EFFECTS OF GRAFTING ON POROUS METAL INGROWTH - A CANINE MODEL

Twenty-five mongrel dogs were studied using implantation of autograft, fresh-frozen allograft, and beta-tricalcium phosphate around a porous -coated chrome-cobalt plug in the distal femoral metaphysis; interfere nce-fit and over-reamed control specimens were also studied. Over the course of this 4-month study, bone ingrowth through the grouting mater ials into the center plug was noted for autologous, allograft, and cer amic specimens. Quantitatively, in terms of push-out strength and hist ology, there were no significant differences between grafted groups; s ignificantly higher push-out strengths were attained in each grafted s ubgroup compared with nongrafted, overreamed control subjects. Ln the setting of uncemented revision total hip arthroplasty, bone-grafting i s frequently required. Because of the limited availability of autogeno us bone and the potential liabilities of allograft material, attention has been given to bone substitutes. On the basis of this preliminary study, bone ingrowth into a porous metal substrate has been documented to occur through autograft, allograft, or ceramic grouting agents. Wi thin the limits of this nonloaded experimental model, it appears that these materials are comparable in terms of their osteoconductive capab ility. Even in the optimal laboratory situation, bone ingrowth does no t appear to occur in a canine model across a nongrafted 2-mm gap with regularity over a 16-week period.