Biomechanical comparison of the bone-screw-fastener to conventional cortical buttress screw in a simulated ex vivo model of equine midbody proximal sesamoid bone fracture repair.
Authors: O'Brien Thomas J, Johnson James W, Kawcak Christopher E, Gadomski Ben C, Carpenter Ryan S, Nelson Brad B
Journal: Veterinary surgery : VS
Summary
# Proximal Sesamoid Bone Fracture Repair: Comparing Modern Fixation Methods Proximal sesamoid bone fractures remain a significant challenge in equine orthopaedics, and selecting the optimal implant configuration directly influences the horse's prospects for return to function. Researchers compared the biomechanical properties of bone-screw-fasteners (BSF) against conventional cortical screws (CS) in an ex vivo cadaver model, using 14 paired forelimbs with simulated mid-body medial PSB fractures repaired in either single or double screw configurations. Both double-screw constructs—whether BSF or CS—demonstrated substantially greater yield strength (approximately 2081 and 2101 N respectively) compared to single-screw repairs (1458–1532 N), with no meaningful difference between screw types when matched for configuration. Notably, all repairs showed greater gap displacement on the abaxial (lateral) aspect of the fracture site compared to the axial (medial) side, suggesting that fixation strategies addressing lateral shear forces warrant further clinical investigation. For practitioners, this research supports the biomechanical superiority of two-screw fixation over single-screw repair regardless of implant choice, though the practical advantages of one screw type over another remain equivalent in this simulated model.
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Practical Takeaways
- •Use two screws rather than one for proximal sesamoid bone fractures to substantially improve repair strength, regardless of whether you choose bone-screw-fasteners or cortical screws
- •The newer bone-screw-fastener technology performs equivalently to conventional cortical screws, so choice between them can be based on other factors such as availability and surgeon preference
- •Consider that mid-body PSB repairs may be vulnerable to abaxial loading forces; surgical planning should account for this mechanical weakness to improve clinical outcomes
Key Findings
- •Double screw fixation (both BSF and CS) achieved significantly higher yield strength (~2081-2101 N) compared to single screw configurations (~1458-1532 N)
- •Single bone-screw-fastener (3.5 mm BSF) showed equivalent biomechanical properties to single 4.5 mm cortical screw for PSB fracture repair
- •Double BSF and double CS configurations were biomechanically equivalent to each other
- •Abaxial gap displacement at failure was significantly greater than axial displacement across all repair groups, suggesting greater vulnerability to abaxial forces