Lesions of the Equine Neck Resulting in Lameness or Poor Performance

Lesions of the Equine Neck Resulting in Lameness or Poor Performance: Lesions of the neck are uncommon causes of pain resulting in either lameness or poor performance. The neck consists of 7 cervical vertebrae, which articulate by both intercentral articulations, and articular process joints (APJs) (sometimes called synovial intervertebral articulations) that have large joint capsules to accommodate the degree of movement between adjacent vertebrae. Interposed between the vertebral bodies are intervertebral fibrocartilages to which is attached the dorsal longitudinal ligament, which lies on the floor of the vertebral canal. The ligamentum flavum connects the arches of adjacent vertebrae. The atlas (the first cervical vertebra) and the axis (the second cervical vertebra) have a unique shape and specialized joints. The atlantooccipital joint is a ginglymus joint, which permits flexion and extension and also a small amount of lateral oblique movement. The atlantoaxial joint is a trochoid or pivot joint; the atlas and head rotate on the axis. The ligament of the dens is strong and fan shaped and extends from the dorsal surface of the odontoid peg (dens) to the ventral arch of the axis. The ligamentum nuchae extends from the occiput to the withers and consists of funicular and lamellar parts. The lamellar part separates the 2 lateral muscle groups. The atlantal bursa is interposed between the funicular part of the ligamentum nuchae and the dorsal arch of the atlas; a second bursa may exist between the ligament and the spine of the axis. The muscles of the neck can be divided into lateral and ventral groups. The neck has 8 cervical nerves, the first of which emerges through the lateral foramen of the atlas, the second between the atlas and the axis, and the eighth between the seventh cervical vertebra and the first thoracic vertebra. The sixth to eighth cervical nerves contribute to the brachial plexus.