Wear Particle Isolation and Implant Preparation

Conventional UHMWPE particles were a generous gift from Dr. Timothy Wright, Hospital for Special Surgery. Particles were isolated from knee joint simulator test supernatants according to established protocols.^{14 (link)} Following isolation particles were washed twice in ethanol (96%, 70%) and, after evaporation of ethanol, suspended in PBS for storage in −80°C. The particles tested negative for endotoxin using a Limulus Amebocyte Lysate Kit (BioWhittaker, Walkersville, MD). The mean diameter of the particles was 0.48 ± 0.10 μm as measured by electron microscopy. Alzet model 2006 (Durect Corporation, Cupertino, CA) osmotic pumps were loaded either with carrier solution (1% BSA-PBS); carrier solution with 15 mg mL⁻¹ UHMWPE particles; or carrier solution with UHMWPE particles and 10 μg mL⁻¹ mouse recombinant IL-4 (R&D Systems, Minneapolis, MN). 6-cm-long vinyl tubing (Durect Corporation), prefilled with the appropriate solution, was used to connect the pumps to the coated or noncoated titanium rods.^{22 (link)}