Evaluation of biodegradable plate and screw systems for fixation of mandible bone fracture fixation in a rabbit model

Abstract

ABSTRACT Introduction: Currently, titanium alloy systems have been used for the treatment of bone fracture. This device has many advantages such as the reduction of healing time and the convenience in operation process. However, concerns about infection, exposure, transcranial migration, and growth restriction when using metal devices were reported in studies. To overcome these problems with the conventional metallic system, a variety of bioabsorbable materials have been developed for the treatment of bone fracture. Plate and screw fixation techniques for fracture healing had been boosted with the development of new biocompatible materials. The aim of this study is to evaluate the effects and safety of recently developed bendable bioabsorbable plate and screw device system in mandibular fracture in a rabbit model. The success of this system in mandibular ramus, which is known for highload- bearing site, might suggest the usefulness of given bioabsorbable plates and screws. Methods: We investigated the efficacy and safety of recently developed bendible bioabsorbable plates and screwwhich are made of PLGA (polylactic-co- glycolic acids) and 100% poly (L-lactic acid) only in a rabbit model. In vivo mandibular fracture model in rabbit was introduced to evaluate the efficacy and biocompatibility of the each fixation system. Twenty-five New Zealand white rabbits for each system were randomly assigned for each system. At 4, 6, 8 and 10 weeks after implantation, tissue specimens were taken from the implanted sites of the rabbits and histological analysis was performed for the each of the specimen. Results: Until 6 weeks, both devices of fixation system showed similar result. After 4 weeks, plates and screws were covered by amorphous connective tissues and overwhelming severe active chronic inflammation in soft tissue has observed. After 6 weeks, the inflammation decreased and some of the specimens exhibited new bone formation around the end of a fracture line. After 8 and 10 weeks, in the case of PLGA made plates and screws, new bone formation was observed with all samples without severe inflammation, implying the healing statue of the bony fracture. Meanwhile, rabbits with PLA plates and screws showed incomplete bone remodeling although new bone formation and increase of bone thickness were observed. Conclusion: Given by these, it could be suggested that biodegradable plate and screw systems that we evaluated in this work be effective for treatment of mandibular fracture, one of the sites under a high load-bearing condition. The adjustment process and long-term followup study is in progress for clinical application of this plate and screw system. ---------------------------------------------------------- Keywords: bioabsorbable plate and screw, bone fixation, PLGA (polylactic-co- glycolic acids), PLA(polylactic acid), biocompatibility Student number: 2011-21883