Analysis of different techniques for injection of the interspinal space in horses.
Authors: Tress, Hennessy, Merle, Jensen, Lischer, Ehrle
Journal: Equine veterinary journal
Summary
# Editorial Summary Spinous process impingement remains a prevalent diagnosis in working horses, yet the optimal technique for delivering therapeutic or diagnostic injections into the interspinal spaces has lacked rigorous validation. Tress and colleagues conducted an ex vivo study using equine thoracolumbar specimens to systematically evaluate three injection approaches (midline, bilateral abaxial, and unilateral oblique), two needle lengths (20G-1½″ and 20G-3½″), two injection volumes (5 mL and 20 mL), and three guidance methods (palpation, radiographic, and ultrasonographic), with computed tomography and anatomical dissection used to assess injectate distribution. The midline approach using a shorter 20G-1½″ needle with 5 mL volume delivered the most accurate, concentrated deposition within the interspinous ligament itself, whilst bilateral abaxial injection produced broad, potentially therapeutic distribution across both sides, and unilateral oblique technique resulted in significantly asymmetrical spread confined to one side; notably, radiographic guidance conferred no accuracy advantage over palpation alone. For practitioners performing these injections clinically, adopting the midline technique with appropriate needle length and modest volume offers the greatest precision for targeted interspinal medication delivery, though the choice of approach may vary depending on whether focal or more diffuse therapeutic distribution is therapeutically intended.
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Practical Takeaways
- •Use midline approach with short 20G needle and 5mL volume for targeted interspinal injections in horses with spinous process impingement
- •Avoid unilateral oblique technique if precision targeting is required, as it creates asymmetrical drug distribution
- •Palpation-guided injection is as effective as radiographic guidance, simplifying the procedure in field settings
Key Findings
- •Midline injection with 20G-1½" needle and 5mL volume achieved the most accurate interspinous ligament injection
- •Bilateral abaxial technique resulted in wide distribution of injectate across the interspinal space
- •Unilateral oblique technique produced significantly asymmetrical unilateral distribution
- •Radiographic guidance did not improve injection accuracy compared to palpation alone