Arthrodesis of the proximal interphalangeal joint in the horse: a cyclic biomechanical comparison of two and three parallel cortical screws inserted in lag fashion.
Authors: Carmalt James L, Delaney Lana, Wilson David G
Journal: Veterinary surgery : VS
Summary
# Editorial Summary: Arthrodesis screw fixation in equine PIP joints When surgically fusing the proximal interphalangeal joint in horses, clinicians must balance biomechanical stability against operative complexity and cost; this 2010 study by Carmalt and colleagues directly compared two parallel cortical screws against three parallel screws to determine whether the simpler two-screw construct could provide equivalent stability. Using cadaveric equine limbs (five pairs of fore- and five pairs of hindlimbs), the researchers inserted either two or three 5.5 mm cortical screws in lag fashion across the PIP joint, then subjected each construct to cyclic loading between −500 and −3500 N in a dorsal-to-palmar (or plantar) direction until failure. No statistically significant differences emerged between the two-screw and three-screw constructs in displacement at failure, ultimate load-bearing capacity, or cycles to failure—with forelimbs tending towards slightly greater displacement than hindlimbs, though not significantly so. For practitioners, this finding supports simplified surgical technique: two parallel 5.5 mm cortical screws provide biomechanical performance equivalent to three screws under cyclic fatigue conditions, reducing operative time and implant costs without compromising construct integrity. The practical advantage of this simpler fixation method makes it particularly valuable for field practitioners or those seeking to reduce both surgical burden and financial outlay in PIP arthrodesis cases.
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Practical Takeaways
- •Using 2 screws instead of 3 for PIP arthrodesis provides equivalent biomechanical strength under cyclic loading, reducing surgical complexity and operative time
- •Surgeons can simplify the procedure and reduce implant burden without compromising structural integrity in this common equine joint fusion
- •This finding supports a shift toward simpler, 2-screw fixation as the standard approach for PIP arthrodesis in routine practice
Key Findings
- •No significant difference in displacement at failure between 2 and 3 parallel cortical screws (P>0.05)
- •No significant difference in force at failure between the two fixation methods
- •No significant difference in number of cycles to failure between 2-screw and 3-screw constructs
- •Forelimb constructs showed trend toward greater mean displacement than hindlimb constructs (P=0.06, not significant)