Lumbar disc herniation is a series of clinical symptoms and signs caused by degeneration of the lumbar disc, rupture of the annulus fibrosus and protrusion of the nucleus pulposus that irritates or compresses the nerve root and cauda equina nerve, commonly known as “lumbar protrusion”. It often causes a lot of pain in life and work, and even disability and loss of working ability. Lumbar disc herniation is the main cause of low back pain and is one of the most common orthopedic clinical disorders, accounting for 10%-15% of patients with low back pain in orthopedic outpatient clinics and 25%-40% of hospitalization cases for low back pain.
The most common symptom in patients with lumbar disc herniation is pain, which can be manifested as low back pain and sciatica, and typical sciatica manifests as radiating pain from the hip, the back of the thigh, the lateral calf to the heel or the back of the foot. According to clinical statistics, about 95% of patients with lumbar synostosis have varying degrees of low back pain and 80% of patients have lower limb pain. In particular, lumbar pain is not only the most common symptom of lumbar disc herniation, but also one of the earliest symptoms.
The pain occurs mainly due to the stimulation and compression of the adjacent tissues (mainly sinus nerve and spinal nerve root) by the herniated and degenerated nucleus pulposus, as well as the overflow of biological substances such as glycoproteins in the nucleus pulposus, the release of histamine and other local chemical inflammation caused by chemical and mechanical radiculitis, resulting in mild or severe chronic low back pain. Moreover, degeneration of the lumbar spine also often occurs simultaneously in other tissues of the lumbar region, such as small intervertebral joints, ligaments, and lumbar muscles, causing local chronic inflammation of these tissues and causing pain. The two factors interact with each other and aggravate each other, making the progressive development of lumbar and leg pain.
I. Definition
The full medical name of lumbar disc herniation should be “lumbar disc herniation”, due to the different names, the Society of Orthopedic Surgeons has defined the naming of lumbar disc lesions as follows.
1, the disc is normal disc without degeneration, all disc tissue is in the disc.
2, disc bulge disc fiber ring ring uniformity beyond the intervertebral space, the disc tissue is not in a limited protrusion.
3, disc herniation disc tissue limited displacement beyond the intervertebral space. The displaced disc tissue is still connected to the original disc tissue, and the diameter of its basal continuous part is larger than the displaced disc part beyond the intervertebral space.
4. The diameter of the displaced disc tissue is greater than the basal contiguous portion and is displaced beyond the intervertebral space. The prolapsed disc tissue mass is larger than the ruptured disc space and is located within the spinal canal through this fissure.
In China, lumbar disc herniation is also referred to as lumbar disc rupture, lumbar disc prolapse, lumbar intervertebral cartilage disc herniation, and lumbar cartilage plate rupture. Although the names and meanings of the above diseases are different, the current unified term is: lumbar disc herniation.
Second, the disease classification
The herniated nucleus pulposus of the lumbar intervertebral disc stops in front of the posterior longitudinal ligament and is called “protrusion”, while the one that crosses the posterior longitudinal ligament into the spinal canal is called “prolapse”.
There are 3 types of herniated nucleus pulposus according to the posterior protrusion site.
1, the posterior lateral protrusion type: the weakest posterior part of the fibrous ring is on both sides of the midline of the intervertebral disc, which is weak in itself and lacks the support of the strong central fibers of the posterior longitudinal ligament, so it is the most common site of lumbar disc protrusion. Clinically it is the most common, accounting for about 80%.
2. Central protrusion type: The nucleus pulposus protrudes through the posterior central part of the fibrous ring and reaches under the posterior longitudinal ligament. In addition to causing sciatic nerve symptoms, it can also stimulate or compress the cauda equina nerve, manifesting as perineal palsy and urinary and fecal disorders.
3. Intraforaminal protrusion and extreme lateral type: The nucleus pulposus protrudes posteriorly through the posterior fibrous ring and posterior longitudinal ligament into the spinal canal and into the intervertebral foramen, which is easily missed, but fortunately its incidence is low, only about 1%.
