Biomechanical assessment of composite versus metallic intramedullary nailing system in femoral shaft fractures: A finite element study

Abstract

Our results suggest that the composite nail can provide a preferred mechanical environment for healing, particularly in transverse shaft fractures. This may help bioengineers better understand the biomechanics of fracture healing, and aid in the design of effective implants.

Recent developments on intramedullary nailing: a biomechanical perspective

“…This, combined with attachment of interlocking screws to the bone fragments, guarantees that the majority of the load is supported by the nail, which shields the bone from the stress and reduces the stimulus required for proper healing to occur. Such effect was perceived as a potential problem and was assumed to cause delayed recovery and nonunion cases . In an attempt to reduce the stress‐shielding effect and promote healing, Grosse and Kempf emphasized nail dynamization , where a fixed end is responsible for ensuring fracture rotational stability, while the opposite extremity is free to slide slightly inside the bone .…”

“…In an attempt to reduce the stress‐shielding effect and promote healing, Grosse and Kempf emphasized nail dynamization , where a fixed end is responsible for ensuring fracture rotational stability, while the opposite extremity is free to slide slightly inside the bone . In the materials field, a strong novelty was also introduced in the 1990s with the adoption of titanium, a new material competing with the until then commonly used AISI 136 LVM ASTM F138 stainless steel (generally known as medical‐grade stainless steel) . Today, both materials are widely accepted; however, there is a preferential tendency for titanium alloy owing to its attractive mechanical properties (see Table ), such as Young's modulus closer to the intact diaphyseal cortical bone, higher fatigue strength and yield strength, and the fact that it is biocompatible and shows less magnetic resonance imaging interference than that observed for stainless steel implants .…”

“…There is insufficient knowledge on the physiological mechanical environment that promotes fracture healing and how to adapt the intramedullary nail rigidity to mimic such an environment. Hence, it remains unclear which is the “ideal” mechanical environment at the fracture site, demonstrating the urgent need for an exhaustive study on this matter, which will also greatly affect future improvement of intramedullary nailing systems …”

“…According to this author, the strength properties demonstrated by intramedullary nails composed of this material should be sufficient to ensure long bone fracture stabilization. The use of reinforced composites allows for adaptation of their mechanical properties on the basis of the requirements by changing the fiber orientation and their arrangement or volume fraction …”

“…The primary goal of fracture treatment is to provide an optimum mechanobiological environment for each stage of fracture healing . Hence, the best way to promote callus development is to allow movements that stimulate and favor healing and to hinder those that may disrupt it .…”