1.How many intervertebral discs are there in the human body? The structure of the human spine is very complex, and there are 33 vertebrae in the spine. There are only 23 intervertebral discs in the whole body because there are no intervertebral discs between the circumferential thrust and the cardinal vertebrae and between the sacral caudal vertebrae. They are all located between two vertebral bodies. The total thickness of the intervertebral discs accounts for 1/4 to 1/5 of the total length of the spine, and the discs in the lumbar region are the thickest, at about 9 mm. Lumbar intervertebral discs are present from lumbar 1 to sacral vertebrae. People often say herniated disc actually refers to the lumbar disc protrusion, in fact, the cervical and thoracic vertebrae have intervertebral discs, can also be herniated, but the symptoms and signs, as well as treatment methods are different. 2.What structures are usually included in the intervertebral disc? The intervertebral disc usually consists of three parts: ① nucleus pulposus, mostly located in the central posterior part of the intervertebral disc, jelly-like, touching a strong elasticity, high water content, generally more than 80, the water content of up to 90 at birth. The volume of the nucleus pulposus increases again and the elasticity and tension increase. The nucleus pulposus is firmly fixed by the annulus fibrosus and the cartilage plates above and below it. In children, the boundary between the nucleus pulposus and the annulus fibrosus is clear, while in adults, the boundary between the two is difficult to distinguish because the fibers of the annulus fibrosus are interwoven with those of the nucleus pulposus. The fibular ring is located around the nucleus pulposus and between the upper and lower cartilage plates, arranged diagonally in concentric circles, with adjacent fibers staggered, the peripheral part of the ring penetrating into the bone of the epiphyseal ring of the vertebral body, the deeper part of the ring attached to the cartilage plates, and the fibers in the center fused with those of the nucleus pulposus. The fibrous ring is a stronger tissue, thicker anteriorly and on both sides and thinner posteriorly. It is reinforced anteriorly by a strong anterior longitudinal ligament and posteriorly by a posterior longitudinal ligament, but the posterior longitudinal ligament is narrower and thinner. The cartilage plate, covering the bone surface in the middle of the epiphyseal ring below the upper vertebral body, constitutes the upper and lower walls of the intervertebral disc and is connected to the cancellous bone of the vertebral body with an average thickness of 1 mm. there are many microscopic pores, which are pathways for water and metabolites of the nucleus pulposus. The cartilage plate in adults is a non-vascular and non-neural tissue, which does not produce pain when injured and cannot repair itself. In its fresh state, it is milky white, transparent and slightly elastic. The edges are thick and the center is thin. The cartilage plate seals the nucleus pulposus together with the fibrous ring so that the nucleus cannot protrude into the vertebral body. If the cartilage plate is incomplete, the nucleus pulposus will protrude into the vertebral body and form a Schmorl node. 3.What is the special function of the human intervertebral disc? The lumbar intervertebral discs play a special function in intervening in the spine to bear the weight of the trunk, link the limbs, maintain the normal physiological posture of the entire body, and perform various movements of the trunk, with the following specific functions: (1) maintain the height of the spine, maintain height, with the development of the vertebral body, the intervertebral discs grow, thus increasing the length of the spine. (2) linking the upper and lower vertebrae of the intervertebral disc and providing a certain degree of mobility between the vertebrae. (3) Subjecting the surface of the vertebral body to the same force, even though there is still a certain degree of inclination between the vertebral bodies, the entire disc is subjected to the same stress through the semi-liquid component of the nucleus pulposus. (4) Cushioning effect. (1) because the elastic structure, especially the nucleus pulposus, is plastic and can be flattened under pressure, so that the force applied to it can be transferred evenly to the fiber ring and cartilage plate in all directions; (2) is the main structure of the spine to absorb shock, playing the role of elastic cushion, so that when falling from a height or sudden load on the shoulder, back or lumbar area, it plays a buffering role in force transmission and plays a role in protecting the spinal cord and important nerves in the brain. (5) Maintain a certain distance and height of the lateral articular processes. Maintain the size of the intervertebral foramen, which under normal circumstances is 3 to 10 times the diameter of the nerve root. (6) Maintain the curvature of the spine, the thickness of the intervertebral disc varies in different parts, in the same lumbar intervertebral disc its front is thick, the rear is thin, so that the lumbar spine appears physiologically convex curve. 