In vivo inflammatory response to silicone elastomer particulate debris

Silicone elastomer particles (Silastic silicone elastomer, Dow Coming, Midland, MI), polymethylmethacrylate particles, and monosodium urate particles smaller than 10 mu m were injected into a rat subcutaneous air pouch lined with synovial membranelike cells. Inflammatory exudate from the air pouch was retrieved at 6 hours, 24 hours, 48 hours, and 72 hours after injection. White blood cell count, tumor necrosis factor, and prostaglandin E(2) were measured in the exudate. White blood cell and tumor necrosis factor levels in the exudate were the highest for the silicone group at 6 and 24 hours. Prostaglandin E(2) was also significantly higher in the silicone group at 24 hours. We conclude that acute inflammation is particle-type specific and that Silicone elastomer particles are acutely inflammatory.