Lumbar disc pathology and symptomatology is only partly well correlated with magnetic resonance imaging (MRI) findings. When a symptomatic patient is not found to have the expected compressive lesions, then the treatment pathway becomes less clear and unconvincing. Radial annular tear with chemical radiculitis and high-intensity zone (HIZ) in MRI are well documented to be the pathology in this subset of patients [1-3]. The resurgence of CT discography and intradiscal anesthetic injections help in confirming this diagnosis. Intradiscal and annular pathology from inside the annulus is visualized only by transforaminal endoscopy. We describe long-term follow-up of our endoscopic annular debridement management protocol under local anesthesia for the noncompressive painful disc with neurologic deficits due to chronic annular tear and chemical radiculopathy.

Patients who have been having radicular pain, burning down their lower limb and neurologic deficits but with no obvious MRI compressive lesion are usually initially treated with a combination of physical therapy, analgesics, neuromodulator drugs, antidepressants and bracing. Most often they are not benefitted and patients end up with multiple physician visits and multiple MRIs done over a period of time along with psychiatric evaluation.

After approval from Institutional Ethical committee of Nandha Medical College (vide - 20/IEC/NMCH/2025), patients retrospectively were selected from records of a single endoscopic spine surgeon with 12 years of practice since 2014 to form a cohort and to satisfy the following.

Inclusion criteria are as follows: (1) Isolated radicular pain, burning and with neurologic motor or sensory deficit in lower limbs. (2) History of at least 3 months pain interfering with activities of daily living (ADL). (3) Trial of nonoperative physical modalities and therapy etc for at least 6 to 8 weeks. (4) MRI that has been reported without any or unrelated compression. (5) No previous intradiscal injections, procedures etc. (6) No previous psychiatric treatment.

Exclusion criteria are as follows: (1) Multiple involved levels. (2) Predominant only back pain and spinal instability on radiology. (3) Spinal deformities or SI joint problems, compression fractures etc. (4) Preexisting neurologic motor sensory disorders. (5) Preexisting diabetic sensory polyneuropathy. (6) Preexisting vascular claudication, absent foot pulse.

Patients on presentation underwent a thorough history and were then clinically examined by the spine surgeon and an in-house physiotherapist. The findings were recorded including modified Oswestry Disability Index (ODI) where the item on sex was substituted with profession/home making, visual analogue scale (VAS) for leg pain and American Spinal Injury Association (ASIA) scores for neurologic deficits [4]. ODI is a validated measure for outcome measurement of back pain [5]. ASIA scoring has been shown to have excellent interrater reliability [6].

Investigations such as lumbosacral spine anterior-posterior, lateral- flexion, lateral-extension x-rays and MRI lumbosacral spine were done. In the x-rays, particular attention was directed to any abnormal mobility according to the criteria of White & Panjabi. MRI was corelated to the patient’s symptoms and signs. All of them did not have any radiologist reported significant compressive lesion to explain their respective symptoms. Presence of HIZ seen as increased signal within the annulus on T2-weighted axial MRI images, other disc compressive lesions, infection, injury etc. were looked for and those patients excluded.

A total of 16 patients between 25–68 years of age (mean, 43.8 years) were included (Figure 1).

There were 7 females and 9 males in the cohort. Right side was involved in 7 and left was involved in 9 patients of our series.

L4–5 was the most common level involved (n=12) and only 4 patients had L5–S1 involvement.

Many of these patients have had multiple MRIs as their problem has been persisting and already multiple physician consultations have been made already elsewhere. Patients were explained about the chronic annular tears, chemical radiculitis and the further invasive investigations, to confirm the same as the pathogenic lesion causing symptoms.

First, lumbar discography was performed according to the guidelines [7] and the findings noted. At the end of discography 2 mL of local anesthetic 1% Lignocard (Lignocaine Hcl Preservative free, NEON laboratories Ltd., India) was injected to find if the patients had adequate pain relief. Functional anesthetic discography (FAD) is the diagnostic procedure that involves the injection of a local anesthetic (e.g., lidocaine or bupivacaine) directly into the suspect disc and has more clinical relevance [8]. Postprocedure CT scan to document the dye flow to the suspect nerve root was then done. Once the patients reported good pain relief post-FAD, they were discharged without any analgesic or neuromodulator drugs. When the patients returned with previous symptoms, they were examined again clinically. With informed consent, they underwent the percutaneous transforaminal endoscopic surgery in the prone position under conscious sedation and local anesthesia at the CT discography confirmed involved side and lumbar level.

