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

To compare four different techniques for synoviocentesis of the equine digital flexor tendon sheath (DFTS).

Fifteen inexperienced operators performed each of the following injection techniques on two cadaveric limbs: Proximal (at the proximal recess of the DFTS), Axial (axial to the proximal sesamoid bone), Base (at the base of the proximal sesamoid bone), and Distal (at the pastern). The number of attempts needed before the needle was assumed to be correctly positioned into the DFTS was recorded and 10 ml of methylene blue was injected. The limbs were dissected to determine the presence of methylene blue in the DFTS, the distance between the needle entrance point and the lateral palmar or plantar (digital) nerve, the degree of subcutaneous leakage and the distance between the border of the leakage zone and the lateral digital nerve.

The Axial (29/30) and Distal (25/30) approaches had the highest numbers of successful injections. The median number of attempts was highest for the Axial approach. The distances from the injection point and from the border of the leakage zone to the lateral digital nerve were longer for Distal and Axial approaches.

In the hands of inexperienced operators, the Axial approach was the most successful technique for injection of the equine DFTS. Sparse subcutaneous leakage and larger distance to the nerve when using this technique might decrease the risk of in-advertent palmar or plantar digital nerve desensitisation when performing DFTS analgesia.