Clinical manifestations, classification, diagnosis and treatment of degenerative spinal stenosis. Literature review.

Medical diagnoses often include a definition of the sagittal size of the spinal canal. Most patients do not understand this definition, which causes them natural concern. What is sagittal size, how does it affect human health, what are the physiological indicators, what causes the deviations and what are their consequences? These questions will be answered in this article.

Sagittal size of the spinal canal

What is a canal in the spine

You should know this in order to more easily understand further, more complex information. The spinal canal is a longitudinal cavity located along the vertebra. It is formed on one side by the posterior wall of the vertebrae, and on the other by flexible discs and vertebrae. Thus, it is limited on all sides by bone tissue, and the diameter of the spinal canal changes depending on the parameters of the vertebrae. The bases of the arches of each vertebra have special connecting slots, with the help of which they are connected into a single spinal column. When connected, these arches leave openings that house the spinal cord.

The spinal canal is a container for the spinal cord, its roots and vessels

Strong ligaments are placed in a circle, they ensure stability of the body position and are able to absorb loads on the spine. Flexibility is ensured by elastic, strong ligaments that line the canal along its overall length. Due to the structural features of the vertebrae, the canal in the vertebra has different sizes depending on its specific location. Normally, the canal has an average area of ​​2.5 cm2, the maximum value is 3.2 cm2.

The canal has different sizes depending on the structure of the vertebrae

To ensure normal functionality, the volume of the canal must be greater than the volume of the brain membrane. The space free from the brain is filled with plexuses of capillaries and fiber. This space is called the epidural, and it is where pain medications are injected during anesthesia. The canal contains the spinal cord with its specific membranes and branches. Physiologically normal blood supply to the bone bodies of the vertebrae and their other parts is provided by three arteries.

Layout of the epidural space

Open surgery or minimally invasive spine surgery?

Modern surgical techniques attempt to minimize exposure or damage to adjacent healthy tissue. Most surgeons attempt to preserve the vertebral ligaments and facet joint capsules to reduce the likelihood of future degeneration or stenosis at the next or adjacent level.

The gold standard surgery for treating spinal stenosis is laminectomy. Modern techniques may use small incisions to access the narrowed area of ​​the canal, but the goals are the same. The area of ​​bone that is causing compression is removed, and soft tissue, such as the hypertrophic ligamentum flavum, is moved away from the spinal cord or nerve roots. This method can be used in the lumbar or cervical spine.

If the surgery is performed through a relatively large incision in the back, it is called open surgery. Another option is minimally invasive surgery, which is performed through several small incisions. The surgeon may use a microscope, an endoscope or a tiny camera and very small surgical instruments.

However, minimally invasive surgery is not suitable for all patients. If the surgeon has to work on many vertebrae, open surgery will likely be necessary.

What is sagittal size

To characterize the state of the canal, the definition of sagittal size is used. The sagittal size characterizes the size of the spinal canal in the anteroposterior direction, from the uppermost section of the canal to the lowest. The dimensions on both sides of the conventional plane of the imaginary anatomical section are taken into account. Such definitions allow us to have a more complete understanding of the state of the spinal canal and enable physicians to specifically classify detected pathological changes in tissue alignment.

Sagittal plane

Geometric shapes of sagittal size

The so-called sagittal section changes depending on age, up to 20 years it increases, up to 50 years the parameters are stable, and later due to degenerative and dystrophic processes they decrease. These are normally occurring physiological processes; medical science cannot currently influence them. The sagittal size in the lower lumbar region decreases most with age, hence the frequent back pain in older people.

Normal dimensions of the spinal canal

Normal cross-sectional values ​​in the area of ​​3–4 vertebrae are ≈ 17 mm and remain the same throughout life. If the size decreases to 13 mm or less, then this is a clear sign of pathological changes in the spinal canal. But for the normal functionality of the spinal cord, not only the area, but also the configuration of the canal is important.

X-ray – spinal canal stenosis

Risks of surgery for spinal stenosis

No surgery is without the risk of complications. Common complications of any surgery include: bleeding, infection, thrombosis, and reactions to anesthesia. If a vertebral fusion is performed at the same time as a laminectomy, there is a greater risk of complications.

