Comparative analysis of contrast distribution in cervical epidural steroid injections utilizing a modified paramedian interlaminar approach with varied needle tip positions: A randomized controlled trial

BACKGROUND

Recent advancements in cervical interlaminar epidural steroid injections have given rise to the modified paramedian interlaminar (mPIL) approach. The objective of this study was to perform an analysis of the contrast spread pattern within the cervical epidural space, taking into account different needle tip positions in the mPIL approach.

METHODS

A total of 48 patients were included in the study and randomly assigned to either the medial or lateral group based on the needle tip's position in the anterior-posterior view. The primary outcome measured was the contrast flow under fluoroscopic visualization. As a secondary outcome, we analyzed the location of the needle tip position in both lateral and contralateral oblique views. Clinical effectiveness was assessed by measuring pain intensity and functional disability post-procedure.

RESULTS

Significant disparities were noted in the ventral distribution of contrast between the medial and lateral groups. In the lateral images, needle tips in the lateral group were positioned more ventrally compared to those in the medial group. Both groups exhibited statistically significant improvements in neck and radicular pain, as well as functional status, 4 weeks after treatment, with no significant differences between them.

CONCLUSIONS

Our results suggest that the ventral dispersion of contrast material during cervical interlaminar epidural steroid injections using the mPIL approach may vary depending on the needle tip location.

[Injection treatment for cervical and lumbar syndromes : Special infiltration techniques]

Minimally invasive injection treatment is indicated particularly in cases of treatment-resistant, painful degenerative alterations of the cervical and lumbar spine, intervertebral disc displacement and radicular syndrome. Through the injections and the supplementation with further conservative, e.g., physical therapy and activating measures, the vicious circle of neural irritation and muscle tension and sympathetic nerve reactions can be interrupted.

Interlaminar versus transforaminal epidural steroid injections: a review of efficacy and safety

Spine intervention is an important treatment option for the management of spinal pain, and the numbers of the most representative epidural steroid injection (ESI) procedures performed are expected to increase significantly in the future along with increased life expectancy and the increasing prevalence of spinal disorders. Therefore, it is important to understand the efficacy of ESIs according to each spinal disorder they are administered to treat, and one must be familiar with the possible complications. In fact, although numerous ESI-related articles have been published, there is still considerable controversy regarding the efficacy of ESI procedures. Furthermore, due to the rarity of serious complications, most instances have been recorded in the form of case reports. In this article, we aimed to review the indications of cervical and lumbar ESIs and to compare interlaminar ESI (ILESI) and transforaminal ESI (TFESI) techniques in terms of analgesic efficacy, possible complications, and safety profiles. This article includes opinions based on the authors' experience with ESI indications and efficacy, and presents practical tips for coping with specific situations related to each complication. By combining the dedicated anatomical understanding of radiologists with image-guided interventions, ESI is expected to stand out in the rapidly expanding field of spine intervention.

2. Cervical radicular pain

INTRODUCTION

Cervical radicular pain is pain perceived in the upper limb, caused by irritation or compression of a cervical spine nerve, the roots of the nerve, or both.

METHODS

The literature on the diagnosis and treatment of cervical radicular pain was retrieved and summarized.

RESULTS

The diagnosis is made by combining elements from the patient's history, physical examination, and supplementary tests. The Spurling and shoulder abduction tests are the two most common examinations used to identify cervical radicular pain. MRI without contrast, CT scanning, and in some cases plain radiography can all be appropriate imaging techniques for nontraumatic cervical radiculopathy. MRI is recommended prior to interventional treatments. Exercise with or without other treatments can be beneficial. There is scant evidence for the use of paracetamol, nonsteroidal anti-inflammatory drugs, and neuropathic pain medications such as gabapentin, pregabalin, tricyclic antidepressants, and anticonvulsants for the treatment of radicular pain. Acute and subacute cervical radicular pain may respond well to epidural corticosteroid administration, preferentially using an interlaminar approach. By contrast, for chronic cervical radicular pain, the efficacy of epidural corticosteroid administration is limited. In these patients, pulsed radiofrequency treatment adjacent to the dorsal root ganglion may be considered.

CONCLUSIONS

There is currently no gold standard for the diagnosis of cervical radicular pain. There is scant evidence for the use of medication. Epidural corticosteroid injection and pulsed radiofrequency adjacent to the dorsal root ganglion may be considered. [Correction added on 12 June 2023, after first online publication: The preceding sentence was corrected.].

