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Journal of Long-Term Effects of Medical Implants

ISSN Print: 1050-6934
ISSN Online: 1940-4379

Journal of Long-Term Effects of Medical Implants

DOI: 10.1615/JLongTermEffMedImplants.v21.i1.70
pages 79-92

Fractionation and Characterization of Particles Simulating Wear of Total Joint Replacement (TJR) Following ASTM Standards

Mrinal K. Musib
Department of Orthopaedic Surgery and Rehabilitation Medicine, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
Subrata Saha
Department of Biomedical Engineering, Florida International University, Miami, FL 33174; Affiliated Professor, Department of Restorative Dentistry, Affiliated Faculty, Department of Oral & Maxillofacial Surgery, School of Dentistry, University of Washington, Seattle, WA 98195

ABSTRACT

Reactions of bone cells to orthopedic wear debris produced by the articulating motion of total joint replacements (TJRs) are largely responsible for the long-term failure of such replacements. Metal and polyethylene (PE) wear particles isolated from fluids from total joint simulators, as well as particles that are fabricated by other methods, are widely used to study such in vitro cellular response. Prior investigations have revealed that cellular response to wear debris depends on the size, shape, and dose of the particles. Hence, to have a better understanding of the wear-mediated osteolytic process it is important that these particles are well characterized and clinically relevant, both qualitatively, and quantitatively. In this study we have fractionated both ultra-high molecular weight polyethylene (UHMWPE) and Ti particles, into micron (1.0−10.0 μm), submicron (0.2−1.0 μm), and nanoparticle (0.01−0.2 μm) fractions, and characterized them based on the following size-shape descriptors as put forth in ASTM F1877: i) equivalent circle diameter (ECD), ii) aspect ratio (AR), iii) elongation (E), iv) roundness (R), and v) form factor (FF). The mean (±SD) ECDs (in μm) for micron, submicron, and nanoparticles of UHMWPE were 1.652±0.553, 0.270±0.180, and 0.061±0.035, respectively, and for Ti were 1.894±0.667, 0.278±0.180, and 0.055±0.029, respectively. The values for other descriptors were similar (no statistically significant difference). The nanofraction particles were found to be more sphere-like (higher R and FF values, and lower E and AR values) as compared to larger particles. Future experiments will involve use of these well characterized particles for in vitro studies.