OP084: A failure-proof surgical technique for marginal resections and angulated osteotomies?

Abstract

Introduction – aims The section defect created in a bone using a saw is primarily in a linear plane. The meeting point of two cuts is a focus for stress concentration and under loading this area is prone to cracks and failure, especially if overcut. This is important for a marginal resection in a load bearing bone such as the mandible. The impact of different design factors were investigated with the aim of developing a simple surgical technique which could be combined with Prophylactic Internal Fixation (PIF) if required. Materials – methods Cadaver sheep tibia samples were scanned and transformed into high definition computer models. Standardized marginal resections evaluated the effect of right angled and sloped osteotomy cuts, different types of overcuts, and two novel design cuts to reduce the likelihood of crack formation and material failure. Four different PIF systems were tested. Numeric simulation using the Finite Element Method was applied to predict failure based on mechanical stress values. This aimed to reproduce our previous laboratory biomechanical bench testing of the sheep tibia model and validate the FEM model. Results – statistics The stress levels in the standard right angled and sloped resections were used as baselines. The overcuts substantially increased stress concentration (up to 196%). Both novel techniques (to be described) significantly reduced stress concentrations (down to 40%). The impact of different designs of PIF was also shown to offer a statistically significant improvement in strength (gained up to 2.6× in bench test and 3.71× in simulation). Conclusions – clinical relevance Avoiding an overcut has an obvious strengthening benefit. Both novel osteotomy techniques improve the stability of the osteotomised bone and are more precisely controlled than a conventional osteotomy technique. We will also illustrate this in clinical scenario.