The Selective Intraperineural Nerve Root Block Study (SINRBS)

Feasibility, Safety and Diagnostic Accuracy of Selective Intraperineural Nerve Root Block for Identifying Compressed Nerve Root in Lumbosacral Radicular Pain. A Prospective Cohort Study

Before lumbosacral decompression surgery for radicular pain, selective nerve root block(SNRB) is a common procedure to identify the responsible compressed nerve root(RCNR) and predict surgical outcomes. However, the diagnostic accuracy of conventional SNRB is unsatisfactory, especially in terms of specificity. The main limitation is the uncontrolled distribution of anesthetics during injection: when anesthetics spread to surrounding soft tissues instead of acting directly on the RCNR, false-negative results may occur with persistent radicular pain; when anesthetics diffuse to two or more nerve roots including the RCNR, false-positive results may occur even if a normal nerve root is punctured, leading to misdiagnosis.

This study aims to evaluate the diagnostic accuracy of a novel three-dimensional computed tomography multiplanar volume reconstruction (3D-CT MPVR) guided selective intraperineural nerve root block(SINRB) for identifying the RCNR in patients with lumbosacral radicular pain. The investigators hypothesize that this technique will achieve higher diagnostic specificity and overall accuracy than conventional SNRB, by ensuring anesthetics are delivered directly to the target nerve root. This improvement will help clinicians make more accurate surgical plans, achieve better targeted decompression, and ultimately improve postoperative pain relief and functional recovery for patients.

The main research questions to be addressed in this study are:

• What is the procedural success rate of SINRB?
• Whether SINRB may cause clinically detectable nerve injury?
• Whether sciatica is relieved after SINRB when only the responsible compressed nerve root is blocked?
• Whether sciatica is relieved after SINRB when only a normal unaffected nerve root is blocked?

Participants will:

• Undergo one or two SINRB procedures and a single-level lumbar decompression surgery
• Get assessment of pain, mobility disorder and neurological function

Study Overview

• Status: Not yet recruiting
• Conditions: Herniated Disc; Radiculopathy Lumbar; Foraminal Stenosis; Radiculopathy Sacral; Radiculopathy Multiple Sites
• Intervention / Treatment: Diagnostic test: Selective Intraperineural Nerve Root Block(SINRB); Procedure: single-level lumbar decompression surgery

Detailed Description

[Background] It has been reported that approximately 85% of sciatica cases result from nerve root compression secondary to lumbar disc herniation or lumbar spinal stenosis, a clinical entity defined as radicular pain that manifests as radiating pain involving the buttocks and lower extremities. For patients with an inadequate response to conservative management, surgical decompression of the compressed nerve root serves as a conventional and highly effective therapeutic option. Furthermore, if the pain generator can be confirmed to arise from a single nerve root, targeted single-level decompression of that individual nerve root is generally sufficient for pain relief. However, limitations of conventional imaging examinations coupled with overlapping innervation territories of multiple lumbosacral nerve roots often make accurate identification of the symptomatic compressed nerve root challenging in certain patient populations. Misidentification of the pathological nerve root may consequently lead to surgical failure. To address this clinical dilemma, diagnostic selective nerve root block (SNRB) is regarded as the most valuable adjunct modality. In routine clinical practice, complete pain remission following SNRB indicates that the nerve root infiltrated by local anesthetics is the primary pain source.

Regrettably, prior relevant studies have demonstrated that conventional SNRB exhibits relatively low overall diagnostic accuracy, failing to achieve satisfactory sensitivity and specificity simultaneously. Uncontrolled diffusion of injectable agents is recognized as the predominant contributor to such poor diagnostic performance. Specifically, unintended anesthetic contamination of adjacent unaffected nerve roots may trigger false-positive outcomes, while insufficient delivery of local anesthetics to the targeted nerve root can result in false-negative findings. At present, no techniques or strategies for precisely regulating drug distribution during SNRB procedures have been reported in the existing literature.

Interestingly, during the nerve root fluorography in some patients in our team, when linear striation opacities are visualized within the nerve root, which indicates occurrence of intraperineural, the contrast medium typically diffuses only inside and around the targeted nerve root. This phenomenon can also be observed in the illustrative images from a previous study on therapeutic SNRB, yet it seems to have attracted little attention from researchers. Additionally, the findings of this study demonstrated that intraperineural injection occurred in approximately 30% of patients undergoing therapeutic SNRB with accidental intraperineural injection, and no cases of neurological injury were documented during follow-up. Therefore, it is reasonable to hypothesize that intraperineural injection is a safe, feasible approach that enables precise distribution of agents to the targeted nerve root.

