Biodegradable interlocking nails for fracture fixation

Serious problems such as stress shielding, allergic reactions, and corrosio n are associated with the use of metallic fracture fixation devices in frac tured long bones. Metal implants often are removed during a second retrieva l operation after fracture healing has completed. A biocompatible implant t hat degrades slowly during implantation would obviate the need for a second operation and save the patient from considerable physical, psychologic, an d financial discomfort. The biodegradable implant must provide the fracture d limb sufficient support for a certain time, allowing early loading. A gra dual transfer of load from the biodegradable implant to the bone would resu lt in a better product of bone healing and avoid stress shielding. In an an imal model using adult sheep, two types of biodegradable polymer interlocki ng nails were tested in comparison with a stainless steel interlocking nail . Fracture healing, mechanical properties of the bones, degradation behavio r in vivo and in vitro, and tissue response were monitored during a 2 1/2-y ear follow-up study. To detect shifts in acid base relations caused by the release of acid compounds, pH measurements were performed. Fracture healing was unimpaired, and the mechanical test results of all three groups were e xcellent, Histologic analysis showed a mild inflammatory response, but no p H shifts were observed. The results: of this study justify additional resea rch on these promising materials.