Back pain is not only a common health problem but is also a significant social economic issue. The prevalence rate ranges from 12% to 35% in a number of studies.¹ Back pain is strongly associated with the degeneration of the intervertebral disc. As estimated, 45% of chronic lumbosacral spinal pain is attributed to be discogenic in origin.² With increasing age or abnormal mechanical loads, degeneration of disc occurs, following loss of hydration of the nucleus pulposus, leading to the tears within the annulus fibrosus. During these processes, nociceptive nuclear material leaks through the outer rim of anuulus. Nerve and blood vessels are increasingly found with degenerative discs.³ Outer annular rupture may facilitate the “leakage” of inflammatory mediators to the adjacent structures. The ingrowth of nociceptors into the deeper layers of the disc may introduce pain reaction to normal mechanical loads. A fracture in the vertebral endplate also can result in the appearance of inflammatory cytokines in the nucleus pulposus. All these mechanisms may cause chronic discogenic pain.⁴

There are no specific symptoms and signs mentioned in the patients' history and physical examination record. More typical features include persistent pain in the low back, groins or legs, depending on the level of the affected disc. Imaging studies, e.g., computed tomography (CT) and magnetic resonance imaging (MRI) are highly effective methods to demonstrate the detailed anatomical abnormalities of the disc. However, they are limited to be only the possible cause of pain.5, 6 The current gold standard in making the diagnosis of discogenic pain is pressure-controlled provocative discography.⁷ However, the value of its prediction has been repeatedly questioned because of the false positive rates. The strictness of diagnostic criteria and the adherence to technical details may allow an acceptable low false positive rate.⁸

No known studies have demonstrated that long-term used medication such as NSAIDs and weak opioids has any significant positive effects for discogenic pain. They are generally recommended in use for 3 months maximally.⁹ No evidence shows effectiveness of physical therapy when compared with other conservative treatments.¹⁰ Compared with conservative treatments, epidural steroid injection in the cases of herniated disc primarily induces anti-inflammatory effects and therefore results in rapid pain reduction. In the long-term follow-up, there are no differences in the outcome when compared with conservative treatment without epidural steroid injection. The indications for operative discectomy are larger disc protrusions and extrusions that show signs of nerve root compression on the image studies. Operative disecectomy can often lead to a more rapid reduction in symptom complaints when compared with a conservative treatment policy. For smaller and focal lesions without nerve compression, the advantages of operative discectomy should be carefully balanced against operative and anesthesia risks, as well as the risk of epidural adhesions after the operation, the so-called postlaminectomy syndrome or the failed back surgery syndrome.¹¹

Various minimally invasive procedures for dicogenic pain treatment have been developed to avoid complications resulting from open surgery in the recent few years. The common goal of these minimally invasive techniques are to remove the herniated nucleus or decompress the nucleus to decrease the volume with resultant reduction of the accompanying pressure on the nerve and inflammatory reaction, as well as ablation of the intradiscal nociceptors.

In this issue of the Acta Anaesthesiol Taiwanica, an article by Lee SC reviews various minimally invasive procedures, which are currently used by pain clinicians such as intradiscal electrothermal therapy (IDET), nucleoplasty, Dekompressor, and targeted disc decompression (TDD).¹² The techniques described above are currently being investigated for effectiveness and complications. There is currently insufficient proof to recommend IDET.⁴ Observational studies suggest that nucleoplasty is a potentially effective minimally invasive treatment for patients with symptomatic disc herniations who are refractory to conservative therapy. The recommendation strongly supports the therapeutic efficacy of this procedure. However, prospective randomized controlled trials of high quality are necessary to give evidence to confirm efficacy and risks and to determine ideal patient selection for this procedure.¹³ There are no randomized, sham studies on percutaneous discectomy using Dekompressor. However, it may be chosen for patients with leg pain and sustained disc herniation. The technique of TDD stems from the IDET but is modified in the markedly shorter active zone. Although the technique is increasingly used and seems to show good results, there is still no established positive evidence for TDD.

The intradiscal procedures are simple to use, with low rates of complications and seemingly effective. Although these minimally invasive procedures may be an effective alternative to surgical treatments, some of them still remain experimental. The definitive value of these treatment strategies must be determined through randomized and controlled studies in the years to come. Future studies should include stricter inclusion criteria. Moreover, as the author of the review article emphasizes, we should keep in mind “treatment should not do harm”.