A biomechanical comparison of headless tapered variable pitch compression and ao cortical bone screws for fixation of a simulated midbody transverse fracture of the proximal sesamoid bone in horses.
Authors: Eddy Alison L, Galuppo Larry D, Stover Susan M, Taylor Kenneth T, Jensen David G
Journal: Veterinary surgery : VS
Summary
# Editorial Summary Proximal sesamoid bone fractures present a significant surgical challenge in equine practice, and selecting the optimal fixation method directly influences both biomechanical stability and long-term outcomes. Researchers used cadaveric equine forelimbs to compare two screw fixation techniques for transverse midbody fractures: the conventional 4.5-mm AO cortical bone screw in lag fashion versus the 4/5-mm Acutrak self-compressing screw, evaluating mechanical properties through axial compression testing to failure on intact limbs, fractured limbs repaired with each screw type, and unrepaired controls. Both fixation methods demonstrated comparable biomechanical properties, with no statistically significant differences between the AO and Acutrak constructs; however, both were substantially weaker than intact sesamoid bones across most parameters, including failure load and overall stiffness. The clinical implication is encouraging for practitioners considering the Acutrak screw, which offers theoretical advantages in reduced soft tissue trauma and superior biocompatibility due to its titanium composition compared to stainless steel, though neither method provides sufficient stability in isolation—mandatory postoperative external coaptation remains essential to supplement initial fixation strength and maintain optimal metacarpophalangeal joint positioning (150–155° dorsiflexion) during the healing phase.
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Practical Takeaways
- •Either AO or Acutrak screws can be used for proximal sesamoid bone fracture repair with equivalent biomechanical outcomes, so screw choice may be based on surgeon preference and biocompatibility considerations
- •External coaptation (splinting/casting) is essential after surgery regardless of screw type to provide additional stability and maintain proper metacarpophalangeal joint angle (150-155°) during healing
- •Consider Acutrak screws as a viable alternative to traditional stainless-steel AO screws, particularly if reduced soft tissue irritation is desired
Key Findings
- •AO cortical and Acutrak self-compressing screws showed no statistically significant differences in mechanical properties for PSB fracture stabilization
- •Both screw constructs were mechanically inferior to intact limbs in load-to-failure capacity
- •Both constructs maintained comparable stiffness to intact limbs
- •Acutrak screws may offer advantages over AO screws due to reduced soft tissue impingement and superior biocompatibility