Biodegradable implants in traumatology: a review on the state-of-the-art

Up to now the internal fixation of fractured bones and joints has been managed by metal implants. There are certain associated disadvantages: the mechanical properties of the metals are stronger than those of cortical bone (“stress-protection”); the removal of the implants requires a second operation; an increasing number of patients are confronted with problems of sensitivity to metal components of the implants, especially nickel. About 40 different biodegradable polymers, copolymers and composites have been developed as substitutes for metal implants in internal fracture fixation. The early experimental and clinical results demonstrate their limitations. From the current point of view, it is not possible to transfer the designs and assembling principles of metal implants in orthopaedic surgery to biodegradable polymers. The attempt to simply mimic metal implants in polymers is condemned to fail from the very beginning. This is a review of the literature and of our first 100 patients operated on using implants made of self-reinforced polyglycolide acid and polydioxanone. The main difficulty with the material is the loss of stiffness in a time interval which is not long enough to guarantee bone healing. The development of a sterile sinus over the site of implantation is a problem also reported by other groups. Certain additives have to be inserted into the polymers to make them visible on conventional X-radiographs. Despite these drawbacks, however, there are indications for the isolated or adjuvant implantation of biodegradable materials. They could be employed in the treatment of osteochondral fractures and other defined injuries. The available literature on these indications will be discussed. A standardized set of possible indications for the use of different biodegradable devices in orthopaedic surgery is presented as are clear contraindications for their use at the present time. For the future, fixation devices adapted to the characteristic properties of polymers and adjusted to specific therapeutic problems will have to be developed.