Influence of neck position on commonly performed radiographic measurements of the cervical vertebral region in horses

OBJECTIVE To determine the influence of various neck positions on cervical vertebral radiographic measurements in horses. ANIMALS 18 client-owned horses examined for lameness but free of cervical disease. PROCEDURES Laterolateral radiographs of the cervical vertebrae from C1 through T1 were acquired for each horse in 3 neck positions (low, neutral, and high). Minimum sagittal diameter, intravertebral sagittal diameter (intra-VSD) ratio, inter-VSD ratio, length of the articular processes joint ratio, vertebral alignment angle, and vertebral fossa angle were measured at each segment in each neck position. Values for the high and low positions were compared with those for the neutral position. RESULTS No significant differences from neutral position values were identified for minimum sagittal diameter, intra-VSD ratio, and vertebral fossa angle as measured in low and high neck positions. Compared with results in the neutral position, the high position resulted in a greater vertebral alignment angle at C3-4 and inter-VSD ratio at C4-5 and a lower length of the articular processes joint ratio at C2-3, C3-4, and C4-5; the low position resulted in a lower vertebral alignment angle at C4-5. However, all observed differences were small. CONCLUSIONS AND CLINICAL RELEVANCE Neck position influenced some radiographic measurements of the cervical vertebrae in horses free of cervical disease. However, because several of these measurements were not or were only minimally affected by neck position, some latitude in neck position may be possible without concern about substantially affecting radiographic measurements in this region.