The concept of cervical spondylosis is internationally ambiguous and often conflates multiple cervical spine disorders, such as cervical disc disease, cervical disc prolapse, and vertebral segmental hypertrophy. Therefore, in English, there are often different terms such as degenerative disc disease, degenerative cervical spine, and cervical spondylosis. However, in reality, the conditions described are basically similar. According to most of the literature and monographs, cervical spondylosis is more commonly accepted. Therefore, this term is often used to represent cervical spondylosis.
I. Definition of cervical spondylosis
Cervical spondylosis is defined as a disease of the cervical spine in which the degeneration of the cervical intervertebral disc itself and its secondary changes irritate or compress the adjacent tissues and cause various symptoms and signs.
Overview of cervical spondylosis
The understanding of cervical spondylosis in China started in the early 1960s, and for a long time before that, the understanding of cervical spondylosis was not sufficient, and some individual scholars even took a negative attitude and basically did not recognize the existence of cervical spondylosis. However, with the progress of clinical medicine, not only orthopedic surgeons, but also neurosurgery, neurology, Chinese medicine, acupuncture, general internal medicine, and physical therapy physicians have found that cervical spondylosis is very common. Especially in recent years, with the extension of the average life expectancy of our people and the improvement of our diagnostic technology, this problem has become more prominent, and cervical spondylosis has become a common and frequent clinical disease.
Although this disease is mainly a degenerative disorder, it is related to a variety of factors. First of all, it should be understood that the anatomy of the cervical spine has special characteristics, as it is the smallest in volume but the most flexible vertebral segment in the spine. It has five joints, and in addition to the same two synovial joints and one intervertebral disc as the lumbar spine, it also has a pair of hook joints (also called Luschka joints). The cervical articular joints are relatively horizontal and arranged in a caudal direction. The anterior curve of the cervical disc allows for extension and lateral bending of the cervical spine, and the tangential alignment of the crooked joints and discs with the nerve roots emanating from both sides plays an important role in the generation and development of clinical symptoms. Because of this special anatomical relationship, the condition is complex, and because of the wide variation among individuals, it is easily confused with other disorders, especially those with similar symptoms caused by adjacent tissue lesions. In addition, the vertebral artery and its channel, i.e., the transverse foramen located on the lateral block of the cervical spine, together with the abundant sympathetic postganglionic fibers surrounding the vertebral artery and the various peculiar symptoms that appear with the lesion add to the mystery of cervical spondylosis. As a result, clinicians, not only beginners but also those who have been working for many years, often find the concept unclear.
Third, the natural regression of cervical spondylosis (natural history)
Cervical spondylosis is caused by degeneration of the cervical vertebral joints, and degeneration is subject to age, and its incidence and degree are increasing with age and becoming more severe. However, cervical degeneration is not the same as cervical spondylosis, and even those with symptomatic cervical spondylosis may heal and cure themselves as the years go by, or, of course, may intensify. But where does the regression go and what percentage of it is in each case? This is the “natural history of cervical spondylosis” that has been the subject of much research in recent years.
Zhao Dinglin et al. have observed the follow-up of different age groups. For those who first had symptoms of cervical spondylosis around the age of 30, about 80% of patients did not have any symptoms in the following 10 years, and only 20% of patients had complaints related to cervical spondylosis, of which about 10% lasted for about 2 to 3 years, and less than 1% lasted for more than 10 years. Gore’s study also showed similar findings when he followed up more than 200 patients with first-onset cervical spondylosis for more than 10 years; nearly 80% of them had reduced neck pain, and more than half of them had disappeared. Thus, it seems that the self-healing or cure rate of people with initial cervical spondylosis symptoms accounts for the absolute majority, so there is no need to be too nervous once cervical spondylosis symptoms appear. However, China is a large country with a population of more than 1.2 billion, and the absolute number of cases is still considerable and should be taken seriously.
