1, lumbar spine X-ray plain film (1) lumbar spine posterior-anterior film (ortho): mostly shows lumbar spine scoliosis sign, vertebral space width in the early stage of the lesion is mostly unchanged; if the disease is longer, it shows the narrowing of the vertebral space and the appearance of various forms of bone spurs at the edge of the vertebral body. The deviation of the spinous process, although more common, is not necessarily of any significance. (2) Lateral lumbar spine film: its diagnostic value is more important than the former. (1) The physiological curve of the lumbar spine disappears in most cases, especially in acute onset. (2) The anterior margin type of the vertebral body type can show typical triangular bone fracture signs on the lateral radiographs. â‘¢The narrowing of the intervertebral space and the formation of bone spurs at the vertebral body edge indicate a long disease duration. (4) Calcification of the intervertebral disc (rare) or calcification of the prolapsed nucleus pulposus (slightly more common), mainly shown on lateral radiographs. (3) Lumbar oblique radiographs: mainly used to exclude lower lumbar arch fractures and lumbosacral (or sacroiliac) joint lesions. In patients with simple disc prolapse, there are no special findings, so it is not necessary to take this film if the diagnosis is clear. 2, CT examination application CT examination of the spine and spinal canal lesions has been widely carried out in the clinic, relatively high resolution CT images, can clearly show the site, size, morphology and nerve roots of the herniated disc, the image of the dural sac pressure displacement, at the same time can show the vertebral plate and ligamentum flavum hypertrophy, small joint hyperplasia hypertrophy, spinal canal and lateral saphenous fossa narrowing, etc., and can be three-dimensional technology to reconstruct the spinal canal and root canal three-dimensional technique to reconstruct the three-dimensional shape of the spinal canal and root canal. From the imaging point of view, the main changes of the disease on CT images are as follows: (1) deformation of the posterior edge of the disc: under normal conditions, the posterior edge of the disc is parallel to the edge of the bony section of the vertebral body; in patients with nucleus pulposus herniation, there is a local protrusion of the posterior edge of the disc. According to the morphology and nature of the local change, disc bulging, protrusion or prolapse (rupture) can be distinguished; the former is an early manifestation of degeneration, while the latter two are intermediate and late changes. (2) Loss of epidural fat: Under normal circumstances, the lumbar region, especially the lumbar 4 to 5 and lumbar 5 to sacral 1 planes, usually has abundant epidural fat in the dural sac, and the morphology and size of the epidural translucent area are symmetrical. When the disc ruptures, the prolapsed nucleus pulposus can replace the low-density epidural fat, and the density is not symmetrical in the plane of disc rupture when observed in comparison between the two sides. (3) Increased soft tissue density in the epidural space: the density of the herniated or prolapsed nucleus pulposus is higher than that of the dural sac and epidural fat, and the soft tissue density shadow in the epidural space represents the herniated fragment (size and location). When the fragment is small and there is a posterior longitudinal ligament attached to the outside, the soft tissue mass shadow is continuous with the disc shadow. When the fragment has ruptured outside the posterior longitudinal ligament and has lost continuity with the disc and is free from the ruptured annulus fibrosus, a detached image may be seen. Depending on the site of disc rupture, the soft tissue density may be located in the midline or posterior lateral border, or in the intervertebral foramen if the rupture occurs entirely at the lateral border. When the herniated fragment is large, soft tissue density may also be demonstrated at levels outside the plane of the diseased disc. Depending on the direction of fragment freeing, it may be located at the posterior edge of the vertebral body below the disc or in the lateral crypt immediately adjacent to the pedicle; it may also be located within the foramen, rather like an enlarged ganglion. (4) Dural sac deformation: The density of the dura mater and its contents is lower than that of the intervertebral disc. In the upper lumbar region, the entire bony spinal canal is occupied entirely by the spinal bursa. The boundary between the edge of the spinal capsule and the edge of the intervertebral disc is clearly demarcated due to the density difference. When the disc is herniated, the dural sac may also be deformed. In the lower lumbar region, the dural sac does not fill the entire bony spinal canal and does not contact the posterior edge of the disc. Only when the disc herniation is large enough to occlude the epidural fat and compress the wall of the spinal sac does the smooth, rounded contour of the spinal sac become deformed and the protruding fragments may compress the nerve roots; there are a few cases that do not cause deformation of the spinal sac. (5) Displacement of the nerve root sheath by compression: Under normal circumstances, the nerve root sheath shows a soft tissue density in contrast to the epidural fat, which is located posterior to the bony spinal canal and medial to the vertebral arch, in a plane slightly below the vertebral arch. When the fragment protrudes posteriorly into the bony spinal canal, it pushes the root sheath backward, and the root sheath is often indistinguishable from the protruding fragment, which is itself a sign of nerve root compression. (6) Calcification of the protruding (de)nucleus pulposus: If the nucleus pulposus has been protruding (de)nucleated for a long time, calcification may gradually form and appear as a consistent change in CT examination. The fragments and the edge of the vertebral space can be phase retarded. (7) CTM examination technique: The diagnostic accuracy of CT examination technique for disc herniation is 80% to 92%. Because of the small amount of X-ray exposure to the patient, CT examination can be classified as a basically harmless diagnostic tool. In addition, the combination of myelography with CT examination (CTM) using a water-soluble contrast agent can improve the accuracy of diagnosis. The above signs are more obvious during CTM examination. In most patients with disc herniation, the nerve root and dural sac compressed by the disc are in the same plane. Free disc prolapse can occur elsewhere in the spinal canal. This test is generally used more rarely, unless it is a last resort. The emergence of magnetic resonance imaging (MRI) can be said to be a major advance in imaging, non-invasive and non-radioactive damage in the past any means of examination can not be compared, its image of human tissue structure display, more accurate and real than the CT examination. The signals shown on MRI images are broadly classified into high, medium and low intensity. Usually, under T1-weighted conditions, the bone cortex, ligaments, cartilage endplates and fibrous rings are of low signal intensity; vertebrae rich in adipose tissue, spinous processes and other osteophytes show medium signal (due to the amount of bone marrow tissue), and intervertebral discs are in between. Adipose tissue has high intensity signal, followed by spinal cord and cerebrospinal fluid. t2 weighting shows more pronounced disc tissue lesions, which show lower signal on T1-weighted images and enhanced on T2-weighted ones. The T2-weighted cerebrospinal fluid signal is strong and bright, resulting in a clearer display of the herniated disc when it compresses the dural sac. MRI examination is important for the diagnosis of disc herniation. Sagittal images at different levels and cross-sectional images of the involved disc allow observation of the morphology of the herniated disc and its relationship with the dural sac, nerve roots, and other surrounding tissues. In addition to obtaining three-dimensional images for diagnosis (with a positive rate of more than 99%), MRI can also be used to locate and distinguish between “bulge”, “herniation” and “prolapse”. “This can facilitate the selection of treatment methods and surgical approaches. Depending on the location of the medullary nucleus protrusion (prolapse), the imaging can show root cuff deficiency (lateral type), root cuff caudal insufficiency (mostly lateral type), dural sac compression (central type) or dural sac with root cuff compression (paracentral type), and other patterns.