Part I: Overview of discogenic lower back pain
Numerous studies since the 1970s have shown that the intervertebral disc is not an innervated organ; there are a large number of nerve branches from the sinus vertebralis in the posterior 1/3 of the fibrous ring and the adjacent posterior longitudinal ligament. There are two main mechanisms by which intervertebral disc degeneration causes pain, one is that the degeneration causes tearing and relaxation of the annulus fibrosus, which destabilizes the intervertebral disc and causes some “abnormal activity” of the disc. On the other hand, the intervertebral disc tissue can release a large amount of chemical factors such as phospholipase A2, substance P, interleukin, etc. during the degeneration process, which can produce chemical stimulation to the nerve endings and cause pain, i.e. “chemical mechanism”.
These mechanical and chemical factors together stimulate the nociceptive nerve receptors located in the posterior longitudinal ligament and the fibrous ring, resulting in pain in the degenerated disc, i.e. Discogenic Pain. According to Zdeblick’s concept, discogenic pain has three main components: Internal Disc Derangement (IDD), Degenerative Disc Disease (DDD), and Segmental Instability. .
The typical symptom of discogenic pain is pain in the midline region of the lower back, sometimes extending to the buttocks on both sides, aggravated by long-distance walking or prolonged sitting, and often not relieved immediately after resting in a recumbent position; deep pressure pain in the spinous process can be detected on examination, and the paraspinal pressure pain is obvious. The pulling pain in the lower extremities is different from the radiating pain of disc herniation, and there are no positive signs of nerve root damage during physical examination.
In addition to being an independent diagnosis, discogenic pain is often involved in constituting the clinical manifestations of some complex lumbar spine diseases, such as some patients with disc herniation and spinal stenosis whose clinical manifestations are dominated by lumbar pain, when the symptoms of lumbar pain should be explained by the above mechanism, and is also the reason for the unsatisfactory relief of lumbar pain symptoms after simple nucleus pulposus removal or simple decompression surgery.
In addition to stimulating the sinus nerve to cause low back pain, the degenerated disc can also stimulate the adjacent nerve roots and cause local radiculitis, which can lead to lower limb referred leg pain in some patients. Clinical care should be taken to distinguish between referred leg pain and radiculopathy (nerve root compression).
The diagnosis of discogenic pain is still controversial, and so far, most scholars believe that only discography has a local diagnostic value for discogenic pain, and its pain provocation effect cannot be replaced by other methods of examination. It should be emphasized that the results of discography should be determined by a combination of imaging performance, the amount of contrast agent injected, and pain provocation; and positive results of imaging must also be combined with clinical symptoms and other imaging performance to make a clinical diagnosis.
Interbody Fusion has been shown to be more effective in resolving discogenic pain, removing the painful disc and restoring local stability, and is usually clinically satisfactory as long as the localization of the pain source is accurate. The widespread use of fusion has brought about some new problems, such as accelerated degeneration of adjacent segments, fusion failure, and fracture of internal fixation. Therefore, the implementation of fusion surgery must be performed under the premise of strict control of indications. In response to the drawbacks of fusion surgery, some new minimally invasive methods have emerged in recent years, and plasma ablation myeloplasty (Coblation Nucleoplasty) is a typical representative of these minimally invasive methods. Its clinical efficacy is described in detail later.
Part II: Working principles and surgical methods of plasma ablation nucleoplasty
I. Working Principle
Myeloplasty uses radiofrequency energy to remove a small amount of nucleus pulposus tissue and form a hole inside the nucleus pulposus. In plasma cold ablation technology (Coblation technology), the effect of radiofrequency energy is to create a plasma field in the local tissue around the electrode and generate a large number of highly ionized particles that carry enough energy to sever the intermolecular ties in the tissue and form a pore. The by-products of this process are inert gases of some molecular weight that can be expelled through the disc puncture channel. The tissue around the foramen is treated with high temperature by thermal coagulation during the withdrawal of the tip. Therefore, the combination of myeloplasty and thermal coagulation removes part of the tissue and creates a hole in the nucleus pulposus, which ultimately reduces the pressure in the disc.
