An analysis of the stability of craniofacial fracture fixation using a mandibular model

Abstract

This thesis aims to investigate the differences in mechanical properties of major miniplating systems used for non compression miniplate osteosynthesis of mandibular fractures, and to determine whether these properties influence treatment outcome. The study was conducted in three parts. Six of the major miniplate systems currently used at the Royal Adelaide Hospital were subjected to bending tests at the University of Adelaide Engineering Department to quantify the relative stiffness of each plate. A wide variation in the mechanical properties of the individual plating systems was identified. In addition the properties of the materials, their biocompatibilty and CT compatibility are discussed. In the second part of the study, patients with recent mandibular fractures were treated using internal fixation with miniplates that were the least stiff as identified earlier. These patients then had a load applied across the fracture, and cephalometric radiographs were taken to detect any deformation of the fracture. No deformation was detected a tolerable loads, suggesting that the pain response protected these patients from a bite force which would deform the malleable miniplates. In the third part of the study, a prospective sample of patients presenting with mandibular fractures was analysed. These patients were treated with a variety of the miniplating systems. The results of treatment as a whole rü/ere compared to identiff any direct benefit consequent on the miniplate selected. Whilst significant differences in stiffness existed between the plating systems and the cost of the miniplates, no significant differences in treatment outcome were identified,red between the noncompression miniplates employed. As no observable benefits have been identified by choice of miniplate, selection should be based on surgical preference, biocompatibility, CT compatibility, and unit cost. Due to the variations in materials, design, properties, CT compatibility and unit costs, it is important not to regard all miniplates as equal and interchangeable.