Wear measurement of highly cross-linked UHMWPE using a ⁷Be tracer implantation technique

Journal Article · Tue Jan 01 00:00:00 EST 2013 · Journal of Biomedical Materials Research Part B: Applied Biomaterials

DOI:https://doi.org/10.1002/jbm.b.32868· OSTI ID:1439040

Wimmer, Markus A.; Laurent, Michel P.; Dwiwedi, Yasha; Gallardo, Luis A.; Chipps, Kelly A.; Blackmon, Jeffery C.; Kozub, Raymond L.; Bardayan, Daniel W.; Gross, Carl J.; Stracener, Daniel W.; Smith, Michael S.; Nesaraja, Caroline D.; Erikson, Luke; Patel, Nidhi; Rehm, Karl E.; Ahmad, Irshad; Greene, John P.; Greife, Uwe

The very low wear rates achieved with the current highly cross-linked ultra-high molecular weight polyethylenes (UHMWPE) used in joint prostheses have proven to be difficult to measure accurately by gravimetry. Tracer methods are therefore being explored. The purpose of this study was to effect a proof-of-concept on the use of the radioactive tracer beryllium-7 (7Be) for the determination of wear in a highly cross-linked orthopedic UHMWPE. Three crosslinked and four conventional UHMWPE pins made from compression-molded GUR 1050, were activated with 109 to 1010 7Be nuclei using a new implantation setup that produced a homogenous distribution of implanted nuclei up to 8.5 μm below the surface. The pins were tested for wear in a six-station pin-on-flat apparatus for up to 7.1 million cycles (178 km). A Germanium gamma detector was employed to determine activity loss of the UHMWPE pins at preset intervals during the wear test. The wear of the cross-linked UHMWPE pins was readily detected and estimated to be 17 ± 3 μg/Mc. The conventional-to-cross-linked ratio of the wear rates was 13.1 ± 0.8, in the expected range for these materials. It was estimated that implantation reduced the average wear rate by approximately 20%, and the oxidative degradation damage from implantation was negligible. Future applications of this tracer technology may include the analysis of location-specific wear, such as loss of material in the post or backside of a tibial insert.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1439040
• Report Number(s): PNNL-SA-83542
• Journal Information: Journal of Biomedical Materials Research Part B: Applied Biomaterials, Vol. 101B, Issue 3; ISSN 1552-4973
• Country of Publication: United States
• Language: English