During the transforaminal endoscopic surgery after sterile draping, under image intensifier the 3 lines were drawn as proposed by Gore and Yeung [9] and point of entry marked. After local anesthesia with 1% Lignocard under mild conscious sedation with injection Fentanyl (1 μg per kg body weight) and injection Midazolam (0.01–0.02 mg per kg body weight), a stab incision was given and a 25-cm-long 18G needle was inserted under C-arm to reach the predetermined annular entry point at medial pedicle line on posteroanterior (PA) and posterior vertebral line on lateral C-arm view. After further local anesthesia infiltration on the annulus, the needle was further inserted inside the disc to lie in the centre on PA view and in the posterior one third of disc in lateral view. Chromodiscogram was done with 1–2 mL of a mixture of injection Omnipaque (Iohexol 350 mg per 1 mL, GE Health Care, USA), saline and Inj Methylene blue (1% 10 mg per mL, Samarth Life Sciences, India) in ratio of 2:1:2 mL and findings noted.

The dilator and sleeve followed the guide wire. The monoportal transforaminal endoscope (Karl Storz, Germany; 3.6-mm working channel, 180-mm length) was then inserted and the procedure started as per the inside-out technique as described by Gore and Yeung [9]. Initial step included subannular decompression to create a working space. Then the scope was shifted more posteriorly to the posterior annulus and posterior longitudinal ligament (PLL) and the pathology was visualized from inside out. The presence of incarcerated degenerated disc fragments in the annular layers was confirmed in all the cases. Only 2 patients had evidence of additional neovascularity under vision during surgery but their MRI did not show any hyper intensity zone preoperattively. The degenerated stained disc fragments were cleared from the posterior annular area using endoscopic forceps and the disc explored for further degenerated loose fragments. The removed fragments were sent for histopathologic study.

Neovascularity which was seen as reddish areas within the posterior half of white annulus were cauterized with 4-MHz high-frequency radiofrequency probe under vision in those 2 patients. After adequate hemostasis was ensured, the procedure was completed with one skin suture and patients transferred to the ward. No platelet rich plasma (PRP) plug or other adjuncts to promote annular healing or annular closure methods were used. They were mobilized immediately as per our surgical protocol.

Postoperative clinical assessment was done with specific emphasis on previous leg pain, burning, any new neurogenic deficits, walking, sitting, and standing time and were recorded. Postoperative MRI was done and assessed for the completion of the intended procedure. They were discharged the next day of surgery. Back care and spine nerve flossing exercises were advised. Lumbosacral corset was given to all patients as a precaution for 4 weeks. They were regularly followed up at 1, 3, 6, and 12 months and further after which the same preoperative assessment test battery of spinal flexion range, VAS leg score, modified ODI and ASIA scoring for neuro deficits were checked and recorded.

Long-term postoperative MRI examination at final follow-up was obtained too in consenting patients. These follow-up MRIs were assessed specifically on the integrity and status of the annular repair. Long-term follow-up was possible in 15 out of the total enrolled 16 patients.

None of the patients had any previous radicular pain except one patient with occasional partial radiation and paraesthesia at an average of 4 months postoperatively. A few experienced occasional episodes of back pain on a few instances initially that did not disturb their ADL within the 3-month follow-up. Nearly all had preoperative activities of daily living (ADL) at final follow-up except one patient who continued to complain of pain but only on working and travel. The average follow-up period was 53.5 months with a maximum of 102 months (Figure 2).

The patients had a full free spine flexion range for their age and prior movement range at final follow-up. No further discal or foraminal injections were given or any intervention done at the index level after the transforaminal endoscopic procedure. There were no complications like further worsening of pain or neurologic deficit, infection, and dural injury.

