Computerized analysis of resorbable polymer plates and screws for the rigid fixation of mandibular angle fractures.

PURPOSE: This computer-based study used finite element analysis (FEA) to assess whether rigid fixation by resorbable polymer plates and screws can provide the required stiffness and strength for a typical mandibular angle fracture.

MATERIALS AND METHODS: Two separate 3-dimensional FEA models of the mandible were generated using 8-noded hexahedral elements. The jaw segments in 1 model were fixed with titanium plates and screws as those in common use today. The jaw segments in the other model were fixed with resorbable polymer plates and screws as used in a developmental product currently in trials. A commercial finite element solver was then applied to this mesh to compute stresses and bone interfragmentary displacements for both titanium fixation and resorbable fixation. Calculated displacements were compared with each other and to established norms for healthy bone regrowth. Calculated stresses were compared with the yield strength of each material. Finally, overall stress patterns in the fractured mandibles were compared with each other.

RESULTS: The study results indicate that titanium fixation more rigidly fixes the 2 bone segments in relative position. However, they also show that resorbable polymers provide sufficient stiffness to meet currently established norms for fracture immobility. Furthermore, the analyses show that resorbable polymers are capable of withstanding the stresses generated by the bite loads of postsurgical patients. The results indicate that mandibles, fixed with either titanium or resorbable materials, show nearly identical stress patterns.

CONCLUSIONS: The resorbable polymer-based plates and screws tested in this investigation are of adequate strength and stiffness for their successful application to the rigid fixation of mandibular angle fractures.