Minimally Invasive Bioabsorbable Bone Plates for Rigid Internal Fixation of Mandible Fractures

Abstract

OBJECTIVES: To optimize design variables of a bioabsorbable bone plate using a finite element model of the mandible and to discover a minimally invasive bioabsorbable bone plate design that can provide the same mechanical stability as a titanium plate. METHODS: A finite element model of a mandible with a fracture in the body was subjected to bite loads. An analysis was run to determine the principal strain in the fracture callus and von Mises stress in a titanium plate. These values were then set as the limits within which the bioabsorbable bone plate must comply. The model then considered a bone plate made of the polymer poly(L-lactide-co-D,L-lactide) (P[L/DL]LA) 70/30. An optimization routine determined the smallest volume of bioabsorbable bone plate that can perform as well as a titanium bone plate when fixating mandibular fractures. RESULTS: A P(L/DL)LA plate volume of 315 mm(2) with a thickness of 1.5 mm provided as much mechanical stability as a commonly used titanium strut structure of 172 mm(2). The peak plate stress was well below the yield strength of the material. CONCLUSIONS: The P(L/DL)LA bioabsorbable bone plate design is as strong as a titanium plate when fixating fractures of the mandible body despite the polymer material having only 6% of the stiffness of the titanium. The P(L/DL)LA plate can be less than half the volume of its strut-style counterpart.