The Relationship amongst Intervertebral Disc Vertical Diameter, Lateral Foramen Diameter and Nerve Root Impingement in Lumbar Vertebra

ABSTRACT

@#Introduction: The vertical diameter of the foramen isdependent upon the vertical diameter of the correspondingintervertebral disc. A decrease in disc vertical diameter hasdirect anatomic consequences to the foraminal diameter andarea available for the nerve root passing through it. Thisstudy is to establish the relationship amongst theintervertebral disc vertical diameter, lateral foramendiameters and nerve root compression in the lumbarvertebra.Materials and Methods: Measurements of the studyparameters were performed using sagittal MRI images. Theparameters studied were intervertebral disc verticaldiameter (DVD), foraminal vertical diameter (FVD),foraminal transverse diameter (FTD) and nerve root diameter(NRD) of both sides. The relationship between the measuredparameters were then analyzed.Results: A total of 62 MRI images were available for thisstudy. Statistical analysis showed moderate to strongcorrelation between DVD and FVD at all the lumbar levelsexcept at left L23 and L5S1 and right L3L4 and L4L5.Correlation between DVD and FTD were not significant atall lumbar levels. Regression analysis showed that a decreaseof 1mm of DVD was associated with 1.3, 1.7, 3.3, 3.3 and1.3mm reduction of FVD at L1L2, L2L3, L3L4, L4L5 andL5S1 respectively.Conclusion: Reduction of DVD was associated withreduction of FVD. However, FVD was relatively wide forthe nerve root even with complete loss of DVD. FTD wasmuch narrower than the FVD making it more likely to causenerve root compression at the exit foramina. Theseanatomical details should be given consideration in treatingpatients with lateral canal stenosis.