Metal wear particle characterization from metal on metal total hip replacements: Transmission electron microscopy study of periprosthetic tissues and isolated particles

TLDR

Metal‑on‑metal total hip replacements elicit a less intense tissue reaction than metal‑on‑polyethylene replacements, possibly due to differing wear‑particle characteristics. The study aimed to characterize metal wear particles in periprosthetic tissues of metal‑on‑metal THRs using transmission electron microscopy, including particles extracted by enzymatic digestion. Tissue samples were collected from 13 patients undergoing revision of cobalt‑chromium‑molybdenum metal‑on‑metal THRs. Most CoCrMo wear particles were <50 nm, round to oval with irregular boundaries, considerably smaller than polyethylene particles, and their high numbers from small volumes may cause fewer local biological effects because corrosion, dissolution, and dissemination reduce long‑term retention. © 1998 John Wiley & Sons, Inc., J.

Abstract

The less intense tissue reaction around metal on metal total hip replacements (THRs) compared to metal on polyethylene (PE) THRs may be explained by the differences in the characteristics of metal wear particles. In this study, transmission electron microscopy was used to study metal wear particles that were either in situ in cells or had been extracted from the cells by a new technique based on enzymatic tissue digestion. The tissues were obtained from 13 patients undergoing revision of metal on metal THRs with cobalt-chromium-molybdenum (CoCrMo) bearing couples. Most of the CoCrMo wear particles were smaller than 50 nm (range 6–834 nm) and round to oval in shape with irregular boundaries. This size range is considerably smaller than that reported for PE particles. While even a small volume of metal wear will produce high numbers of particles, the apparently less severe local tissue reaction to metal particles may be due to the possibility that corrosion, dissolution, and dissemination of metal particles may result in fewer local biological effects than the long-term retention of PE particles in the periprosthetic tissues. © 1998 John Wiley & Sons, Inc. J. Biomed Mater Res, 42, 103–111, 1998.