In vitro cyclic biomechanical properties of an interlocking equine tibial nail.
Authors: McDuffee L A, Stover S M, Taylor K T
Journal: Veterinary surgery : VS
Summary
# Editorial Summary Tibial fractures in horses present a significant surgical challenge, particularly when considering which fixation methods will reliably stabilise bone fragments throughout the healing process. McDuffee and colleagues tested cadaveric equine tibiae fitted with interlocking nails under cyclic loading (compression, bending and torsion) for 740,000 cycles at physiologically realistic loads, measuring both fatigue life and strain patterns at the fracture site. Whilst compression and bending loads showed fatigue life exceeding the typical 8–12 week healing timeline, torsional loading failed well before adequate healing could occur; additionally, only compressive loading produced gap strains small enough to permit direct bone union, with all three loading modes generating strains compatible with slower secondary bone healing. The research indicates that current stainless steel interlocking nail designs require substantial modification—particularly increased bending stiffness and improved torsional resistance—before they can be reliably recommended for adult equine tibial fractures, with implications for case selection, post-operative management protocols, and the need for supplementary external support during the critical healing window.
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Practical Takeaways
- •Equine interlocking tibial nails in their current design may be inadequate for fracture stabilization without modifications; bending and torsional forces are problematic
- •If using these nails clinically, expect longer healing times or supplementary stabilization may be needed to account for insufficient torsional resistance
- •Design improvements to increase bending stiffness and torsional strength should be prioritized before routine clinical adoption
Key Findings
- •Compression and bending fatigue life exceeded the time required for bone healing, but torsional fatigue life did not
- •Compressive gap strains were compatible with primary bone formation, while bending and torsional strains required secondary bone formation
- •Current stainless steel equine interlocking nail design lacks sufficient bending stiffness and torsional fatigue resistance for long-term fracture stability