The effect of porous surface configuration on the tensile strength of fixation of implants by bone ingrowth.

In an attempt to gain information that could be directly applied to the design of clinical porous-surfaced prostheses intended for biological attachment by bone ingrowth, the tensile strength of the bone-implant interface was expressed as a function of 2 fundamentally different porous-surface configurations. Using powder metallurgy techniques, standard 3-hole fracture fixation plates were prepared with both a single and a multiple layer of spherically shaped metal powder particles on the bone-contacting surface to produce implants with different porous surfaces. These plates were implanted onto the lateral aspect of canine femurs for periods of 4, 6, 8, 12, 18, and 24 weeks. Mechanical tests were performed to measure the tensile strength of fixation of the implants by the ingrowth of bone. The results of the mechanical tests indicated that implants with the multiple particle layer surfce configuration develop a greater tensile strength of fixation than do implants with the single particle layer surface configuration. In addition, this fixation strength develops more quickly if the cortical bone is petaled prior to implantation. These findings should be considered when designing porous-surfaced implants intended for fixation by bone ingrowth.