The influence of head and neck position on radiographic examination of the intervertebral foramina of the neck of horses at latero-lateral projection

Spondylarthrosis of the cervical articular process joints can lead to compression of the spinal cord and the nerve roots. Affected horses may show neck pain and stiffness as well as ataxia and forelimb lameness. Among other signs, these pathological changes can be identified by the reduction of the intervertebral foramina on radiographs. This study tests the hypothesis that head and neck position influences the size of the intervertebral foramina as depicted radiographically. Radiographs in latero-lateral projection were taken of the cervical spines of clinically unaffected horses in three different head and neck positions and the lengths of the vertebral bodies were measured. The dimensions of the intervertebral foramina was determined with the aid of the distance between the extremitas craniolis and the cranial articular processes of the same vertebra and the distance between the extremitas caudalis and the cranial articular processes of the following vertebra. The lengths of the vertebral bodies and the distance between the extremitas cranialis and the cranial articular processes of the same vertebra showed no variations. The distance between the extremitas caudalis and the cranial articular processes of the following vertebra of the fourth to seventh cervical vertebrae were significantly greater in flexion than in physiological and extended positions. When comparing the extended and physiological positions a significant difference could be detected for the distance between the extremitas caudalis and the cranial articular processes of the following vertebra of the seventh cervical vertebra only. Our study demonstrates the importance of the head and neck position when evaluating radiographs of cervical spines of horses. For a sound evaluation of such radiographs, the head and neck position of the horse should be standardized.