Finite Element Analysis of Intramedullary Nail for Treatment of Femoral Shaft Fractures

Intramedullary nailing (IM) has been a reliable treatment for a wide variety of long bone fractures in orthopedic trauma since Küntscher’s first operation in 1940. Using the IM for treatment of long bone fracture sounds superior than the bone plate in many aspects, however, there are few key points have been discussed from time to time, such as ream or unream the medullar cavity when nail implanting, antegrade or retrograde for the distal end fracture, number of screws to obtain the stability of nail-bone complex, and others. Bucholz (1987) in evaluating 185 cases and concluded that the weakest point of the IM nail was located near the screw hole of distal end. Fatigue failure might occurred in case of fracture site being within 5cm or too close to the screw hole( Bucholz, 1987; Wei, 1989, Wu 1992). Bending moment was considered to be the failure load (Kinast, 1987). Implementation without reaming the medullar cavity was favorite by Duwelius (1995) and Hass (1995) for the reason of short operation time and less complication. But the undreamed nailing might result in delay union and screw failure ( Blachut, 1997). This study was focused to find the solution of the nail failure mechanism as well as fatigue life of the nail at different fracture locations, and the loosening effect on selected fastening screws by finite element analysis.