Percutaneous Spinal Interventions for Chronic Pain Management

Chronic neck and back pain are two of the most common and disabling complaints seen in primary care and neurology practices. Most commonly these come in the form of cervical and lumbar radiculopathy, lumbar spinal stenosis, and cervical and lumbar facet arthropathy. Treatment options are widespread and include nonpharmacological, pharmacological, surgical, and interventional options. The focus of this review will be to discuss the most common interventional procedures performed for chronic cervical and lumbar back pain, common indications for performing these interventions, as well as associated benefits and risks. These interventions alone may not suffice to improve the quality of life in those suffering from chronic pain. However, an understanding of the interventional pain options available and the evidence behind performing these interventions can help providers incorporate these into a multimodal approach to provide effective pain management that may allow patients an improved quality of life.

Evaluation of lung function and clinical features of interlaminar cervical epidural steroid injections: a randomized controlled trial

OBJECTIVE

Interlaminar cervical epidural steroid injections (ICESIs) are commonly used to treat axial neck pain and cervical radicular pain. However, local anesthetics can spread to and block the phrenic nerve and upper segments of the thoracic spinal cord where the sympathetic innervation of the lungs emerges. Therefore, changes in lung function may occur following ICESIs.

METHODS

The primary outcome measure was the pulmonary function test (PFT) result 30 minutes before and after ICESI with ropivacaine (0.1875% or 0.25%). The secondary outcome measure was the comparison of the pain scores and functional disability between the two concentrations of ropivacaine 4 weeks after the ICESIs.

RESULTS

Fifty patients were randomly assigned to either the R1 (0.1875% ropivacaine) or R2 (0.25% ropivacaine) group. No significant difference was observed between the pre-ICESI and 30-minute post-ICESI PFT results within each group, and no difference was observed between the two groups. After 4 weeks of treatment, both groups showed a significant decrease in pain scores and functional disability; however, no significant differences were observed between the two groups.

CONCLUSIONS

This study showed no significant change in lung function after ICESIs in either group and no local anesthetic concentration-based difference in the clinical efficacy of the ICESIs.

Clinical Efficacy of Epidural Injections of Local Anesthetic Alone or Combined with Steroid for Neck Pain: A Systematic Review and Meta-Analysis

Aims

To compare the effectiveness of cervical epidural injections of local anesthetic with vs. without a steroid.

Methods

Three databases (PubMed, Embase, and Cochrane library) were used to search and assess all clinical randomized controlled trials regarding the clinical efficacy of epidural injections from January 01, 2009, to October 31, 2020. Cochrane review criteria and the Interventional Pain Management Techniques-Quality Appraisal of Reliability and Risk of Bias Assessment instrument were used to evaluate the methodologic quality of the included studies. Qualitative and quantitative analyses were performed according to best evidence synthesis principles and by single-arm meta-analysis, respectively.

Results

Based on the search criteria, 4 RCTs were qualitatively and quantitatively analyzed in the single-arm meta-analysis. Treatment with lidocaine alone or with the steroid resulted in decreases of 4.46 and 4.29 points, respectively, in pain scores and of 15.8 and 14.46 points, respectively, in functional scores at 6 months. Similar trends were observed at the 1-year follow-up: pain scores decreased by 4.27 and 4.14 points, while functional scores decreased by 15.94 and 14.44 points in patients with neck pain who received lidocaine without or with the steroid, respectively. In the 3 studies that reported 2-year follow-up data, patients with neck pain treated with lidocaine or lidocaine + steroid showed 4.2- and 4.14-point decreases, in pain score and 15.92- and 14.89-point decreases, respectively, in functional scores.

Conclusions

The studies showed level I (strong) evidence for short- and long-term improvements in pain relief and functionality with cervical epidural injections of local anesthetic alone or with a steroid in the management of neck pain.

Comparison of contralateral oblique view with the lateral view for fluoroscopic-guided cervical epidural steroid injection: a randomized clinical trial

BACKGROUND

Cervical epidural steroid injection is associated with rare but potentially catastrophic complications. The contralateral oblique (CLO) view may be a safe and feasible alternative to the lateral (LAT) view for fluoroscopic-guided cervical epidural steroid injection. However, evidence for the clinical usefulness of the CLO view for cervical epidural steroid injection is lacking. We assessed the clinical usefulness of the CLO view for cervical epidural steroid injection in managing cervical herniated intervertebral discs.