Fourth, the etiology of cervical spondylosis
The cervical spine, located at the upper end of the spine, between the head, chest and upper limbs, is the segment of the spine with the smallest volume, but the greatest flexibility and the highest frequency of activity. Therefore, since birth, as the body develops, grows and matures, degenerative lesions gradually appear due to various loads, strains and even trauma. Among them, especially the cervical intervertebral disc, not only the degeneration process begins earlier, and is an important factor in triggering or promoting degenerative changes in other parts of the cervical spine tissue. If there is developmental cervical spinal stenosis, it is more likely to develop. The pathogenic factors are described as follows.
(A) Degenerative changes of the cervical spine
This is the main cause of the development of cervical spondylosis, so some people call this disease cervical disc disease, which can be seen its importance. Among the structures of the cervical vertebrae, degeneration of the intervertebral disc is particularly important and is often regarded as the “culprit”, and a series of pathological anatomical and pathophysiological changes evolve from the degeneration of the intervertebral disc. The factors of cervical spine degeneration are described below.
Intervertebral disc degeneration]
The intervertebral disc composed of the nucleus pulposus, the fibrous ring 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 under the premise of maintaining the normal anatomical state of the cervical spine. If it starts to degenerate, it loses its normal function due to its altered morphology, so that it eventually affects or disrupts the intrinsic balance of the bony structure of the cervical spine and directly involves the mechanical structure of the vertebrae themselves. Therefore, we regard degeneration of the cervical intervertebral disc as the main factor in the occurrence and development of cervical spondylosis.
1. Fibrous annulus: It mostly starts at the age of 20. In the early stage, there is transparent degeneration of fibrous tissue, thickening and disorder of fiber arrangement, and gradually cracks or even complete fracture form a 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 current occupational characteristics, the current increase in white-collar occupations, due to the need to bury their heads in the flexed neck position and hard work, especially for a long time, so that the nucleus pulposus is squeezed to the posterior and increase the compressive stress there. Early degeneration of the fibrous ring may be stopped or restored if the causative factors are removed early. On the contrary, under the continuous action of pressure, once the fissure is formed, 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: this water-rich and elastic mucin (proteoglosis also translated as proteoglycan) tissue is mostly on the basis of the former degeneration and secondary degeneration. It usually appears after the age of 24, but there are also early onset cases. The linear relationship between the decrease in mucin and the water content of the disc leads to water loss and loss of water absorption, with a corresponding decrease in volume, and a gradual replacement of the normal tissue by fibrous tissue, when the nucleus pulposus becomes rigid and further leads to changes in 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 annulus fibrosus. 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 a series of processes such as subligamentous periosteal separation and hemorrhage may be formed. The degenerated and sclerotic nucleus pulposus may also cross the posterior longitudinal ligament fissure and enter the spinal canal. In the early stage, such invasion of the nucleus pulposus into the spinal canal is reversible and can be returned by effective treatment; once adhesions are formed with the tissue in the spinal canal, it will be difficult to return.
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 is thinned and 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 processes are interrelated and mutually constrained, and when the lesion reaches a certain stage, they are mutually causal and form a vicious circle that is not conducive to the recovery of the disease.
Emergence of ligament-disc gap and hematoma formation
In the early stage of cervical spondylosis, due to the degeneration of the intervertebral disc, not only does the nucleus pulposus, which has lost water and hardened, gradually move to the back or front of the vertebral joint and finally protrude below the ligament, thus causing the separation of the ligament together with the periosteum from the cortical bone around the vertebral body while increasing the local pressure, but also the degeneration of the intervertebral disc itself can cause the loosening and abnormal activity of the intervertebral joint, thus intensifying the tearing of the ligament and the periosteum This accelerates the formation of the ligament-disc gap.
The ligament-disc interstitial hematoma is formed after the separation of the posterior ligamentous space, which is often accompanied by local microvascular tearing and bleeding. 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 will be greater and constitute a vicious circle, making the condition increasingly aggravated and developing to the next stage.
[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 the coexistence of new and old lesions.
