A Modified Intramedullary Nail Interlocking Design Yields Improved Stability for Fatigue Cycling in a Canine Femur Fracture Model

Document Type

Article

Publication Date

4-11-2012

Publication Title

Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine

Abstract

Intramedullary nailing has evolved to become the standard of care for most diaphyseal femoral and tibial fractures, as well as an expanding number of metaphyseal fractures. Owing to the unstable nature of some fractures, the intramedullary device may be subjected to significant stresses owing to a lack of solid cortical contact after nailing. In such cases, excessive interfragmentary motion (due to construct toggle) has been shown to occur. Such motion increases the likelihood of a non- or delayed-union. In the current study, two versions of a modified, angle stable interlocking design were subjected to fatigue testing in a segmental defect fracture model representing a canine femur. As a control, a third group of constructs were stabilized with a traditional nail that allowed a small amount of toggle. All constructs were subjected to 50,000 fatigue cycles representing 12 weeks of cage activity at physiologic levels of combined axial-torsional loading. Torsional testing pre- and post-fatigue revealed 4.6 ± 1.3° of toggle in the traditional nail and no toggle with the angle stable nail designs. The stable nails were also significantly stiffer in axial compression and torsion before and after cycling. These data indicate that the enhanced stability of the modified interlocking designs can be maintained throughout fatigue cycling in a challenging fracture model.

Volume

226

Issue

6

First Page

469

Last Page

476

DOI

10.1177/0954411912443627

ISSN

ISSN: 0954-4119, Online ISSN: 2041-3033

Rights

© 2012 Institution of Mechanical Engineers

Link to Full Text

Share

COinS