The Biodegradable Intramedullar Nail - Biomechanical Results and Tissue Response 4 Years after Implantation in Sheep -

Abstract

The conventional metal intramedullar nail has considerable drawbacks. A second operation is often needed to remove the nail after fracture healing. The stress-shield phenomenon can cause impaired fracture healing, and there is the possibility of infection, allergic reaction and corrosion.To avoid these problems a biodegradable interlocking nail was developed. Ideally, the biodegradable intramedullar nail will lose its strength gradually during a controlled degradation pattern and the load on the fractured bone will gradually shift from implant to bone.The results of a long term follow up study (4 years) in an animal model using adult sheep are presented in this paper.A self-reinforced polylactide intramedullar nail was used for the fixation of an artificially made femoral fracture.The following parameters were subject of investigation: clinical fracture healing, radiological results, mechanical properties of the bones and local and regional histological response.Macroscopically some shortening and angulation of the fractured femora was observed. The clinical healing was unimpaired and the mechanical tests were excellent in four sheep. Histological analysis showed a mild tissue response and a partial degradation of the implant.