COMPARISON OF THE INFLAMMATORY RESPONSE TO PARTICULATE POLYMETHYLMETHACRYLATE DEBRIS WITH AND WITHOUT BARIUM-SULFATE

Particulate polymethylmethacrylate debris has been implicated in the i nflammatory response observed surrounding loosened cemented implants. The rat subcutaneous pouch model and the Howie implant model (used to study bone resorption) were used to quantify the response to mechanica lly produced endotoxin-free polymethylmethacrylate debris with and wit hout 10% (wt/vol) BaSO4. In the rat subcutaneous pouch model, the infl ammatory response to polymethylmethacrylate particles containing BaSO4 was greater than the response to plain polymethylmethacrylate particl es of similar size. Increased inflammation was measured by leukocyte c ounts and levels of prostaglandin E(2), tumor necrosis factor, and neu tral metalloprotease. In addition, particulate polymethylmethacrylate with BaSO4 caused significantly greater bone resorption in the Howie m odel than did particulate plain polymethylmethacrylate. In in vitro st udies, particulate polymethylmethacrylate with BaSO4 stimulated more p rostaglandin E(2), neutral metalloprotease, and tumor necrosis factor from human monocytes in culture and stimulated greater proliferation o f synovial cells than did particulate plain polymethylmethacrylate. Th e presence of BaSO4 appears to significantly intensify the inflammator y response to polymethylmethacrylate debris.