The average leg pain VAS had decreased substantially from 8.2 to 2 by 3 months postoperatively. The mean VAS for leg pain was 0.3 at final follow-up. One patient had undergone instrumented fusion elsewhere for backpain and difficulty in ADL 4 months after index procedure and was lost to final follow-up (Figure 3).

The motor and sensory neurologic deficits showed increasing recovery at an average of 12 weeks average (range, 8–14 weeks) and continued to show improvement over time (Table 1).

At the same time, the modified ODI scores had decreased and improved from 50.7 to 21 at an average of 3 months postoperatively. At final follow-up the modified ODI scores were only one on average (range, 0–3) (Figure 4).

A senior surgeon aged 65 years had been suffering from left radiculopathy and burning in L5 root area that was worsening over time and increasingly limiting his professional work and ADL for past 4 years. Multiple consultations had been obtained from many hospitals with around 4 MRI scans all of which showed a mild disc bulge on the right side, opposite the patient’s left-sided symptoms. He had been subjected to all nonoperative treatments and psychiatric evaluation too. The condition worsened to an extent that he could not finish his meal sitting and drive too. All the delay and suffering happened due to compressive lesion on all the previous 4 MRIs and the symptom side did not correlate to the mild disc bulge seen on the opposite side (Figure 5).

After clinical examination with the senior author that clinically confirmed left L5 radiculopathy with deficit, a CT discogram was suggested. With informed consent, the procedure was performed according to the established discogram protocol but without a control adjacent disc injection. The intraoperative C-arm picture after L4–5 discogram showed a posterior epidural dye leak and also to the left side traversing root (Figures 6 and 7).

The postdiscogram CT scan confirmed the dye spread to the left L5 traversing root and none to the right side (Figures 8 and 9).

After the injection, the patient experienced temporary relief from left-sided symptoms for 3 weeks. Once the pain returned, endoscopic annular debridement and removal of the intervening degenerate disc material under local anesthesia was offered to him and proceeded with. Postoperative MRI confirmed the adequacy of the intended procedure (Figure 10).

He was on regular spine care exercises and was reviewed regularly. At last visit 8 years and 6 months after the endoscopic surgery, he did not have any radicular pain and had normal ADL and was practicing his profession as a surgeon. The MRI at 8.5 years posttransforaminal endoscopy showed evidence of annular fibrosis and healing on the left side (Figure 11).

The treatment of compressive disc lesions with MRI proven nerve compression is well established and with predictable results. In the lumbar disc, high prevalence of morphologic changes due to ageing are also found without any symptoms [10]. Age-related changes occur from the inside out [11] and progress over many years [12]. There is a subset of patients with disabling pain, burning and deficit without any compression on MRI. The causative lesion of pain can be detected on MRI only in about 50% of the studied patients [13,14].

Abnormalities detected on MRI can be asymptomatic too, with studies showing that 30% of people who have never had spinal symptoms will have an abnormal MRI of the lumbar spine [15,16]. Back pain is multifactorial, with nociceptors within degenerate discs [17], neuropathic pain [18], and psychosocial factors [19] all contributing to the patient’s symptoms. Recalcitrant pain on the other hand is associated with discrete structural changes in the peripheral anulus [20] and vertebral endplate [21].

The main pathology that is described in these noncompressive symptomatic discs is a toxic annular tear or ulcer causing chemical radiculitis and HIZ due to neovascularity and granulation tissue. Annular tears are present in more than half adult patients and are invariably present in the elderly normally [22]. Annular tears can happen from outside in, where they have a good chance of healing as the periphery of the annulus has good blood supply and high proportion of cellular elements. In contrast the tears that happen from within inside out cannot heal as healing is hindered by the presence of the interposed degenerated disc material within the layers and lack of blood supply. They tend to progress over time, with repetitive injury and can reach the PLL or epidural space where they form toxic annular tears. These tears by virtue of their nonhealing nature are a conduit for neovascularity into the inner layers of the annulus and outside leak of chemical mediators of inflammation produced by disc degeneration.