Third, the cause of morbidity
1, degenerative changes
At present, it is believed that the basic etiology is degenerative changes of the lumbar intervertebral disc. Degeneration is the objective law of birth, growth, decay and death of all living things, and because of the special physiological function of the lumbar spine, the degeneration of the lumbar intervertebral disc is earlier than other tissues and organs, and the progress is relatively fast. This process is a long-term, complex process.
The so-called lumbar disc degenerative changes: that is, due to the compression of the disc by weight, coupled with the lumbar and often flexion, posterior extension and other activities, easy to cause extrusion and wear of the disc, especially the lower lumbar intervertebral disc, thus producing degenerative changes. Degenerative changes in the lumbar intervertebral disc is the basis for the occurrence of this disease.
2.Other factors
1, the role of external forces: in daily life and work, some people tend to have long-term lumbar improper force, excessive force posture or incorrect body position and so on. For example, long-term bending work of coal miners and construction workers need to often bend over to lift heavy objects. These long-term repeated external force caused by the injury of the intervertebral disc over time, aggravating the degree of degeneration.
2, the weakness of the intervertebral disc itself anatomical factors.
(1) The intervertebral disc gradually lacks blood circulation and has a poor repair capacity after adulthood, especially after degeneration has occurred, and the repair capacity is even weaker.
(2) The posterior lateral fibrous ring of the disc is weaker, while the posterior longitudinal ligament is significantly reduced in width at the lumbar 5 and sacral 1 planes, and the strengthening effect on the fibrous ring is significantly weakened.
(3) congenital anomalies of the lumbosacral segment: deformities of the lumbosacral segment can increase the incidence, and these anomalies often result in unequal width of the vertebral space and often cause more rotational strain on the synovial joints, so that the fibrous ring is subjected to variable pressure and accelerates degeneration.
3, race, genetic factors: the incidence of people of color is lower; for example, the incidence of Indians and black Africans is significantly lower than other ethnic groups.
Common predisposing factors
(1) increased abdominal pressure: such as violent coughing, constipation when straining to defecate, etc.
(2) Improper lumbar posture: When the lumbar region is in a flexed position, sudden rotation can easily trigger herniation of the nucleus pulposus.
(3) Sudden weight-bearing: Sudden increase in lumbar load without adequate preparation can easily cause herniated nucleus pulposus.
(4) Lumbar trauma: Acute trauma can affect the fibular ring, cartilage plate and other structures, which can cause the herniated nucleus pulposus to degenerate.
(5) Occupational factors: such as car drivers in a sitting position and bumpy state for a long time, easy to induce disc protrusion.
Four, the pathogenesis
It is generally believed that there are three mechanisms of lumbar disc herniation causing back and leg pain.
1, mechanical compression mechanism
The herniated disc compresses the nerve roots, cauda equina, dura mater, etc., blocking their venous return and reducing capillary blood flow, affecting the nutrition of the nerve roots and further increasing edema, thus increasing the sensitivity of the nerve roots to pain, which is the main cause of lumbar pain. However, as research has progressed, it has been found that this concept does not explain all clinical manifestations Some patients have severe disc herniation and significant compression visible on imaging data with mild clinical symptoms. Numerous studies have shown that mechanical compression of nerve roots is not the only cause of low back pain.
2. Inflammatory response mechanism
Inflammatory congestion and edema of the nerve roots are often found during surgery. The reason for this is that the ruptured disc releases many chemical irritants that cause an inflammatory response in the affected nerve root or spinal ganglion. At this time, the nerve roots become more sensitive to pain, and even without the direct compression of the protruding nucleus pulposus, symptoms of low back pain may occur.
3.Neurohumoral mechanism
Biochemicals and neuropeptides play an important role in pain perception. The dorsal root ganglion is the manufacturing site and delivery station of many neuropeptides in the body, and the intervertebral disc fibrous ring, posterior longitudinal ligament and joint capsule area are rich in neuropeptides. The release of neuropeptides during injury can directly stimulate the surrounding receptors and trigger pain.
V. Pathophysiology
The pathological process of lumbar disc herniation can be roughly divided into three stages.
