Where is the lumbar disc?

In life, we often hear the name of a disease, which is lumbar disc herniation. Of course, those who suffer from this disease are generally middle-aged and elderly people, and there are very few young people. But everyone knows that our spine is a whole piece, and the so-called lumbar spine is not often treated. So the question is, what is the specific location and structure of the so-called lumbar spine in medicine?

Basic structure

The annulus fibrosus is divided into three layers: outer, middle and inner. The outer layer is composed of collagen fiber bands, and the inner layer is composed of fibrous cartilage bands. The anterior and lateral parts of the annulus fibrosus are the thickest, almost twice as thick as the posterior part. The posterior part is the thinnest, but generally also has 1-2 layers of fibers. The annulus fibrosus is arranged in tight and oblique layers, surrounding the nucleus pulposus and forming the outer part of the intervertebral disc, like a coiled spring, connecting the upper and lower vertebrae to each other, maintaining the liquid component of the nucleus pulposus, and maintaining its position and shape. The annulus fibrosus may become loose due to long-term improper posture or external impact. Once the annulus fibrosus becomes loose, the nucleus pulposus will shift and stimulate the nerves, which is commonly known as lumbar disc herniation. The cartilage plate is a transparent, avascular cartilage tissue. There is one above and below the vertebral body. Its average thickness is 1 mm. It is thinner and more translucent in the central area and is located within the posterior bone ring. There is no nerve tissue in the cartilage endplate, so when the cartilage endplate is damaged, it neither produces pain symptoms nor can it repair itself. The avascular cartilage plates above and below the vertebrae are like the cartilage in the knee and hip joints. They can withstand pressure, protect the vertebrae, buffer pressure, and connect the vertebrae and intervertebral discs for nutrient exchange. In early childhood, this is the growth area of ​​vertebral bone.

Before the age of 20, the lumbar intervertebral disc has blood vessels, which gradually disappear and its water content decreases year by year. In the fetus, the water content of the annulus fibrosus and nucleus pulposus is 80% and 90% respectively. At the age of 30, these figures drop to 60% and 75% respectively.

symptom

1. Low back pain: Almost most patients with lumbar disc herniation will experience low back pain. Patients feel persistent dull pain in the lower back, which is relieved when lying down but aggravated when standing. It is generally tolerable and the patient can move the lower back moderately or walk slowly. The other type is sudden spasmodic severe pain in the lower back, which is unbearable and requires bed rest, seriously affecting life and work.

2. Leg numbness, chills, and limping when walking: In many cases, numbness of the lower limbs is accompanied by pain. A small number of patients may experience simple numbness, and a small number of patients feel chilly or cold in their lower limbs. This is mainly due to the stimulation of the sympathetic nerve fibers in the spinal canal. The mechanism and clinical manifestations of intermittent claudication are similar to those of lumbar spinal stenosis, mainly because the pathological and physiological symptoms of secondary lumbar spinal stenosis may occur in the case of nucleus pulposus protrusion.

3. Radiating pain in the legs: Almost four-fifths of patients with lumbar disc herniation will experience radiating pain in the legs. It often occurs after low back pain is relieved or disappears. It manifests as radiating irritation or numbness from the waist to the back of the thighs and calves, reaching the soles of the feet. Severe patients may experience electric shock-like pain from the waist to the feet, often accompanied by numbness. Those with mild pain can walk with a limp; those with severe pain need to rest in bed, with more frequent postures of flexing the waist, hip, and knees.

4. Symptoms of cauda equina: Mainly seen in central nucleus pulposus herniation, which is relatively rare in clinical practice. Numbness and tingling in the perineum and urinary and bowel dysfunction may occur. Women may also experience urinary incontinence and men may experience impotence. In severe cases, incontinence and incomplete paralysis of both lower limbs may occur.