The following risks should be considered:

• The vertebrae may not fuse. Among the many reasons why vertebrae do not fuse, the most common are osteoporosis, obesity and malnutrition. Smoking is by far the biggest factor that can interfere with fusion.
• Deep vein thrombosis (DVT) is a potentially serious condition caused by blood clots forming inside the veins of the lower extremities. If the clots break off and travel through the bloodstream into the lungs, a deadly condition occurs - thromboembolism. Therefore, prevention of thrombosis with compression stockings and the use of anticoagulants is necessary.
• Hardware fracture. The metal screws, rods and plates used to stabilize the spine are called "hardware". The device may move or break before the vertebrae are completely fused. If this happens, another operation may be required to fix or replace the hardware.
• Bone graft migration. In rare cases (1 to 2%), the bone graft may quickly move out of its correct position between the vertebrae shortly after surgery. This is more likely if hardware (plates and screws) were not used to secure the bone graft. This complication is also more likely if multiple levels of vertebral fusion have been performed.
• Transitional syndrome (adjacent segment disease). This syndrome occurs when the vertebrae above or below the fusion receive additional stress. Additional stress can eventually lead to degeneration of adjacent vertebrae and cause pain.
• Nerve damage or persistent pain. Any spinal surgery carries a risk of damaging nerves or the spinal cord. The damage can cause numbness or even paralysis. However, the most common cause of persistent pain is nerve damage from the herniated disc itself. Some disc herniations can cause permanent nerve damage, and in such cases, decompression surgery may not be effective. However, even with this outcome, spinal cord stimulation or other treatments are recommended.

Anatomical characteristics of sagittal size

The canal begins at the point where the spinal nerve departs from the entrance (dual sac). In the area of ​​the vertebrae of the neck, it is directed forward and outward. The posterior wall is the plate of the arch, limited by the upper process. This arrangement affects the formation of shapes and sagittal dimensions. The absolute parameters of the channel and nerve indicate the capabilities of the body's protective reserves. Between both anatomical formations there is a free space that can, to a certain extent, compensate for degradation or physical damage to the vertebrae and adjacent tissues.

Sagittal and frontal diameters of the spinal canal

The difference in these sizes shows the protective function capabilities of the body, and their ratio, taking into account the contents, characterizes the reserve space of the spine. In normal condition, the central spinal canal has a space of no more than 5 mm. It is greatest in the upper spine, where the reserve reaches a maximum of 7 mm. The reserve is least in the latinal recess; in this place the free space does not exceed one millimeter, but in practice it is often completely absent. It is in this place that the risks of impaired nerve functionality as a result of degradation or damage to the vertebral discs are greatest.

If you want to learn in more detail the structure of the human spine, its sections and functions, and also consider the causes of diseases, you can read an article about this on our portal.

Decompression surgery for spinal stenosis

To remove tissue that is pressing on the nerves, the following techniques can be used in surgical treatment of stenosis:

Foraminotomy

: if part of the disc or bone growth (osteophyte) compresses the root at the exit from the spine (in the foraminal canal) onto the nerve, then a foraminotomy can be performed - it allows you to increase the size of the intervertebral foramen and relieve pressure on the root.

Laminotomy

. Unlike foraminotomy, the surgeon creates a hole in the vertebral plate, which puts pressure on the nerve structures, and thus restores the full transmission of impulses along the nerve fibers.

Laminectomy

: Sometimes laminotomy is not enough. The surgeon may need to remove all or part of the plate, a procedure called a laminectomy. This operation can be performed on many levels without any harmful effects.

Indirect decompression

is a variation of decompression surgery that relieves pressure on the nerves by moving apart rather than removing the bones. This method of surgery can be performed using instruments (intervertebral devices or cages). Even artificial discs can perform some indirect decompression, restoring height between adjacent vertebrae.