4.What are the factors that induce lumbar disc herniation? The basic factor constituting lumbar disc herniation is degenerative disc disease, and the factors inducing lumbar disc herniation are roughly divided into the following categories: (1) Trauma: Trauma and accumulated strain are important causes of lumbar disc herniation. The lumbar spine is physiologically convex and the intervertebral disc is thin in the back and thick in the front. When people bend over, the nucleus pulposus moves to the back and generates resistive elasticity, the size of which is proportional to the size of the weight-bearing pressure, and if the weight-bearing pressure is too great, the nucleus pulposus may break through the fibrous ring and protrude, protrude or separate due to degeneration of the fibrous ring and its own existing defects. Protrusion means that the nucleus pulposus is still wrapped by the outer fibers of the annulus fibrosus; protrusion means that the nucleus pulposus bursts out from the posterior fibers of the annulus fibrosus and is under the posterior longitudinal ligament; separation means that the nucleus pulposus has protruded beyond the annulus fibrosus and the posterior longitudinal ligament and the nucleus pulposus is free in the spinal canal. When the strain is accumulated, the nucleus pulposus cannot be filled normally for a long time, which affects the nutrient supply of the annulus fibrosus, resulting in damage to the annulus fibrosus that is not easily repaired, and in the long run, small fissures appear in the weak points of the degenerated intervertebral disc. This kind of fissure more in the posterior part of the fibrous ring, can involve different depths of the fibrous ring, can also appear in the cartilage plate, into the channel of the nucleus pulposus protrusion. (2) Excessive weight bearing: Heavy physical labor and weight lifting often cause early degeneration of the intervertebral disc due to excessive loading. When the spine weight 100kg, the normal intervertebral disc gap narrowing 1.0mm, lateral expansion 0.5mm. and when the intervertebral disc degeneration, negative the same weight, the vertebral gap narrowing 1.5 ~ 2mm, lateral expansion 1mm. lumbar spine is heavy and difficult to avoid a variety of non-physiological posture under weight, which requires the lumbar spine and intervertebral disc at any time to withstand a variety of different external forces, such as more than its capacity, that may Caused by trauma, over time, cumulative strain injury can occur, that is, to accelerate the process of intervertebral disc degeneration, and may produce herniation on the basis of disc degeneration. (3) long-term vibration: car and tractor drivers at work, long-term sitting and bumpy state, the lumbar intervertebral discs under greater pressure. It was determined that when the driver stepped on the clutch, the disc pressure increased by about double. Such long-term repeated intervertebral disc pressure increase, lumbar intervertebral disc pressure continues to increase, in addition to continuous vibration can involve the microcirculation, resulting in intervertebral disc nutritional disorders, oxygen partial pressure and cell activity significantly reduced, thus accelerating the process of lumbar intervertebral disc degeneration, and even produce lumbar disc herniation. (4) the impact of bad posture: people in the completion of a variety of work, need to constantly replace a variety of positions, including sitting, standing, lying and difficult to avoid a variety of non-physiological posture, bad posture often triggers the occurrence of this disease. If a person is fixed in a certain position for a long time, the compressed intervertebral disc cannot be restored to its normal form. The loss of fluid in the disc makes it thinner and thinner, and the outer edge becomes weak. This is a progressive effect, and it is this degeneration that makes the disc susceptible to rupture and forces the nucleus pulposus to prolapse. (5) Deformity of the spine: In patients with congenital