Static and dynamic bending strength of the leg

Schreiber, Philip Hosier, Mechanical and Aerospace Engineering, University of Virginia
Crandall, Jeff, School of Engineering and Applied Science, University of Virginia
Pilkey, Walter D., School of Engineering and Applied Science, University of Virginia
Miksad, Richard, School of Engineering and Applied Science, University of Virginia

This thesis evaluates the injury threshold and relative contribution of bending moment and axial compressive force during static and dynamic loading of the tibia/fibula complex. The efficacy of the Tibia Index, a combined stress analysis for predicting leg injury in automobile crashes, is also determined. Ten unembalmed cadaver legs were tested in quasi-static three-point bending, and twelve legs were subjected to dynamic three-point bending to compare static versus dynamic bending strength and energy to failure. Nine legs were subjected to dynamic three-point bending with a superimposed static axial compressive load. Legs were mounted with simple supports potted to the distal and proximal ends of the tibia/fibula complex, with the soft tissue structure maintained in tact. Impacts were delivered at mid-shaft, and directed posterioanteriorly. Load sensors measured forces delivered to the simple supports and impactor. High speed video recorded impactor displacement. Strain gauges mounted to the anterior and posterior tibia and fibula measured strain and strain rate at the outer-most fibers. CT scans provided cross-sectional properties of the bones along the longitudinal axis of the leg. Dynamic bending exhibited a 69% higher breaking strength than legs subjected to quasi-static loading, with fractures showing a greater degree of comminution. In tests where a 4448N axial compressive load was superimposed upon a three-point bending load, the strength of the leg complex decreased by 17%. Axial compression appears to increase the bending moment in the tibia due to the curvature of the bone. The strength of the tibia in both bending and compression is weakest in the distal third region.

MS (Master of Science)
human leg, human bone, bending strength

Local Note: "[Department of] Mechanical and Aerospace Engineering."

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