Clinical Application of Resorbable Biomaterials in Reconstructive Surgery

Abstract

Until now we don’t really know how much stability is needed for undisturbed bone healing. Usual metal fixation in fracture treatment is without any doubt a successful procedure. Cortical bone and steel are very different materials, especially concerning the elastic properties. The elasticity constant of bone is only 1/10 of implant steel, and tensile strength is 10 times lower. In the months following internal fixation, bone substance is decreasing as a matter of deviation of force over the implant. The removal of metal implants is followed by a period of weakened bone (stress protection) with the danger of refractture or second fracture. Bone healing is a dynamic procedure, starting with no stability at all up to regulär strength. The idea of biodegradable implants depends on the reflected image of the bone, that means a decreasing weightbearing of the material. After months, the whole material has disappeared completely and no secondary surgery is needed. Besides the costs, time of treatment and uncomfort of the patient descends. Polymer materials which are hopeful for this indication are Polyglycolide, Polylactide, Polydioxanone and Polyhydroxy- butyrate. The physical data are well known and do not differ fundamentally. They can be improved by higher molecular weight and various kinds of treatment after polymerisation. Copolymers are investigated as well as Compound materials. Because we need a complete system for internal fixation, the development of biodegradable implants has five aims: the replacement material for K-wires, flexible wires, cords, plates and screws.