Ultrasound-guided subscalene approach for the brachial plexus in dogs: a descriptive cadaveric study

To describe the ultrasound anatomy of the subscalene groove, evaluate the feasibility of an in-plane subscalene approach to the brachial plexus (BP) and compare one- and two-point injection techniques for BP staining in canine cadavers.

Prospective, randomized, descriptive anatomical study.

Nineteen thawed male and female adult canine cadavers [mass 3-40 kg, body condition scores 4-6/9 (range)].

Ultrasonography and anatomical dissections were performed in two cadavers to study the relationship between cervical muscles and the ventral branches of the last three cervical spinal nerves (C6, C7, C8) and the first thoracic spinal nerve (T1). Seventeen thawed cadavers were then used to assess nerve staining following ultrasound-guided subscalene injections. Group 1 dogs (G1, n = 17) were injected with 0.4 mL kg^-1 of dye cranial to C8 in the subscalene groove using a single injection point. Group 2 dogs (G2, n = 17) were injected with dye in the same intermuscular plane, split into two injections: 0.3 mL kg^-1 cranial to C8 and 0.1 mL kg^-1 cranial to C7 on the contralateral side. Staining was considered successful if C6, C7, C8 and T1 were stained circumferentially (>1 cm) and unsuccessful if any branch was unstained. Outcomes were analyzed using Fisher's exact test, with significance set at p < 0.05.

Sonoanatomy matched anatomical dissections, with target nerves identified in all cadavers. Staining success rates were 41% in G1 and 88% in G2 (p = 0.0104). Median (range) stained ventral branches were 3 (2-4) in G1 and 4 (3-4) in G2.

The ultrasound-guided subscalene approach facilitated reliable identification of the BP at the subscalene groove. Successful staining of all target nerves required two injection aliquots. Future clinical studies are warranted to assess the applicability and efficacy of this technique in live animals.