Normal Range of Measurement of Lumbar Spinal Canal in MSCT

The knowledge of normal diameter of lumbar spinal canal is very important for diagnosing lumbar spinal canal stenosis and also for performing spinal surgeries at the lumbar level by Neurosurgeons and Orthopedicians. However, it varies widely among ethnic groups and between sexes in the same ethnic group . Spinal canal stenosis (defined as the narrowing of central spinal canal) is a condition in which the anteroposterior (AP) and lateral dimensions of the bony spinal canal are less than normal for corresponding age and sex. Back pain is the commonest manifestation of lumbar canal stenosis which usually results from lumbar spondylosis. Lumber lordosis is a problem of adults, but is now being increasingly seen in youth, probably due to lifestyle changes. Multiple factors play a role in spondylosis, but if it is associated with spinal canal stenosis, its management differs. Radiological evaluation forms an important part in the evaluation and management of lumbar spondylosis. But it requires clear understanding of the normal dimensions of lumbar vertebrae for particular age \& sex . Multislice computed tomography (MSCT) scans provides a noninvasive, non-operator dependent method of direct imaging of the spinal canal without injection of intra thecal contrast and is better than MRI for bony detail as in osteophytes. Though there is a wide variation in the capacity of spinal canal in patients who are clinically and radiologically normal. It is said that those with smaller canals are more likely to have symptoms from nerve root compression . By determining normal ranges of spinal canal diameter investigators can make early diagnosis in individuals who have lower diameters of spinal canal. These individuals are predisposed to spinal canal stenosis, which is a major cause of spinal radiculopathies. The recent use of CT for the measurements of the vertebral dimensions such as canal diameter and vertebral dimension has led to better evaluation of vertebral morphometry as compared with x-ray and cadaveric studies . CT scan measurement of lumbar spine demonstrated a mean AP canal diameter between 12 mm and 14 mm with a measurement of 11.5 mm considered small. On CT scan, electronic measurement of the sagittal diameter of the normal bony canal is 11.5 mm . These differences in dimension of the spinal canal across studies demands necessity of study of dimension of the spinal canal in every ethnic group.