In 1983 Denis proposed the concept of three-column classification, suggesting that the stability of the spine depends on the integrity of the middle column and is not determined by the posterior ligamentous complex structure. Denis proposed a three-column classification dividing the spine into anterior, middle, and posterior columns. Anterior column: anterior longitudinal ligament, anterior 1/2 of the vertebral body, and anterior part of the intervertebral disc; middle column: posterior longitudinal ligament, posterior 1/2 of the vertebral body, and posterior part of the intervertebral disc; posterior column: arch, ligamentum flavum, and interspinous ligament. In 1984, Ferguson refined the concept of three-column classification proposed by Denis, considering the anterior 2/3 of the vertebral body and intervertebral disc as the anterior column and the posterior 1/3 as the middle column, which is a more unanimously accepted concept of three-column classification, and any injury to the middle column is an unstable fracture. Secondary lumbar spinal stenosis Secondary lumbar stenosis Secondary lumbar stenosis is also called acquired lumbar stenosis. I. Etiology Acquired pathogenic factors: degeneration, trauma, instability, deformity, neoplasia, inflammation and other factors. For example: trauma, degeneration, deformational osteitis, spinal tuberculosis, septic infection of the spine, tumor, lumbar synostosis, spondylolisthesis, and medically acquired lumbar stenosis. Classification 1. central spinal stenosis; 2. lateral saphenous stenosis; 3. neurogenic stenosis; 4. mixed stenosis. Pathological changes: 1) osteophytes at the posterior edge of the vertebral body, hypertrophy and ossification of the posterior spinal ligament, disc protrusion, etc., resulting in a smaller anterior and posterior diameter of the central canal or narrowing of the lateral saphenous fossa; 2) hypertrophy of the articular process resulting in narrowing of the lateral saphenous fossa; 3) shortening or coalescence of the vertebral arch causing narrowing of the sagittal or transverse diameter of the spinal canal; 5) narrowing of the intervertebral space, compression of the nerve root by the disc yellow space, and distortion of the nerve root; 6) epidural lesions, adhesions and cysts. (a) Clinical manifestations (1) Age > 40 years; (2) Central spinal stenosis with lumbosacral pain or hip pain, less radiating pain, neurogenic interstitial claudication; (3) Lateral saphenous fossa stenosis and nerve root stenosis with radiating pain, which is continuous and can be radiated to the legs. (ii) Signs 1. rarely; 2. late onset of sensory, motor and reflex hypoesthesia. V. Diagnosis On X-ray: orthogonal: the distance between the two sides of the pedicle is less than 18MM, spinal stenosis; lateral: the distance from the posterior edge of the vertebral plate to the junction of the vertebral plate and the spinal prominence is less than 13MM, spinal stenosis. VI. Treatment Depending on the stenosis to reduce instability and rebuild the stability of the vertebral body.