OP111: Biomechanical evaluation of mandible segmental reconstructions using different methods of fixation

Abstract

A reconstruction plate is conventionally used for internal fixation and load bearing across a segmental defect often created following a resection for malignancy. The aim of this study was to evaluate whether a uniform plate design is suitable for managing the more common types of segmental defects. This study may also promote a better understanding of the critical sites of a reconstructive structure and the ideal plate characteristics required to support bone regeneration whilst decreasing the likelihood of fixation failure. A detailed patient based edentulous mandible model was developed from CBCT/DVT scanning using standard reverse engineering techniques. A uniform reconstruction plate was modeled and utilized. The finite element analysis was used to compare the commonly used combinations of screw fixations (non-locking or locking and bicortical or monocortical). The most common symmetrical and asymmetrical segmental mandibular resections were analysed. The stress values within the plate, screws and implant/bone interface were recorded. The common practice of inserting a minimum of 3 screws either side of the resection was effective. In general the screws closest to the resection showed significantly higher stress levels (60–320 MPa). The inter-segmental movements with different plate strengths were studied as this can influence the potential for bone regeneration. The unilateral defect reconstruction allowed the smallest deformation while the symphyseal bone support was the highest quality. This study has identified the most effective position, number and type of screw anchorage points for a uniform plate reinforcement of the common segmental defects. Future works will focus on the overall load bearing capacity and movements of differing types of reconstruction plate and screws to optimize and redistribute the remaining effective strength of the plate to facilitate the design of novel bone regenerative scaffolds.