Introduction

Chronic low back pain is a highly prevalent public health problem and the leading cause of disability-adjusted life years (DALYs) globally (1,2). Although approximately 50 % of patients show improvement within the first year, a significant subgroup progresses to chronic refractory pain, the prevalence of which increases with factors such as age, smoking, and obesity (3,4).

Lumbar spinal stenosis is one of the most common causes of chronic refractory low back pain. It is estimated to affect millions of patients worldwide and is associated with a considerable clinical and economic burden, due to the complexity of its management and the need for advanced interventions (5).

Conventional treatment includes pharmacological therapy, physical rehabilitation, and epidural steroid injections (ESI), with variable efficacy that is often limited in duration (6). In this context, percutaneous epidural adhesiolysis using the Racz catheter has demonstrated greater efficacy than ESI in the management of lumbar radiculopathy; however, its long-term results remain heterogeneous and controversial (7).

In recent years, the development of steerable catheters has marked a significant technical advancement, as they allow for targeted placement in the anterior epidural space and facilitate access to specific anatomical regions for the selective administration of drugs and the mechanical lysis of adhesions. This increased precision could translate into better clinical outcomes; however, the available evidence regarding its impact, particularly on functional outcomes, remains limited (8).

Furthermore, most interventional pain studies have focused predominantly on reducing pain intensity, with less emphasis on assessing functional disability, a key component of the overall burden of the disease.

Therefore, the objective of this study was to evaluate the clinical efficacy, the temporal evolution of pain, and functional disability following navigable caudal epidural neuroplasty in patients with refractory chronic low back pain. In this way, the clinical and demographic factors associated with the therapeutic response were explored.

Materials and methods

Study design and participants

This study is a retrospective cohort conducted at the Pain Medical Center in Monterrey, Nuevo León. All data were obtained from the patients’ medical records.

Patients were included who had a diagnosis of refractory chronic low back pain (defined as pain lasting longer than 3 months) associated with lumbar spinal stenosis confirmed by magnetic resonance imaging, who did not show clinical improvement with conservative treatment or with previous epidural interventions, including transforaminal or caudal epidural steroid injections, and who underwent percutaneous epidural neuroplasty using a navigable catheter during the period from 2023 to 2024. All patients who met the criteria during the study period were included consecutively. The indication for the procedure was based on clinical-radiological correlation, without systematic performance of electrodiagnostic studies.

The exclusion criteria were: active systemic infection, infection at the injection site, uncontrolled diabetes mellitus, coagulation disorders, and a history of allergic reactions to local anesthetics, corticosteroids, or contrast media.

This study was conducted in accordance with institutional clinical protocols, was approved by the institutional ethics committee, and was carried out in accordance with the principles of the Declaration of Helsinki. The device used is a navigable epidural catheter system with regulatory approval in the United States (FDA). In the local setting, its use was carried out under institutional supervision and in accordance with current clinical protocols. Due to its retrospective design and the use of anonymous data, a waiver of informed consent was requested.

Technical aspects of navigable catheter neuroplasty

Using a navigable epidural catheter system (EDEN Controlcath® 18 mm, manufactured by JMT, Korea), it consists of a body with a lever and a tube designed for insertion into the epidural space. Its proximal end functions as a port for drug administration. The lever allows the operator to adjust the catheter’s direction for precise navigation and features a locking mechanism that allows the desired position to be fixed (9).

Recent publications have described the navigable neuroplasty technique (8,9). After sterile preparation of the area, the mid-sacral crest and the sacral hiatus—corresponding to the loss of continuity of the medial sacral crest—were identified, marking the midline (Figure 1A). The fluoroscope was adjusted until a true lateral view of the sacral hiatus was obtained, defined by the alignment of the greater sciatic notch or the acetabula, with the former being preferred. To identify the sacral hiatus, anatomical landmarks were marked in relation to the medial sacral crest, locating the hiatus at the intersection between the posterior wall and the floor of the sacrum (Figure 1B).

Next, the sacral hiatus was marked on the lateral view, and 5 cm was measured caudally to determine the entry point. A 1 % lidocaine solution was injected from the skin to the sacrococcygeal ligament, and an incision was made with a #11 scalpel to facilitate trocar insertion. Initial access was performed at a 45° angle until contact was made with the yellow ligament and a loss of resistance was felt; the angle was then reduced to 30° and advanced to the S3-S4 levels.

An epidurography was performed with 1-2 mL of contrast medium to confirm diffusion into the epidural space on anteroposterior and lateral views. Once the proper position was confirmed, an additional 5 mL of nonionic contrast was administered to identify filling defects and locate the sites for adhesiolysis. Subsequently, the needle was withdrawn, leaving the plastic sheath in place, and the navigable catheter was advanced to the S2 level.

