A biomechanical comparison of headless tapered variable pitch and AO cortical bone screws for fixation of a simulated lateral condylar fracture in equine third metacarpal bones.

Summary

# Editorial Summary Lateral condylar fractures of the third metacarpal bone represent a significant orthopaedic challenge in equine practice, yet limited evidence exists to guide surgeons in selecting between different screw fixation systems for this anatomically demanding location. Galuppo and colleagues conducted an in vitro biomechanical study comparing 4.5-mm AO cortical screws against 6.5-mm headless tapered variable pitch (Acutrak Plus) screws across both insertion characteristics and fracture fixation performance in equine MC3 specimens. The Acutrak Plus screws required significantly greater insertion torque and force, though insertion time proved comparable between systems; notably, the AO screws demonstrated superior mechanical strength and stiffness when stabilising the simulated lateral condylar fracture, with substantially higher shear loads to failure and resistance to deformation. For practitioners selecting fixation methods for this common injury, these findings suggest that whilst the Acutrak Plus design offers specific advantages (such as self-tapping capability and reduced stress on bone), the biomechanical superiority of the AO system in resisting the shear forces typical of lateral condylar loading may favour its use in cases where maximal stability and load-bearing capacity are prioritised during the critical healing phase.

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Key Findings

• •AP screws required significantly less drilling, tapping, and insertion torque compared to AO screws
• •Both screw types demonstrated similar mechanical shear strength and stiffness for MC3 fracture stabilization
• •AP screw insertion was faster and required less force than AO screw insertion

Conditions Studied