I. Degenerative changes of the cervical spine
Degenerative changes of the cervical spine are the main cause of the development of cervical spondylosis, among which the degeneration of the intervertebral disc is particularly important and is the first factor in the degeneration of the structures of the cervical spine, and thus evolves a series of pathological anatomy and pathophysiological changes of cervical spondylosis.
(I) Disc degeneration
The intervertebral disc, consisting of the nucleus pulposus, the annulus fibrosus, and the upper and lower cartilage plates of the vertebral body, is a complete anatomical form that closely connects the upper and lower vertebral bodies and ensures the normal physiological function of the cervical spine while maintaining the normal anatomical state of the cervical spine. When the disc begins to degenerate, it loses its normal function due to the change in morphology, which in turn affects or disrupts the biomechanical balance of the cervical spine motion segments producing a series of changes in each of the associated structures. Therefore, we regard degeneration of the cervical intervertebral disc as the main factor in the occurrence and development of cervical spondylosis.
1. The degeneration of the fibrous ring mostly starts after the age of 20, and the early stage is transparent degeneration of the fibrous tissue, thickening and disorderly arrangement of the fibers, and gradually cracks or even complete fracture form the fissure visible to the naked eye. The degree of lesion and the direction and depth of fiber fracture are often consistent with the degree of degeneration of the nucleus pulposus, the direction of pressure and intensity. Fibular ring fracture is generally more common on the posterior side, which is not only related to the thicker fibular ring tissue in the front and the posterior position of the nucleus pulposus center point, but also related to the occupational characteristics, some jobs often need to bend the head in the flexed neck position, especially for a long time, so that the nucleus pulposus is squeezed to the posterior and increase the compressive stress there. If the early degeneration of the fibrous ring can be removed early, it is possible to stop its development or restore it. On the contrary, once the fissure is formed under continuous pressure, it is difficult to recover due to the lack of good local blood supply, thus providing a pathological and anatomical basis for the posterior protrusion or prolapse of the nucleus pulposus.
2, the nucleus pulposus, a water-rich and elastic mucin tissue, is mostly degenerated on the basis of the former degeneration and secondary degeneration. It usually appears after 24 years of age, but there are also early onset cases. Because of the linear relationship between the decrease of mucin and the water content in the intervertebral disc, it causes the loss of water and the loss of water absorption function, and its volume is reduced accordingly, and gradually its normal tissue is replaced by fibrous tissue, at which time the nucleus pulposus becomes stiff and further leads to the change of its biomechanical properties. In cases of high local load, trauma and strain, the rate of degeneration is accelerated by the increase of pressure in the intervertebral space. On the other hand, the degenerated nucleus pulposus may protrude to the edge along the fissure formed by the fibrous ring. At this point, if the fibrous ring is completely broken, the nucleus pulposus may reach the posterior longitudinal ligament or the anterior longitudinal ligament below, and may form a series of processes such as subligamentous periosteal separation and hemorrhage. The degenerated and sclerotic nucleus pulposus may also cross the posterior longitudinal ligament fissure and enter the spinal canal. In the early stage, such protruding nucleus pulposus is reversible and can be returned by effective treatment; if once it enters the spinal canal and forms adhesions with the vertebral bone, it is difficult to be returned.
3, cartilage plate degeneration appears later. Early in the degeneration first cause functional changes, so that the role of the translucent membrane as a body fluid nutrient exchange is reduced. When the cartilage plate thinning has formed obvious degeneration, its nourishing effect is further reduced, or even completely disappeared. In this way, the degeneration and aging of the fibrous rings and the nucleus pulposus are intensified.
The above three are an interrelated and mutually constraining pathological process, and when the lesion enters a certain stage, they are mutually causal and form a vicious circle to accelerate the development of cervical spondylosis.
(II) Emergence of ligament-disc gap and hematoma formation
This process is crucial to the occurrence and pathogenesis of cervical spondylosis and is the anatomical basis of its pathology from cervical disc disease into osteopathic cervical spondylosis. In fact, in the early stages of cervical spondylosis, the degeneration of the intervertebral disc not only causes the displacement of the dehydrated and sclerotic nucleus pulposus to the posterior or anterior part of the vertebral joint and finally to the lower part of the ligament, thus increasing the local pressure and causing the separation of the ligament and periosteum from the peripheral cortical bone of the vertebral body, but also the degeneration of the disc itself can cause the loosening and abnormal movement of the intervertebral joints, which further increases the tearing of the ligament and periosteum. Tearing of the ligament and periosteum is exacerbated and the formation of the ligament-disc gap is accelerated.
