Evaluation of the feasibility of equine in-vivo ultrasound technique for the medial branch of the dorsal ramus of the cervical spinal nerves.

Ultrasound-guided local anaesthesia is commonly used in veterinary orthopaedics for horses. This study aimed to assess an in vivo ultrasound technique for the medial branch of the dorsal branch of the cervical spinal nerves (MB-DBCSNs) in horses and compare the performance of clinicians with different experience levels. Ten healthy, skeletally mature horses were examined using radiographic and ultrasound (US) techniques in the cervical area (C3-C7). Four operators with varying experience conducted US examinations using a 10 MHz linear and 6 MHz curvilinear transducer over ten training sessions. The number of cervical nerves visualized was recorded. A chi-square test was used to analyse the impact of training, anatomical location, and operator experience on the identification of facet joints. Operator agreement was evaluated with Cohen's K test. The operators assessed 80 MB-DBCSNs, with radiographs and identified 70 healthy and 10 pathological facet joints. Training significantly improved visualization success, reaching 90% in later sessions. Cranial facet joints (C3-C5) were more frequently visualized (81%) than caudal ones (C5-C7) were (59%). US performance was influenced by the operator's skill, and agreement among operators ranged from slight to fair. Overall, practice improved cervical nerve visualization in vivo, particularly for cranial nerves, but the technique requires a long learning curve because of low levels of operator agreement.