1.Pre-protrusion
The nucleus pulposus may become fragmented or scar-like connective tissue due to degeneration and injury; the degenerated fibrous ring may become thin and soft or produce fissures due to repeated injury. Patients at this stage may have low back discomfort or pain, but no radiating lower extremity pain. In some cases, the nucleus pulposus may protrude due to one big violence.
2.Protrusion period
When the pressure of intervertebral disc increases due to trauma or normal activities, the nucleus pulposus protrudes from the weak point or rupture of the fibrous ring. The herniated material irritates or compresses the nerve roots, which means that radiating lower limb pain occurs, or compression of the cauda equina nerve causes urinary and fecal dysfunction. In elderly patients, the entire fibrous ring may become weak and loose due to disc degeneration, and the disc may diffusely bulge out to the periphery.
3.Late stage of herniation
After lumbar disc herniation, the disc itself and other adjacent structures can undergo various secondary pathological changes after a long course of the disease.
VI. Disease triggering
The basic factor of lumbar disc herniation is disc degeneration, but certain precipitating factors can cause the intervertebral space pressure to increase and cause the nucleus pulposus to herniate. Such triggering factors are often related to the following factors.
1, the age factor: lumbar disc herniation prevalent age in the 30-50 years. The average age of surgery is at 40 years. Therefore degeneration may be an important factor.
2. Height and gender: It is believed that being too tall also predisposes to lumbar herniation. And the incidence of men is 5 times that of women.
3, increased abdominal pressure: about 1/3 of patients clinically have clear factors that increase abdominal pressure before the onset of the disease, such as violent coughing, sneezing, breath holding, forceful defecation, etc.. Make the abdominal pressure increase, disrupting the equilibrium between the vertebral joint and the spinal canal.
4, bad position: people in the completion of a variety of work, the need to constantly change a variety of positions to relieve the lumbar stress. Such as long-term in a certain position unchanged, can lead to cumulative local injury. Especially in the long-term bad posture is more likely to induce the disease.
5, occupational factors: heavy manual workers have the highest incidence, white-collar workers have the lowest. Automobile drivers due to long-term bumps and vibration state, the disc under pressure and repeated changes, also prone to induce disc protrusion.
6, cold and damp: cold or damp can cause small blood vessel contraction, muscle spasm, so that the pressure on the intervertebral disc increases, which may cause the rupture of the degenerated intervertebral disc.
Seven, disease symptoms
1.Lumbar pain
Low back pain is the first symptom to appear in most patients with this disease, with an incidence of about 91%. A small number of patients have only leg pain without low back pain, so it is said that not every patient will definitely have low back pain. There are also some patients who have low back pain first and then leg pain after a period of time, while the low back pain reduces or disappears on its own, and when they come to the clinic, they only complain of leg pain. The pain is mostly tingling, often accompanied by numbness, soreness and swelling.
2.Radiation pain of lower limbs
Low back and leg pain is easy to attack after trauma, exertion and cold, each time for about 2-3 weeks, and can be gradually relieved. The pain is often relieved by resting in bed during the attack. People who engage in heavy physical labor, especially those who repeatedly bend over, have a high chance of having low back pain. People who lack exercise and have poor low back muscle strength are also prone to low back pain even if they occasionally bend over to lift heavy objects or sprain their back. Any factors that increase abdominal pressure, such as coughing, forceful defecation, laughing, sneezing, lifting heavy objects, chronic coughing, etc., are likely to trigger low back pain, or aggravate the already occurring low back pain.
3.Limitation of lumbar activities
The forward flexion and back extension activities of the lumbar spine in patients with lumbar disc herniation are closely related to the degree of disc herniation. If the annulus fibrosus is not completely ruptured, the lumbar spine takes the forward flexion position and the posterior extension is limited. The reason is that when the lumbar spine is flexed forward, the ligamentum flavum between the vertebral plates is tensed, increasing the volume of the spinal canal and the posterior space of the intervertebral space, and the corresponding increase in tension of the posterior longitudinal ligament makes the herniated nucleus pulposus partially return, thus reducing the symptoms of nerve root compression.
