SEDL / STP / STP1008-EB / STP10363S

Testing Method for Evaluating Bending Stiffness and Torsional Stability of Femurs Implanted with Intramedullary Nails

Butts, MK
Research assistant and director, Orthopedic Biomedical Laboratory, and assistant chairman and chairman, Hennepin County and Metropolitan Medical Centers, Minneapolis, MN

Bechtold, JE
Research assistant and director, Orthopedic Biomedical Laboratory, and assistant chairman and chairman, Hennepin County and Metropolitan Medical Centers, Minneapolis, MN

Hoeltzel, DA
Assistant professor, Columbia University, New York City, NY

Kyle, RF
Research assistant and director, Orthopedic Biomedical Laboratory, and assistant chairman and chairman, Hennepin County and Metropolitan Medical Centers, Minneapolis, MN

Gustilo, RB
Research assistant and director, Orthopedic Biomedical Laboratory, and assistant chairman and chairman, Hennepin County and Metropolitan Medical Centers, Minneapolis, MN

Pages: 6    Published: Jan 1989

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Abstract

A testing method to evaluate the performance of intramedullary (IM) nails in stabilizing femur fractures and to compare the effects of different design features is presented in this study. Techniques are described for preparing specimens, creating fractures, potting bones for testing with electrohydraulic materials testing machine, testing in bending and torsion, and measuring flexural stiffness and torsional stability. Flexural stiffness is calculated from the moment versus deflection curve. The femur is rotated to 10 deg from neutral, and the torque generated at this forced rotation is recorded. The torque is then released by rotating the femur back to the neutral position, and the angle at which the torque returns to zero is recorded as the springback angle. The springback angle indicates the amount of slippage between the intramedullary nail and bone, or their relative stability in torsion.