Finite element analysis of a femoral retrograde intramedullary nail subject to gait loading.

Intramedullary nails are routinely used in the treatment of fractures of the femur. While their effectiveness has been demonstrated clinically, a number of complications, including bone refracture and implant failure, persist. This paper presents novel three-dimensional finite element (FE) models, at four stages of gait, of: (i) a realistic femur analogue known as third generation composite bone, and (ii) a system consisting of an intramedullary nail implanted in the femur of (i). A comparison of experimentally measured strains on the surface of the femur with those predicted by the FE model revealed good agreement. The models were then used to identify implant/bone load sharing patterns, and areas of stress concentration in both the intramedullary nail and the bone, when statically locked by one or two screws at either end. The results of this study can be used to guide future implant design and surgical procedure.