Evaluation of Intervertebral Disc Space Width Between 10th and 11th Thoracic Vertebrae in Cats Using Radiography and Magnetic Resonance Imaging

Background: It is well known that the T10–T11 intervertebral disc space is usually narrower than the adjacent intervertebral disc spaces in most dogs. However, whether the T10–T11 disc space is narrower than the adjacent disc spaces is not well-established in cats. Objectives: To measure the intervertebral disc space width of the T10–T11 disc space and to compare it with that of the adjacent disc spaces using radiography and magnetic resonance imaging (MRI). Methods: In Groups 1 (101 clinically normal cats) and 2 (32 cats without spinal diseases from T8 to T13), dorsal width (DW), central width (CW) and ventral width (VW) of the T8–T13 disc spaces were measured by radiography or MRI. Significant differences of the DW, CW and VW among disc spaces measured by radiography and MRI were evaluated. Intra- and interobserver reliabilities were measured by intraclass correlation coefficient. Results: In Groups 1 and 2 using radiography, the DW and CW of the T10–T11 disc space were significantly narrower than those of adjacent disc spaces (p < 0.05). The DW of the T8–T12 disc spaces was significantly narrower than that of the T12–T13 disc space in Group 1 using radiography. In Groups 1 and 2 using radiography, the CW and VW of the T8–T11 disc spaces were significantly narrower than those of the T11–T13 disc spaces. In Group 2 using MRI, the DW of the T10–T11 disc space was significantly narrower than that of the T11–T13 disc spaces. The VW of the T8–T11 disc spaces was significantly narrower than that of the T11–T13 disc spaces. Conclusion: The T10–T11 intervertebral disc space on radiography is statistically narrower than the adjacent intervertebral disc spaces in normal cats. The cranial thoracic intervertebral disc spaces (T8–T11) are usually narrower than the caudal thoracic intervertebral disc spaces (T11–T13) on radiography and MRI.