Comparison of medial and lateral ultrasound-guided approaches for periarticular injection of the thoracolumbar intervertebral facet joints in horses

Objective: To compare ultrasound‐guided lateral and medial approaches for periarticular injections of the thoracolumbar intervertebral facet joints (IFJ). Study Design: Experimental cadaveric study. Sample Population: Adult equine cadavers (n=4). Methods: IFJ (T12–T13 to L5–L6) were identified by ultrasound (transducer perpendicular to the spine axis) and insertion of a 13 cm, 18 g spinal needle monitored until bone contact using medial (right side) and lateral (left side) approaches. Number of needle insertions at each site, needle repositioning, and insertion depth were recorded. On bone contact 2 mL latex was injected. Intraarticular deposition, distance of latex from the closest articular margin, and presence of latex in the multifidus muscle were established by dissection. Results: Of 96 attempts, only 1 site require reinsertion of the needle; however, 46% of the injections required needle repositioning. Mean ± SD insertion depth was 8.5 ± 1.1 cm. Most injections (86%) were intraarticular and 96% were at or within 0.5 cm of the closest articular margin. Needle insertion relative to the transducer (lateral, medial) had no effect on the distance from the latex to the closest articular margin and all injections were performed into the multifidus muscle. Conclusions: Ultrasound‐guidance facilitated accurate periarticular injection of thoracolumbar IFJ irrespective of using a medial or lateral approach.