As posterolateral aspect of the annulus fibrosus (AF) has a greater content of vertically oriented fibers there is focal weakness, which probably explains why most annular fissures are at the posterior or posterolateral aspect [23]. There are 3 main factors that contribute to annular tear pain—mechanical, chemical, and immunogenic. Disc proteoglycans are highly negatively charged and when they leak out through the chronic annular ulcers, they cause radicular pain referred to as chemical radiculitis. The extruded disc material and chemical byproducts of disc breakdown have high antigenicity and elicits production of interleukins, tumor necrosis factor alpha, substance P and cytokines. Chemical radiculitis over time can cause motor and sensory deficits. Based on study by Marshall et al. [24], McCarron et al. [25] first put forth the idea that a torn annulus and disc material causing inflammation without physical nerve root compression could cause low back and or radiating lower limb pain. Leakage of chemical mediators or inflammatory cytokines into epidural space through annular tear might be the primary pathophysiologic mechanism of radiating leg pain in patients with no disc herniation on MRI [1,26]. There is ample evidence for chemical radiculopathy to produce neurologic deficit [1,2,24]. The use of copious irrigation during the transforaminal surgery helps in washing out the local high concentration of chronic inflammation chemical mediators and decreasing the patient’s symptoms. Once this chemical irritation was stopped, this led to the neurologic recovery and pain relief for our patients. Nucleus pulposus has been shown to induce axonal degeneration, myelin oedema, and reduce nerve root conduction velocity [2,26]. Transforaminal endoscopic mechanical removal of the interposed degenerative nucleus helps in reducing the neural inflammation and degeneration giving good bed for the post op annular repair to proceed.

Discography in its history has had its ups and downs with conflicting reports [27,28]. Now, it has been accepted as a valuable tool in the investigation of discogenic back pain with clear guidelines on procedure and standardized reporting [29]. Systematic review has showed that lumbar provocation discography performed according to the International Association for the Study of Pain criteria may be the only tool for evaluating chronic lumbar discogenic pain and chemical radiculitis. CT discography procedure done in our patients were in accordance with the above guidelines. Currently, there are no noninvasive investigations to demonstrate or prove chemical radiculitis other than FAD.

Since Aprill and Bogduk [30] described a HIZ in 1992, positive correlation between HIZ and degree of annular disruption was observed in many studies but were not in some. At best nowadays, HIZ can be considered as an unreliable marker for discogenic back pain but can be a tool to suggest discogram as the next logical step of low back pain (LBP) diagnosis. A recent meta-analysis of 11 studies shows a strong relationship between the HIZ and pain reproduction and that HIZ can be an effectively predict discogenic LBP [3]. Presence of HIZ on MRI was only suggestive of discogenic LBP and not radiculopathy associated with deficits. In our limited series, there was no MRI evidence of HIZ in any of the patients.

Pain is a physiologic symptom and the current noninvasive radiologic investigations that rely on anatomy can neither always prove nor quantify it. None of the studies on discogenic LBP where patients were treated by transforaminal endoscopy have included prior CT discography to confirm their diagnosis [31,32]. In all our patients, postdiscography CT scan confirmed the dye spread to the involved nerve and side with a 100 % concordance. In addition, in many of our patients in addition to the cardinal lesion of radial annular tear, there were evidence of peripheral circumferential tears but these were not leaking dye outside the annulus.

Since Yeung and Gore [33] described toxic annular ulcer first in 2011 as an annular lesion which is symptomatic and characterized by pain-sensitive granulation tissue within the tear, attention has been drawn to the endoscopic treatment of these lesions which in conventional open posterior surgery was fusion of the spinal segment. Endoscopic laser to seal tears, other techniques like the Discseel, Xclose, and INclose implants, modified sutures, annular anchors etc. were not used in any of our patients. Biologic augmentation of the repair with injection of PRP plug in the annular defect without annular repair also was not done [34].

Healing of the AF is a complex and time-consuming process that lasts from many months to 2 years. This continuous process is influenced by various factors as it has limited blood supply and less cellularity. Factors that influence annular healing are as follows: (1) Age and overall health—nutrition, exercise, and underlying comorbid conditions. (2) Smoking and other factors like body mass index and avoiding prolonged sitting, excessive twisting, and loading strain. (3) Extent of intraoperative annular damage.

