"Biological" internal fixation of long bone fractures: a biomechanical study of a "noncontact" plate system

Based on existing knowledge of noncontact plates, an experimental prototype of a nonperiosteal contact internal fixation implant ("noncontact internal fixator") has been designed. The construct rigidity of osteotomised synthetic composite femora, fixed with the noncontact fixator and a reamed, statically-locked intramedullary nail were compared in axial compression, two plane bending and torsion in four types of diaphyseal fractures. With the exception of axial loading in the presence of extensive comminution, the fixation stability provided by the noncontact fixator is significantly higher than that of the tested intramedullary nail. Any degree of cortical contact between the two main fragments is important for the stability of this nonperiosteal contact fixation system under axial load. Appropriately-designed "internal fixators" could provide not only a number of biological and technical advantages, but also fixation stability comparable and in certain aspects superior to that of other fixation methods.