Biomechanical comparison of different fixations of femur-interlocking-nails

Abstract 

Objective. A new design of intra-medullary nailing fixation is investigated in this study. The strength properties of the new design are compared to the standard fixation method.

Design. The bone-implant-compound is examined by using experimental methods.

Background. Failure of bone substance in the region of the interlocking screws is a complication in particular in treating fractures of osteoporotic bone. A new additional implant is investigated, which should improve the fracture fixation of the bone-implant-compound.

Methods. The experiments were performed by using an universal testing machine. The bone-implant-compound was loaded by different compressive forces and the stiffness of the bone-implant-compound was measured. The maximum force to failure was also determined by a destructive test.

Results. The experimental results indicate that the additional implant increases the stiffness of the bone-implant-compound. The highest stress concentrations occur at the drill holes of the interlocking screws. Failure of the bone-implant-compound occurs at higher maximum forces by using the additional implant.

Conclusions. The additional implant improves the strength of the bone-implant-compound. In the case of osteoporotic bone, the use of the additional implant is recommended.

Relevance

In surgical treatment of fractured femurs, the fracture is bridged by a medullary nail fixed with interlocking screws. Failure of bone substance in the region of the interlocking screws is the most common complication in the treatment of osteporotic bone. With the aim of preventing this complication, a new additional implant is developed and investigated.

Keywords:  Biomechanics, Fracture of femur, Strength analysis