The spinal canal of the lumbar spine consists of the foramina of each lumbar vertebra and the connecting tissue between them, housing the spinal cord and its perineurium, spinal nerves, and cauda equina. The anterior wall of the lumbar spinal canal is the vertebral body, the back of the intervertebral disc and the posterior longitudinal ligament, and the posterior wall of the spinal canal is the lamina and the ligamentum flavum. The anterior and posterior walls of the spinal canal are divided by the lateral angles, and the left and right lateral angles are flanked by the vertebral arch, which extends into the intervertebral foramen. When a herniated disc or inflammation of the intervertebral joints occurs, the lateral angles can be reduced, affecting the nerve roots and the lateral part of the dural sac. The lumbar spinal canal is connected by the vertebral foramina of each lumbar vertebra, and the vertebral foramen has two diameters, the sagittal diameter is the longest distance from the follow-up of the vertebral body to the inner edge of the union of the two vertebral plates. The transverse diameter of the foramen is the widest distance between the inner edges of the outward protrusion of the vertebral roots on both sides. The sagittal diameter distance is the most clinically significant. It is generally accepted that a sagittal diameter of 10 mm – 13 mm can be classified as relative spinal stenosis. If there is a bulging disc or a 2 mm bone spur at the posterior edge of the vertebral body causing minor compression, nerve compression symptoms can occur. A sagittal diameter of lo mm or less is absolute spinal stenosis and is clinically referred to as lumbar spinal stenosis. Of course, the diagnosis of lumbar spinal stenosis can also be made if the sagittal diameter of the spinal canal is less than 13 mm and there are signs and symptoms of spinal stenosis in combination with clinical symptoms. In some cases, the sagittal diameter of the spinal canal is less than 10 mm. However, without clinical symptoms and signs, even a diagnosis of lumbar spinal stenosis has no clinical significance. The diagnosis of lumbar spinal stenosis should also depend on the transverse diameter of the spinal canal. In some patients, the sagittal diameter is greater than 13 mm, but there is hypertrophic calcification of the ligamentum flavum, and extrusion of the dural sac may also result in lumbar spinal stenosis. In patients with lumbar spinal stenosis, the storage space within the spinal canal, including the epidural and subarachnoid spaces, is completely lost. Most patients with primary lumbar spinal stenosis develop symptoms of nerve root or cauda equina compression in young adulthood and have little to do with acquired factors. In patients with secondary lumbar spinal stenosis, such as spinal stenosis formed after a lumbar disc herniation, symptoms mostly disappear after the herniated disc is repositioned or dislocated, mostly with the smallest sagittal diameter of the spinal canal in lumbar 4.