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Unformatted text preview: d required implantation of the IM rod.
Upon questioning, the young man revealed that he was wearing expensive Nike sneakers and that the
pavement he landed on was concrete. He also noted that he slipped immediately after impact since there
was ice on the ground. Since he was not expecting the fall, he was in a gait type upright position at the
instant of impact (see Figure). He also mentioned that he was sure he landed on only one foot since his
other foot got caught in the retaining wall during the fall.
Checking with the implant catalogue, you found out that the IM rod was manufactured of cold-worked
316L stainless steel. Looking up your biomaterials textbook, you found that the yield strength of this
alloy was 700 MPa and its elastic modulus is 200 GPa. Discuss, in your expert opinion, why you think the implant failed. As part of your answer, compare the
stresses at the site of implant fracture against the yield strength of the implant material.
• Use conservation of energy to estimate velocity just before impact; and the impulse-momentum theorem
to estimate the peak force at impact. For the latter, assume that the force-time profile at impact, as would
be measured if there were a force platform under the young man’s foot during the impact, is as shown
below (see Figure).
• Use composite beam theory for calculation of stresses. Since the cortical bone in his implanted femur is
newly healed bone and therefore not fully mine...
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This document was uploaded on 03/08/2014 for the course BIOE 119 at Berkeley.
- Fall '10