Experimental comparison of biomechanical properties of intramedullary femoral nails with different distal locking systems

Intramedullary nails are widely used in the treatment of long bone's shaft fractures and extremity lengthening operations. Intramedullary nails are supported by different components. The most important and mostly used components are interlocking screws. These screws provide resistance against rotational movements and fracture line narrowing by locking the intramedullary nail both from proximal and distal ends. Thus, fracture line recovers faster. Some deformations may occur on intramedullary nail in time. Similar situations may also occur on interlocking screws and this may cause nail failure. Screw failures are generally seen on distal interlocking screws. Failure type can be seen as load failure or fatigue failure. Screws with different sizes or different materials are being manufactured to minimize these failures. These failures are also being minimized by implanting the screws on different directions. Within the scope of this thesis, two nailing systems, which have basically different distal interlocking systems, were compared by applying biomechanical tests. One of these systems is traditionally used system and the other is newly designed nailing system distally locked with a stiffer locking screw. Static torsional, static axial compression and fatigue tests were applied for both systems. No distal screw failure was detected in novel system, but it caused different problems and it did not show outstanding results. In conclusion, novel system is not reliable enough to substitute the traditional system.