Low back pain is very common in clinical practice, but the symptoms of low back pain vary from patient to patient, and can be described as highly variable. Common diseases that can cause low back pain include lumbar disc herniation, lumbar spinal stenosis, lumbar instability and many low back pains caused by soft tissue lesions in the lumbar region. These diseases have typical clinical features, such as lumbar disc herniation with typical radiating pain in the lower extremities and neurological localization signs in the corresponding segment, lumbar spinal stenosis with typical intermittent claudication, and lumbar instability with lumbar pain during activity that can be relieved by braking and intervertebral slippage instability as seen in lumbar dynamic force images.
However, there are many patients with lumbar pain who do not have lumbar disc herniation, spinal stenosis and lumbar instability, which cannot be explained by the above theories, and they were generally treated as soft tissue pain in the lumbar region in the past. With the improvement of people’s understanding and the development of examination methods, the concept of “discogenic low back pain” was proposed, and it is believed that disc pathology itself can also cause low back pain.
At present, it is believed that the mechanisms of discogenic pain are mainly as follows.
(1) A large number of sinus nerves are distributed in the dorsolateral aspect of the disc fiber ring, the posterior longitudinal ligament, and the ventral dura;
(2) Increased number of injury receptors in the degenerated disc endplates, nucleus pulposus, and annulus fibrosus;
(3) Disc degeneration, rupture of the inner fibrous annulus, and lateral movement of the nucleus pulposus, stimulate the production of a large number of inflammatory mediators, which act on the injury receptors of the sinus nerve to cause pain;
(4) disc degeneration, narrowing of the intervertebral space, and a certain amount of abnormal mechanical movement may be generated between the vertebrae, causing pain due to stimulation of the nerve endings of the fibrous annulus.
The clinical manifestations of discogenic pain are mainly atypical lumbar and leg pain, dull pain with vague localization in the lumbar region, posterior hip region, anterior and posterior femur, greater trochanter, groin, perineum, and testes, and the symptoms are aggravated after prolonged sitting, standing, and activity. The age of onset is usually around 40 years old. It may be accompanied by radicular radiating pain in the lower extremities, but there is no numbness, weakness or other manifestations of nerve root injury. Physical examination is generally free of signs of nerve damage, and the straight leg raise test is often negative, or there is low back pain without significant leg pain.
Diagnostic criteria are not yet uniform, but the diagnosis is generally made through a combination of several aspects.
(1) The site of low back and lower extremity pain does not correspond to the localization of the nerve root;
(2) Recurrent symptoms with a disease duration of more than six months;
(3) Positive CT discography;
(4) MRI single-segment disc with low signal;
(5) If there is small joint degeneration, closure of small joints can be performed, except for pain caused by small joint degeneration. It is important to emphasize the importance of a positive discography for the diagnosis of discogenic pain. Only a correct discogram can be helpful in the diagnosis.
We appreciate that the requirements for discography should be.
(1) The needle should be inserted on the contralateral side of the pain so as not to irritate the nerve roots when inserting the needle on the same side of the pain causing false positive results;
(2) The angiogram should show disc degeneration;
(3) Induce pain consistent with the complaint, which should include the location and nature of the pain;
(4) There should be at least one adjacent intervertebral space as a negative control. The mechanism of occurrence of positive discography may be related to the dispersal of degenerative chemicals near the receptors by the contrast agent and mechanical pressure to produce pain in sensitive nerve fibers. We have clinically applied CT-guided discography in more than 30 cases for the adjunctive diagnosis of discogenic pain, and it does have a clear diagnostic role for clinical purposes.
There are many treatment options available for intervertebral discogenic pain. These include conservative treatment, minimally invasive surgery, artificial nucleus pulposus replacement, lumbar disc replacement, and spinal fusion. Conservative treatment includes bed rest, physical therapy, traction, massage, and non-steroidal anti-inflammatory drugs, and most patients improve with conservative treatment.
Minimally invasive intervertebral disc surgery is currently more popular is disc thermotherapy, including intradiscal electrothermal therapy, percutaneous intradiscal radiofrequency thermocoagulation, etc. The treatment effect is reported differently and is not yet certain. Other minimally invasive procedures such as percutaneous chemical melting of the nucleus pulposus and percutaneous intradiscal hormone injection are rarely used because they can only provide short-term pain relief and have poor pain relief.
Spinal fusion is a very mature procedure with a history of more than 60 years, and its treatment mechanisms are.
(1) Removal of pain-causing factors from the intervertebral disc;
(2) Elimination of intervertebral micromovements;
(3) protection of the diseased intervertebral disc from stress stimulation. There are many fusion methods, and it is best to choose anterior or posterior intervertebral fusion for reliable fusion and high fusion rates. Posterior posterolateral fusion is slightly less effective due to incomplete discectomy and low fusion rate. Due to the disadvantages of fusion such as pseudarthrosis formation and accelerated degeneration of adjacent segments, artificial nucleus pulposus and disc replacement has come into being in recent years.
Advantages of artificial nucleus pulposus replacement.
(1) Reconstruction of intervertebral disc and spine function;
(2) Restoration of intervertebral height;
(3) Reducing the stress irritation in the intervertebral disc. It is suitable for those who are 18 years old or older and have no abnormalities in the posterior spine structure. At present, it is carried out in a few hospitals in China and has achieved good therapeutic results, but if the operation technique is not satisfactory, the rate of prolapse of the placed artificial nucleus pulposus is high.
Artificial disc replacement is also a new procedure in recent years, which was just approved by the FDA for clinical application in the United States last year and has been used in Europe for more cases, but it has not been carried out in China for a long time.
The advantages of artificial disc replacement are.
(1) Complete removal of the diseased disc – eliminating discogenic pain;
(2) Restoration of intervertebral height – full mobility of nerve roots;
(3) Restoration of physiological anterior convexity – biomechanical balance is obtained;
(4) restoration of motor function – prevention of degeneration of adjacent segments. We have performed dozens of artificial disc replacement surgeries with a follow-up time of about 1 year, and have achieved good treatment results in the near future.
In conclusion, discogenic low back pain is often misdiagnosed due to its atypical clinical symptoms, which are different from common clinical conditions. Physicians are advised to think of the possibility of discogenic pain if they encounter patients with atypical low back pain and to perform discography to identify it if necessary. Most patients can improve with conservative treatment, and only a small number of patients require surgical treatment.
The general order of choice for treatment is conservative treatment, minimally invasive surgery, artificial nucleus pulposus replacement, lumbar disc replacement, and spinal fusion, each of which has its own advantages and disadvantages and can be selected according to the conditions, technical strength, and indications of the respective hospitals.