A Method to Isolate and Characterize Wear Debris from Synovial Fluid and Tissues

Joint fluid and tissues have very different compositions and usually far fewer particles than simulator lubricant. When isolating particles, the main goal is to produce complete digestion of the organic compounds (hyaluronic acid, nucleic acid, fats, etc.) with minimal loss of particles and minimal agglomeration. In the present study, a previously developed protocol for extracting particles from the bovine serum used in joint simulator testing was extended for use with synovial fluid and tissues from patients with prosthetic joints. The new protocol enables the recovery of any coexisting particles (for example, metallic and ultra-high-molecular-weight polyethylene particles) from joint fluids and tissues with minimal degradation. It can be applied to very small volumes of fluid or a few milligrams of tissue. Because the protocol does not require filtration, there is greater recovery of nano-sized particles, with far less tendency for agglomeration. This provides a more accurate evaluation of the size spectrum of the particles and facilitates an accurate analysis of the composition of individual particles that is not possible when they are agglomerated. This facilitates improved understanding of the wear mechanisms that produced the particles, as well as their biological consequences.