The prevalence of low back pain is estimated at 31%, with a lifetime prevalence ranging between 60% and 80%.1,2 In recent years, the application of ultrasonography (US) for administering injections in chronic pain management has expanded considerably, due to the numerous advantages that US offers over other imaging modalities, such as ease of use, the absence of ionizing radiation, portability, cost- effectiveness, enhanced visualization of soft tissues (including muscles, ligaments, and blood vessels), and real-time needle advancement visualization.3,4   However, the challenges of precision, accuracy, reliability, and patient safety associated with US-guided procedures must be thoroughly addressed. 5-6

Therefore, we designed and conducted this prospective interventional study to assess the accuracy of US-guided periradicular needle placement in the lumbar neural foramen as confirmed by fluoroscopic imaging.

The study has been conducted in the Department of Anesthesiology at Dr. R.P.G.M.C, Kangra at Tanda, Himachal Pradesh for a period of 12 months, starting from December 2022 after obtaining institutional ethical committee approval and  registering at Clinical Trial Registry India vide no. CTRI/2023/03/051144.  This was a prospective interventional study. The primary objectives of study was to determine the accuracy of US-guided periradicular needle placement in the lumbar transforaminal space, as verified by fluoroscopy with secondary objectives  to evaluate the complications associated with US-guided transforaminal periradicular needle placement, including accidental intravascular, intraneural, or subarachnoid injection during selective nerve root injection and further assessment of the effectiveness of pain relief using the verbal numeric rating scale (VNRS).  The study was performed on 100 nerve roots in 40 patients of either gender aged 18-65 years with a BMI between 18 and 35 who had presented to our pain clinic with lower back pain and radiculopathy confirmed by MRI(Image-1:A& B) and not responding to conservative treatment of at least 6  weeks.. Patients with history of CVA with neurological deficits, severe degenerative disc disease, segmental instability, bleeding diathesis and pregnancy were excluded from the study.

Patients meeting the inclusion criteria were enrolled in the study after obtaining written informed consent. Pre-procedural evaluations were conducted for each patient, determining the nerve root level for injection based on symptoms, clinical examination, and MRI findings.

On the day of the procedure, patients were allowed a light meal in the morning. In the operation theatre, intravenous access was established, and patients were positioned prone on the operation table with a pillow under the abdomen to reduce lumbar lordosis. Vital signs were monitored before and during the procedure.

A single expert anesthesiologist familiar with the US and fluoroscopy-guided interventions performed the procedures under aseptic conditions using a FUJIFILM SonoSiteEdgeII portable ultrasound machine with a 2-5MHz curved probe. (Image-2) The gain was maximized for optimal visualization of bone surfaces. A posterior sagittal ultrasonography was performed, followed  by skin marking to identify spinal levels. Longitudinal and axial scans were conducted to visualize anatomical structures. (Image-3,4&5) After anesthetizing the skin with 1-2ml of 1% Lignocaine, a 23-G, 90mm Quincke's spinal needle was inserted using the in-plane technique, ensuring real-time visibility of the needle path. The needle was advanced to the target, and its position was confirmed by fluoroscopy.(Image-6) 0.5 to 1 ml of contrast (iohexol 300 mg/ml) was injected to confirm needle placement. If correctly placed, 0.5ml-1ml of dexamethasone (4mg/ml) followed by 1-2ml of 0.125% Bupivacaine was administered.(Image-7) Patients were monitored pre-procedurally, during, and post-procedurally at 5 minutes, 30 minutes, and two hours.

The Procedural Observations of study were as  below:

1. Ultrasound Visibility Score (UVS): The visibility of nine neuraxial structures was scored on a scale of 0-3, with total scores categorized as Good (>18), Average (9-18), or Poor (<9).
2. Number of Attempts: Defined as reaching the site without withdrawing the needle from the skin.
3. Number of Adjustments: Defined as needle redirection without withdrawal.
4. Localization Time: Time taken to reach the desired site from skin puncture.
5. Radiation Exposure: Number of fluoroscopy shots to confirm needle tip position.
6. Bone Contact: Whether the needle touched the bone cortex.
7. Complications: Recorded any intravascular, intra-neural, or subarachnoid injections.
8. VNRS: Assessed pain relief on follow-up.

