Analysis of different techniques for injection of the interspinal space in horses.

Background: Impingement of spinous processes (SPs) is commonly diagnosed in the equine athlete. For diagnostic and therapeutic purposes, local injections are performed at the level of the space between adjacent spinous processes in affected horses.

Objectives: To assess the accuracy of different techniques for the local injection of the interspinal space in the equine thoracolumbar spine.

Study design: Ex vivo experimental study.

Methods: Equine thoracolumbar spine specimens were used to compare three techniques for needle insertion (midline; bilateral abaxial; unilateral oblique), two needles (20G-1½″; 20G-3½″) and two volumes (5 mL; 20 mL) for local injection of the interspinal space. Additionally, needle insertion based on radiographic, ultrasonographic guidance, or palpation was assessed. Computed tomographic analysis and anatomical dissection were performed to evaluate the distribution of the injected volume.

Results: The most accurate injection of the interspinous ligament was achieved when the midline injection method using a 20G-1½″ short needle and a volume of 5 mL was used. Wide distribution of the injected volume was observed when the bilateral abaxial injection technique was utilised. The unilateral oblique injection technique led to significantly asymmetrical unilateral distribution of the injectate. Radiographic guidance did not increase the accuracy of the injection.

Conclusion: The midline injection method is the most reliable technique for the targeted injection of the thoracolumbar interspinal space.