Second, the operation points of myeloplasty
1.Position: prone position, local anesthesia, anesthesia for the whole process of needle insertion beyond the intervertebral disc.
2.Puncture needle position: mark the horizontal line consistent with the treatment gap under fluoroscopy, and take 8-10cm of the midline on this line as the needle entry point
3, C-arm guidance on the affected side 8-10cm from the midline with a special puncture needle and skin at 35-45° puncture, the tip of the needle should reach the medial edge of the fibrous ring. The correct position of the blade tip under fluoroscopy: orthostatic image is standardized by the medial edge of the vertebral arch, and lateral position is standardized by the posterior 1/3 to 1/4 of the vertebral body.
4.Gently withdraw the puncture needle 2mm outward, pull out the needle core, place the lumbar spine special plasma knife and make the tip of the knife head exceed the tip of the puncture needle by 5mm, mark this point as the starting point of perforation and ablation (near point), then slowly advance the knife head in the direction of perforation to the diagonal medial edge of the fibrous ring, stop when resistance is obviously felt, and move the metal card at the back end of the knife head to this point to fix it. This point is used as the end point (distal point) of perforation ablation.
5. Under C-arm surveillance, with the energy set to 2, depress the ablation key on the foot pedal of the plasma surgery system, slowly advance the plasma tip to the end point (farthest point) for perforation, and then depress the thermal coagulation key to return in the same direction at a speed of 5mm/sec to complete ablation of the crura in one direction.
6.The same method is careful to ablate in another 5 directions of 2, 4, 6, 8, and 10 points of the wren.
7.Pull out the tip of the knife, load the puncture needle core and then pull out the puncture needle and cover the eye with a sterile dressing.
8.Caution
A. Keep parallel to the vertebral space
B. The patient feels lumbar pain but no radiating pain to the lower extremity when penetrating to the fibrous ring.
C. Stop puncture and change the needle tip position when there is radiating pain to the lower extremities.
D. Soreness or mild pain in the lumbar region during treatment is a normal condition and should be explained to the patient.
Part III: Clinical study data
1.Data and methods
1.1, General situation
There were 20 male cases and 42 female cases in this group; age ranged from 22 to 55 years old, with an average of 37.4 years old. There were 37 cases who presented with lower back pain alone, 17 cases with low back pain accompanied by leg pain, and 8 cases with low back pain accompanied by pain in the perineal area. Preoperatively, all cases were examined by X-ray and MRI. 44 cases showed mild narrowing of the intervertebral space on X-ray, and the rest had no clear changes; MRI of the lumbar spine showed that there was a general decrease in T2 phase disc signal, 28 cases showed Modic changes, and 22 cases showed a clear “High Intensity Zone (HIZ)” at the posterior edge of the intervertebral disc. No clear compression of nerve structures was seen in all cases. Discography was routinely performed before myeloablation. 42 cases had typical pain, 16 cases had atypical pain, and 4 cases were negative. In this group, 33 cases with 1 interspace, 24 cases with 2 interspaces and 5 cases with 3 interspaces were treated by ablation.