METHODS

Patients were randomly assigned to receive fluoroscopic-guided cervical epidural steroid injection under LAT view or CLO view at 50±5° degrees groups. The primary outcome was the needling time comparison between the two groups. Secondary outcomes were comparison of first-attempt success rate, needle tip visualization and location, total number of needle passes, final success rate, crossover success rate and false-positive/negative loss of resistance. Complications and radiation dose were also compared.

RESULTS

The needling time significantly decreased in the CLO than in the LAT group. The first-attempt success rate was significantly higher in the CLO compared with the LAT group. The needle tip was clearly visualized (p<0.001) and located more often on (or just anterior to) the ventral interlaminar line (p<0.001) in the CLO than in the LAT group. There were significantly fewer needle passes (p=0.019) in the CLO than in the LAT group. There were no significant differences in the final success, crossover success, false-positive/negative loss of resistance or radiation dose between the groups. Two (5.9%) cases in the LAT group experienced complications.

CONCLUSION

The CLO view may be recommended for fluoroscopic-guided cervical epidural steroid injection, considering its better clinical usefulness over the LAT view.

Evaluation of Contrast Flow Patterns with Cervical Interlaminar Epidural Injection: Comparison of Midline and Paramedian Approaches

Background and objectives: The purpose of this study was to compare and to analyze contrast spread patterns between the paramedian and midline approaches to cervical interlaminar epidural injection (CIEI). Materials and Methods: We retrospectively enrolled 84 CIEI cases that had been performed for unilateral cervical spinal pain from April 2019 to April 2020. After 3 mL of contrast had been injected into the epidural space, fluoroscopic images were obtained. The CIEI was divided into a midline (Group M, n = 42) and a paramedian (Group P, n = 42) approach by anteroposterior imaging. The P Group was classified into a more medial (Group Pm, n = 26) and a more lateral (Group Pl, n = 16) group. Using ImageJ on an anteroposterior image, we assessed the grayscale brightness ratio of the ipsilateral or contralateral side of the vertebral body as well as the intervertebral disc space one level just above the needle location. We identified the dispersion of contrast into the ventral epidural space. Results: The grayscale brightness ratio was significantly higher in Group P than in Group M (p < 0.001). The incidence of ventral epidural spread in Group M was 57.1% versus 88.1% in Group P, which was significantly different (p = 0.001). Conclusions: The fluoroscopic CIEI finding in the paramedian approach predominantly showed an excellent delivery of the injectate to the ipsilateral side in comparison to the contralateral side. This showed a greater advantage in delivery toward ventral epidural space as compared to the midline approach.

Modification of the Cervical Transforaminal Epidural Steroid Injection Technique Based Upon the Anatomic Angle of the Superior Articular Process on MRI

Objective

A modification of the conventional technique for cervical transforaminal epidural steroid injection (CTFESI) has been developed. This technique may, theoretically, decrease the likelihood of the needle encountering the vertebral artery and spinal nerve. The approach uses angle measurements of the superior articular process ventral surface from the patient’s axial MRI as a guide for fluoroscopic set-up and needle trajectory. This report aims to compare contrast flow patterns of the modified approach with those of the conventional technique.

Design

Retrospective chart review and prospective blinded analysis of contrast flow patterns. Setting. Outpatient interventional physiatry practice.

Methods

A retrospective blinded qualitative review of fluoroscopic images was performed to compare contrast flow patterns of CTFESIs performed using the modified approach with those using the conventional technique. A detailed description of the modified approach is provided in this report.

Results

Ninety-seven CTFESI procedures were used for flow analysis. The modified approach resulted in a statistically significant greater percentage of injections with epidural flow: 69% [95% CI = 57–82%] modified approach vs. 42% [95% CI = 28–56%] conventional approach. The modified technique also showed a statistically significant higher percent of injections categorized as having an ideal flow pattern, that of predominate epidural and/or intraforaminal flow: 65% [95% CI = 52–78%] vs. 27% [95% CI = 14–40%].

Conclusions

A modification of the conventional CTFESI technique, developed for the purpose of improved safety, may provide superior contrast flow patterns when compared to the conventional approach.

