The role of transforaminal nerve block in the treatment of lumbar disc herniation and spinal canal stenosis

INTRODUCTION

Disc herniation is widely known as the leading cause of lumbar and leg pain restraining one’s mobility and, far worse, unable to care for themselves and perform the routine activities of daily living.^[1] Moreover, lumbar disc herniation (LDH) and lumbar central spinal stenosis (LCSS) are two main factors responsible for lower back pain in older people, where LCSS can also be due to LDH.^[2,3] Most LDH develop on the L4-5 or L5-S1 levels.^[4,5] In addition, younger individuals are at higher risk of recurrent LDH.^[6] On the other hand, lumbar canal stenosis (LCS) is described as progressive spinal canal narrowing with nerve root impingement resulting in degeneration, which is most commonly reported in the older population. Furthermore, patients with LCS often suffer from intermittent claudication, which is the main diagnostic feature.^[7] Pain resulting from these conditions is usually the trigger to seeking medical care.

Given that there is no cauda equina syndrome nor progressive neurologic deficit, an elective lumbar disc surgery can be performed when the pain persists for a minimum of 6 weeks following non-operative treatments.^[8] However, even with a success rate as high as 92–98%, studies revealed that there is no statistically significant difference between operative and non-operative treatment outcomes in the long run.^[8] Therefore, longitudinal evaluation on 7–20 years of follow-up showed that satisfactory findings were only reported in 64% of study patients.^[9] Nevertheless, the previous evidence reported that it is not always necessary to perform surgery in the cases of LCSS or LDH.^[10]

Many studies proved the efficacy of transforaminal nerve block with rapid pain relief as a treatment for disc herniation. It became the main treatment administered for lumbar and leg pain due to LDH.^[11-14] Lidocaine is mostly used as a nerve block with its rapid onset of action, efficacy, and duration, which can be administered alone or combined with steroids for these conditions’ treatment. However, there are still contrasting findings on which treatment strategy is sufficient.^[2] Nevertheless, it also has some drawbacks, including the dependence on the operator’s expertise when injected blindly and accidental injuries to neighboring nerves or vessels. Therefore, it is important to evaluate its effectiveness and drawbacks.^[1] To better illustrate this point, this study aimed to assess patients undergoing transforaminal nerve block for LDH and LCS management.

MATERIALS AND METHODS

RESULTS

A total of 440 patients presented to the hospital suffering from the lower back pain from either LDH or LCS and underwent transforaminal nerve blocks during the study period. Their clinical and demographic data are presented in [Table 1]. The participants were 18–96 years old, with a mean age of 54.2 ± 14.9 years. Women were slightly predominant compared to men (54.3% vs. 45.7%). The number of patients who underwent transforaminal nerve block was almost similar during the three years, with the highest percentage in 2021 (39.5%). The causes of seeking treatment mainly were due to LCS (50.7%) followed by LDH (47.3%), 2 cases had both diagnoses, and the others had different etiologies such as degenerative disease with scoliosis and micro-decompression. [Table 2] shows the distribution of the sites with the highest proportion in the L4-L5 level (38.9%), followed by L4-L5 and L5-S1 levels (28.2%) and L5-S1 level (17.5%). The visual analog scale (VAS) pain score was highest on the pre-injection time point (7.1 ± 1.1) and decreased after the injection to reach 2.7 ± 1.04 after 6 months. Similarly, the Oswestry Disability Index was high during pre-injection (64.9 ± 7.5) and decreased to 19.3 ± 16.2 only after 1-day post-injection and 13.2 ± 3.8 after 6 months. A total of 393 patients (89.3%) who underwent transforaminal nerve block had significant improvement, while 5.7% had micro-decompression and 5% had microdiscectomy.

Repeated measures ANOVA showed that the mean VAS pain score was significantly different between time points (F [2.434, 951.509] = 2054.537, P < 0.0001). Furthermore, Bonferroni post hoc showed that the VAS pain score was statistically significantly decreased from pre-intervention to 1 day, 3- and 6-month post-intervention, and even between all the post-injection periods. As for the Oswestry disability index over time, the mean also was significantly different between time points (F [2.007, 780.713] = 9612.77, P < 0.0001), yet no difference in the post hoc analysis between 3 months post-intervention and 6 months post-intervention (0.049 [95% CI, −0.139–0.237) mg/L, P = 1) [Figure 1].

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Figure 1:

Visual analog scale pain score and Oswestry disability index over time (P < 0.0001).