Follow-up evaluations were conducted on day one, one week, six weeks, and twelve weeks post-procedure for VNRS .

During statistical analysis of observed parameters  Categorical variables were presented as numbers and percentages, while quantitative data were presented as means ± SD or medians with inter quartile ranges. Data normality was checked using the Shapiro-Wilk test. Non-parametric tests were used for non-normal data. Mann-Whitney, Kruskal-Wallis, Wilcoxon signed-rank, Chi-Square, Fisher’s exact, and Bhapkar tests were applied where appropriate. Statistical analysis was conducted using SPSS version 25.0, with significance set at p < 0.05

The accuracy of US- guided periradicular needle placement in Lumbar transforaminal space as verified under fluoroscopy was determined and results are as follows.

The visibility of anatomical structures during ultrasound-guided procedures shows that 92.5% of cases had good visibility, with a mean score of 21 out of a possible range of 16 to 22. Only 7.5% of cases had average visibility, indicating that most procedures benefited from clear ultrasound imaging.(Figure 1)

Demographic characteristics and the Total Ultrasound Visibility Score (TUVS) analysis shows no significant differences in visibility scores across different age groups, genders, or BMI categories, suggesting that these factors did not affect the quality of ultrasound imaging during the procedures(Figure 2)

The association between age and various procedural parameters, including the success of needle positioning, the number of attempts and adjustments required indicates that younger patients (≤40 years) had higher success rates with fewer attempts and adjustments. In contrast, older age groups, particularly those over 60, required more attempts and adjustments, particularly at the L5-S1 level. This suggests that age may influence the ease of needle placement during the procedure.(Table 1 )

Table 1: Association of Parameters with Age (Years)

*Fisher's exact test, ‡Kruskal Wallis test, NF; Neural Foramina.

The impact of gender on procedural outcomes, including needle positioning success, number of attempts, and radiation exposure shows no significant differences between males and females in these parameters, indicating that gender did not significantly influence the success or difficulty of the procedure.(Table 2)

Table 2: Association of Parameters with Gender

• Mann Whitney test, * Fisher's exact test, NF; Neural Foramina.

The relationship between body mass index (BMI) and procedural success shows that underweight patients (<18.5 kg/m²) had a higher failure rate in needle positioning and required more attempts and adjustments, particularly at the L5-S1 level. This suggests that lower BMI might be associated with more challenges in achieving accurate needle placement.(Table 3)

Table 3: Association of Parameters with Body Mass Index (kg/m²)

*Fisher's exact test, ‡Kruskal Wallis test, NF; Neural Foramina.

The pain levels before and after the procedure using the Verbal Numeric Rating Scale (VNRS) shows a significant reduction in pain, with the majority of patients reporting no pain or only mild pain during follow-up. This indicates the procedure was effective in providing pain relief.(Table 4)

Table 4: Comparison of Pre-Procedural VNRS for Pain with Post-Procedural VNRS on Follow-Up

The study's findings reveal that the Total Ultrasound Visibility Score (TUVS) was predominantly favourable, with 92.5% of cases demonstrating good visibility. The mean UVS was 21 ± 1.4, indicating consistently high imaging quality. These results align with those of Sahu DK et al7, who found good visibility in 55% of cases, although our study showed a higher percentage of cases with excellent visibility. The TUVS in our study did not significantly vary with age, gender, or BMI (p > 0.1), suggesting that US visibility is largely consistent across different demographic profiles. This consistency supports US as a reliable imaging modality in diverse patient populations.