[Application of image-guided injection for cervical and lumbar syndromes]

The X‑ray image-guided injection methods are an important tool for the treatment of cervical and lumbar pain syndromes. For the application of these methods it is necessary to have a differentiated consideration of cervical and lumbar pain syndromes. This leads to a decoding of complaints to assignable pain generators, which enables a targeted injection method. Depending on the origin of pain, injections are placed at the nerve root or the joints. Thus, the vicious cycle of pain can be stopped. A correct technical procedure is of enormous importance. Particular attention must be paid to the pharmacological effects and special complications. A monitoring and precautionary measures are mandatory.

Cross-sectional CT Assessment of the Extent of Injectate Spread at CT Fluoroscopy-guided Cervical Epidural Interlaminar Steroid Injections

Background Previous studies analyzed contrast agent spread during cervical interlaminar epidural steroid injections (CILESIs) by using planar fluoroscopy and reported wide variance of the rate of spread to the ventral epidural space (VES). Cross-sectional CT allows for direct viewing of contrast agent in the VES, providing improved spread assessment and thereby informing needle placement decisions when targeting pain generators. Purpose To determine the extent of injectate spread at CT fluoroscopy-guided CILESI, with particular attention to the VES and bilateral neuroforamina, by using cross-sectional CT. Materials and Methods This study reviewed 83 consecutive CT fluoroscopy-guided CILESIs at which a postprocedural cervical spine CT was performed (June 2016 to December 2017). All procedures used the same injectate (2 mL corticosteroid, 3 mL contrast agent). Postprocedural CT scans were reviewed for the presence of contrast within the VES, dorsal epidural space, ipsilateral neuroforamen, and contralateral neuroforamen in every cervical interlaminar level. Descriptive data are presented as frequencies or means. McNemar tests or hierarchical logistic models were used to assess associations between covariates and contrast agent spread to particular locations. Results The study cohort included 73 individual patients (59% women; 43 of 73) (mean patient age, 57.6 years ± 11.5 [standard deviation]). Mean number of levels of cranial spread were 0.6 level for VES, 1.9 levels for contralateral neuroforamen, 2.1 levels for ipsilateral neuroforamen, and 3 levels for dorsal epidural space. No VES spread in any level was found with 35% (29 of 83) of injections. VES spread was more likely to occur in the level of needle placement (43%; 36 of 83) than in other interlaminar levels (19.5%; 97 of 498; P < .001). Spread was more likely to occur in the neuroforamen ipsilateral to the needle approach compared with contralateral (P < .001). Conclusion Cervical interlaminar epidural steroid injections have injectate spreads with a mean of less than one level cranially in the ventral epidural space (VES) and approximately two levels in the neuroforamen. VES spread occurs more frequently at the level of needle placement and within the ipsilateral neuroforamen. © RSNA, 2019.

Cervical Epidural Steroid Injection: Parasagittal versus Midline Approach in Patients with Unilateral Cervical Radicular Pain; A Randomized Clinical Trial

Objective

To compare parasagittal interlaminar cervical epidural steroid injection (PSIL-CESI) and the classic midline interlaminar cervical epidural steroid injection (MIL-CESI) in terms of pain relief and functional improvement in patients with unilateral upper extremity radicular pain.

Methods

This was a randomized clinical trial being conducted in a single pain center in Tehran. Twenty-six patients were allocated into two groups of 13, undergoing either PSIL-CESI or MIL-CESI. After confirmation of radiocontrast spread in the epidural space by fluoroscopic guidance, dexamethasone 8 mg and bupivacaine 0.125% in a volume of 5 ml were delivered to the epidural space. Evaluation of functional state and pain intensity before and 1 month after the procedure was accomplished using the neck disability index (NDI) and the numeric rating scale (NRS) respectively.

Results

Demographic and baseline characteristics of the cases showed no significant statistical difference. Improvements in the NDI and the NRS were observed in both groups; meanwhile, improvements were more pronounced in the PSIL-CESI group as compared to the MIL-CESI group (P<0.001). With the PSIL approach the ventral spread of radiocontrast was significantly higher (38%) than with the MIL approach (0.7%) (P<0.001). All patients in PSIL group showed radiocontrast spread ipsilateral to the painful side and all patients in the MIL group showed a midline distribution of radiocontrast.

Conclusion

PSIL-CESI provides superior pain relief and improvement of functional disability in patients with unilateral upper extremity radicular pain in comparison to the classic MIL-CESI.

Clinical trial registry

IRCT20180524039816N1.

