The synovial response to intra-articular acrylic cement particles in guinea pigs.

The histology and cytology of the tissue response to intra-articular insertion of particles of acrylic bone cement containing barium sulphate has been studied in the guinea pig knee joint. Following insertion of the acrylic, fibrinous debris admixed with particles became adherent to the synovial membrane. Cell proliferation at the interface between the debris and the synovial tissue engulfed the debris, and a new layer of intimal lining cells formed over its surface. This process led to incorporation of the particles into vascularized subintimal tissue. The response to subintimal acrylic cement particles was by multinucleate giant cells (macrophage polykaryons), macrophages and fibroblasts, with a variable amount of intermingled fibrosis. After incorporation was complete, the long-term (3 months to 1 year) subintimal response acquired a basically stable histological appearance amongst which no zones of tissue necrosis were found. However, in some instances it did contain foci of neutrophil infiltration, and it is possible that such foci are a reaction to minor episodes of cell damage.