BIOMECHANICAL COMPARISON OF TITANIUM AND STAINLESS STEEL LOCKING SCREWS FOR INTRAMEDULLARY NAILING

Background Intramedullary nailing is a widely accepted treatment method for femoral fractures. Failure of locking screws is often a threatening complication, particularly on comminuted fractures. For comminuted fractures, the locking nails are load-bearing devices. The load transfer between fractured fragments is made through especially the locking screws for these load bearing situations. Nonunion, malunion, delayed union, shortening, and nail migration are the expected results if early failure of locking screws is present with comminuted fractures. In this study our aim was to compare the bending resistance of titanium and stainless steel locking screws. Methods We tested 60 locking screws in six groups (titanium, stainless steel, unthreaded, low threaded and high threaded) in a steel tube that has 30 mm inner diameter, which imitates the lesser trochanter level. We determined the yield points at three-point bending tests that permanent deformation started in the locking screws using an axial compression testing machine. Results The three-point bending resistance of 5 mm low threaded titanium locking screws (bending at 1413 N loading) was 46.5 % less than the three-point bending resistance of 5 mm low threaded stainless steel locking screws (bending at 2171 N loading) (p Conclusions Therefore, stainless steel locking screws instead of titanium ones must be preferred in comminuted femur shaft fractures. In intramedullary nailing of comminuted or long oblique femur fractures, a locking screw should be 5 mm low threaded or unthreaded stainless steel or 5 mm unthreadedtitanium. Five mm high threaded titanium or stainless steel screws must not ever be used as a locking screw. Level of Evidence 5 Disclosure Authors declare that there is no conflict of interest related to the present study.