An in vitro biomechanical investigation of an equine interlocking nail.
Authors: McDuffee L A, Stover S M, Bach J M, Taylor K T
Journal: Veterinary surgery : VS
Summary
# Editorial Summary: Equine Interlocking Nail Biomechanical Properties Researchers from UC Davis biomechanically tested an experimental equine interlocking nail (EIN) device using twelve cadaveric equine tibiae to establish whether the construct could withstand the loads encountered during normal ambulation in adult horses. The tibiae were tested under compression, three- and four-point bending, and torsional loading, with mechanical properties directly compared against published estimates of in vivo loads. Whilst the EIN-stabilised composites demonstrated compressive yield loads of 11 kN and bending moments of 216 Nm—both exceeding expected postoperative demands—the mean torsional yield load of 156 Nm fell below the torsional forces anticipated during walking. These findings highlighted a critical mechanical limitation: the device could theoretically support weight-bearing and bending forces but lacked sufficient torsional rigidity, meaning horses would likely experience construct failure when the tibia experienced the rotational forces inherent in normal movement. Although the interlocking nail concept showed promise from a biological standpoint (potentially reducing soft tissue trauma compared to plate fixation), the authors concluded that the device required substantial engineering refinement before clinical application in adult horses could be justified, making alternative fixation methods more reliable for tibial fracture repair at that time.
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Practical Takeaways
- •EIN is not currently suitable for tibial fracture repair in adult horses due to inadequate torsional strength during weight-bearing
- •The device may have biological advantages worth pursuing, but mechanical redesign is necessary before clinical application
- •Torsional loads during walking present the primary biomechanical challenge for interlocking nail designs in equine tibia
Key Findings
- •EIN-stabilized tibiae demonstrated compressive yield load of 11 kN and bending moment of 216 Nm, both exceeding estimated in vivo postoperative loads
- •Torsional yield load of 156 Nm was insufficient compared to expected in vivo torsional loads during walking
- •Device provided adequate compression and bending stability but failed torsional stability requirements for weight-bearing in adult horses