Bone growth to metal implants is regulated by their surface chemical properties.

Bony ingrowth to control (non-treated) and heat-treated stainless steel and Ti-6Al-4V implants into the medullary canal of the femur in rats was studied by mechanical, chemical and Auger electron spectroscopic methods. At all time intervals up to 35 d post-implantation, the shear strengths of the heat-treated Ti-6Al-4V and stainless steel implants were significantly higher (1.6-fold to 3.4-fold) than in control implants. Using Auger electron spectroscopy depth profiling methods, it was found that the heat treatment modified the implant surface composition significantly, resulting in a thicker oxide layer and other chemical changes. It is concluded that heat treatment of metal implants prior to their insertion alters their chemical surface properties and augments bony ingrowth to them.