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 <i>in vivo</i> 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 <i>in vivo</i>, particularly for cranial nerves, but the technique requires a long learning curve because of low levels of operator agreement.