[Experimental study on plates of various stiffness--on their effects on the bones and rigidity in fracture...

Recently, there has been a tendency to use larger plates such as an AO compression plate in the operative treatment of fractures. However, it was found that the rigid plate fixation for a long period greatly have an effect on the cortex and bone strength. In this regards, the author studied the influences on the cortex and bone strength after long fixation with three types of plates which have large differences in stiffness. Moreover, the rigidity of fracture immobilization was investigated for each plate. The experimental results in mature rabbits as experimental animals showed that the least thinning of the cortex was obtained by use of high density polyethylene (HDP) plate with lowest rigidity and bone strength decreased with increasing rigidity of the plate. However, the fracture site fixed with a HDP plate showed malunion. On the other hand, a carbon fiber polybutylene-telephthalate composite (CFP) plate which has the elastic modulus almost corresponding to that of the tibiofibular bone of a rabbit had less influences on the bone cortex as compared to a stainless steel plate with highest rigidity. Therefore, a CFP plate had less influences on the bone and gave a moderate rigidity in fracture immobilization.