Impact of fractured tibia implant fixation devices on bone stiffness during bending test

This study focuses on evaluating the failure resistance of a previously reduced tibia with internal fixation implants as PLate (PL) or InterMedullary Nail (IMN), subjected later to a tibial lateral trauma. To replicate this type of trauma, which can be caused by a road accident, a three-point bending test is considered using experimental tests and numerical simulations.

The withstand evaluation of the tibia-PL and tibia-IMN structures was conducted by following the load transfer through, the bone and the used implants. The analysis, up to tibia failure, required the use of an elasto-plastic behavior law coupled to damage. The model parameters were identified using experimental tests.

Il was shown that the tibia-IMN structure provided a bending resistant load up to three-times higher than the tibia-PL. In fact, the used screws for plate fixation induced a high level of stress in the vicinity of threaded region, leading to a crack initiation and a damage propagation. However, in tibia-IMN structure the highest stress was generated in the trapped zone between the loader and the nail, promoting crack formation.

From a biomechanical point of view, the structure with IMN is safer than the structure with PL, whose fixation induces earlier damage in bone.