An in vitro biomechanical comparison of equine proximal interphalangeal joint arthrodesis techniques: two parallel transarticular headless tapered variable pitch screws versus two parallel transarticular AO cortical bone screws inserted in lag fashion.
Authors: Gudehus Timm, Sod Gary A, Riggs Laura M, Mitchell Colin F, Martin George S
Journal: Veterinary surgery : VS
Summary
# Editorial Summary Arthrodesis of the equine proximal interphalangeal joint remains a common surgical intervention for degenerative joint disease, yet optimal fixation technique remains debated. This in vitro biomechanical study directly compared two popular implant strategies—paired headless tapered screws (Acutrak Plus) versus paired cortical bone screws in lag fashion—by cyclically loading five pairs of cadaveric forelimbs until construct failure under axial compression. The cortical screw constructs substantially outperformed the headless tapered screws, withstanding a mean of 57,723 cycles to failure compared to just 35,322 cycles, representing a 63% improvement in fatigue resistance. Whilst this cadaveric compression model has inherent limitations that may not fully replicate the complex loading patterns of the weightbearing digit, these findings suggest that traditional AO cortical screws inserted as lag screws warrant preferential consideration over headless tapered designs when pursuing PIP arthrodesis in clinical cases where construct durability under cyclic loading is paramount.
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Practical Takeaways
- •For PIP joint arthrodesis procedures, traditional AO 5.5 mm cortical screws in lag fashion provide superior construct stability and fatigue resistance compared to Acutrak Plus headless screws
- •Consider AO cortical screw technique as the preferred method for PIP arthrodesis when biomechanical stability is the priority
- •This in vitro data supports continued use of established AO lag screw fixation rather than switching to newer headless screw designs for this procedure
Key Findings
- •AO cortical screws in lag fashion achieved mean 57,723±8488 cycles to failure versus 35,322±4698 cycles for Acutrak Plus screws
- •AO-TLS fixation demonstrated significantly superior resistance to cyclic fatigue under axial compression (P<0.05)
- •Two parallel transarticular AO cortical bone screws outperformed Acutrak Plus tapered variable pitch screws by approximately 63% in fatigue resistance