Compressive forces achieved in simulated equine third metacarpal bone lateral condylar fractures of varying fragment thickness with Acutrak Plus screw and 4.5 mm AO cortical screws.
Authors: Lewis Andrew J, Sod Gary A, Burba Daniel J, Mitchell Colin F
Journal: Veterinary surgery : VS
Summary
Lateral condylar fractures of the equine third metacarpal bone are significant injuries requiring rigid fixation to promote primary bone healing and maintain joint congruity. Lewis and colleagues conducted an in vitro biomechanical study on 12 pairs of cadaveric metacarpal bones, creating simulated fractures at three different fragment thicknesses (20, 12, and 8 mm) and measuring interfragmentary compression achieved by either 6.5 mm Acutrak Plus or 4.5 mm AO cortical screws. The 4.5 mm AO screws generated substantially greater compressive force across all fragment thicknesses, producing compression values that were 78.4%, 73.8%, and 65.8% higher than Acutrak Plus in the 20, 12, and 8 mm groups respectively. Whilst compression characteristics improved with thinner fragments, Acutrak Plus screws remained significantly weaker throughout. The authors advise exercising caution when selecting Acutrak Plus fixation for complete lateral condylar fractures, reserving this option only for thin-fragment cases where interfragmentary compression is less compromised—an important consideration for practitioners selecting fixation methods based on fracture morphology and the biomechanical demands of primary bone healing.
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Practical Takeaways
- •When fixing lateral condylar fractures in MC3, AO cortical screws provide superior interfragmentary compression and should be preferred for complete fractures and thick fragments
- •If using Acutrak Plus screws, limit them to cases with thin lateral condyle fragments (≤12 mm) where compression is relatively better, though still inferior to AO screws
- •Rigid fixation with adequate interfragmentary compression is critical for successful healing of these fractures—screw choice directly affects this outcome
Key Findings
- •AO cortical screws generated significantly greater compressive pressure than Acutrak Plus screws across all fragment thicknesses (P<0.05)
- •Acutrak Plus compression was only 21.6% of AO screw compression at 20 mm fragment thickness, improving to 34.2% at 8 mm thickness
- •Compression characteristics improved with thinner fracture fragments for Acutrak Plus screws but remained significantly inferior to AO screws in all groups