The ligament-disc interstitial hematoma is formed when the ligament separates posteriorly from the vertebral space and is accompanied by local microvascular tears and hemorrhage. This hematoma can directly stimulate the sinus-vertebral nerve endings distributed on the posterior longitudinal ligament and cause various symptoms, and also increase the pressure under the ligament, so that a series of symptoms such as neck discomfort, soreness and heaviness in the head and neck can occur. At this point, if the cervical spine continues to be in abnormal activities and poor posture, the local compressive stress is greater and constitutes a vicious circle, making the condition increasingly aggravated and developing to the next stage.
(C) Bone spur formation at the vertebral body edge
With the formation of a hematoma in the subligamentous space, fibroblasts become active and gradually grow into the hematoma, gradually replacing it with granulation tissue. If new tears and new hematoma formation continue to occur at this space, the same vertebral segment may show a microscopic view of both new and old lesions. As the hematoma mechanizes, ossifies, and deposits calcium salts, it eventually forms a bone flab that protrudes toward the spinal canal or toward the anterior edge of the vertebral body. This bone superfluous can be due to repeated local trauma, continuous stretching of the surrounding ligaments and other factors, and gradually increase in size through bleeding, mechanization, ossification or calcification, and become increasingly hard in texture. Therefore, in advanced cases, the bony redundancy is very hard, especially in those with multiple trauma, and can be as hard as ivory. The formation of osteophytes can be seen in any vertebral segment, but cervical 5-6, cervical 6-7 and cervical 3-4 are the most common. From the same vertebral segment, the first occurrence is mostly at the hook protrusion, followed by the posterior edge of the vertebral body and the anterior edge of the vertebral body.
(IV) Degeneration of other parts of the cervical spine
Degeneration of the cervical spine is not limited to the intervertebral disc and the adjacent vertebral body edges and hook vertebral joints, but should also include.
1, small joints mostly degenerate after intervertebral disc degeneration causing intervertebral joint instability and abnormal activity. The early stage is superficial cartilage, and gradually spreads to deeper layers and subchondral bone, eventually forming injurious arthritis. Finally, due to local degeneration and other secondary joint space narrowing and bone spur formation, resulting in the narrowing of the anterior and posterior diameters of the intervertebral foramen and the upper and lower diameters, so as to easily stimulate or compress the spinal nerve roots, and affect the blood flow of the root vessels and the return of the spinal meninges to the nerve branches, resulting in a series of clinical symptoms.
2, the yellow ligament mostly begins to degenerate on the basis of the first two degenerations. Its early manifestation is ligament laxity, and gradually hyperplasia, hypertrophy, and protrusion into the spinal canal. At a later stage, calcification or ossification may occur. Although this secondary lesion is different from that of developmental cervical spinal stenosis, when the neck is elevated and extended, the symptoms of cervical spondylosis are also easily induced or aggravated, mainly because the ligament is wrinkled and protrudes into the spinal canal, resulting in stimulation or compression of the spinal nerve root or spinal cord.
3, the anterior longitudinal ligament and posterior longitudinal ligament degeneration is mainly manifested by the ligament itself fibrous hyperplasia and sclerosis, the late formation of calcification or ossification, and consistent with the lesion vertebral joint. This phenomenon may be regarded as a natural protective effect of the body. As the ligament sclerosis and calcification can directly play a local braking effect, thus increasing the stability of the cervical spine and slowing down the further development and deterioration of cervical spondylosis.
(E) Reduced sagittal diameter and volume of the spinal canal
Due to the aforementioned causes, the internal volume of the vertebral canal is reduced, mainly due to posterior nucleus pulposus, invagination of the posterior longitudinal ligament and ligamentum flavum, and loosening and hyperplasia of the crooked vertebral joint and small joints. These acquired secondary factors cause the internal volume of the vertebral canal to be reduced and also reduce the sagittal diameter of the vertebral canal, thus constituting one of the direct causes of spinal cord and spinal nerve root irritation or compression. At this point, if there are other limited pathogenic factors. For example, nucleus pulposus prolapse, traumatic displacement of vertebral segments, bone spur formation and other occupational factors can cause or aggravate the symptoms of neurological involvement.