The overall accuracy of needle placement in our study was 98%, with success rates varying slightly across different lumbar levels. Notably, the L5 level presented more challenges, with a slightly lower accuracy of 93.33% compared to higher levels. This is consistent with the findings of MasoudHashemiet al8, who reported accuracy rates between 80% and 100% across lumbar levels when using ultrasound guidance for transforaminal epidural injections. Similarly, Yang G et al9 reported an 85% accuracy rate for ultrasound-guided lumbar TFEIs, slightly lower than our findings, which may reflect differences in technique or patient selection. Our results suggest that US guidance is a highly effective method for needle placement, particularly when combined with fluoroscopic confirmation.

The study also analyzed the number of attempts and adjustments required for successful needle placement. We observed that younger patients (≤40 years) generally required fewer attempts, while older patients, particularly those aged 61-70, needed more adjustments. This trend highlights the increasing complexity of needle placement in older patients, particularly at the L5-S1 level. Sato et al10 also noted challenges in accessing the L5/S1 foramen, suggesting that alternative approaches, such as out-of-plane techniques, may be more effective in certain cases.

The mean time for needle placement in our study was significantly lower than in other studies. For example, Sahuet al7 reported a mean time of 1506 seconds for US-guided needle placement, whereas our mean time was approximately 242.49 seconds. This discrepancy may be due to differences in procedural experience, patient selection, and the specific techniques employed. Additionally, our study reported minimal radiation exposure, with a mean of 3.7 C-arm shots per procedure. This is consistent with findings by GüvenKöseSet al11, who highlighted the benefits of US guidance in reducing radiation exposure compared to fluoroscopy alone. The limited use of fluoroscopy in our study, restricted to confirming needle position, contributed to the low radiation doses, enhancing patient safety.

We encountered no significant complications, such as intravascular or intra-neural injections, during the study. Minor complaints, such as post-procedural soreness, were managed with NSAIDs, and no severe adverse effects were reported. These outcomes are in line with the findings of Sahu DK et al7, who also reported a lack of complications in their study. The safety profile of US-guided transforaminal injections, as demonstrated in our study, reinforces the technique's utility in clinical practice.

Our study also demonstrated significant pain relief following the procedure, as measured by the Verbal Numeric Rating Scale (VNRS). The reduction in pain scores was consistent across all follow-up intervals, with a statistically significant p-value of <0.0001. These findings are comparable to those of Wenxing Z et al12, who reported similar improvements in pain and functional disability following lumbar transforaminal epidural injections guided by either US or fluoroscopy. Our results support the efficacy of US-guided injections in managing radicular pain, offering a viable alternative to traditional fluoroscopic methods.

This study has several limitations. Firstly, the sample size was relatively small, which may limit the generalizability of the findings. Secondly, the study was conducted at a single centre, which may introduce selection bias. Thirdly, the reliance on fluoroscopic confirmation, while necessary for accuracy, still exposes patients to some level of radiation. Additionally, the study did not include a control group receiving fluoroscopy-only guided injections, which could provide a direct comparison of outcomes. Finally, the long-term efficacy and safety of ultrasound-guided transforaminalperiradicular nerve root injections were not assessed beyond the three-month follow-up period. Future studies with larger, multicenter cohorts and extended follow-up periods are needed to validate these findings and further establish the benefits of this technique.

This study concluded  that ultrasound-guided lumbar transforaminalperiradicular nerve root injections are a highly accurate, safe, and effective technique for managing radicular pain, with a 98% overall accuracy and significant pain relief observed across all follow-up intervals. The consistently high ultrasound visibility, minimal radiation exposure, and absence of major complications further affirm the utility of ultrasound as a primary imaging modality in spinal interventions. These findings, consistent with and building upon previous research, support the integration of ultrasound guidance into routine clinical practice for spinal pain management, providing a viable, efficient, and patient-friendly alternative to traditional fluoroscopic methods.

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