Novel technique for prevention of rotation of the distal phalanx relative to the hoof wall in horses with acute laminitis.
Authors: Carmalt, Carmalt, Henderson, Allen, Wilson
Journal: American journal of veterinary research
Summary
# Editorial Summary Rotation of the distal phalanx (P3) relative to the hoof wall remains a major pathological feature of acute laminitis, driving pain and tissue damage in affected horses. Carmalt and colleagues investigated whether a 5.5-mm cortical bone screw placed through the dorsal hoof wall into P3 could mechanically prevent this rotation whilst being tolerated by the horse. Their three-part study progressed from biomechanical testing on cadaveric limbs (mean pullout force 3,909 N, sufficient to resist the deep digital flexor tendon pull in 500-kg horses) through tolerance trials in sound horses (which showed excellent acceptance with no post-removal lameness) to a proof-of-concept trial using oligofructose-induced laminitis. Whilst screw placement proved biomechanically sound and well-tolerated, the laminitis-affected horses in the treatment groups showed no significant pain relief and continued to develop subtle P3 displacement compared to controls; only the dorsal hoof wall geometry ratios differed meaningfully between treated and untreated laminitic animals. Although the technique demonstrates sufficient mechanical strength and surgical feasibility for clinical application, the lack of pain alleviation and persistent radiographic displacement in experimentally laminitic horses suggests that mechanical P3 stabilisation alone does not address the underlying pathophysiology driving acute laminitis, necessitating further research into naturally occurring disease before clinical adoption.
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Practical Takeaways
- •This technique has adequate biomechanical strength to resist flexor tendon pull in normal horses, but further development is needed before clinical application in acute laminitis cases
- •Screw placement and removal were well tolerated procedurally, suggesting the technique itself is not harmful to normal foot tissues
- •The technique failed to prevent P3 rotation or improve pain in experimentally induced laminitis, indicating additional research on laminitis pathophysiology and screw positioning is necessary before recommending for field use
Key Findings
- •Mean screw pullout force was 3,908.7 ± 1,473.4 N, sufficient to counteract deep digital flexor tendon pull in 500-kg horses
- •Cortical bone screws placed through dorsal hoof wall into P3 were well tolerated in clinically normal horses with no lameness development
- •In laminitis-induced horses, screw placement did not alleviate pain signs or prevent increases in distance between P3 and dorsal hoof wall
- •Screw insertion depth was the only variable positively affecting pullout force, and dorsal hoof wall ratio changes were the only treatment-associated variable