4.Scoliosis
This is a postural compensatory deformity adopted by patients with lumbar disc herniation to reduce pain. The lumbar vertebrae are bent to the left or right, and the spinous process can be found to be skewed by touching the spinous process in the middle of the back, but this is not a unique sign of lumbar disc herniation, as about 50% of normal people also have a skewed spinous process.
5. Limping
The claudication that occurs in lumbar disc herniation is mostly intermittent, i.e., pain and weakness in the lower limbs after walking a certain distance, and the symptoms can be relieved after bending down or squatting to rest, and the person can still continue walking. With the passage of time, the symptoms gradually and slowly aggravate, before the appearance of the above-mentioned symptoms of standing time or walking distance gradually shorten the shorter the walking distance, the more serious the disease.
6.Sensory numbness
In patients with lumbar disc herniation, some of them do not experience pain in the lower limbs, but only numbness in the limbs, mostly due to compression of the nerve proprioceptive and tactile fibers by the disc tissue. The outer thigh is a common area of numbness, which can be felt as a burning sensation when in contact with clothing and pants, and can be aggravated by prolonged standing. The cause of lateral thigh sensory disturbance is usually a bulging annulus fibrosus or joint degeneration,
It is not due to disc herniation.
Eight, auxiliary examination
1.X-ray
The density of the nucleus pulposus, fibrous ring and cartilage plate included in the lumbar intervertebral disc is low and does not show up under X-ray, so clinically the lumbar X-ray of patients with lumbar herniation may only have some non-specific changes or even no abnormal changes. Therefore, the plain X-ray of the lumbar spine alone cannot be used as a direct basis for the presence or absence of lumbar disc herniation. However, X-rays can detect degenerative changes and structural abnormalities in the lumbar spine, which are important in indicating disc degeneration and can exclude other lumbar spine disorders such as lumbar tuberculosis, tumors and lumbar spondylolisthesis. A typical patient with lumbar disc herniation can make a preliminary diagnosis through history, physical signs and X-ray plain film.
2.CT examination
CT of the lumbar spine can clearly show the site, size, morphology and nerve root and dural pressure of the herniated disc, as well as the hypertrophy of the ligamentum flavum, small joint hyperplasia, narrowing of the spinal canal and lateral saphenous fossa. The accuracy rate of the diagnosis of lumbar disc herniation reaches 80%-92%.
3.Magnetic resonance imaging (MRI)
MRI has no radiation, can be multi-directional imaging (cross-sectional, coronal, sagittal and oblique), shows better anatomical details, is more sensitive to subtle pathological changes in tissue structures (e.g. infiltration of bone marrow), and can exclude nerve and spinal tumors, etc. For some fall into the spinal canal of the nucleus pulposus tissue will not be missed.
4.Myelography
Myelography uses the space of the subarachnoid space in the spinal canal to show the internal structure of the spinal canal by injecting a contrast agent and taking a film under X-ray. At present, water-soluble contrast agent is commonly used, which can show the dural cavity, cauda equina and nerve root sheath more clearly. The diagnosis of lumbar disc herniation can reach about 90%. The main radiographic manifestations are signs of dural sac compression and signs of nerve root sheath compression. However, due to the wide application of CT and MRI in the clinic, which are non-invasive and have a higher diagnostic rate, the application of myelography in the clinic has been greatly reduced; and because of its large side effects, which may even cause serious conditions such as paraplegia, it is now advocated to be used with caution.
5.Electromyography
Electromyography is a method of electrophysiological examination of peripheral nerves and muscles, which can be used to observe and record the electrical activity of muscles at rest, active contraction and stimulation of the peripheral nerves innervating them, and can also be used to measure the conduction velocity of peripheral nerves. In lumbar disc herniation, electromyography reflects the status of the corresponding nerve root by examining the excitability of the muscles in both lower extremities; and the distribution of abnormal electrical activity is used to determine the segment of disc herniation and nerve root compression. In patients with spinal nerve root and cauda equina nerve compression, the positive rate of EMG can reach 80%-90%, but it is not the first choice compared with CT and MRI, and it can be used to assist in the diagnosis and judgment of nerve root compression, and it can also be used as one of the indicators to judge the recovery of nerve roots after treatment.
