In vitro cyclic biomechanical properties of an interlocking equine tibial nail.

This research investigates the biomechanical properties of an equine interlocking nail used in the treatment of tibial fractures in horses. The study indicates that improvements are required to increase the nail’s bending stiffness and torsional fatigue life, as the current design and material do not provide sufficient long-term stability for fracture healing.

Methods Used in the Study

• Thirteen adult horse tibia bones that have undergone gap osteotomies (a surgical procedure that creates a gap in the bone) were used in the research.
• The bones, which were stabilized with an equine interlocking nail, were subjected to a series of biomechanical tests.
• The tests were administered in vitro (outside of the natural environment) under various conditions like axial compression, 4-point bending, and torsion.
• Various specimens were exposed to different load levels, representing the estimated in vivo loads and engaged in cyclic biomechanical testing at 2 Hz for 740,000 cycles.
• The researchers calculated fatigue life and gap strain to assess the performance of the nail.

Results of the Study

• The findings revealed that the compression and bending fatigue life were longer than the time necessary for bone healing, but this was not the case for torsional fatigue life.
• The gap strains under compressive loads were small enough to support fracture healing via primary bone formation but not under bending or torsional loads.
• Gap strain under all types of loads – compressive, bending, and torsional – were found to be compatible with indirect, or secondary, bone formation.

Conclusions Drawn from Research

• The results concluded that modifications are necessary in the design and material of the equine interlocking nail to increase its bending stiffness and torsional fatigue life.
• The current stainless steel equine interlocking nail is unlikely to provide long-term stability for fracture healing in adult equine tibiae without modifications.