A NOVEL DEVICE TO INVESTIGATE THE EFFECT OF RESIDUAL TENSION IN NATURAL TISSUE IMPLANTS

摘要

Natural collagen tissue implants derived from fetal bovine dermis are an attractive alternative to polymers for use in soft tissue repair. Constitutive relationships for this material are typically determined in vitro on a universal testing machine. However, upon implementation, tissue remodeling may cause the material properties to change rapidly. The literature indicates that the level of in vivo strain and the corresponding stress field may promote either tissue adaptation or undesirable resorption. The present work investigates a novel device for eventual use as an implantable tensometer. The device is not intended to be a substitute for material characterization on a universal testing machine, but rather a new device, representing a basic mechanical system that would facilitate the development of an even smaller instrument on the scale to be implanted in laboratory animals. An instrument of this type would enable the in vivo characterization of biomaterials under a prescribed load. The new device uses springs to generate a force on the biomaterial sample. Results show that the device creates a diminishing force that reaches quasi-static equilibrium displacement with acellular collagen implants (n=11) of varying cross sectional areas under different loads. Reaching an equilibrium displacement is an essential starting point for an implantable instrument. Changes from the equilibrium position may forecast a threshold stress to initiate resorption. In addition, knowledge on resorption rate may be obtained.