Enhancement of bony in-growth to metal implants by combining controlled hydroxyapatite coating and heat treatment

The rate of bony in-growth to heat-treated and controlled hydroxyapatite metal implants made of either titanium alloy (Ti-6Al-4V) or stainless steel (SS) 316L inserted to the medullar canal of the femur in rats was investigated. It was found that while partial coverage of hydroxyapatite (HA) did not cause a significant elevation of their bonding strength when compared with nonheated implants, HA, and heat treatment caused a significant (p < 0.01) elevation of 3.1-fold in the bonding strength of the implants to the host bone. A similar phenomenon to that found for the titanium alloy implants was found to be true for the SS implants as well. It is concluded that the novel approach presented in this article, that is, to heat treat implants as well as controlled partial coating of them by HA, prior to their insertion to host bone, produce an enhancement of bone growth to metal implants greater than utilization of each method alone. Our findings may be used to further enhance bony in-growth to metal implants in several clinical settings, producing avid implants with superior integration capabilities.