Biomechanical Analysis of Three Different Types of Implants in Humeral Diaphysis Fractures

Objective: The purpose of this study was to evaluate the mechanical behavior of three different types of implants used in the osteosynthesis of comminuted humeral shaft fractures. Materials and methods: We used 16 Sawbones® composite synthetic bones. We created a medial third osteotomy and we removed a 38mm thick fragment. We instrumented the fractures with 3 types of implants: an intramedulary nail, two types of locked plates and a "classic" DCP. All of them were submitted to torsion essays in external and internal rotation as to obtain the same amount of torque. The loading-deforming diagrams were compared and statistically analysed for each type of implant. Conclusions: The shorter locked plate (LCP-Synthes®) seems to be the most rigid implant for each type of loading essay, the mean values of the loading forces being the highest in the entire group. The intramedullary nail proved to be the most elastic implant on all types of loading. In external rotation, the DCP gives surprisingly values of torsion forces relatively close to the longer locked plate (AxSOS - Stryker®). This seems to be related to the different "working length" of the different plates and also to the different total length of the implants.