and secondary spinal deformities, the pressure on different parts of the fibrous ring varies and there is often torsion, which tends to accelerate the degeneration of the disc. Cold: Many patients with lumbar disc herniation do not have a history of trauma and strain, but only cold, which may be due to developmental defects in the intervertebral discs, and the cold causes muscle spasm and small blood vessel constriction in the low back, reducing local blood circulation, which in turn affects the nutrition of the intervertebral discs. At the same time, muscle tension, spasm, resulting in the internal pressure of the intervertebral disc is elevated, especially for the degenerated intervertebral disc, can cause further damage, resulting in the nucleus pulposus protrusion. (6) Smoking: the relationship between smoking and low back pain may be: ① smoking increases coughing, thus increasing disc pressure and abdominal pressure, making the spine tense and increasing the rate of disc bulging and permanent herniation; ② smoking reduces bone mineral content, causing changes in the microstructure of the spine; ③ smoking impairs fibrinolysis and increases fiber deposition and scar formation, leading to chronic infection and low back pain; ④ smoking reduces vertebral body blood flow, which affects the intervertebral metabolic balance, therefore accelerating the degeneration process and making the spine more susceptible to mechanical deformation and trauma. In addition, smoking increases coughing, coughing increases abdominal pressure, strengthens the nerve roots of the herniated disc and implicates the nerve roots of existing inflammation, which obstructs venous return and further increases edema, thereby increasing the sensitivity of the nerves to pain. 5, who are more likely to suffer from lumbar disc herniation? Lumbar disc herniation occurs in the following groups of people: (1) In occupation: Lumbar disc herniation is seen in all walks of life, with no significant difference in incidence between manual and mental workers. There is no significant difference in the incidence rate between manual and mental workers. The incidence rate is higher in heavy manual workers than in light manual workers, and higher in pure mental workers than in light and mixed mental and physical workers. (2) Age: The disease generally occurs in young adults aged 20-40 years, with more men than women, accounting for about 75% of the overall incidence. (3) on the body type: generally too obese or too thin people are prone to lumbar disc herniation. (4) in the work environment: cold and wet work and living environment is prone to lumbar disc out. (5) In heredity: People who have had lumbar disc herniation in their family have a several times higher incidence than those who do not have the disease in their family. Developmentally: Patients with developmental abnormalities, such as lumbar sacralization, sacral lumbarization, sacral cleft, and disintegration of the vertebral arch, can affect the normal function of the lumbar spine and add extra load to the lumbar musculature. It is easy to induce lumbar disc herniation. (6) in physical quality: in clinical practice can find such a pattern, suffering from lumbar disc herniation some usually have better physical quality, in these patients few people at the same time suffer from hypertension, coronary heart disease, diabetes and other common diseases. In terms of lifestyle habits, the amount of smoking is associated with the incidence of low back pain. 6.Why are lumbar 4 to lumbar 5 and lumbar 5 to sacral 1 disc herniations most common? From a biomechanical point of view, the lumbar 4 to lumbar 5 and lumbar 5 to sacral 1 intervertebral discs are under the greatest pressure and have the greatest mobility, while the posterior longitudinal ligaments located in these two segments are relatively narrow (only 1/2 the width of the upper part), so the lumbar 4 to lumbar 5 and lumbar 5 to sacral 1 intervertebral discs are the most easily damaged parts, and clinically the lumbar 4 to lumbar 5 and lumbar 5 to sacral 1 disc herniations are the most common. 