Fiber metal composites in the fixation of skeletal prosthesis

Abstract To serve as a component of a load‐bearing skeletal prosthesis, a porous material should offer the following attributes: (1) pore channels over 100μ in diameter; (2) continuity of pore channels; (3) matrix material inert and compatible with animal tissues; (4) manufacturable as thick coatings or thin‐walled complex surface assemblies; (5) manufacturable to precision dimensions; (6) large compliance comparable to bone; (7) crack resistance, particularly under impact. A porous composite was manufactured by molding and sintering short metal fibers, which fulfilled all of these requirements. The composite was manufactured both with titanium and Vitallium fibers. Experimental implants were performed in dogs and rabbits indicating peripheral bone formation around the implant at 2 weeks and penetration from 3 weeks on. Shear strength values at the prosthesis‐bone interface were in the range of 20 kg/cm 2 3 weeks after implantation. Femoral prostheses implanted in dogs revealed fixation by bone formation and maintenance by bone ingrowth up to 1 yr following implantation. Massive incorporation with bone of skeletal segmental replacements for the baboon's femur were seen up to 3 months following implantation. Practical problems that can be encountered with the use of porous fiber metal composites for prosthesis fixation relate to: (1) the possibility of long‐term corrosion occurring in an implant with a very large surface area; (2) technical problems with implantation requiring intimate contact between the fiber metal surface and the bone and (3) the difficulties in removing an implant which has failed for mechanical reasons requiring that a device manufactured using fiber metal composites for fixation be absolutely failure free from a mechanical viewpoint.