IX. Diagnosis of symptoms
(a) Low back pain and radiating pain of one lower limb
This is the main symptom of the disease. Low back pain often occurs before leg pain, or both may occur simultaneously; most of them have a history of trauma, or may have no clear cause. The pain has the following characteristics.
1. Radiating pain is transmitted along the sciatic nerve and goes straight to the lateral calf, dorsum of the foot or toes. In the case of lumbar 3-4 interval herniation, radiating pain to the front of the thigh is produced due to compression of the lumbar 4 nerve root.
2.All actions that increase the pressure of cerebrospinal fluid, such as coughing, sneezing and defecation, can aggravate the lumbago and radiating pain.
3.The pain increases with activity and decreases after rest. Bed position: Most patients adopt lateral recumbency and flex the affected limbs; individual severe cases have pain in all positions and can only bend their hips and knees in bed to relieve symptoms. In combination with lumbar spinal stenosis, there is often intermittent claudication.
(B) Scoliosis deformity
The main bend is in the lower back and is more pronounced in forward flexion. The direction of scoliosis depends on the relationship between the herniated nucleus pulposus and the nerve root: if the herniation is located in front of the nerve root, the trunk is usually bent to the affected side.
Left: If the herniated nucleus pulposus is located in front of the nerve root, the spine bends to the affected side, and the pain increases if the bend is to the healthy side.
Right: The nucleus pulposus is located in front of the nerve roots, and the spine is bent to the healthy side, and the pain is increased if the bend is to the affected side.
(C) Restriction of spinal movement
The herniated nucleus pulposus compresses the nerve roots and causes protective tension in the lumbar muscles, which can occur unilaterally or bilaterally. Due to the tension of the lumbar muscle, the physiological lumbar convexity disappears. The anterior flexion and posterior extension of the spine is restricted, and radiating pain to one lower limb may occur during anterior flexion or posterior extension. The restriction of lateral bending is often only on one side, according to which it can be differentiated from lumbar spine tuberculosis or tumor.
(D) Lumbar pressure pain with radiating pain
There is a limited pressure pain point next to the spinous process on the affected side of the disc herniation site, accompanied by radiating pain to the calf or foot, which is important for diagnosis.
(v) Positive straight leg raising test
Due to the difference of individual physique, there is no uniform degree standard for the positive test, and attention should be paid to the comparison of both sides. A positive test is when the leg elevation is limited on the affected side and radiating pain is felt to the calf or foot. Sometimes numbness occurs in the affected leg while lifting the healthy limb, which is caused by the pulling of the nerve on the affected side, and this is of great value for diagnosis.
(F) Neurological examination
In the case of lumbar 3-4 herniation (lumbar 4 nerve root compression), the knee reflex may be decreased or disappeared, and the medial calf sensation may be decreased. In the case of lumbar 4-5 herniation (lumbar 5 nerve root compression), the dorsal sensation of the anterolateral foot of the lower leg is reduced, and the extension and 2-toe muscle strength is often reduced. In the case of lumbar 5-sacral 1 herniation (sacral 1 nerve root compression), there is hypoesthesia of the posterior and lateral calf, hypotonia of the 3rd, 4th and 5th toe muscles, and hypotonia or disappearance of the Achilles tendon reflex. The affected limb may have muscle atrophy if the nerve compression symptoms are severe.
X. Diagnostic points
Lumbar disc herniation is common in young and strong people, especially in manual laborers or long-time sitting workers, and there is no significant difference in incidence between men and women. When the following symptoms appear, lumbar disc herniation can be suspected, and with imaging examination, it is not difficult to make a diagnosis.
1. There is lumbar pain above the waist after trauma or unilateral lower limb pain.
2, the site of lumbar pain is mostly located on one side of the lower back, and leg pain is mostly radiating pain from the hip to the distal end on one side, which may be accompanied by numbness.
3.Unilateral saddle area (the part in contact with the seat of the bicycle) or one side (bilateral) of the lateral calf, the dorsal or medial side of the foot pain or numbness, or pain and numbness at the same time.
4. Pain in the lower back or leg, which can be mostly relieved after bed rest and reappears after getting out of bed and moving around for a period of time.