Using the postoperative efficacy of single-segment single-nerve-root decompression as the gold standard for identifying the compressed nerve root, the present study aimed to investigate the diagnostic accuracy, safety, and technical feasibility of selective intraperineural nerve root block (SINRB) in patients with radicular pain. A double-blind approach was implemented, with participants and assessors masked to the nerve root status (responsible vs. non-responsible) during evaluations. Meanwhile, to improve the success rate of intraperineural injection, to the best of our knowledge, the present study is the first to adopt three-dimensional computed tomography multiplanar volume reconstruction (3D-CT MPVR) imaging to visualize the anatomical course of the nerve root within the intervertebral foramen.

[Sample Size Estimation] To ensure adequate statistical power for accurately evaluating the diagnostic accuracy of selective intraperineural nerve root block (SINRB) in identifying the responsible compressed nerve root (RCNR) in patients with radicular pain, sample size calculation was performed based on diagnostic test design principles, incorporating the following key parameters: (from preliminary pilot data) an expected sensitivity of 95%, specificity of 96%, 95% confidence level, ±5% margin of error, and a 10% allowance for potential missing data or patient dropout. Using the single-proportion estimation method, the required numbers of positive and negative events were calculated separately for sensitivity and specificity. The sample size required for sensitivity was 80 cases, and for specificity was 66 cases. Accordingly, we plan to enroll 66 patients with single-level lesions (anticipated to yield one positive and one negative result each) and 14 patients with multi-level lesions (anticipated to yield one positive result each). This sample size sufficiently meets the statistical power requirements for the primary study objective-evaluating the sensitivity and specificity of SINRB for RCNR identification-ensuring the scientific rigor, stability, and generalizability of the study findings.

• Study Type: Interventional
• Enrollment (Estimated): 80
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Lingjiang Li, Attending physician; Phone Number: +86 29-83661911; Email: lilingjiang11@126.com

Study Locations

• China
  • Shaanxi
    • Xi'an, Shaanxi, China, 710026
      • Xi'an Honghui Hospital (North Campus)
      • Contact: Ziqiang Yan; Phone Number: +86 29-86520907; Email: honghuixiaozhao@163.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria

• Unilateral sciatica >1 month with activity/daily life impairment.
• Suspected L5/S1 root compression at L4-5/L5-S1 with unconfirmed pain correlation, including disc herniation (MSU 1-B/1-A/2-A), lateral recess/foraminal stenosis (Lee grade 2/3), atypical sciatica, or imaging-exam inconsistency.
• Candidates for single-segment, single-root lumbar decompression, electing surgery after informed consent.

Exclusion Criteria

• No significant pre-SINRB/surgery pain, or weakness/numbness as primary symptom.
• Unidentifiable responsible compressed nerve root (RCNR) per surgery.
• Suspected compression of the same nerve root at more than one segment.
• Pregnancy, active malignancy, or surgical contraindications.
• Inability to cooperate with assessment due to comorbidities or dysfunction.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Diagnostic
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Preoperative Diagnostic SINRB for Responsible Compressed Nerve Root(RCNR) Localization; All enrolled subjects will undergo the same standardized surgical procedure.; For patients with a single suspected lesion and RCNR (typically with ambiguous imaging findings), 2 separate SINRBs are performed (firstly at a non-responsible control root, then at the suspected RCNR) to rule out placebo effect and non-lumbar pain sources. If ≥50% pain relief occurs after the first block, the second SINRB is given the next day after local anesthetic clearance, and patients compare pain relief differences between the two sessions. If relief is less than 50%, the second SINRB is delivered after a 20-minute interval.; For patients with multiple nerve roots compressed, 1 SINRB is performed at the target nerve root to confirm that single-level surgical decompression can achieve complete pain relief. If complete pain relief or resolution of motor dysfunction is not achieved after the first injection, a second SINRB will be administered to an alternative suspected root to identify the true RCNR.

