Measurement of Intervertebral Disc Heights in the Lumbar Spine. Comparison of X-Ray and Magnetic Resonance Imaging, Method of Measurement and Determination of Inter-observer Reliability.

Purpose: Retrospective radiological examination (X-ray and MRI) aims to investigate the diagnostic value of various methods of measurement with regard to the determination of the intervertebral disc heights of the lumbar spine.

Methods: Of 130 patients without detectable damage to the intervertebral discs, the X-ray and MRI images of the lumbar spine were evaluated. The measurements were made either in the center line (Hurxthal) or in the 2-point method according to Dabbs or in the 3-point method according to Fyllos.

Results: The average intervertebral disc height for all measured segments was 8.8 mm (SD 1.4 mm). In the Hurxthal measurement, the significantly (p < 0.001) highest values were measured with an average of 9.1 mm (SD 1.3 mm). The average readings for the Fyllos method were 7.5 mm (SD 1.2 mm) and according to Dabbs 6.7 mm (SD 1.2 mm). The measured values of Observer I were on average 1.2 mm (SD 0.3 mm) smaller than those of Observer II (p < 0.001). The highest interobserver correlation was found in the measurements in projection radiography in the AP method according to Dabbs and Fyllos. The measured values in men were 0.5 mm (SD 0.01 mm) larger than in women (p < 0.001), regardless of the method. The height of the intervertebral discs increases significantly until the age of 40, but beyond the age of 40, the height of the intervertebral discs either remains constant or falls off slightly, but not significantly. The lordosis angle of the lumbar spine and the concavity index of the vertebral bodies showed no correlation with the measured disc heights.

Conclusions: The radiological measurements to determine the intervertebral disc height have only moderate reliability. The results of X-rays are superior to those of MRI examination. The most accurate results are provided by measurements based on exact landmarks of the vertebral bodies. The method according to Dabbs seems to be the most accurate at the moment. There is no clear age-atypical chondrosis in patients without intervertebral disc damage.