1.Incidence and danger Low back pain is one of the most common symptoms among elderly patients. With the aging of the body’s endocrine and immune functions, the normal structure of the crest changes and the normal mechanical characteristics are lost, leading to an increase in the incidence of low back pain. About 60% of the elderly have experienced low back pain. Four to six percent of these older adults have severe conditions. Low back and leg pain in the elderly accounts for more than 1/3 of the total orthopedic outpatient clinics in our hospital. Low back pain is a serious threat to the health and quality of life of the elderly. The milder ones are depressed and their self-confidence decreases. Normal social activities are reduced. In serious cases, it can lead to paralysis and complete loss of working ability, causing a serious burden to the society and family. 2.Characteristics of back and leg pain in the elderly. (1) Slow onset, long duration and repeated attacks. (2) The structure of the symptoms is complex and diverse, and the back and leg pain is persistent or intensifies episodically, and the symptoms cannot be relieved by resting in bed. (3) The location of the lesion is multi-source and multi-segmental. (4) The etiology is multifactorial. Most elderly people have different degrees of crestal deformity, osteoporosis or instability, and some have single-segment or multi-segment lumbar disc herniation. (5) There are many factors to be considered in treatment, and most elderly people are combined with chronic diseases such as diabetes, hypertension and heart disease, which make surgery and anesthesia risky and technically demanding. (6) Due to the presence of crestal deformity and osteoporosis, coupled with the reduced coagulation ability of the elderly, there is relatively more postoperative intravertebral bleeding, resulting in postoperative symptoms not being completely relieved, or recurring after the symptoms have disappeared for a period of time, and corresponding medication or physical therapy is required. 3. Common causes of low back pain in the elderly include the following: (1) crestal deformity (accounting for about 5% of low back pain in the elderly). Crest deformities mainly include degenerative lumbar scoliosis, vertebral deformation caused by osteoporosis, idiopathic scoliosis when young, and other crest deformities that continue to worsen in old age. The deformed crest changes the normal physiological curvature of the crest and causes extensive degeneration of the crest, and the deformed crest strains and compresses the internal crestal medulla and nerve roots, and the imbalance of the body caused by the crestal deformity also causes abnormal weight-bearing of bones, muscles, ligaments, etc., long-term fatigue, and eventually various symptoms of low back pain. Although the incidence of low back pain caused by crestal deformity in the elderly is relatively low, the absolute number of patients is large and the consequences are serious, patients are almost unable to walk, completely lost the ability to work, and even paralyzed in bed. (2) Osteoporosis (the incidence of the elderly is more than 70%). Bone is the ideal structural material for the human body and plays a role in weight-bearing and leverage in the human body. In the elderly, with the aging of the body’s endocrine and immune functions, the normal composition and structure of bone changes and loses its normal mechanical properties, leading to osteoporosis. Postmenopausal elderly women, smoking, alcohol abuse, sedentary work, low calcium intake and the use of specific medications such as hormones are high risk factors for the development of the disease. Currently, with the increase in the elderly population, the number of patients with osteoporosis has increased. Pain is the most common and dominant symptom of osteoporosis. Excessive bone conversion and increased bone resorption can cause generalized bone pain, but low back pain is the most common. (3) Lumbar disc herniation (4.7% – 11.7% prevalence in the elderly) The elderly are highly susceptible to lumbar disc herniation due to dehydration of the lumbar disc nucleus pulposus and laxity of the lumbar spinal ligament. Herniated discs alone are relatively rare, and most are combined with stenosis and instability of the lumbar spine. Special attention needs to be paid in the treatment. (4) Lumbar spinal stenosis (the incidence of the elderly is about 40%). Degenerative lumbar spinal stenosis in the elderly initially begins with disc degeneration. The lumbar intervertebral disc in the elderly develops malnutrition, loss of proteoglycans and water, activation of collagenase, weakness of the fibrous ring due to cumulative strain, and herniation or bulging of the lumbar intervertebral disc in response to injury and other predisposing factors. The lumbar spine is degenerated by the intervertebral disc, the intervertebral space becomes narrower, the stress level in the front decreases, while the posterior structures including the small joints rise, and the tension on the ligaments increases significantly, which naturally causes small joint injury, inflammation, hyperplasia, hypertrophy, slippage, degeneration of the vertebral plate, vertebral body, yellow ligament, etc., tissue hypertrophy, the effective volume of the central spinal canal and intervertebral foramen of the nerve root canal decreases, and the lumbosacral nerve root and cauda equina nerve appear. Corresponding compression symptoms and signs. (5) Degenerative instability of the lumbar spine (accounting for about 15% of the incidence in the elderly). Due to the laxity of the crestal ligaments in the elderly, the stiffness of the lumbar segments decreases, resulting in the inability to maintain the normal relationship between them under normal loading conditions stimulating the bone marrow and nerve roots causing pain, and can cause continuous severe pain due to interlocking of the small articular processes. (6) Lumbar spondylolisthesis (accounting for 8% – 10% of lumbar and leg pain in the elderly). The causes of lumbar spine slippage causing low back pain are more complex, because the vertebral body is shifted forward, the normal gravity of the human body is destroyed, and the abnormal stress can cause the lumbar back muscles, ligamentous tissues, intervertebral discs, etc. to be in a state of strain and pain. Lower lumbar instability, traumatic microarthritis, and lumbosacral joint disorders can also cause unspeakable pain and discomfort. When the vertebrae move forward, contact between the spinous processes of the upper and lower vertebrae can lead to the formation of pseudarthrosis, which causes back pain when the lumbar back is extended. Protrusion of the superior joint of the inferior vertebral body may also protrude into the intervertebral foramen of the slipped vertebral body to compress the superior nerve root, causing lumbar and leg pain.