectively. Metal-on-metal total disc replacement components have significant increases in circulating metal (less than 10-fold that of controls at 4 ppb-Co and 3 ppb-Cr or ng/mL). Debris reactivity is local and systemic. Local inflammation is caused primarily by ingestion of debris by local macrophages, which produce pro-inflammatory cytokines TNFα, IL-1β, IL-6, and PGE2. Systemic responses associated with implant-debris have been limited to hypersensitivity reactions. Elevated amounts of in the liver, spleen, etc of patients with failed TJA have not been associated with remote toxicological or carcinogenic pathology to date. Implant debris are differentially bioreactive. Greater numbers are pro-inflammatory; the smaller-sized debris are more bioreactive by virtue of their greater numbers (dose) for a given amount of implant mass loss (one 100-μm-diameter particle is equivalent in mass to 1 million 1-μm-diameter particles). Elongated particles are pro-inflammatory (ie, aspect ratio of greater than 3). Metal particles are more proinflammatory than polymers, ceteris paribus.ConclusionSpinal arthroplasty designs have been in use for more than 20 years internationally; therefore, concerns about neuropathology, toxicity, and carcinogenicity are mitigated. Debris-induced inflammation still depends on the individual and the type of debris. The consequence of debris-induced inflammation is continued; vigilance by physicians is recommended monitoring of spinal implants using physical exams and testing of metal content and bioreactivity, as is planning for the likelihood of revision in younger individuals.

Quantifying subtle but persistent peri-spine inflammation in vivo to submicron cobalt–chromium alloy particles

“…Reportedly, spinal implant debris elicits a macrophage-mediated response with increased levels of local pro-inflammatory cytokines, osteoclastogenesis and cellular apoptosis [8,13,29,40]. The results of this in vivo study support this and this response is both dose dependent and can persist over the long term.…”

“…Metal-on-metal total disc arthroplasties and fusion implants have been shown to produce wear debris particles in both the micron and submicron sizes [13,18,27,32,35]. Recent retrieval analysis of metal-on-metal total disc arthroplasty debris by Guyer et al [12] has reported the CoCr-alloy implant debris to be primarily in the submicron range.…”

CORR Insights®: Periprosthetic UHMWPE Wear Debris Induces Inflammation, Vascularization, and Innervation After Total Disc Replacement in the Lumbar Spine

“…Further muddying the waters, especially in studying failed TDRs, is that many of the failures have a mechanical component, component subsidence or loosening, that might itself be the cause of pain. Similarly, previous case studies [3] in humans and experiments using animal models have demonstrated that the pain is more likely due to the inflammation that is part of the biologic reaction to debris and not a neuropathic effect.…”

“…Still, reports of osteolysis and adverse local tissue reactions (ALTRs) similar to those seen around hip and knee replacements have emerged [3], substantiating the continuing concern that the biological reaction to debris may be an important factor limiting the longevity of disc replacements. Veruva and colleagues have provided additional compelling evidence that these concerns are warranted, and have begun to explore the hypothesis that a link exists between the presence of debris in local tissues and evidence of biological responses consistent with increased pain.…”

Mass Loss and Ion Elution of Biomedical Co&ndash;Cr&ndash;Mo Alloys during Pin-on-Disk Wear Tests

“…The main concern in using these metal-based hip replacements is the formation of wear debris 2) and ion elution, 3) which seem to be closely related to the microstructure and precipitates of the CoCrMo alloy implants. It is well known that the phase, morphology, size and distribution of the precipitates affect the properties of CoCr Mo alloys.…”