Biomechanical comparison of slotted and nonslotted interlocking nails in distal femoral shaft fractures.

The torsional and compressive biomechanical characteristics of slotted and nonslotted interlocking nails in distal femoral shaft fractures were evaluated. Slotted (Grosse-Kempf) and nonslotted (Russell-Taylor) locked nail systems were implanted in anatomic specimen femora, which were then tested in torsion and axial compression. For torsional studies, each femur was transversely sectioned distal to the isthmus; for axial loading, a distal 3-cm section of bone was removed. The mean peak torsional stiffness of the femora fixed with nonslotted nails was 0.955 Nm per degree, which was significantly greater than that (0.300 Nm per degree) for the femora fixed with the slotted nails. However, when loaded to failure in compression, the nonslotted nail group failed at a mean load of 2490 N compared with 3050 N for the group fixed with the slotted devices. These results could be due in part to the lesser rigidity of the slotted nail, which may have facilitated greater load sharing with bone and increased resistance to compression failure.