The catheter was advanced to the affected nerve root, positioning the tip in the anterior epidural space at the subpedicular level (posterior edge of the vertebral body) on the lateral view. One milliliter of contrast was administered to confirm the position, followed by 5 ml of local anesthetic with a corticosteroid and subsequently 5 to 10 ml of 0.9 % saline solution. Finally, the catheter was removed, and its integrity was verified.

Racz exercises were prescribed during the recovery period. Following the procedure, periodic assessments of the patient’s perceived pain were conducted. The sequence of the procedure is shown in Figure 2.

Demographic data and outcome assessment

Prior to the procedure, all patients rated their pain using the Numerical Rating Scale (NRS), on a scale of 0 to 10 points.

Clinical variables included age, sex, body mass index (BMI), hypertension, diabetes mellitus, smoking, and alcohol consumption, which were obtained from medical records.

Pain intensity and its variation, measured using the NRS, were recorded at four time points: baseline (pre-procedure), immediate postoperative, at 3 months, and at 6 months. Adverse events and clinical follow-up were documented individually in the medical records.

Statistical analysis

Categorical variables were described using frequencies and percentages. Continuous variables were assessed for normality using the Shapiro–Wilk test, which revealed a non-normal distribution; therefore, nonparametric tests were used for comparative analyses.

Longitudinal comparisons between repeated measurements were performed using the Wilcoxon signed-rank test for paired samples. Effect size was estimated using Cohen’s d coefficient to quantify the magnitude of change in pain intensity and functional disability.

Interindividual variability was described using standard deviations of the differences between paired measurements.

A p-value < 0.05 was considered statistically significant.

Results

TAll patients completed follow-up and were included in the analysis. During the study period, 47 patients with refractory chronic low back pain (spinal stenosis, radiculopathy associated with disc herniation, and radiculopathy secondary to post-surgical fibrosis) who underwent percutaneous epidural neuroplasty with a navigable catheter were included. All patients completed follow-up and were included in the analysis (Figure 3).

The mean age was 64.4 ± 12 years, with a predominance of males (n = 30, 63.8 %). The average duration of the procedure was 64.0 ± 17.6 minutes. Systemic hypertension was the most common comorbidity (48.9 %), followed by diabetes mellitus (31.9 %) and obesity (27.7 %). Alcohol consumption and smoking were reported in 14.9 % and 8.5 % of patients, respectively. Most patients were classified as ASA II (61.7 %) (Table I).

Lumbar spinal stenosis was the most prevalent diagnosis (70.2 %), followed by radiculopathy associated with disc herniation (51.1 %) and post-surgical epidural fibrosis (29.8 %) (Table I).

Pain intensity, assessed using the numerical rating scale (NRS), showed a statistically significant decrease at all time points (p < 0.001). Comparison between the baseline measurement and the immediate postoperative period revealed a significant reduction (W = 25.5, p < 0.001). Additional reductions were observed between the immediate postoperative period and 3 months (W = 95.5, p = 0.041), as well as between 3 and 6 months (W = 47.5, p = 0.018) (Table II).

The effect size showed a large impact in the immediate period (d = 1.44), followed by a smaller effect between the immediate period and 3 months (d = 0.33), and a moderate negative effect between 3 and 6 months (d = −0.39) (Table II).

The interindividual variability in the analgesic response, expressed as the standard deviation of the paired differences, was 3.51 points between baseline and the immediate period, 3.26 between the immediate period and 3 months, and 3.25 between 3 and 6 months (Table II).

Longitudinal analysis of functional disability using the Oswestry Disability Index (ODI) showed a significant reduction throughout the follow-up period. The ODI decreased from 34.4 ± 4.0 at baseline to 16.7 ± 5.2 at 1 month, 16.3 ± 4.8 at 6 months, and 16.3 ± 4.9 at 12 months (Table III).

Paired comparisons revealed statistically significant differences from baseline at all time points (p < 0.001). The absolute reduction was −17.7 points at 1 month and −18.1 points at 6 and 12 months, equivalent to an approximate relative decrease of 52-53 % in functional disability.

No statistically significant differences were observed between ODI scores at 1, 6, and 12 months. The effect size was very large in the baseline vs. 1-month comparison (d ≈ 3.7) and remained high at 6 and 12 months (d > 4.0).

More than 90 % of patients achieved a clinically significant reduction in ODI (≥ 10 points), and a considerable proportion had reductions of more than 50 % from baseline.

Discussion

The results of this study show that percutaneous epidural neuroplasty using a navigable catheter is associated with a significant reduction in pain intensity for at least six months in patients with refractory chronic low back pain secondary to lumbar spinal stenosis.

The observed diagnostic heterogeneity reflects a real-world clinical scenario, which may influence the generalizability of the results.