The Effectiveness of Fluoroscopically Guided Cervical Transforaminal Epidural Steroid Injection for the Treatment of Radicular Pain; a Systematic Review and Meta-analysis

Objective

Determine the effectiveness of fluoroscopically guided cervical transforaminal epidural steroid injection (CTFESI) for the treatment of radicular pain.

Design

Systematic review and meta-analysis.

Subjects

Persons aged ≥18 years with cervical radicular pain due to disc herniation or degenerative spondylosis.

Comparison

Sham, placebo procedure, or active standard of care treatment, excluding alternative versions of epidural steroid injection.

Outcomes

The primary outcome measure was patient-reported improvement in pain of at least 50% from baseline, assessed four or more weeks after the treatment intervention. Secondary outcomes included validated functional assessment tools and avoidance of spinal surgery.

Methods

Randomized or nonrandomized comparative studies and nonrandomized studies without internal control were included. Three reviewers independently assessed publications in the Medline, PubMed, and Cochrane databases up to July 2018. The Grades of Recommendation, Assessment, Development and Evaluation (GRADE) system was used to evaluate risk of bias and overall quality of evidence. A meta-analysis was conducted for comparative measures of effect and for within-group response rates if applicable.

Results

There were no studies with an internal comparison group (control group) meeting the review’s definition of comparison group. Therefore, comparative measures of effect were not calculated. In cohort studies, pooled response rates were 48% (95% confidence interval [CI] = 34–61%) at one month and 55% (95% CI = 45–64%) at three months.

Conclusions

Approximately 50% of patients experience ≥50% pain reduction at short- and intermediate-term follow-up after CTFESI. However, the literature is very low quality according the GRADE criteria, primarily due to a lack of studies with placebo/sham or active standard of care control comparison groups.

Dispersal Pattern of Injectate After Cervical Epidural Steroid Injection Evaluated With Magnetic Resonance Imaging

STUDY DESIGN

Prospective, nonrandomized, clinical study.

OBJECTIVE

Epidural steroid injections (ESIs) are an important diagnostic and treatment modality for spine pathology. The success of these injections has been attributed to the anatomic location reached by the injectate. This study evaluates injectate dispersal patterns after cervical interlaminar ESI using magnetic resonance imaging (MRI).

METHODS

Patients between the ages of 18 and 85 years with cervical radiculopathy were identified. After obtaining consent for study participation, a gadolinium-enhanced cervical ESI was administered via an interlaminar approach under fluoroscopic guidance. Study participants underwent a cervical spine MRI within 15 minutes of administering the injection. Craniocaudal dispersal and the presence or absence of circumferential dispersal was assessed.

RESULTS

The injectate dispersed a mean of 8.11 cm in the cranial direction, 6.63 cm in the caudal direction, and 360° circumferentially. No adverse events related to the ESI were reported.

CONCLUSIONS

Fluoroscopy-guided cervical interlaminar ESI resulted in nearly uniform circumferential dispersal within the epidural space with multilevel migration in the cranial and caudal directions. MRI is a safe and accurate tool to evaluate spinal injectate dispersal.

Ultrasound-Assisted Lumbar Interlaminar Epidural Dye Injection and Evaluation of Its Distribution by Anatomical Dissection

Background: Epidural steroid injections are frequently used to treat lumbar radicular pain. However, the spread of a solute in the epidural space needs further elucidation. We aimed at assessing the distribution of green dye in the epidural space after lumbar epidural injection on cadavers.

Methods: We performed ultrasound-guided injections of green dye between lumbar vertebrae 4 and 5 in 24 cadavers. The cadavers were randomly divided into group A and B according to the volume of injected dye; 3 ml in group A (n = 13) and 6 ml in group B (n = 11). Accuracy of the needle insertion and patterns and distributions of the spread were compared between the groups. After local dissection, we examined the spread of dye in dorsal and ventral epidural spaces and presented the distribution as whole numbers and quartiles of intervertebral segments. Mann-Whitney U Test was used to compare distribution of dye spread between groups A and B. Wilcoxon Signed-Rank Test was used to compare the spread of dye in cranial and caudal direction within the group. We considered P < 0.05 as significant.

