FUNCTIONAL CONSIDERATIONS IN IMPLANT DESIGN

Abstract

The normal physiological response to essentially all implanted foreign objects or materials, in both bone and soft tissue, is encapsulation in fibrous (scar) tissue. Thus, most all implants (including bone cement) are eventually fixed or attached within the structures of the body by this biologically dynamic, unstable, fibrous tissue interface. An important functional consideration in the long-term success or failure of any implant design is the response it elicits in the fibrous tissue capsule, and in turn, the response of surrounding structures to the fibrous capsule. Both biocompatibility and biomechanical aspects can be important. Fibrous tissue is known to remodel when subjected to gentle stress or pressure, and hypertrophy can be initiated by either chemical, biological, or mechanical stimulus. Most of the reactions which occur in fibrous tissue and the adjacent structures of the body are predictable, and account for many of the problems and complications which occur in implants. Whenever possible implant design should use the fibrous tissue response it elicits to help support the reconstructive procedure, and force-transfer to adjacent structures should duplicate those encountered in normal anatomy to the greatest extent possible.