Causes of pathological changes in the sagittal size of the canal

The sagittal size in the vast majority of cases decreases; expansion is possible only as a result of very severe spinal injuries that cause a violation of the integrity of the vertebrae. Such situations arise after strong mechanical impacts and cause extremely negative consequences, including general paralysis or death.

Spinal stenosis

A decrease in sagittal size parameters is caused by structural disorders of the vertebrae, which have a different nature of appearance. Negative changes can appear both as a result of congenital pathologies, and against the background of acquired diseases or the consequences of an unhealthy lifestyle. The primary pathological process is accompanied by anomalies in the development of vertebral arches, dysplasia, the formation of cords and other abnormalities in the development of the young body. Such pathologies should be identified in the early stages of development; a timely diagnosis allows medicine to completely eliminate the risks of negative consequences.

Consequences of changes in sagittal size

The first studies on narrowing of the spinal canal were published by the journal Portal in 1803. The pathology was discovered in patients with rickets and venereal diseases at a late stage. With the development of medical science and the expansion of the number of cases studied, the classification of painful conditions caused by a decrease in the sagittal dimensions of the canal has changed. If they are caused by sequestration and disc herniation, then these conditions of the body do not belong to stenosis. Stenosis, according to modern definitions, is a long-term and slow-in-area narrowing of the canal. At the same time, negative consequences accumulate gradually; doctors have time to use effective modern treatment methods. Based on the actual values ​​of the sagittal size of the canal, the narrowing criteria are determined and the final diagnosis is made.

Spinal stenosis - diagram

Table. Main types of stenosis.

Taking into account the specific area of ​​the spine where the decrease in sagittal size is localized, the stenosis can be spinal, lateral or central.

Spinal stenosis is a chronic process characterized by pathological narrowing of the central spinal canal

Outpatient diagnostics aims to clarify not only the degree of narrowing of the canal, but also the geometry of the pathology and its nature. Taking into account these in-depth examinations, the type of stenosis is determined: total or intermittent, polysegmental or monosegmental, symmetrical on both sides of the vertebrae or unilateral.

1. Total . The pathological narrowing permanently compresses the spinal cord. The situation is very difficult, the organs for which the compressed area of ​​the brain is responsible are completely paralyzed.
2. Intermittent . The decrease in sagittal size is point-like; areas with a normal cross-section alternate with areas with a reduced cross-section. The pathology affects the spinal cord over a relatively large extent.
3. Monosegmental . The pathology concerns only one vertebra; neighboring areas have normal physiological indicators.
4. Polysegmental . Deviations are found in two or more segments of the spine; the causes can be either congenital or acquired.
5. Symmetrical . The spinal cord is compressed symmetrically on both sides or along the entire circumference. The pathology narrows the sagittal lumen in a ring-like manner.
6. One-sided . The spinal cord is compressed in only one area, on the left or right side, in front or behind.

There are several types of stenosis

Approaches to the treatment of PS

To date, therapeutic strategies for patients with PS have not been fully defined because there is insufficient convincing evidence of the effectiveness of various treatment options. Treatment tactics are based on existing clinical symptoms, and not on CT or MRI data. The patient's walking distance is the most significant criterion for the effectiveness of therapy [14, 15].

Treatment of PS consists of a comprehensive and individualized approach, including recommendations for changes in lifestyle and physical activity, prescription of drugs from the NSAID group, anticonvulsants, vasoactive drugs, in particular venotonics, prostaglandin E1, calcitonin, epidural administration of glucocorticosteroids and local anesthetics, B vitamins.

Current guidelines for the treatment of chronic lumbar pain recommend the active use of non-drug methods. When managing patients with subacute and chronic back pain, rational psychotherapy and various types of exercise therapy are important [16]. The effectiveness of physiotherapeutic methods for the treatment of back pain, including exposure to infrared radiation and magnetic fields, is currently being studied [17–19]. Therapeutic pain-relieving patch NANOPLAST forte contains two components: rare earth metals and infrared radiation producing powder. Thus, NANOPLAST forte combines both of these effects: it acts with a constant magnetic field and soft heat on the affected area. In a prospective comparative randomized placebo-controlled study involving 60 patients with acute/exacerbation of chronic back pain syndrome, N.A. Szostak et al. (2017) found that the use of the NANOPLAST forte patch had a more pronounced analgesic effect compared to the use of placebo [20].

