Uncemented Fixation

Abstract

In parallel with using cement for fixing knee components to the bone, other investigators were convinced that a better method was to coat the components with a porous surface so that the bone would grow into the pores, forming a rigid and long-lasting bond. The feasibility was first demonstrated using porous ceramics, but this proved to be impractical because of fabrication problems of the components themselves. Another approach was to use crimped and sintered metal fibers, forming pads which could be sintered into pockets in solid metal components. Alternately, a porous layer was formed directly on the metal substrate by sintering a layer of small metal beads on the surfaces of the components. The earliest designs using these methods were the Miller-Galante (MG) knee and the porous-coated anatomic (PCA) knee. It was soon found that in order for ingrowth to occur, initial rigidity of the components to the bone was needed, which was not easy to achieve in the knee. Experiments by Volz showed that interface motions could be minimized if components were initially screwed in place, and this was successful until the screws themselves caused other problems. Today, new surfaces show promise for achieving the same reliability as cemented fixation, but more time is needed to compare long-term results.