The inflammatory response associated with the use of resorbable orthopedic fixation devices can be eliminated by incorporating a long acting buffer into a poly(lactic-co-glycolic acid), """"""""PGLA"""""""", fixation device which will neutralize acidic degradation products. The inclusion of the osteoconductive calcium phosphate, hydroxyapatite (HA), as a buffer in a PLOA-based fixture effectively moderates the rate of pH decline as the fixture degrades. HA promotes bony ingrowth, obviates loosening of the fixture, and acts as a buffer. It is the objective of this project to stabilize the mechanical characteristics of this fixture via the use of self-reinforcing fibers. The concept of self- reinforcement of the fixture implies the formation of a composite material comprised of reinforcing fibers of a composition similar in chemical structure to either the polymeric PGLA component of the fixture or the buffering calcium phosphate component of the fixture. The Phase II experimental design will focus on preclinical in vivo development of two functional reinforced fixture candidates, based on the requirement of """"""""substantial equivalence"""""""" to obtain FDA 5l0k approval. Structural performance in both small (rabbit) and large (sheep) animal models will be characterized. The small animal model will be used to screen two selected fiber candidates, whereas the large animal model will be used to test the final fixture configuration. The main goal of the rabbit experiments will be to develop the temporal history of the osteotomy healing in relation to fixture degradation. The final fixture will be employed in the sheep model with the objective of demonstrating functionality equivalent to commercially available fixation devices.
Of the more than 1.1 million fractures in the U.S. each year, greater than 470,000 require internal fixation devices to stabilize the fracture during the healing process. While there is significant clinical demand for resorbable devices, available products have not been widely adopted because of inflammatory responses to degradation. Our studies show that a buffered resorbable fixation device may ameliorate these responses. Development of the necessary strength will address the clinical demand for acceptable resorbable orthopedic materials.
| Hile, David D; Doherty, Stephen A; Trantolo, Debra J (2004) Prediction of resorption rates for composite polylactide/hydroxylapatite internal fixation devices based on initial degradation profiles. J Biomed Mater Res B Appl Biomater 71:201-5 |
