Evaluation of a new optical measuring system for experiments on fractured human mandibles: A biomechanical feasibility study in maxillofacial surgery

Objectives: Biomechanical loading on human mandibles was performed and a new optical measurement device was introduced for the quantification of interfragmentary movement in fractured mandibles stabilized with different osteosynthesis systems. Materials and methods: Comparison tests were performed with monocortical non-locking double plates and bicortical single locking plate. For the experiments on a specialized test bench, 18 ex vivo fractured human cadaveric mandibles were tested. Interfragmentary motion was detected in all three spatial dimensions using the optical measurement device PONTOS®. The movement was investigated over increasing incisal force and one summarized parameter was investigated. Results: For the maximal tested load of 300 N m, the resultant interfragmentary movements in the two investigated groups were 2. 96 ± 1. 85° for the fixation with two conventional miniplates (six hole, profile 1. 0 mm) and 4. 53 ± 2. 49° for single bicortically fixed locking plates (four hole, profile 1. 5 mm). For both plate systems, we used the 2. 0 mm screw system. Conclusions: The test bench in combination with the new optical device PONTOS^® can test the primary stability of osteosynthesis. We offer a solution to the problem of rate of twist of the mandible as well as typical rotational problem in recent measurements. Further, the method can be used for development of new osteosynthesis products. Clinical relevance: Pseudoarthrosis formation is a common problem based on unsatisfying fixation of the fracture gap. The here presented combination of mechanical tests and numerical simulations can provide support for an improved treatment of fractured mandibles.