Comparison of four techniques for synoviocentesis of the equine digital flexor tendon sheath: a cadaveric study.

This research compares the efficacy of four different techniques for injecting into the sheath of the digital flexor tendon in horses. The study concluded that the axial approach, one of the four techniques tested, was the most successful particularly when performed by operators with little experience.

Methodology

• The study utilized fifteen operators with less or no experience who performed each of the four injection techniques— Proximal, Axial, Base, and Distal— on two horse cadaveric limbs.
• The proximal approach targeted the proximal recess of the digital flexor tendon sheath (DFTS), the axial one was performed axial to the proximal sesamoid bone, the base technique took place at the base of the proximal sesamoid bone, while the distal approach was done at the pastern.
• For every technique, the researchers recorded the number of attempts it took before the needle was assumed to be correctly positioned into the DFTS.
• Once correctly positioned, 10 ml of methylene blue was injected and the limbs were then dissected for analysis.

Results

• The analysis involved determining the presence of methylene blue in the DFTS, the distance between the needle entrance point and the lateral palmar (front) or plantar (back) digital nerve, the degree of subcutaneous (beneath the skin) leakage, and the distance from the border of the leakage zone to the lateral digital nerve.
• Out of the four techniques, the Axial and Distal approaches recorded the highest numbers of successful injections, 29/30 and 25/30 respectively.
• However, the Axial approach had the highest median number of attempts, indicating that while it eventually had a high success rate, it often required more attempts to achieve correct placement.
• The Distal and Axial approaches demonstrated greater distances from the injection point and from the border of the leakage zone to the lateral digital nerve, a positive indication as it minimizes the risk of potential nerve damage.

Conclusion

• The study concludes that for inexperienced operators, the Axial approach proves to be the most successful technique for injecting the equine DFTS.
• Furthermore, the Axial method exhibited sparse subcutaneous leakage and a larger distance to the nerve, factors that could reduce the risk of inadvertent desensitization of the palmar or plantar digital nerve during DFTS analgesia (pain relief).