Structural properties of interlocking nails, canine femora, and femur-interlocking nail constructs

R. T. Dueland, Lars Berglund, R. Vanderby, E. Y S Chao

Research output: Contribution to journalArticle

65 Citations (Scopus)

Abstract

Using standard material testing techniques (bending stiffness, torsional stiffness, and maximum torque to failure or yield torque), the structural properties of interlocking nails (IN), canine femora, and IN/femur constructs were determined. Specimens that were tested included: 6 and 8 mm diameter IN with 5 to 10 screw holes (n = 18), and intact canine femora (n = 10), which also, with an IN inserted, formed the intact construct (IC) group, (n = 10). Specimens in the IC group were first tested with an 8 mm diameter IN with zero screws, followed by one and two screws (4.5 mm diameter) in the proximal and distal femur. A fracture model construct (FMC), (n = 14), consisting of a transverse femoral osteotomy with a 3 mm gap, was used with either 6 mm or 8 mm IN. In the 6 mm FMC, one and two 3.5 mm screws were used sequentially in the proximal and distal femoral segment. In the 8 mm FMC, one and two 3.5 mm screws and one and two 4.5 diameter screws were used similarly. When bending forces were applied parallel to IN screw holes, mean IN stiffness was 20% less than with forces perpendicular to the holes (n = 18), (P < .05). Eight-millimeter IN were 220% stiffer in torsion and 270% stiffer in bending than 6 mm IN (P < .05). Six-millimeter IN had approximately 32% of the bending stiffness and torsional stiffness of intact femurs (P < .05). Eight-millimeter IN had 93% and 79% of the bending stiffness and torsional stiffness, respectively, of intact femurs. Intact femur constructs (8 mm IN with four, 4.5 mm screws) had 147% of the bending stiffness (P < .05), and similar torsional stiffness and maximum torque, as intact femora (P > .05). The mean values of 6 mm FMC with four screws (3.5 mm) were 21% and 33% in torsional stiffness and bending stiffness, respectively, of intact femora values. When tested in torsion, 8 mm FMC failed by bone fracture; 6 mm FMC, in contrast, underwent plastic deformation. In comparing FMC stabilized with an 8 mm IN with two screws (4.5 mm diameter) in each bone segment, to intact femurs, the maximum torque was similar, FMC torsional stiffness was 40% (P < .05), and FMC bending stiffness was 65% (P < .05). These 8 mm FMC percentages are comparable to human IN fracture model construct values, indicating that the 8 mm IN/four screw construct should provide adequate stabilization for many canine diaphyseal femoral fractures.

Original languageEnglish (US)
Pages (from-to)386-396
Number of pages11
JournalVeterinary Surgery
Volume25
Issue number5
StatePublished - Sep 1996
Externally publishedYes

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nails (equipment)
Nails
femur
Femur
screws
Canidae
dogs
torque
Torque
thighs
Thigh
femoral fractures
materials testing
Materials Testing
bone fractures
Femoral Fractures
Bone Fractures
Osteotomy

ASJC Scopus subject areas

  • veterinary(all)

Cite this

Structural properties of interlocking nails, canine femora, and femur-interlocking nail constructs. / Dueland, R. T.; Berglund, Lars; Vanderby, R.; Chao, E. Y S.

In: Veterinary Surgery, Vol. 25, No. 5, 09.1996, p. 386-396.

Research output: Contribution to journalArticle

Dueland, R. T. ; Berglund, Lars ; Vanderby, R. ; Chao, E. Y S. / Structural properties of interlocking nails, canine femora, and femur-interlocking nail constructs. In: Veterinary Surgery. 1996 ; Vol. 25, No. 5. pp. 386-396.
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