Lumbar spinal stenosis is a common cause of refractory chronic low back pain, with an estimated prevalence of 11-39 % based on clinical and radiological criteria (10). Initial management includes conservative treatment, such as physical therapy, analgesic medication, use of orthoses, and epidural injections, with variable efficacy (11). In refractory cases, surgical intervention may be considered (12); however, comparative results between surgical and nonsurgical treatment have been inconsistent, and surgery is associated with reported rates of adverse events ranging from 10 % to 24 % (13-15).

On the other hand, surgery may not be the answer for all patients who do not improve with conservative measures. In fact, certain conditions such as degenerative lumbar spondylolisthesis have shown that surgical benefits may depend on the patient’s age, a finding that could be extrapolated to patients with lumbar spinal stenosis (16).

In this context, minimally invasive interventional therapies have gained prominence. However, there is limited evidence regarding the efficacy of percutaneous epidural neuroplasty with a navigable catheter in this population. The ability of these systems to access the anterior epidural space in a targeted manner and position themselves in the subpedicular region could represent a significant technical advantage, as it allows for a more precise intervention at the pathophysiological site of pain (8,9).

In our cohort, a significant reduction in pain intensity was observed at all follow-up points. The effect size was substantial in the immediate period, with a gradual decrease over time, while pain levels remained below baseline. This pattern suggests a sustained analgesic benefit, albeit with partial attenuation during the medium-term follow-up.

From a technical standpoint, the ability to consistently reach the anterior epidural space in 100 % of cases may have contributed to the observed results by optimizing the lysis of adhesions and the targeted distribution of drugs. This aspect represents a potentially significant difference compared to conventional systems without navigation capabilities.

The demographic data observed in this study are consistent with the previous literature. Systemic hypertension and diabetes mellitus were the most frequent comorbidities, which is consistent with reports describing similar prevalences in patients with lumbar spinal stenosis (17). Furthermore, it has been suggested that diabetes mellitus may be associated with a less favorable response to epidural interventions (18).

A key finding of this study is the significant and sustained improvement in functional disability, as assessed by the Oswestry Disability Index (ODI). The magnitude of the reduction, close to 50 % from baseline, exceeds the clinically important change (CIC) threshold, indicating clinically significant functional improvement. This result is consistent with the evidence that positions the ODI as a key outcome measure in assessing the impact of chronic low back pain (19,20).

The temporal pattern of functional improvement showed early recovery starting in the first month, followed by a stabilization phase without clinically relevant deterioration up to 12 months. This pattern, in contrast to the slight attenuation of the analgesic effect, has been previously described and may reflect additional mechanisms beyond analgesia, including improved mobility, reduced local inflammation, and modulation of peripheral and central sensitization (6,21-23).

The concordance between pain reduction and functional improvement supports a multidimensional clinical benefit, in line with current recommendations that emphasize the importance of assessing patient-centered outcomes, such as functionality and quality of life, in addition to pain intensity (24).

From a comparative perspective, the observed functional outcomes could be explained by the technical advantages of navigable systems over conventional epidural adhesiolysis with a Racz catheter. While traditional systems allow for less targeted lysis, navigable catheters facilitate selective access to the anterior epidural space, which could optimize both the mechanical intervention and drug delivery (18,25).

Despite these findings, the exact mechanisms by which navigable neuroplasty modulates refractory chronic low back pain have not been fully elucidated. Although a predominant mechanical component has been proposed, the available evidence remains limited (25).

Regarding safety, no relevant complications or adverse events were recorded during the procedure or at follow-up, supporting the safety profile of this technique in the studied cohort (7).

This study has limitations inherent to its retrospective design and relatively small sample size. Furthermore, the absence of a control group limits the ability to make direct comparisons with other therapeutic modalities. The lack of systematic electrodiagnostic studies constitutes an additional limitation of the study.

Future prospective, multicenter studies with larger sample sizes will be necessary to confirm these findings, evaluate the long-term durability of the effect, and identify predictive factors for response.

Overall, the results of this study suggest that navigable caudal epidural neuroplasty represents an effective and safe therapeutic alternative, with the potential to impact both pain intensity and functional disability in patients with refractory chronic low back pain. The number of prior interventions was not systematically recorded, which could influence the observed therapeutic response.

Conclusion

Navigated caudal epidural neuroplasty was associated with a significant and sustained reduction in pain intensity, along with a clinically relevant improvement in functional disability in patients with refractory chronic low back pain. The concordant improvement in NRS and ODI supports a multidimensional therapeutic effect, with early functional recovery that is maintained over time despite a slight attenuation of the analgesic effect.

These findings suggest that targeted access to the anterior epidural space could optimize therapeutic precision and contribute to the observed clinical outcomes. Navigable neuroplasty represents a minimally invasive, safe, and effective alternative in patients who do not respond to conservative therapies. Prospective controlled studies are required to confirm long-term durability and optimize patient selection.

Conflict of interest

None.

Funding

None.

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