A quantitative study of the tissue reaction and its relationship to debris production from a joint implant.

An attempt has been made to refine the quantitative evaluation of the tissue response to a prosthesis using the goat hip as an experimental model. Total joint replacement was performed in six goats; in three the cup was made of conventional ultrahigh molecular weight polyethylene and in three a new silane cross-linked ultrahigh molecular weight polyethylene was used. The pseudocapsule of the hips was examined histologically at 15, 19 and 24 months following surgery. Small and large polyethylene debris were visualized using semi-crossed polars and were counted. Giant cells were counted after staining with toluidine blue as were macrophages which were identified by dense staining after the acid phosphatase reaction. The amount of small birefringent debris was closely related to the number of macrophages in the pseudocapsule. This method of assessment may be helpful in comparing the tissue reaction of different polymers.