1.2. Operation technique: The plasma ablation technology (Coblation Neucleoplasty) of ArthroCare (Sunnyvale, California, USA) was used, the mainframe was System 2000 and the plasma head was D-perc Spine Wand . The patient was placed in the prone position and routinely disinfected with a sheet. The puncture point is at the level of the lesion space, 8 cm from the spinous process, and the lateralization depends on the operator’s custom. The disc is punctured with a 17-gauge trocar. Under television X-ray surveillance, the tip of the puncture needle is removed after it has passed through the annulus fibrosus to the nucleus pulposus, leaving the working channel intact. The plasma tip was inserted into the nucleus pulposus through the working channel, and to ensure the safety of the treatment process, the ablation started at the inner layer of the entering side of the annulus fibrosus and ended at the inner layer of the contralateral annulus fibrosus. The treatment intensity is set to 3 levels, and the “Coblation key” is pressed with the foot, and the treatment tip is inserted slowly to the end point for 15-20 seconds, at which time the bubbles are seen to overflow from the outside of the working channel; then the “Thermal Coagulation key” is pressed with the foot ( Coagulation) to slowly withdraw the treatment tip to the starting point according to the entry speed. The process is repeated six times, marked by the 6, 8, 10, 12, 2, and 4 points of the circular opening of the puncture needle. After completion of treatment, 1-2 ml of broad-spectrum antibiotics were injected into the intervertebral disc.
1.3, postoperative treatment: patients try to rest in bed on the day after surgery, and the next day, straight leg raising training is feasible, and wear a periapical waist to get out of bed, and the amount of activity is gradual.
1.4. Observation indexes and functional assessment: the intensity of pain and its changes were recorded using Visual Analog Pain Scale VAS, and the results were recorded preoperatively, postoperatively, and at each time of follow-up, respectively; the modified StaufferCCoventry rating system (see Table 1) was used to evaluate the daily activities and satisfaction rate after surgery [1].
Excellent: complete pain relief and return to previous daily activities and exercise.
Good: significant pain relief (≥70% relief), return to work, no or mild limitation of daily exercise, no or minimal use of analgesics.
OK: partial relief of pain (≥ 30% relief), partial return to work, limited daily exercise, frequent use of analgesics.
Poor: no pain relief or little relief (relief ≤ 30%), unable to work, severe limitation in daily work and life, regular use of analgesics
The assessment results were satisfactory for those who were excellent and good, and unsatisfactory for those who could and were poor
2.Results
The follow-up time of 62 cases in this group was 38 months-65 months, with an average of 47 months. The follow-up time points were 1 week postoperatively, 6 months postoperatively, 1 year postoperatively, and the final follow-up. The visual pain scale score (VAS) was used to observe changes in pain; the modified StaufferCCoventry rating system (see Table 1) was used to evaluate postoperative daily activities and satisfaction rates [1].
2.1: Changes in visual pain scale score (VAS) before and after surgery: preoperative VAS score: 5.4-8.5, mean 6.8; 1 week postoperative: 3.7, 6 months postoperative: 3.4; 12 months postoperative: 3.4, final follow-up: 4.1.
2.2. Postoperative satisfaction rate according to the modified StaufferCCoventry rating system: 1 week postoperative: 87%; 6 months postoperative: 84%; 12 months postoperative 86%; final follow-up: 68%.
The VAS pain scores and satisfaction rates indicate that this method maintains a more satisfactory outcome in the treatment of discogenic lower back pain over a period of longer than 3 years.
2.3. Comparison of surgical results between single- and multi-gap (more than 2).
2.4, surgical complications: most patients could experience postoperative discomfort at the puncture site, which disappeared within 3 days; one case of intervertebral discitis in the treated gap appeared in this group, and the original pain symptoms were relieved significantly after treatment, and the patient was able to move around on the ground on the second day and basically returned to normal after 1 week. In contrast, low back pain appeared 5 weeks after the operation, and the symptoms worsened rapidly, and he came to our hospital in the 6th week, and was diagnosed as discitis after examination, which was cured by bed rest and local braking. There was no nerve injury after ablation in this group of patients.