Second, developmental cervical spinal stenosis
In recent years, it has been clear that the internal diameter of the cervical spinal canal, especially the sagittal diameter, has a very close relationship not only to the occurrence and development of cervical spondylosis, but also to the diagnosis, treatment, selection of surgical methods and prognosis of cervical spondylosis. It is often seen clinically that some people with severe cervical degeneration and significant bone growth do not develop cervical spine disease, mainly because of the wide sagittal diameter of the cervical spinal canal and the large compensatory gap in the spinal canal. In some patients, the cervical degeneration is not very serious, but the symptoms appear early and are more severe. It can be seen from the imaging data that the size of the actual diameter of the cervical spinal canal is the main factor that determines the appearance of neurological symptoms early or late or whether they appear.
Comparative clinical studies have shown that the sagittal diameter of the cervical spinal canal is 2,7 to 3,2 mm wider in normal people with cervical spondylosis than in those with cervical spondylosis. In addition to compression symptoms based on cervical spine degeneration, cervical spinal stenosis is prone to spinal cord injury after trauma. Even minor trauma is easy to develop, and the symptoms are more serious. On the contrary, those with larger spinal canal meridians are less likely to develop and have less symptoms. In addition, the sagittal diameter of the spinal canal also has an impact on the prognosis of cervical spondylosis, and those with large spinal canals not only have faster results with various non-surgical or surgical therapies, but also have a lower reoperation rate, a better prognosis and a lower recurrence rate.
Third, chronic strain injury
Chronic strain injury refers to a variety of over-limited activities that exceed the maximum normal physiological range of activity or the local tolerable hourly value. Because it is different from obvious trauma or accidents in life and work, it is easy to be ignored, but it has a direct relationship with the occurrence, development, treatment and prognosis of cervical spondylosis, such strain injury and cause mainly from the following three situations: 1.
1, poor sleep position about 1/3 to 1/4 of a person’s life is spent in bed. Therefore, bad sleep position because of its long duration and the brain in a resting state can not be adjusted in time, it is bound to cause paravertebral muscles, ligaments and joints of the imbalance. The side with high tension is prone to different degrees of strain due to fatigue, and the imbalance outside the spinal canal and the spinal canal tissue, thus accelerating the degeneration process of the cervical spine. So in the clinic can often be found in many cases of the first symptoms are after waking up.
2, improper work posture a large number of statistical materials show that certain workload is not large, the intensity is not high, but in a sitting position, especially the incidence of cervical spondylosis is particularly high in low-headed workers, including domestic workers, embroidery workers, office workers, typing scribe, instrument assembly line assembly workers and so on. In addition to the strain on the muscles and ligaments at the back of the neck caused by long-term head down, the internal pressure of the intervertebral discs is also much higher than in the normal position in the flexed neck, and can even be more than double. In addition, for the same reason, certain occupations where the head and neck often turn in one direction, such as operating room nurses, traffic police and teachers, are also prone to neck strain injury.
3, inappropriate physical exercise normal physical exercise can help health, but more than the neck endurance activities or sports, such as head and neck as a weight-bearing support point of the human body inversion or somersault, can increase the load on the cervical spine, especially in the absence of correct guidance. In addition, certain folk head and neck practice methods, such as the current popular practice of the eighteen methods, should not be advocated for those who have degeneration of the cervical spine; otherwise, not only can aggravate the degenerative changes of the cervical spine, and even accidents can occur, especially for those who have symptoms of spinal cord compression, should avoid exercise activities that increase the amount and frequency of head and neck activities to slow down the degenerative changes of the cervical spine.
Fourth, congenital deformity of the cervical spine
During the health examination or comparative study radiographs of the cervical spine in normal people, it is often found that there are various abnormalities in the cervical spine, of which about 5% are obvious skeletal deformities. However, when compared with patients with cervical spondylosis, the number of deformities of the cervical spine in the latter is about double that of normal individuals. This indicates that the skeletal variation is related to the occurrence of cervical spondylosis. The following five deformities are more common in clinical practice and have a greater correlation with the development of cervical spondylosis. Cervical 2 to 3 and cervical 3 to 4 are the most common, followed by cervical 4 to 5, which are mostly fused into one, with three fused sections being rare, and double fusion of two sections at one or two intervals is also rare.
As the vertebrae fuse, the original activity of the intervertebral joint between the two vertebrae is inevitably transferred to the adjacent upper and lower vertebrae. According to the biomechanical characteristics of the cervical spine, when the cervical 3-4 vertebral segments are congenitally fused, the degeneration of the next vertebral segment is significantly increased due to the increased load on that segment, and even injurious arthritis may occur, if accompanied by developmental stenosis of the spinal canal, the onset of which is earlier. The onset of the disease is delayed in those with a wide spinal canal, or those close to the upper cervical spine.