An in vitro biomechanical comparison of two interlocking-nail systems for fixation of ostectomized equine third metacarpal bones.
Authors: Lopez M J, Wilson D G, Trostle S S, Markel M D
Journal: Veterinary surgery : VS
Summary
# Editorial Summary: Interlocking-Nail Fixation Systems for Equine Third Metacarpal Fractures Surgical repair of third metacarpal bone fractures in horses remains challenging, particularly when significant bone loss is involved, making the biomechanical properties of fixation systems a critical consideration for clinical outcomes. Lopez and colleagues conducted an in vitro mechanical testing protocol comparing two interlocking-nail configurations on ostectomized equine MC3 specimens: a conventional design with parallel screw placement proximal and distal to a 1-cm bone defect, and a modified system in which the distal screws were offset at 30 degrees to the proximal screws. The offset-screw design demonstrated superior resistance to bending and torsional forces compared to the parallel configuration, offering potentially greater construct stability in the immediate post-operative period. These findings suggest that offsetting interlocking screws may reduce the risk of implant failure and non-union, particularly in cases requiring substantial bone removal or where extended rehabilitation periods are anticipated. Equine surgeons using interlocking-nail systems for MC3 repair should consider this biomechanical advantage, though clinical validation and assessment of long-term outcomes in live horses would strengthen the evidence for routine adoption of the modified technique.
Read the full abstract on PubMed
Practical Takeaways
- •When using interlocking nails for MC3 fracture repair, consider the modified offset-screw design as it provides superior biomechanical stability and may reduce risk of fixation failure
- •The 30-degree offset configuration improves load sharing and may lead to better long-term outcomes and faster return to function in high-performance horses
- •This design innovation could reduce post-operative complications and improve healing rates in surgical candidates for MC3 fractures
Key Findings
- •Modified interlocking nail system with 30-degree offset screws provided superior mechanical stability compared to standard parallel-screw configuration
- •Offset screw design reduced stress concentration and improved load distribution across the ostectomized MC3 site
- •Both systems maintained fixation integrity, but offset design showed improved resistance to torsional and bending forces in biomechanical testing