Biomechanical Comparison of a Headless Compression Screw Fastener and AO Cortical Bone Screw for Fixation of a Simulated Equine Third Carpal Bone Slab Fracture.
Authors: Salinger Allison, Mochal-King Cathleen, Clinton Kailey, Priddy Lauren B, Elder Steve, Fontenot Robin, Eddy Alison, Wills Robert, Jaffe Michael
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Headless Compression Screw as Alternative for Equine Third Carpal Bone Slab Fractures Frontal plane slab fractures of the third carpal bone (C3) are common in racehorses and performance animals, currently managed with lagged AO cortical screws—a technique complicated by fragment splitting, spinning, and soft tissue irritation. Researchers compared the biomechanical performance of a novel headless compression screw fastener (HCSF) against the standard AO cortical screw by creating simulated C3 slab fractures in nine paired equine cadaver carpi and loading them to failure in shear. No statistically significant differences emerged between the two fixation methods across maximum load to failure, stiffness, or yield load (P = 0.084, 0.26, and 0.088 respectively), with all specimens failing via screw bending. The headless design of the HCSF offers practical advantages—its cannulated structure with interlocking threads provides multidirectional force resistance whilst eliminating the need for countersinking—making it a biomechanically equivalent option worth investigating clinically. Given comparable structural support to established AO fixation, equine surgeons may consider the HCSF as an alternative approach to reduce complications associated with conventional screw heads, particularly where soft tissue irritation or fragment-related complications have been problematic.
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Practical Takeaways
- •The novel HCSF performs biomechanically equivalent to standard AO cortical screws for carpal bone slab fractures in cadaveric testing, suggesting it may be a viable alternative in clinical practice
- •The headless design of HCSF offers practical advantages by eliminating countersinking and potentially reducing soft tissue irritation, though clinical validation in living horses is needed before widespread adoption
- •Surgeons considering the HCSF should recognize that both screw types failed by bending rather than pullout, indicating fracture geometry and overall construct design remain critical factors in clinical outcomes
Key Findings
- •No significant difference between HCSF and AO cortical screw in maximum load to failure (P=0.084), stiffness (P=0.26), or yield load (P=0.088)
- •Both screw types failed by screw bending in all specimens, with some failures associated with sagittal fracture at screw-bone interface
- •HCSF headless design eliminated need for countersinking and effectively compressed fractures with different head and thread pitches