Characterization of an innovative intramedullary nail for diaphyseal fractures of long bones.

In this paper, an innovative design of nail for fractures occurring on long bones has been investigated. Its functioning is based essentially on sliding of conical surfaces, located in a spindle and in holding pins. Spindle and holding pins are connected together by a sleeve. The sliding transforms the rotational and translational motion of the spindle to a radial expansion of the holding pins, protruding inside the intramedullary canal. In order to evaluate mechanical behavior of the prosthesis different benchmarks and tests were numerically performed by an FE code. Results confirm good performances in terms of strength, under compression, bending and torque loading. Moreover, a complete model of the nail implanted on a tibia, has been developed and tested evaluating two loading configurations. Results confirmed a satisfactory behavior of the nail in terms of stress and strain shielding, comparable to the others traditional systems of prosthesis. In conclusion, this kind of nail appears to offer a good solution for elderly patients, which could not endure complications due to a complex surgery, as distal or medial screws are not necessary.