As the hematoma mechanizes, ages, and deposits calcium salts, it eventually forms a bony flab (or spur) that protrudes into the spinal canal or into the anterior edge of the vertebral body. This bulge can grow in size and harden through bleeding, mechanization, ossification, or calcification due to repeated local trauma, continuous stretching of the surrounding ligaments, and other factors. Therefore, in advanced cases, the bone superfluous is very hard, especially in those with repeated trauma, it can be like ivory, thus making it more difficult for surgical resection and certainly increasing the chance of risk. The formation of bone superfluous can be seen in any vertebral segment, but it is most common in cervical 5-6, cervical 6-7 and cervical 3-4. In terms of the same vertebral segment, the first occurrence is at the hook, followed by the posterior edge of the vertebral body and the anterior edge of the vertebral body.
Degeneration in 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 degeneration occurs after intervertebral disc degeneration causing intervertebral joint instability and abnormal activity. The early stage is superficial cartilage, and gradually spreads to deep and subchondral layers, 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 diameter of the intervertebral foramen and the upper and lower diameter, 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, so that a series of symptoms appear in the clinic.
2, ligamentum flavum: mostly on the basis of the first two degeneration began to degenerate. Its early manifestations are ligamentous laxity, and gradually hyperplasia, hypertrophy, and protrusion into the spinal canal. In later stages, calcification or ossification may occur. Although this secondary lesion is different from that of developmental cervical spinal stenosis, it is also easy to induce or aggravate the symptoms of cervical spondylosis when the neck is elevated and extended, 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 the posterior longitudinal ligament: its degenerative changes are mainly manifested by the fibrous hyperplasia and sclerosis of the ligament itself, and at a later stage, calcification or ossification is formed, and it is consistent with the diseased vertebral joint. This phenomenon may be regarded as a natural protective effect of the body. As the hardening and calcification of the ligament 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.
Reduced sagittal diameter and volume of the spinal canal
Due to the aforementioned causes, the internal volume of the vertebral canal is reduced in the first place, among which posterior nucleus pulposus, posterior longitudinal ligament and yellow ligament invagination, loosening and hyperplasia of the hook vertebral joint and small joints are the main causes, and these acquired secondary factors cause the internal volume of the vertebral canal to be reduced while the sagittal diameter of the vertebral canal is also reduced, thus constituting one of the direct causes of spinal cord and spinal nerve root irritation or compression. At this time, if there are other limited pathogenic factors. For example, nucleus pulposus prolapse, traumatic displacement of vertebral segments, bone spur formation and other occupational factors may cause or aggravate the symptoms of neurological involvement.
(ii) Developmental cervical spinal stenosis
Cervical spondylosis and cervical spinal stenosis are essentially twin brothers. In recent years, it has been recognized that cervical spinal stenosis with clinical symptoms is an independent disorder.
(III) Chronic strain injury
Overview
Chronic strain injury refers to a wide range of activities that exceed the maximum normal physiological range of activity or the local tolerable value. Because it is different from obvious trauma or accidents in life and work, it is easy to be ignored. However, in fact, it is the most important factor constituting the degeneration of cervical spine bone and joint, and has a direct relationship with the occurrence, development, treatment and prognosis of cervical spondylosis.
Causes of chronic strain injury
This kind of strain injury and the cause mainly from the following three conditions.
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 a number of cases of the first symptoms are after waking up.
2, improper work posture: a large number of statistical materials show that the incidence of cervical spondylosis is particularly high in certain workloads, intensity is not high, but in a sitting position, especially in low head workers, including domestic workers, embroidery workers, office workers, typing scribes, assembly workers on the instrument assembly line, etc.. 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 activities or sports that exceed the endurance of the neck, for example, American soccer (with the head on the ball), head and neck as a weight-bearing support point of the human body handstand or somersault, etc., can increase the load on the cervical spine, especially in the absence of proper guidance. Of course, if a head and neck trauma is caused by a mistake, the consequences are more serious. In addition, certain folk head and neck exercises should not be advocated for those who have degeneration of the cervical spine; otherwise, not only can the degenerative changes of the cervical spine be aggravated, but even accidents can occur, especially for those who have symptoms of spinal cord compression, any exercise activities that increase the amount and frequency of head and neck activities should be completely prohibited to prevent irreversible consequences.