7.Why is the lumbar disc herniation easy after 20 years old? The adult intervertebral disc tissue has no blood supply and relies on lymphatic infiltration to maintain nutrition, and only the surface layer of the annulus fibrosus has a small amount of blood supply. The development of the intervertebral disc peaks at the age of 20, and degenerative changes in the disc begin after the age of 20, with the water content of the nucleus pulposus gradually decreasing. As a result of dehydration, the tension of the nucleus pulposus decreases and the disc becomes thinner. At the same time, the proteoglycan content of the nucleus pulposus decreases, collagen fibers increase, and the nucleus pulposus loses elasticity. Strenuous body movements can cause the layers of fibers of the annulus fibrosus to rub against each other and produce glassy changes, thus losing elasticity and eventually leading to fiber rupture. The cartilage plate becomes electrically thin and incomplete with age, and produces cartilage cystic degeneration and chondrocyte necrosis, and the attachment point of the fibrous ring is also relaxed, coupled with the fact that the posterior lateral aspect of the fibrous ring of the lumbar intervertebral disc is weaker, and the posterior longitudinal ligament running through the vertebrae at the back of the vertebral body gradually narrows below the plane of the 1st lumbar vertebra, and the width between the 5th lumbar vertebra and the 1st sacral vertebra is only half of the original, thus creating a weakness in the natural structure. The intervertebral disc has no blood circulation, weak repair ability, and the lumbar spine is the hub of the body’s weight-bearing and activities, so a slight external force may cause the intervertebral fibrous ring to rupture, resulting in the nucleus pulposus coming out of the rupture, compressing the nearby nerve roots and causing back pain and leg pain. The labor intensity of young and strong people, especially the lumbar force, repeated flexion and extension of the rotation of the action, increasing the chance of lumbar injury, so the disease is common in patients after the age of 20. 8.What are the nerves involved in lumbar disc herniation? The main clinical symptom of lumbar disc herniation is nerve damage, involving the lumbosacral plexus and involving the femoral nerve, foraminal nerve and sciatic nerve, and the resulting symptoms are motor and sensory disorders in the above innervated areas. The femoral nerve comes from the lumbar 2-lumbar 4 spinal nerve, which is the thickest of all the branches of the lumbar plexus, and travels in the iliac recess between the psoas major and iliopsoas muscles, sending out muscle branches distributed to the psoas major and iliopsoas muscles, and immediately divides into three branches after passing through the inguinal ligament to the thigh, and innervates the muscles and skin of its distribution area. Quadriceps muscle branch. Saphenous nerve, distributed below the patella, anteromedial aspect of the small intestine to the medial edge of the foot. The anterior cutaneous branch, which distributes in the anterior aspect of the thigh. The femoral nerve can be damaged when the lumbar 3-4 disc is herniated, manifesting pain and discomfort or abnormal sensation in the groin and anterior thigh. The foraminal nerve is derived from the lumbar 2-4 spinal nerve and descends into the small pelvis from the lumbaris major muscle and exits the pelvis through the foraminal canal, which is divided into two terminal branches. (1) Anterior branch: it comes out of the pelvis before the external muscle of the foramen ovale and travels behind the pubococcygeus muscle, the longus muscle and before the shortus muscle, with the terminal branch being the cutaneous branch, which is divided into the skin of the medial side of the thigh, and sometimes over the knee to the medial side of the calf. ②Posterior branch: It travels between the short retractor muscle and the greater retractor muscle. The foramen magnum nerve innervates the external foramen magnum, pubococcygeus, adductor, and femoralis muscles, and is distributed to the hip joint. When the herniated nerve infringes on the foramen magnum nerve, it may manifest as pain or numbness in the deep hip area. The sciatic nerve comes from the lumbar 4-lumbar 5 nerve root and the sacral 1-sacral 3 nerve root. It is the thickest of all nerves. The sciatic nerve exits the pelvis to the buttocks through the inferior foramen of the pear-shaped muscle, travels downward in the deep side of the gluteus maximus muscle, crosses the posterior aspect of the internal closed muscle, the upper and lower I muscles and the femoral square muscle in turn, innervates these muscles, and descends along the posterior aspect of the great retractor muscle, between the semitendinosus, semimembranosus and biceps femoris, sending muscle branches to the flexors of the thigh on the way. The sciatic nerve divides into the tibial and common peroneal nerves before it reaches the N fossa, innervating all the muscles of the lower leg and foot and the sensation of the skin of the lower leg and foot except for the saphenous