Fourteen mature New Zealand white female rabbits were allocated into two groups. Group 1 received a bolus doughy Simplex polymethylmethacrylate (PMMA) cement injected into the proximal tibia through a drill hole. Group 2 received an equal volume of particulate PMMA cement powder. The operated but nonimplanted left tibiae served as controls. The animals were killed after four months. The membrane surrounding the implant area was harvested aseptically and grown in tissue culture. The supernatants were assayed for prostaglandin E2 (PGE2) via radioimmunoassay. Bulk cement specimens produced on average 12.39 +/- 4.11 ng PGE2 on the right experimental side and 12.29 +/- 3.56 ng PGE2 on the left control side (not statistically different). Cement powder specimens produced 8.82 +/- 1.64 ng PGE2 on the right experimental side, which was statistically different from 4.21 +/- 0.88 ng PGE2 produced on the left control side. The ratio of PGE2 values for the right divided by the left side and the arithmetic difference between right and left sides were significantly higher in the particle group compared with the bulk group. Small, undigestable cement particles may be phagocytosed by foreign-body giant cells and histiocytes and then extruded into the extracellular compartment, along with substances such as PGE2. PGE2 has been implicated as the biologic mechanism for stimulating the bone lysis associated with prosthetic loosening.
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