ENHANCED STABILITY OF UNCEMENTED CANINE FEMORAL COMPONENTS BY BONE INGROWTH INTO THE POROUS COATINGS

The following questions were answered in this study: (1) What is the i nitial stability of proximally porous-coated canine femoral components ? (2) Does bone ingrowth occur under these conditions? (3) Is the stab ility enhanced by tissue ingrowth in vivo? The stability of proximally porous-coated femoral components of canine total hip arthroplasties a fter 6 months to 2 years of in vivo service in dogs was measured in vi tro using displacement transducers under loads simulating canine midst ance. This was compared with the stability of identical components und er the same loading conditions immediately after implantation in vitro in the contralateral femurs. The femurs were then sectioned and bone ingrowth into the porous coatings was quantified. The results showed t hat immediately after implantation the implants can move as much as 50 mu m, but that the bone ingrowth into porous coatings of canine femor al components can occur even under such conditions. These data also su ggested that the relative motion existing at the time of insertion can be reduced to very small amounts (< 10 mu m) by bone ingrowth.