The size of the annular defect can affect healing outcomes and recurrence rates [35]. Systematic review and meta-analysis show that annular defect width after lumbar discectomy is an underreported modifier of patient outcome. Risk for symptom recurrence and reoperation is higher in patients with large versus small annular defects following lumbar discectomy [36]. Smallest surgical footprint as in monoportal transforaminal endoscopy with less than 1 cm has the best chance of annular healing in contrast to open or other endoscopy assisted interlaminar surgeries.

In our study, these patients underwent the classic inside-out transforaminal endoscopic disc procedure in 3 main steps each addressing the 3 main pathologies namely—physically removal of intervening degenerate disc material in the annulus under vision, Radiofrequency cauterization of any neoneurogenesis or neovascularity and disc lavage of the pathogenic chemicals released during degeneration [37]. Continued repair and prevention of degeneration require long-term remodeling and host cell infiltration, extracellular matrix degradation and synthesis, contributory inflammation. The stages of annular repair bear great similarity to general stages of wound healing. The ideal outcome of biologic annular repair is to regenerate a fully functioning intervertebral disc with contained hydrated nucleus pulposus within a uniform AF with continuous, aligned fibers [38].

Our study is the only long-term follow-up of patients with noncompressive painful discs with deficits treated with transforaminal endoscopic procedure showing definite clinical utility and annular healing in spite of not using any annular healing adjuncts and sticking only to our surgical protocol of debridement of annulus of the degenerated disc material and intradiscal lavage. The average follow-up of 53.5 months can be considered nearly long term. None of our patients had any disc recurrence at final follow-up.

In our study, nearly all patients at final follow-up had full standing flexion range of motion. This is in contrast to the published finding that there is a trend toward spinal stiffening with the increasing degeneration. Concentric and radial tears had no effect on the spinal flexibility [39].

Analysis of the last follow-up MRI shows near reconstitution of the annular margins with fibrosis, no nerve compression and no further worsening of annular signal on T2-weighted images. It has been reported that in patients hyperintensity on T2-weighted magnetic resonance images and enhancement of annular tears alone could not be used to determine the acuity of annular tears [40]. In the last follow-up MRI of our operated patients, the axial T2-signal protocol did not show any increased hyperintensity in the annulus indicating that fibrous healing had taken place. There was no disc reherniations in our series. This observation has so far not been reported in literature and also serves as a proof of concept for establishing annular healing in disc surgery. When combined with the newer annular healing adjuncts like PRP and other repair methods in future the results can only be expected to improve further.

Local anesthesia for transforaminal endoscopic spine surgery has already stood the test of time and only in a few countries in the world it is practiced under general anesthesia but with intraoperative neuro monitoring needing considerable resources. In our surgery under local anesthesia, patient serves as the biological live neuromonitoring and at the same time many risks involved with full general anesthesia are avoided. These patients do not need any bladder catheterization and are mobilized within an hour of surgery to the rest room. Other key advantages include early return to work and sports and safety for the elderly with multiple co morbidities and high risk of general anesthesia [41].

Limitation of our study include being a retrospective case series with lack of randomization, single-surgeon series, lack of blinding, and low in numbers. These type of procedures in these patients with such a difficult to prove diagnosis cannot have any other group of patients to compare. Results of HIZ causing discogenic back pain and its transforaminal endoscopic management though proven in literature cannot be used as comparison to this cohort of patients who have no abnormality on MRI. In this type of patients, it is only natural that the numbers are low due to their relative paucity. Further multicentric studies with pooling of data from various surgeons can give more validity to our management protocol.

Our study is an exclusive and currently the only one that has objectively proved the treatment of symptomatic annular tears with chemical radiculopathy by transforaminal endoscopic treatment under local anesthesia with long-term follow-up.

Treatment of these previously intractable complaints must be guided by better understanding of the pathology and attention surgically to the essential lesions in noncompressive disc with radiculopathy after CT discogram confirmation. For these patients, one can expect good sustained relief after transforaminal surgery under local anesthesia.