ABSTRACT
Enhancing cementless fixation is defined here as accelerating or augmenting bone formation in the porous coating or on the surface of an orthopaedic implant (see chap. 2 for a review of the basic concepts underlying cementless fixation.). As a matter of definition, we will restrict use of the term ‘‘bone ingrowth’’ in the rest of this chapter to porous coatings, where bone grows into the interstices of the implant surface (e.g., into the void spaces of a porous surface made from beads or fiber metal). We will use the term ‘‘bone ongrowth’’ to describe situations in which there is no surface macroporosity and at the level of the light microscope the bone often appears to be directly attached to the implant material
The early studies of retrieved implants suggested that bone ingrowth was only obtained sporadically. These observations motivated many of the initial efforts to augment cementless fixation, including bone ingrowth and ongrowth enhancements. As implant designs improved and the retrieval analyses focused on post-mortem cases where the implants had apparently functioned well (see chap. 2), it became apparent that in most cases some degree of bone ingrowth occurred. Nevertheless, the need remains to reduce
the time required to obtain secure mechanical fixation of the implant to the host bone or to ensure that fixation occurs in situations where it otherwise would be problematic (e.g., revision joint replacement).
