Overview
The horse has seven cervical vertebrae (vertebral formula C7, T18, L6, S5, Cd15–21); the third to seventh, the typical ones, are described here. They are long and robust and form the base of the long, mobile neck that the horse uses for grazing and for balancing the body in motion. The cervical spine describes an S-shaped curve: it descends from the poll and rises again at the thoracic inlet.
Key features
- Body (corpus vertebrae): long, with a convex cranial head and a concave caudal fossa, joined by intervertebral discs. Ventrally it carries a marked ventral crest.
- Spinous processes: almost absent from C3 to C6, reduced to a low ridge. The nuchal ligament takes over their role in supporting the head. C7 has a short but distinct spinous process.
- Transverse processes: divided into two tubercles and pierced by the transverse foramen, through which the vertebral artery and vein run. On C6 they carry a broad ventral lamina, sometimes palpable at the base of the neck.
- Articular processes: large, with wide, almost horizontal surfaces that allow great lateral and dorsoventral mobility.
- C7: lacks a transverse foramen and has a caudal costal fovea for the head of the first rib.
Clinical relevance
- Cervical stenotic myelopathy (wobbler syndrome): compression of the spinal cord by stenosis of the vertebral canal, vertebral malformation or osteoarthritis of the articular processes. It causes symmetrical ataxia, worse in the pelvic limbs. It is most common in fast-growing young males (Thoroughbreds, sport horses). In the youngest animals compression is usually dynamic at the cranial segments (C3–C5), and in somewhat older ones static at the caudal segments (C5–C7).
- Osteoarthritis of the articular processes: in adult horses, mainly between C5 and C7; it causes neck stiffness and pain and can compress nerve roots.
- Intramuscular injections in the neck: given in the triangle bounded by the nuchal ligament dorsally, the cervical vertebrae ventrally and the scapula caudally, so as not to reach the vertebrae or the ligament.