3.Discussion
3.1. Clinical characteristics of discogenic lower back pain: At present, the term discogenic lower back pain has appeared more widely in the domestic and foreign literature, but there is a lack of uniform understanding of its clinical manifestations, imaging features and diagnostic basis. We emphasize the principle of combining symptoms, signs and imaging examinations in the diagnosis, and based on the experience of more than 300 cases, we believe that the following points should be noted in the diagnosis of discogenic lower back pain: (1) young and middle-aged patients complaining of lower back pain after sitting or standing for a long time, with no special manifestation on X-ray and MRI manifestation of bulging disc should be highly suspected of this disease; (2) extreme flexion of the hip and knee in the supine position (2) the aggravation of low back pain in supine position with extreme hip flexion and knee flexion, as well as deep pressure pain at the spinous process of the relevant segment are important signs of the disease; (3) discography, the so-called “gold standard” for diagnosis, is affected by many factors, so its diagnostic value cannot be unilaterally emphasized
In the diagnosis of discogenic lower back pain, some scholars believe that in addition to the clinical features, the T2-weighted image of High Intensity Zone (HIZ) and Modic changes on MRI images can provide some reference for the diagnosis of this disease, but so far there is no definite conclusion.
3.2. The mechanism of action of plasma ablation technology in the treatment of discogenic lower back pain: At present, the more affirmative view is that the site of action of this technology is the nucleus pulposus of the intervertebral disc, therefore, it is often referred to as plasma ablation nucleoplasty (Coblation Nucleoplasty) in the literature, through ablation and vaporization of the nucleus pulposus tissue to reduce the pressure in the intervertebral disc, thus playing a role in relieving Yung C. Chen conducted a trial using human spine specimens and the results confirmed a significant reduction in intradiscal pressure after plasma ablation [2]. However, we have seen other cases in the clinic where such patients had typical clinical symptoms, imaging showed heavy disc degeneration, and contrast was seen to be injected very easily during discography with severe leakage, indicating that there was no high pressure state in the disc. In addition, these patients had atypical and sometimes even negative pain provocation tests. Some attempts have been made to treat such cases, i.e., also with plasma ablation myeloplasty, and the results showed satisfactory results in some patients, especially in single-segment cases. In the cases presented here, of the 12 cases with atypical pain and negativity in the single interstitial group, 6 (50%) had excellent results at the end follow-up. Therefore, we believe that plasma ablation technique, when acting on the nucleus pulposus tissue, has the potential to have an inhibitory effect on the inflammatory response within the disc, in addition to reducing the intradiscal pressure. In this regard, we performed animal studies and found that plasma ablation inhibited the activity of phospholipase A2 (PLA-2) in degenerated intervertebral discs in rabbits (paper to be published), and similar findings have not been reported in the literature. while confirming that plasma ablation can reduce intra-disc pressure, Yung C. Chen’s study also found little decompressive effect in severely degenerated discs [2]. Therefore, further studies are needed regarding the mechanism of action of plasma ablation techniques.
3.3. Prospects of plasma ablation technique for nucleoplasty: In this aspect of using this technique for the treatment of lumbar discogenic lower back pain, China has basically started in parallel with foreign countries [3, 4], and although it has been 4-5 years, all the initial clinical reports seen in the literature so far are within 1 year, and Gibson and Waddell, in a meta-analysis of surgical treatments for intervertebral disc disease noted that plasma ablation technique (Coblation Nucleoplasty) and intradiscal endothermic therapy (IDET) are the main representatives of percutaneous puncture techniques, but both lack randomized controlled prospective studies and therefore no definitive conclusions about their efficacy [7]. In our group of cases, the results at a mean follow-up of up to 4 years showed a final overall satisfaction rate of 68%, especially in the single gap group with a high satisfaction rate of 81%, which should become a satisfactory clinical outcome. We always emphasize the need to strictly control the indications for surgery and never relax the control of the indications with the aim of increasing the number of clinical applications. In this regard we consider that the clinical characteristics of the patient are important; cases with a single gap are best selected; we believe that discography should be routinely performed, but because the factors affecting discography results are too complex, the selection of cases should not simply emphasize the positive results of typical pain replication, especially for segments with more severe degeneration. Based on the clinical follow-up results in this study, we believe that plasma ablation technique can be a minimally invasive, simple, and safe option in the treatment of discogenic lower back pain, with better results in single gap cases.