Improving the distal fixation of intramedullary nails in osteoporotic bone.

Twenty-four mildly osteoporotic human femurs were used to examine the fixation stability of several types of distal locking screws in osteoporotic femoral condylar segments. The fixated femurs were axially loaded to 1000 N at a rate of 100 N/sec to assess the locking screws' resistance to motion and then sinusoidally cycled to 10,000 cycles with a 500 N load to assess axial stability. Of the four screw configurations tested, the standard screws and the standard screws placed at a 30 degree crossing angle were significantly more stable (p < 0.05) than the step screw and osteoporotic bolt.