innervation zone. Sciatica is the main symptom of lumbar disc herniation. The sciatic nerve is actually composed of the common peroneal nerve and the tibial nerve, and these two nerves are encircled by a sheath of connective tissue from the beginning to above the N fossa, but the fibers of the two nerves are not crossed together. It then descends vertically between the greater trochanter and the sciatic tuberosity to the posterior femur. Variations of the sciatic nerve in the pelvis and buttocks are present in approximately 40% of the population. As the sciatic nerve or other parts cross the pear muscle, pain is produced by the effect of muscle contraction and compression, called pear muscle syndrome. 9.What are the symptoms of lumbar disc herniation? (1) Low back pain: Low back pain is the most common symptom of lumbar disc herniation and the earliest symptom. 95% or more of patients have this symptom. Low back pain can appear before leg pain, which accounts for the majority of cases, and can also appear at the same time as leg pain or after the lumbar pain is alleviated, persistent low back dull pain is common, the sensory site of such pain is deep, inaccurate localization, is a kind of limited or widespread pain. It is relieved by lying down and intensified by standing or overexertion (different from lumbar strain). In some patients, the pain is spasmodic and severe and unbearable. It resembles colic and can last for days or even weeks (unlike spinal stenosis), and its onset is usually acute. Some patients have low back pain at the time, days, months, or even years after a definite lumbar trauma, and some patients have low back pain that can occur suddenly for unknown reasons. (2) Sciatica; since 95% of lumbar disc herniation occurs in the lumbar 4 to lumbar 5 and lumbar 5 to sacral 1 intervertebral spaces, lower extremity radiating pain accounts for 80%, of which the posterior type (spinal canal type) can account for 95%. The radiating pain of lower limbs is divided into two kinds of stabbing pain and severe electric shock-like pain, and the former is common. The pain is mostly one-sided, and very few (central type and paracentral type) show bilateral lower extremity pain, and the pain can be aggravated by coughing and sneezing. Sciatica mostly occurs gradually and mostly starts in the buttocks with gradual downward radiation. In a few cases, the pain may be radiated from the bottom to the top. However, the site of radiation depends on the location of the lumbar disc herniation: ①Lumbar 5 to sacral 1 disc herniation, radiating pain through the posterior N fossa of the thigh to the posterior side of the calf, ankle and little toe. ②Lumbar 4 to lumbar 5 disc herniation, radiating pain through the lateral posterior thigh, N fossa to the lateral side of the calf, the dorsum of the foot and the toes. ③Lumbar 3 to lumbar 4 disc herniation, radiating pain through the anterior thigh down to the anterior inner calf and the anterior inner dorsum of the foot. A herniated disc in the upper lumbar spine may have symptoms of a herniated disc in the lower lumbar spine. This is related to the outward or slightly centered position of the herniated disc. Sciatica on one side can be converted to the opposite side. Low back and leg pain can be continuous or intermittent. The nature of the pain is often paresthesia, pins-and-needles pain, or burning pain, or in severe cases, knife-like pain, and in severe cases, the patient often adopts various positions to try to relieve the pain. (3) Pain in the inguinal region; in high lumbar disc herniation, the herniated disc can compress the lumbar l, 2 and 3 nerve roots, resulting in pain in the inguinal region in its innervated area. In addition, low-level disc herniation can also cause pain in the groin or perineal region. This pain is mostly a pulling pain. (4) Intermittent claudication: pain, numbness or weakness in the lower extremities as the patient walks for increasing distances, with symptoms reduced or relieved by stopping to rest or bending p squatting. Walking distance of tens of meters or hundreds of meters appears disc herniation secondary to lumbar spinal stenosis, and for congenital developmental spinal stenosis (small sagittal diameter), the prolapsed nucleus accentuates the degree of spinal stenosis, thus inducing this symptom. (5) Muscle paralysis or muscle weakness: muscle paralysis occurs when the nerve root is severely compressed; muscle weakness is more common and is related to the nerve distribution area. Numbness: Some patients with lumbar disc herniation do not have lower limb pain but only numbness of the limbs, and