A histopathologic comparison of the tissue reaction to prosthetic materials in the knee joint of rats.

The five kinds of prosthetic materials: powders of cobalt alloy, stainless steel, alumina ceramic, HDP plastic and bone cement, were injected to the knee joints of 16 rats for each material. Two controls were used, one with saline solution and the other untreated. Some of the rats were sacrificed at one week, being left untreated. Some of the rats were sacrificed at one, four, 12 and 25 weeks after injection. The knee joints of these rats were taken out for a histopathologic study. The main changes were fibrosis and granulation due to foreign bodies, but no remarkable change in the degree of tissue reactions was observed within each material group, nor did the length of period have any effect thereon. Comparing the degree of the above changes caused by each material in the tissue, ceramic powder showed the most significant change, followed by bone cement, HDP, stainless steel and cobalt alloy powder, in that order. No tumorous condition was observed.