In 2013, a Cochrane systematic review was published, according to which the use of calcitonin in the treatment of patients with intermittent claudogenic claudication was comparable to the placebo effect. There was also some effectiveness in improving walking parameters with prostaglandin E1 (low-quality evidence) and gabapentin and vitamin B12 (very low-quality evidence). Epidural glucocorticoids are effective in reducing pain, improving functional status, and improving quality of life in the short term compared with home exercise or physical therapy. Gymnastics is effective in the short term for reducing leg pain and disability compared to no treatment [21]. There are indications that anticonvulsants are ineffective for intermittent claudogenic claudication, but the review does not provide data on the effectiveness of this group of drugs in the presence of neuropathic pain [22].

According to the 2013 Clinical Guidelines (NASS), there is insufficient evidence to determine the effectiveness of the use of drugs and non-pharmacological methods for the treatment of clinical manifestations of PS. At the same time, according to the recommendations of the working group experts, a short-term course of active exercise therapy is indicated for patients with PS. For the treatment of claudogenic intermittent claudication, the use of epidural blocks with corticosteroids in the short term (up to 6 months) is effective, and the interlaminar method of administration has a higher level of evidence (B) than the sacral and transforaminal approaches (level of evidence C). Data on the long-term effectiveness of epidural blocks are conflicting. The use of a corset is effective in reducing pain and improving motor activity, in particular walking, in patients with PS (level of evidence B). Conservative therapy leads to improvement over 2–10 years in many patients [13].

The use of various types of epidural blockades in the treatment of PS is controversial. In a systematic review, Manchikanti et al. (2016) in the treatment of this category of patients demonstrated the effectiveness of epidural blockades with lidocaine or in combination with glucocorticosteroids, while epidural administration of other drugs, such as bupivaquine or saline, did not show a significant effect [23]. A meta-analysis of 13 randomized controlled trials involving 1465 patients with PS demonstrated the high effectiveness of the use of epidural blocks with local anesthetics and in combination with glucocorticosteroids in reducing pain (by more than 50%), as well as the degree of vital activity, determined by the Oswestry scale, the need for use narcotic analgesics [24]. A recent review showed the high effectiveness of epidural blocks (level A evidence) in both short-term symptomatic relief and long-term prognosis, highlighting that the addition of corticosteroids does not significantly affect treatment outcome [25].

At the same time, the British clinical guideline (NICE UK 2016) does not recommend the use of epidural blocks for the treatment of claudogenic claudication in PS [26]. More than half of the patients have a favorable prognosis [27] when conservative therapy is prescribed; however, if treatment is ineffective and the neurological deficit progresses, further neurosurgical intervention is suggested, usually laminectomy, sometimes in combination with the use of fixation systems [2, 8, 28]. However, the data obtained from various types of neurosurgical interventions are quite contradictory. Kovacs et al. (2011) indicate that surgical treatment showed a greater effect compared to conservative therapy in terms of reducing the severity of pain, the degree of impairment of daily activities, and improving the quality of life, but did not have a significant effect on walking parameters [29]. The Spine Patient Outcomes Research Trial (SPORT), which followed patients for 4 years, also demonstrated greater effectiveness of surgical operations for PS and spodylolisthesis than conservative treatment; however, in 13% of cases complications were observed or repeated interventions were required [30]. A longer period of observation of patients with moderate and severe manifestations of PS who underwent decompression operations showed a better outcome, including in patients over 75 years of age [13]. Several prospective studies [31–33] have convincingly demonstrated the superiority of neurosurgical intervention in patients with PS over conservative therapy. The rate of favorable outcomes after surgery ranged from 64 to 85% [6].

