Effect of Cortical Screw Diameter on Reduction and Stabilization of Type III Distal Phalanx Fractures: An Equine Cadaveric Study.
Authors: Kay Alastair T, Durgam Sushmitha, Stewart Matthew, Joslyn Stephen, Schaeffer David J, Horn Gavin, Kesler Richard, Chew Peter
Journal: Veterinary surgery : VS
Summary
# Editorial Summary: Cortical Screw Diameter in Distal Phalanx Fracture Repair Type III distal phalanx fractures—sagittal splits extending into the articular surface—remain challenging to manage in practice, particularly regarding optimal screw selection for lag fixation. Researchers used cadaveric distal phalanges from 12 horses (24 specimens total) to systematically compare 4.5 mm versus 5.5 mm cortical screws, creating standardised sagittal fractures, reducing them with either screw diameter, and then subjecting specimens to incremental loading up to 1335 kg whilst monitoring fracture gap closure via fluoroscopic imaging. The 5.5 mm screws significantly reduced initial fracture gaps and—critically—prevented gap expansion at locations 3 cm distal to the articular surface during load application, whereas 4.5 mm screws provided neither benefit; both screw sizes allowed compression and closure at the articular surface itself when weight was applied. For practitioners managing these notoriously problematic fractures, these findings suggest that 5.5 mm cortical screws offer biomechanically superior reduction and stability throughout the fracture site, potentially improving healing outcomes and reducing complications associated with persistent fracture gaps and non-union.
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Practical Takeaways
- •Use 5.5 mm cortical screws rather than 4.5 mm screws when performing lag screw fixation for Type III distal phalanx fractures to achieve superior reduction and stability
- •5.5 mm screws provide better control of fracture gap expansion in the distal fragment under weight-bearing loads, which should improve healing outcomes
- •Even with optimal screw diameter, anticipate some fracture gap closure at the articular surface during loading, necessitating careful post-operative management and monitoring
Key Findings
- •5.5 mm cortical screws significantly reduced fracture gaps whereas 4.5 mm screws did not achieve significant reduction
- •5.5 mm screws constrained fracture gap expansion 3 cm distal to the articular surface under incremental loading up to 1335 kg
- •Compressive loading closed fracture gaps at the articular surface in all groups regardless of screw diameter
- •5.5 mm cortical screws were more effective than 4.5 mm screws in restricting distal fracture gap expansion under load