Results: Data were obtained from all 24 cadavers. Median levels of dorsal cranial dye distribution in groups A and B were 2 and 4 (P = 0.02), respectively. In the dorsal caudal−2 and 2, respectively (P = 0.04). In the ventral epidural space cranial dye spread medians were−0 and 2 in groups, respectively (P = 0.04). Ventral caudal spread was 0 and 1, respectively (P = 0.03). We found a significant difference between cranial and caudal dye distribution in group B (P < 0.05). In group A the dye spread was bilateral. In group B cranial and caudal dye spread was observed.

Conclusions: Ventral dye flow was observed in 50% of injections. Bilateral spread of dye occurred in 63%, and more often in group A. Cranial spread was slightly higher than caudal spread in group A despite a smaller injected volume, and significantly higher in group B following a larger volume.

[Injection therapy for cervical and lumbar syndromes]

In cervical and lumbar pain syndromes special injections are key for effective pain therapy. Depending on the origin of pain injections are placed at the nerve root or the joints. Thus, the vicious cycle can be stopped. A correct technical procedure is of enormous importance. Because pharmacological effects and special complications are possible, monitoring and precautions are mandatory.

Fluoroscopically Guided Epidural Injections of the Cervical and Lumbar Spine

Advances in imaging and the development of injection techniques have enabled spinal intervention to become an important tool in managing chronic spinal pain. Epidural steroid injection (ESI) is one of the most widely used spinal interventions; it directly delivers drugs into the epidural space to relieve pain originating from degenerative spine disorders-central canal stenoses and neural foraminal stenoses-or disk herniations. Knowledge of the normal anatomy of the epidural space is essential to perform an effective and safe ESI and to recognize possible complications. Although computed tomographic (CT) or combined CT-fluoroscopic guidance has been increasingly used in ESI, conventional fluoroscopic guidance is generally performed. In ESI, drugs are delivered into the epidural space by interlaminar or transforaminal routes in the cervical spine or by interlaminar, transforaminal, or caudal routes in the lumbar spine. Epidurography is usually performed before drug delivery to verify the proper position of the needle in the epidural space. A small amount of contrast agent is injected with fluoroscopic guidance. Familiarity with the findings on a typical "true" epidurogram (demonstrating correct needle placement in the epidural space) permits proper performance of ESI. Findings on "false" epidurograms (demonstrating incorrect needle placement) include muscular staining and evidence of intravascular injection, inadvertent facet joint injection, dural puncture, subdural injection, and intraneural or intradiscal injection. ^©RSNA, 2016 An earlier incorrect version of this article appeared online. This article was corrected on December 22, 2016.

Can repeat injection provide clinical benefit in patients with cervical disc herniation and stenosis when the first epidural injection results only in partial response?

Epidural steroid injection (ESI) is known to be an effective treatment for neck or radicular pain due to herniated intervertebral disc (HIVD) and spinal stenosis (SS). Although repeat ESI has generally been indicated to provide more pain relief in partial responders after single ESI, there has been little evidence supporting the usefulness of this procedure. The purpose of this study, therefore, was to determine whether repeat ESI at a prescribed interval of 2 to 3 weeks after the first injection would provide greater clinical benefit in patients with partial pain reduction than intermittent ESI performed only when pain was aggravated. One hundred eighty-four patients who underwent transforaminal ESI (TFESI) for treatment of axial neck and radicular arm pain due to HIVD or SS and could be followed up for 1 year were enrolled. We divided the patients into 2 groups. Group A (N = 108) comprised partial responders (numeric rating scale (NRS) ≥ 3 after the first injection) who underwent repeat injection at a prescribed interval of 2 to 3 weeks after the first injection. Group B (N = 76) comprised partial responders who did not receive repeat injection at the prescribed interval, but received intermittent injections only for aggravation of pain. Various clinical data were assessed, including total number of injections during 1 year, NRS duration of <3 during 1 year (NRS < 3 duration), and time interval until pain was increased to require additional injections after repeat injection in Group A, or after first injection in Group B (time to reinjection). Groups A and B were compared in terms of total population, HIVD, and SS. In the whole population, HIVD subgroup, and SS subgroup, patients in Group A required significantly fewer injections to obtain satisfactory pain relief during the 1-year follow-up period. Group A showed a significantly longer time to reinjection and longer NRS < 3 than Group B did. Repeat TFESI conducted at 2- to 3-week intervals after the first injection in partial responders contributed to greater clinical benefit compared with intermittent TFESI performed only upon pain aggravation, with fewer TFESI sessions.