Spinal osteochondrosis and intervertebral disc
Osteochondrosis of the spine is a dystrophic pathological process of the spine that begins with intervertebral discs with subsequent damage to other parts of the spine. With osteochondrosis of the spine, the cervical and lumbar parts are primarily affected, as they most susceptible to movement and overload.
In terms of such overloads, the thoracic spine is reliably protected and fixed by the chest (due to the ribs and sternum). Therefore, protrusion or herniated disc at the thoracic level with osteochondrosis of the spine is quite rare in clinical practice. In some cases, spinal osteochondrosis is clinically manifested by various neurological disorders.
The intervertebral disc is a kind of "shock absorber" between adjacent vertebral bodies. The human spine is an axial organ that performs the function of providing a vertical posture under static and dynamic loads in a wide range.
As you know, the intradiscal pressure is positive and amounts to 5–6 atmospheres, which in itself excludes the possibility of “repositioning the fallen disc” during manipulation, as stated by some “specialists” in manual therapy.
The distribution of intradiscal pressure in a person performing work in a sitting position or slightly flexing the trunk shows that the posterior parts of the intervertebral disc are somewhat unloaded than the anterior ones. This means that intradiscal pressure is directed towards the spinal canal and has a predominant effect on the posterior arch of the annulus fibrosus and the posterior longitudinal ligament. The dystrophic process develops first of all in this part of the intervertebral disc, and the possibility of herniation towards the spinal canal is the highest.
This peculiarity of the distribution of loads across the intervertebral disc makes it possible to understand the reason for the high frequency of osteochondrosis of the intervertebral disc and its complications in persons of a "sedentary" profession in comparison with people performing dynamic work. During dynamic work, all parts of the intervertebral disc are loaded more or less evenly, than the likelihood of a local dystrophic lesion of the intervertebral disc decreases.
When examining patients with pain in the lower back and leg on tomographs (CT or MRI), the following signs of hernial forms of osteochondrosis of the lumbar spine are revealed:
Change in the state of the contour and size of the intervertebral disc
This sign of a hernia or protrusion of the intervertebral disc can be considered the main and constant symptom of diagnosis. The protrusion of the intervertebral disc is often found and is often accompanied by a decrease in its height. In these cases, part of the intervertebral disc protrudes beyond the boundaries of adjacent vertebrae. Similar changes in the intervertebral disc can occur in middle-aged people, and they often do not manifest themselves as painful sensations. Therefore, there is a serious danger of overdiagnosis of hernias or protrusions of intervertebral discs. The relative sizes of the intervertebral disc, the ratio of the edge of the vertebral body, and the edge of the adjacent intervertebral disc are important.
Normally, the edges of the body and the edges of the intervertebral disc correspond to each other. In pathology, the cartilaginous tissue of the intervertebral disc extends beyond the border of the vertebral bodies.
Intervertebral disc protrusion
With herniated intervertebral disc, local protrusion of the disc of various sizes outside the vertebral bodies is observed. Terminologically, it sounds in the definition of different authors as a local protrusion of the disc or protrusion of the intervertebral disc. The two terms are used interchangeably and usually represent different degrees of the same condition. In this case, the nucleus pulposus remains inside the fibers of the annulus fibrosus, which weakens and stretches.
Prolapse, extrusion, or herniated disc
Disc prolapse, or otherwise extruded disc, is formed when the nucleus pulposus penetrates through the annulus fibrosus, in which case the fragments of the nucleus are located under the posterior longitudinal ligament. It is not always possible to distinguish these types of disc herniation with CT of the spine. In these cases, it is necessary to carry out discography.
Sequestration or fragmentation of the intervertebral disc
With sequestration or fragmentation of the disc, the disc material leaves the intervertebral space, penetrates through the posterior longitudinal ligament into the epidural tissue, migrating in the epidural space. A free fragment can be located at a long distance from the disc, moving both cranial and caudal, and (very rarely) intradurally.
The usual rule is that a hernia compresses the root located under the intervertebral disc, that is, a herniation or protrusion of the L4 – L5 intervertebral disc compresses (squeezes) the L5 nerve root. With a lateral hernia or protrusion of the intervertebral disc, the nerve root in the intervertebral foramen can be compressed, and then with a hernia or protrusion of the L4 – L5 disc, the L4 nerve root will be compressed.
In the practical work of a neurosurgeon, it is important to determine what type of intervertebral disc herniation a given patient has - protrusion, prolapse, or sequestration of the intervertebral disc.
Radiological classification of herniated discs
- Protrusion of the intervertebral disc or local protrusion - the nucleus pulposus remains within the stretched annulus fibrosus. The intervertebral disc is deformed in the horizontal plane. The height of the protrusion does not exceed 1/3 of its width.
- Intervertebral disc prolapse - the nucleus pulposus breaks the annulus fibrosus and penetrates through it. The posterior longitudinal ligament remains intact, the nucleus pulposus is located subglotically. In some cases, there are tears of the longitudinal ligament that do not allow large fragments to pass through. The posterior contour of the intervertebral disc becomes tuberous. The height of the protrusion exceeds one-third of its length.
- Sequestration or fragmentation of a herniated intervertebral disc - disc material is located in the epidural space and freely migrates in it.
