Biologic Fixation of Total Hip Implants

Biologic fixation of total hip replacement implants with porous surfaces by means of bone ingrowth became a clinical reality largely through the many experimental studies that were carried out in the 1960s, 1970s, and 1980s. Polymethylmethacrylate bone cement had been the material of choice for implant fixation until then, when it was realized that bone can grow into the porous surfaces of implants if appropriate pore geometries are provided. Porous metals, polymers, and ceramics had been investigated as candidate implants, and porous-coated metal implants were chosen on the basis of the advances in sintering technologies, biocompatibility, and strength considerations (Fig. 1). Consistently obtaining bone growth into functioning total joint replacement components under the conditions of physiologic loading, however, remained a problem. Canine studies were critically important in defining the conditions necessary for consistent bone growth into these devices and thus in the development of porous-surface prostheses for biologic fixation. Our experience with such studies is presented here.