Description and evaluation of four ultrasound-guided approaches to aid spinal canal puncture in dogs

Abstract

Objective: To describe four ultrasound-guided approaches to the lumbar and thoracic spine to aid spinal canal puncture in the dog and to evaluate the feasibility of the technique.

Study design: Prospective experimental study.

Animal population: Two canine cadavers.

Methods: In the first part of the study, the ultrasonographic appearance of the interlaminar space in the lumbosacral, lumbar and thoracic regions was described. In the second part of the study, four operators attempted a real-time, ultrasound-guided approach to the vertebral canal. Each operator performed the technique 20 times in total: five times at the lumbosacral junction, five in the thoracic region, five in the lumbar region with an in-plane approach, and five in the lumbar region with an out-of-plane approach. Computed tomography (CT) was used to confirm the position of the needle. The procedure was considered successful when the tip of the needle was observed within the vertebral canal. The success rate was calculated for each approach and operator. Fisher's exact test was used to compare differences between approaches and operators.

Results: In all cases, visualization of a ventral, parallel and straight hyperechoic line (floor of the vertebral canal) was considered a necessary prerequisite for successful positioning of the needle within the vertebral canal. A straight hyperechoic line (ligamentum flavum or dura mater) closer to the ultrasound probe was visualized in both the median lumbosacral approach and the transverse lumbar approach. The success rate overall was 81%; for the lumbosacral approach, 100%; for the thoracic approach, 80%; for the in-plane lumbar approach 95%; and for the out-of-plane lumbar approach, 45%. These differences were statistically significant (p < 0.001).

Conclusions and clinical relevance: The sonographic description of these approaches was considered adequate for performing spinal canal puncture. In-plane techniques achieved a higher success rate than out-of-plane ones. Further studies are needed to evaluate them in a clinical setting.

Keywords: approach; dog; spine; ultrasound.