EVALUATION OF BONE-GROWTH INTO POROUS HIGH-DENSITY POLYETHYLENE

Bone growth into porous polyethylene rods was studied as a function of time and pore structure. Previous studies indicated the biocompatibility of solid polyethylene materials which are currently being used clinically. Porous polyethylene rods were implanted in the femurs of mongrel dogs which were sacrificed 4, 8 and 16 wk postoperatively. The implants were then sectioned and examined histologically and microradiographically. Quantitative techniques were employed to determine the amount of bone ingrowth as a function of time and pore size. The pore structures of the materials were evaluated using optical microscopy and Hg intrusion porosimetry. Porous polyethylene is apparently capable of accepting bone growth into pores as small as 40 .mu.m. The optimum rate of bone ingrowth was observed in pore sizes of approximately 100 to 135 .mu.m, with no increase in the rate of bone ingrowth observed in samples possessing larger pore sizes. No adverse tissue response was found at implant times up to 16 wk in pore sizes of 100 .mu. or larger.