SEDL / STP / STP918-EB / STP19343S

Fatigue Crack Growth and Crack Arrest in the Nails Used for Intramedullary Fixation of Femur Fractures

Mattheck, C
Institut für Reaktorbauelemente, Arbeitsgruppe Zuverlässigkeit und Schadenskunde im Maschinenbau, Karlsruhe,

Kneifel, B
Institut für Reaktorbauelemente, Arbeitsgruppe Zuverlässigkeit und Schadenskunde im Maschinenbau, Karlsruhe,

Morawietz, P
Institut für Reaktorbauelemente, Arbeitsgruppe Zuverlässigkeit und Schadenskunde im Maschinenbau, Karlsruhe,

Pages: 16    Published: Jan 1986

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Abstract

The fractures of large bones are often fixed by use of intramedullary nails. Sometimes these nails show cracks originating at the end of their slot and also at perforations which are necessary for the screws of interlocking nails. In this paper it is shown that notch stresses near these perforations are responsible for crack initiation. A fracture mechanical analysis is carried out in order to calculate the stress-intensity factor for such cracks under physiological loading. Fatigue considerations are presented, and conditions for crack arrest are shown. A new nail profile is proposed which reduces the notch stresses significantly.