Arthrodesis of the equine proximal interphalangeal joint: a mechanical comparison of 2 parallel 5.5 mm cortical screws and 3 parallel 5.5 mm cortical screws.
Authors: Read Emma K, Chandler Diane, Wilson David G
Journal: Veterinary surgery : VS
Summary
# Editorial Summary Proximal interphalangeal joint arthrodesis remains a valuable surgical option for managing chronic pastern joint disease in horses, yet the optimal fixation construct remains debated. Read and colleagues conducted a biomechanical comparison of two competing screw configurations by testing cadaveric equine limbs to failure under three-point bending, using five pairs of limbs and comparing two parallel 5.5 mm cortical screws against three parallel 5.5 mm screws placed in lag fashion. The researchers found no statistically significant difference between the two-screw and three-screw constructs in either maximal bending moment or stiffness (P<0.05), with all specimens ultimately failing through bone fracture or screw bending rather than construct loosening. For practitioners, these findings suggest that two carefully placed 5.5 mm parallel cortical screws provide equivalent biomechanical strength to three screws whilst reducing operative time, soft tissue trauma, and implant costs—making the simpler two-screw technique a defensible choice for routine PIP arthrodesis cases in weight-bearing bending loads. However, clinicians should note that this in vitro study evaluated only bending forces and may not fully capture the complex multiplanar loading or long-term clinical outcomes that occur in working horses, warranting continued clinical observation of both techniques.
Read the full abstract on PubMed
Practical Takeaways
- •Two parallel 5.5 mm cortical screws are sufficient for PIP joint arthrodesis—using three offers no mechanical advantage and increases surgical time and cost
- •Either configuration can be expected to tolerate normal bending forces under similar loading conditions
- •Simpler surgical technique with two screws reduces anesthetic time and soft tissue trauma without compromising construct strength
Key Findings
- •No significant difference in bending moment or stiffness between 2-screw and 3-screw PIP arthrodesis constructs (P<0.05)
- •All constructs failed by bone fracture or screw bending under 3-point bending load
- •No significant effect of treatment, side, or end on maximal bending moment or stiffness
- •2 parallel 5.5 mm screws provide equivalent biomechanical strength to 3 screws with reduced surgical complexity