Hernias or protrusions of the intervertebral disc are subdivided according to localization, depending on their relation to the anterior wall of the spinal canal:
- total hernia or protrusion of the intervertebral disc
- central or median hernia or protrusion of the intervertebral disc
- paramedian hernia or protrusion of the intervertebral disc (located between the midline and the line connecting the medial edges of the articular processes)
- lateral, foraminal hernia or protrusion of the intervertebral disc (located outside the inner edge of the articular processes)
- extraforaminal hernia or protrusion of the intervertebral disc (far lateral)
This classification of herniated or protruded intervertebral disc seems to be the most convenient for the operating neurosurgeon. The classification of a herniated or protruded intervertebral disc is radiological and allows the selection of an adequate surgical approach during the operation.
There is no doubt that clinical manifestations in various types of hernias or protrusions of intervertebral discs may not correlate with their radiological characteristics. So the median, according to radiological methods of examination, hernia or protrusion of the intervertebral disc often manifests itself clinically as lateral or paramedian, or even, as an extreme option, can be an accidental finding.
MRI classification (Pfirrmann) of lumbar intervertebral disc degeneration:
|Homogeneous bright white disc structure
|Inhomogeneous white disc structure, horizontal stripes possible
|Clear separation between annulus fibrosus and disc nucleus
|Disc height slightly or moderately reduced
|Collapse (decline) of disk space
Sagittal MRI images of the lumbar spine in T2 mode are used to assess intervertebral disc degeneration. A. Degeneration of intervertebral discs according to Pfirrmann: mostly heterogeneous black discs without any separation between the nucleus and the annulus fibrosus; collapse (collapse) of discs at the levels of L1-L2 and L4-L5 vertebrae. B. Lumbar intervertebral discs with high elasticity with a low degree of degeneration according to Pfirrmann; a homogeneous structure of discs with a bright hyperintense signal and normal height is visible.
Changing the physical properties of the intervertebral disc
Densitometric examination of the intervertebral disc allows to reveals in some cases an increase in the density of the nucleus pulposus tissues due to its calcification, in other cases a decrease in the density of the nucleus. By the densitometric density, one can indirectly judge the prescription of the formation of an intervertebral disc herniation. "Young" hernias or protrusions of the intervertebral disc have a homogeneous structure, with a density of 60–80 N and not always clear contours. Long-term intervertebral hernia or protrusion has a high density and heterogeneous structure. Separately, it should be said about the appearance of air cavities in the intervertebral disc, called the vacuum effect. It is the most striking sign of nucleus pulposus dystrophy.
Changes in the tissues around the intervertebral disc
The maximum changes in the epidural tissue can be determined at the level of the last lumbar discs. The epidural space at the level of the L5 – S1 intervertebral disc is wider and contains a significant number of vessels, which on CT of the spine looks like a soft tissue component located symmetrically near the disc. Behind the vertebral body, in the midline, there is Betson's venous plexus, which looks like a soft tissue formation. This mass can be mistaken for a sequestered herniated disc.
The dura mater and roots are normally surrounded by fat. Changes in adipose tissue are also determined densitometrically. They consist of the inhomogeneity of the densitometric density of the cellulose, indicating an adhesion process.
Obliteration of the epidural space with tissues of increased density or the presence of a soft tissue component at the level of the disc indicates the sequestration of the nucleus pulposus. In addition, sometimes it is possible to determine an increase in the volume of epidural tissue below the level of hernia or protrusion of the intervertebral disc, which is associated with the expansion of the epidural veins below (caudal) the level of compression.
Changing the contour or position of the dural sac
With median, paramedian hernias or protrusions of intervertebral discs, the dural sac is displaced backward, taking the shape of a bean or crescent. With lateral hernias or protrusions of the intervertebral discs, the dural sac moves to the side. Only in the case of foraminal hernias or protrusions of intervertebral discs could the dural sac be considered intact.
Changing the position of the nerve roots
Most often, the roots in the zone of conflict with the disc are poorly visualized, which is especially characteristic of sequestered hernias or protrusions. In such cases, the proposed location of its location can be determined by an imaginary trajectory connecting the “pre-hernia” and “post-hernial” images of the root. In other cases, a herniated disc displaces the root asymmetrically. With large sequestered hernias or protrusions and a pronounced adhesive process, the hernia and paradisiacal tissues do not differentiate and look like a single conglomerate.
The following CT changes in the extrasaccal portion of the root are also distinguished:
Treatment of herniated disc and intervertebral disc protrusion
At the first stage of a patient's treatment with a herniated disc in our clinic, it is proposed to undergo an intensive course of conservative therapy, which lasts up to 5-6 days and is carried out in an outpatient clinic. As our clinical practice shows, in 50% of cases in patients with clinical manifestations of compression of the nerve root by a herniated intervertebral disc, it is possible to achieve a significant reduction or complete elimination of the symptom of pain with the restoration of impaired sensitivity and existing muscle weakness. In case of mild or complete ineffectiveness of conservative therapy (persists pain, sensory disturbances, and muscle weakness in the innervation zone of the nerve compressed by the disc herniation), we hospitalize the patient for surgical treatment.
Attention! Conservative treatment is not performed in patients with symptoms of cauda equina compression, which is manifested by dysfunction of the pelvic organs, such as urinary retention with perineal numbness. This neurological complication in a patient is an absolute indication for neurosurgical surgery, which must be performed urgently.
Depending on the severity of the manifestations and the causes of pain in the leg and lower back in a patient with protrusion or herniated intervertebral disc, the following therapeutic actions are possible:
- drug therapy (NSAIDs, analgesics, hormones)
- therapeutic injections - injection of drugs into the canal cavity
- manual therapy (non-surgical "reduction" of the vertebral disc herniation using muscle, articular and radicular techniques)
- physiotherapy (UHF, TENS, etc.)
- surgical treatment