Microdamage at the pin-bone interface of external skeletal fixation pins after short-term cyclical loading ex-vivo

K. Cohen; R.P. McCabe; V.L. Kalscheur; R. Vanderby Jr; M.D. Markel; P. Muir

doi:10.1055/s-0038-1632765

Veterinary and Comparative Orthopaedics and Traumatology, Table of Contents

Vet Comp Orthop Traumatol 2003; 16(02): 88-92
DOI: 10.1055/s-0038-1632765

Original Research

Schattauer GmbH

Microdamage at the pin-bone interface of external skeletal fixation pins after short-term cyclical loading ex-vivo

K. Cohen

¹Comparative Orthopaedic Research Laboratory, School of Veterinary Medicine, and the Orthopaedic Biomechanics Laboratory

,

R.P. McCabe

²Department of Orthopaedic Surgery, School of Medicine University of Wisconsin-Madison, Madison, WI

,

V.L. Kalscheur

¹Comparative Orthopaedic Research Laboratory, School of Veterinary Medicine, and the Orthopaedic Biomechanics Laboratory

,

R. Vanderby Jr

²Department of Orthopaedic Surgery, School of Medicine University of Wisconsin-Madison, Madison, WI

,

M.D. Markel

¹Comparative Orthopaedic Research Laboratory, School of Veterinary Medicine, and the Orthopaedic Biomechanics Laboratory

,

P. Muir

¹Comparative Orthopaedic Research Laboratory, School of Veterinary Medicine, and the Orthopaedic Biomechanics Laboratory

› Author Affiliations

Abstract

Summary

This study determined microdamage associated with external fixation pin insertion and short-term cyclical loading, using an ex vivo ovine tibial model. Orthofix tapered blunt-tipped 3.5/4.5 mm fixation pins and Apex® self-drilling self-tapping fixation pins, 4 mm in diameter, were used. After insertion, the constructs were either loaded in cantilever bending or not loaded. Constructs were then bulk-stained in basic fuchsin, and calcified sections were made. The sections were reviewed qualitatively and the microcrack surface density (Cr.S.Dn, μm/mm²) was quantified at the pin-bone interface. The pattern and quantity of microdamage induced was significantly influenced by fixation pin design and cortical region within the cisor transcortex, but not short-term cyclical loading. Overall, Cr.S.Dn was significantly increased with use of the Orthofix fixation pin (P < 0.01). Cr.S.Dn was also increased in the medial cis-cortex, compared with the lateral transcortex (P < 0.05). Diffuse damage within the medial cis-cortex was higher with the Orthofix pin. In contrast, the Howmedica Apex® fixation pin caused fracture of the periosteal region of the lateral transcortex, but relatively little microdamage within the medial cis-cortex. In this model as a consequence of pin insertion, fixation pin design had significant specific damage effects on both the medial cis-cortex and the lateral trans-cortex

Keywords

Microdamage - external fixation pin - cyclical loading

Full Text

References

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