[Strength testing of pins made of human femur cortical bone]

For biomechanical evaluation of cortical bone as a potential source for internal fixation devices, pins of 2 and 3 mm in diameter were made from fresh human femora and subjected to bending loads. Some of the pins were tested without further treatment; others were defatted and dried in acetone solution. Of the acetone-treated pins, some were autoclaved either at 121 degrees C for 20 min or at 134 degrees C for 8 min. Acetone treatment of the pins caused a 5.5% increase in bending strength (p < or = 0.05) and a 6.6% increase in the elastic modulus (p < or = 0.05). The mean bending strength of the acetone-treated pins was 257 +/- 52 N/mm2 and the mean elastic modulus was 18,346 +/- 1292 N/mm2. Autoclaving of the pins at the lower temperature for a longer time led to a decrease in the bending strength of up to 16% and at the higher temperature for a shorter time to a decrease of up to 41%. To compare the strengths of the cortical and synthetic pins, 2-mm Biofix pins were also tested. The Biofix pins showed a 25% higher bending strength than the acetone-treated pins but a 12.5% lower elastic modulus. It should be noted that in animal studies the synthetic Biofix pins showed a 20% loss of strength within 2 days after implantation in situ.