An In Vitro Assessment of Wear Particulate Generated From NUBAC: A PEEK-on-PEEK Articulating Nucleus Replacement Device

Study Design. In vitro biotribological wear particulate investigation. Objective. To characterize poly-ether-ether-ketone (PEEK)-OPTIMA wear particulate generated from a series of wear tests used to evaluate the wear resistance and long-term biodurability of NUBAC, a PEEK-on-PEEK articulating nucleus replacement device, and compare with wear particulate associated with hip and knee total joint arthroplasties. Summary of Background Data. The use of PEEK in spinal arthroplasty represents a unique application of this material. Clinically, osteolysis, osteolytic changes, and adverse reactions to metal ions have been documented in spinal arthroplasty. Therefore, it is critically important to analyze the PEEK wear particulate to evaluate its resultant biologic reactivity. Historically, scanning electron microscopy (SEM) has been used for wear debris characterization. Light scattering, specifically laser diffraction, has also been successfully used. The combined use of both techniques may provide a more comprehensive analysis than either method alone. Methods. Proteinacious serum containing PEEK wear debris generated from four groups of devices from separate wear tests underwent enzymatic and acid digestion. The particulate was analyzed using laser diffraction in duplicate, followed by SEM analysis. Results. Laser diffraction analysis demonstrated a relatively large mean particle diameter on the basis of particle volume (16.5-40.0 mu m) as compared with particle number (0.9-2.2 mu m). For all groups, more than 50% of debris was larger than 5.0 mu m. SEM analysis revealed a mean particle size consistent with the number-based laser diffraction results. The morphology of the wear particulate appeared to be similar for all the groups analyzed. Conclusion. The analysis of the particles generated from an articulating PEEK-on-PEEK nucleus replacement device shows debris within size ranges typical of other total joint arthroplasty implants, with relatively round morphology, along with the results suggesting a reduced particle load. These attributes tend to diminish the potential of these PEEK particles to elicit an inflammatory response.