A review of biomechanical studies of intramedullary nails

Fracture management is becoming less conservative, and more frequently surgical intervention is the treatment of choice. Intramedullary nailing is a modern surgical method of internal fracture fixation used in long bones such as the femur, tibia and humerus. The nails' function is to stabilize the fracture fragments, allowing load transfer across the fracture site while maintaining anatomic alignment of the bone. There are a large number of different intramedullary nails available commercially but no universal guideline stating the conditions at which each nail will perform at its optimum. Numerous animal, biomechanical and clinical studies have documented the performance of the nails. Biomechanical studies have shown that in torsion, slotted nails have a considerably lower rigidity than non-slotted nails but that in bending, the slot makes little difference to the nails' behaviour and so the two nail types have similar stiffnesses. Studies also recommend that in unstable fractures an interlocked intramedullary nail is essential if limb shortening or malunion is to be avoided. It is the aim of this review to outline the work that has been published to date on the biomechanical testing of intramedullary nails and to highlight areas that require further investigation.