the numbness area is still distributed according to the area of nerve involvement. (6) Cauda equina syndrome: It is mainly seen in central and paracentral lumbar disc herniation and is rarely seen clinically. When there is a huge herniation, the cauda equina nerve below the nearby plane can be compressed, resulting in severe bilateral sciatica, perineal numbness, unfavorable defecation and urination, pseudo-incontinence in female patients, and impotence in male patients. Others: Patients with lumbar intervertebral herniation have also been reported to have caudal pain and chills in the affected limbs, calf edema, foot drop, etc. 10.What are the physical signs of lumbar disc herniation? Signs of lumbar disc herniation include: (1) Lumbar deformity: ① The physiological curve of the lumbar spine decreases or disappears, and a flat waist appears. In order to avoid or reduce the pain caused by nerve compression by the herniated nucleus pulposus in lumbar disc herniation, the physiological anterior convexity of the lumbar spine becomes shallow due to increased posterior tension and posterior ligamentous tension in the lumbar spinal space, which tries to bring back or partially bring back the herniated nucleus pulposus. In case of combined lumbar spinal stenosis, there may be a posterior convexity deformity. ② Scoliosis. In order to reduce pain, the erector spinae muscle (sacrospinous muscle) spasms, limiting the range of motion of the lumbar spine to reduce the tension of the nerve roots, so lumbar disc herniation produces scoliosis, which occurs in the direction of lumbar scoliosis can be bent both to the affected side and to the healthy side. This depends on the position of the herniated nucleus pulposus in relation to the adjacent nerve roots. (2) Gait changes: Those with more severe symptoms may have a constrained posture, leaning forward or limping when walking. In severe cases, it is difficult to walk with normal weight bearing, often with hands on the waist, torso leaning forward, hip protrusion, lumbar stiffness, and sometimes need to support crutches to walk with difficulty. In severe cases, the patient needs the support of others to take steps. Paraplegia may occur in rare cases. (3) Pressure points: mainly located in the paravertebral area. It is about 2cm to 3cm from the midline. Radiating pain along the nerve roots in the lower extremities may occur when pressure is applied. Interspinous and supraspinous pressure pain can also occur, but percussion pain is the main focus. If the pressure pain is not obvious when examined in prone position, the patient can be asked to adopt standing position and examined in extended p-abdominal position, which is easy to detect. Some people have statistics: the appearance rate of pressure pain with radiating pain is 61.5%, and only pressure pain without radiating pain is 38.5%. (4) Restriction of lumbar activities; in the case of lumbar disc herniation, activities in all directions will be affected to varying degrees. The anterior flexion position causes increased lumbar pain and sciatic nerve radiating pain; when moving laterally, the pain decreases when moving to the healthy side and increases when moving to the affected side: posterior extension activities generally do not increase pain, but posterior extension activities are restricted and pain is obvious, and the diagnostic value is greater. (5) Muscle atrophy of the lower limbs: In lumbar disc herniation, the lumbosacral nerve roots, which are the lower nerve units, are damaged, and the muscles innervated by them may have different degrees of muscle atrophy. A small number of severe patients may lose the ability to actively dorsiflex the ankle joint or cam toe. Nerve dysfunction: ① Sensory nerve dysfunction: numbness, pain sensitivity and hyperalgesia can occur when the nerve is compressed by a herniated lumbar disc. Sensory changes in the dermatomal area are significant for the localization of the herniated disc, but cannot be characterized. (ii) Motor nerve dysfunction: reduced motor strength is a more reliable sign, but the muscular nerve is often innervated by multiple nerve roots, so some of the muscle strength reduction may not be so obvious. ③Reflex dysfunction: it can be hyperactive (early nerve compression), or it can be diminished or absent. In the case of unilateral disc herniation from lumbar 3 to lumbar 4, the knee reflex on the affected side is weakened; in the case of unilateral disc herniation from lumbar 4 to lumbar 5, the knee reflex is unchanged, and in the case of disc herniation from lumbar 5 to sacral 1, the heel reflex is weakened or disappears.