At the same time, a Cochrane systematic review [34] showed that to date there is no convincing data on the effectiveness of surgical treatment in relation to pain and the degree of impairment of daily activities in patients with clinically significant PS. There is also no data on the greater effectiveness of using fixation systems than standard decompression [35, 36], and when using an interspinous fixation, a higher percentage of re-interventions is observed [34]. Another Cochrane systematic review [37] analyzed the outcome of neurosurgical interventions for PS compared with a multimodal conservative approach and did not find convincing evidence of greater effectiveness of one or another treatment method. However, it has been shown that complications such as hematomas, fractures, respiratory disorders, as well as strokes and myocardial infarctions were observed during surgical operations in 10–24% of cases and were absent during conservative treatment. Thus, it is important for clinicians to inform patients about possible treatment methods and take a balanced approach to choosing further management tactics [37]. According to a meta-analysis, exercise therapy has a similar effect in spinal PS when compared with decompression surgeries [38].

There is no convincing evidence for early surgical intervention, since the duration of conservative therapy administered before surgery does not affect the further outcome of neurosurgical treatment [39]. Installation of stabilizing systems in patients with stenosis without instability is not recommended [40]. In patients with PS and intermittent claudication caused by spondylolisthesis, the use of stabilizing systems is most justified. However, there is no convincing evidence to recommend a standard treatment method to achieve durable arthrodesis. When choosing neurosurgical management tactics, an individual and balanced approach is recommended, taking into account both the patient’s characteristics and the doctor’s experience [13, 40].

Symptoms of a decrease in the sagittal size of the canal

Depending on the specific location where pathologies appear, the symptoms of the disease also change. But in all cases there is pain, it can be aching or shooting, local or diffuse, strong or weak. Increased compression causes increased pain; in the future, patients cannot do without painkillers.

If there is a problem in the lumbar spine, lameness, numbness in the legs, muscle weakness and impaired reflexes of vital functions appear. In complex cases, paresis of the limbs and dysfunction of the pelvic organs develop. In the last stages, neurodystrophic changes increase, and vegetative-vascular disorders begin. The last fourth stage of reduction in sagittal size leads to complete paralysis of the limbs.

Symptoms of lumbar stenosis

Stabilizing surgery for spinal stenosis

Not all patients undergoing surgery for spinal stenosis will require stabilization, also known as spinal fusion. Stabilization is especially useful in cases where one or more vertebrae have slipped out of alignment, causing instability in the motion segments of the spine. In these cases, slipping of the vertebrae can lead to compression of the nerve structures. The need for stabilization also depends on how many vertebrae will be involved during the operation. For example, if a surgeon needs to remove lamina (using a laminectomy) in several vertebrae, the spine without these structures may become unstable. In this case, spinal fusion surgery may be required to stabilize the spine.

Spinal stabilization surgeries have been performed for many years. This operation can be performed either separately or simultaneously with decompression surgery. When stabilizing the spine, the surgeon creates an environment where the vertebrae will fuse over time (usually over several months or longer).

The surgeon will use a bone graft (usually the patient's own bone) or a biological substance (which will stimulate bone growth). The surgeon may use spinal instrumentation such as rods, screws, or plates to increase stability and aid bone healing. Fusion (fusion) will stop movement between the vertebrae, providing long-term stability.

The results of surgery to correct spinal stenosis are usually good. Typically, 80% to 90% of patients are pain free after surgery.

Diagnostics

An accurate diagnosis can be found only after a special outpatient examination of the patient. They necessarily include methods that allow you to visually see the state of the channel. Depending on the patient’s condition, radiography, computed tomography or magnetic resonance imaging may be prescribed. Based on the images obtained, an experienced doctor can draw the right conclusions and develop effective treatment regimens. We must remember that in some cases the disease can only be localized by surgical methods. These are very complex operations and have high risks of negative consequences.

MRI of the spine

Types of surgeries for spinal stenosis

Typically, surgeons use 2 surgical methods for spinal stenosis:

• Decompression: The surgeon removes tissue that is pressing on the nerve structure, which creates more space in the spinal canal (for the spinal cord) or in the foraminal canals (for the nerve roots).
• Stabilization: The surgeon's task is to limit movement between the vertebrae.