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DISCUSSION

In patients suffering from lower back and leg pain, the etiology is usually due to LCS, intervertebral disc protrusion/ extrusion, and intervertebral disc degeneration.^[15] Pain management is essential in the treatment of these patients until disease resolution. Transforaminal nerve blocks as a minimally invasive approach were proven in this study to be an effective treatment for these patients with improved pain in the short term. The transforaminal epidural injection was reported to be a safe and effective treatment module as a non-surgical treatment for LCS and LDH.^[16] Many mechanisms have been described, such as that the corticosteroids stop the arachidonic acid production resulting in the inhibition of the pain-generating pathway or directly relieving central pain sensitization. Another possibility is that the nerve roots stretch due to injections in the epidural space, causing the lysis of neural adhesions, with more pain relief. Alternative hypotheses reported cell membrane stabilization, enhancement of neuronal blood flow and washing out different inflammatory mediators such as interleukin-1 and tumor necrosis factor.^[17]

Findings suggested a positive effect, as almost all patients suffering from pain secondary to LDH and LCS and underwent transforaminal nerve block had significant improvement in the short-term phase (less than a day) without any reported complications. Literature reported three different modalities of epidural steroid injections: Caudal, requiring a greater volume of medication, and interlaminar, which delivers near the site desired. The third modality is transforaminal, which is the most preferred modality because it is target-specific and requires a smaller amount of administrated treatment to act on the pathology.^[18] In addition, no additional complications were recorded in our sample. The previous evidence reported an association between corticosteroid use and possible complications, including higher blood glucose levels in diabetic cases, yet reported a higher absorption rate of extruded hernias.^[19] This was aligned with the previous literature where the epidural block has been proven effective and used in treating acute pain, yet, its long-term effect is still controversial.^[20]

A previous Chinese study compared patients receiving either lumbar transforaminal epidural block (LTEB) or simple, comprehensive treatment (physiotherapy, massage, and traction) to assess its efficacy in treating low back pain. Findings showed that the proportion of women was higher than men in both groups (60.6% in the LTEB arm and 57.8% in the controls), which aligns with our results.^[21]

Present findings reported the etiology behind the treatment was mostly due to LCS (50.7%) followed by disc bulge (47.3%) were sites with the highest proportion in the L4-L5 level (38.9%), followed by L4-L5 and L5-S1 levels (28.2%) and L5-S1 level (17.5%). L4-5 decompression is necessarily combined with L5-S1 foraminal enlargement in L5 radiculopathy caused by the double crush at the central L4-5 and foraminal L5-S1 levels.^[22] The L5-S1 foraminal stenosis, also known as lumbosacral foraminal, presents distinct anatomical and functional characteristics given to the lumbosacral junction being more prone to major loading from the trunk. Given its pathology, the risk of narrowing of the canals in the spine is mainly in the lower lumbar segments. Mostly involving the described levels in our findings, such as the L5 nerve root (75%) in addition to the L4 root (15%).^[23] However, previous evidence highlighted that on the level of lumbosacral junction, the cause of L5 nerve root compression is usually extraforaminal LDH, accounting for 1–12% of total LDH, or stenosis caused by reduced L5-S1 disc height.^[24]

During the reduced pain period, the patients should gradually increase their activities and start simple exercises for muscle toning and back strengthening. After the procedure, many precautions must be respected: (a) It is important that someone else drive the patient home, (b) walking is allowed right after, and avoiding lifting heavy objects, bending the back, sitting for a long time or on the floor, and (c) the patient can start physiotherapy after 2 days from the procedure.^[25]

Our descriptive study has some limitations, such as the cross-sectional design, which is less potent than a cohort study. In addition, the information has been gathered from a single center, so the results cannot be generalizable.

CONCLUSION

This study showed that transforaminal nerve blocks were found effective as a temporary alternative treatment with proven efficacy in quick pain relief. Most benefits are described in the immediate or early phase after the injection.

AUTHORS’ CONTRIBUTIONS

YS confirms responsibility for the study conception and design, data collection, analysis and interpretation of results, and manuscript preparation. YKS and ZR did all statistical analysis and interpretation, writing of the results. BT contributed to the final writing of the research paper. All authors have critically reviewed and approved the final draft and are responsible for the manuscript’s content and similarity index.

ETHICAL APPROVAL

Ethical approval was obtained from Al-Sharaf Orthopedic and Spine Specialist Center with the following approval number ALSOSC/1796, dated 25 December 2018.