Measurements in a lateral radiograph:
(1) height of the anterior space between upper and lower vertebral borders in millimeters
(2) height of the middle space between the upper and lower vertebral bodies in millimeters
(3) height of the posterior space between the upper and lower vertebral bodies in millimeters
(4) longitudinal diameter of the vertebral body in millimeters
intervertebral disc space ratio =
= SUM(anterior, middle and posterior measurements) / (longitudinal diameter)
Since the vertebral body diameter should be relatively constant, any change in the ratio should be do to a change in the 3 height measurements.
The ratio can be used to compare the intervertebral space before and after surgery (see Table 4, page 2047).
postoperative ratio as percent of preoperative ratio =
= (postoperative ratio) / (preoperative ratio) * 100%
Limitations:
• Any change in the ratio would not indicate which of the 3 heights had changed.