Diagnostic test: Selective Intraperineural Nerve Root Block(SINRB); The patient was placed in a standard prone position. The cutaneous puncture point was confirmed via large C-arm oblique fluoroscopy with the projection angle strictly consistent with the preoperative protocol.All puncture manipulations were completed by an experienced spinal surgeon. Under intermittent fluoroscopic guidance, the puncture trajectory was adjusted to keep the needle parallel to the fluoroscopic beam, followed by slow needle advancement until radiating pain was evoked in the patient. The needle was further advanced approximately 1 mm, and 0.2 mL contrast medium was injected subsequently. The visualization of a linear streak shadow within the nerve root confirmed intraneural positioning. The needle was fixed in situ, and 0.5 mL lidocaine was injected.; Procedure: single-level lumbar decompression surgery; All patients underwent single-level lumbar surgery with either endoscopic or conventional open single nerve root decompression, and postoperative anteroposterior and lateral lumbar radiographs were routinely obtained for imaging evaluation.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
The change from baseline in standing impairment	Standing impairment was documented via separate video recordings before and after each SINRB procedure, as well as on the second day of postoperative ambulation. Upon completion of data collection, Video recordings of all participants were randomly shuffled, and independent assessors evaluated the presence or absence of standing impairment for each video. Assessors were blinded to the type of nerve root injected (responsible vs. non-responsible), final surgical outcomes, clinical information, imaging results, and the number of SINRB sessions. Video content: The patient was instructed to stand upright with chest out, head raised, and lumbar spine maintained in an extended position for 20 seconds. Assessment Criteria: Standing impairment was defined as present if the patient voluntarily bent forward/backward or left/right during the test due to intolerable radicular pain and failed to maintain the initial upright posture. Otherwise, standing impairment was considered absent.	Baseline, 5mins after SINRB, the second day after ambulation, and 1 month postoperatively
Change from baseline in walking impairment	Walking impairment was evaluated using the same recording and blinding protocols as those for standing impairment. Video content: Patients maintained an upright position and kept uninterrupted walking for 500 meters. Judgment criteria: "walking disorder" was defined as present if voluntary termination of walking occurred before completing 500 meters due to intolerable radicular pain. Otherwise, walking impairment was considered absent.	Baseline, 5mins after SINRB, the second day after ambulation, and 1 month postoperatively
Change from baseline in straight leg raising impairment	The straight leg raising (SLR) impairment was evaluated using the same recording and blinding protocols as those for standing impairment. Video content: The straight leg raising (SLR) test was performed sequentially on the unaffected side and the affected side. Assessment criteria: The projection of the heel of the elevated leg onto the contralateral (non-elevated) leg was used as the observation index. "Presence of SLR impairment on the affected side" was defined as: the heel projection on the affected side failing to reach the patella due to intolerable radicular pain, whereas the heel projection on the unaffected side reached the patella or cephalad to it. "Absence of SLR impairment on the affected side" was defined as: the heel projection reaching the patella at maximum SLR on the affected side, with or without tolerable radicular pain.	Baseline, 5mins after SINRB, the second day after ambulation, and 1 month postoperatively
Subjective pain relief	After each SINRB/operation, movements previously inducing severe pain (e.g., standing, walking, lying flat, stair climbing/descending) were repeated. Video questions: "Where was your worst pain during movement pre-procedure?"; "Where do you feel pain now? Point to it."; "Does residual pain affect walking speed/distance?"; "How much has pain decreased post-SINRB/surgery?" (options: no significant relief; relief with activity-limiting residual pain; essential relief [residual pain not affecting activities]; pain disappeared). Pain relief assessment followed the same recording and blinding protocols as for standing impairment.	5mins after SINRB, the second day after ambulation, and 1 month postoperatively

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Result of SINRB	This outcome measure is a derived variable automatically generated from the primary outcome measure according to a predefined scoring rule. After the independent assessors completed evaluating activity impairment and subjective pain relief in each video, all results were matched with corresponding patients and tabulated. SINRB test results were judged by the following criteria: For patients with activity impairment, results were positive if all activity impairments resolved (with or without residual pain), otherwise negative. For patients without activity impairment, results were positive if subjective pain relief was rated as "pain disappeared", otherwise negative.	5mins after SINRB
Overall clinical assessment after lumbar spine surgery	This outcome measure is a derived variable automatically generated from the primary outcome measure according to a predefined scoring rule. Compared with preoperative status, if all movement impairments resolve postoperatively, or the original pain is rated as "essential relief" or "pain disappeared", the decompressed nerve root is defined as the true responsible compressed nerve root(RCNR) and the sole source of pain. If pain relief does not meet the above criteria during the initial postoperative assessment, a telephone follow-up will be conducted at 1 month after surgery for re-evaluation. If the patient reports "essential relief" or "pain disappeared" at follow-up, the decompressed nerve root is still regarded as the RCNR and the sole source of pain; otherwise, it is not considered the sole source of pain.	the second day after ambulation, and 1 month postoperatively
The occurrence of complications	The occurrence of complications during the puncture procedure, including hematoma at the puncture site, infection, allergic reactions, and other related complications, will be recorded in detail.	24hs after SINRB
Changes in neurological function before and after SINRB	Changes in neurological function before and after SINRB. Baseline neurological assessment is performed before the first SINRB, including superficial sensory examination of the affected side (medial malleolus , dorsum of the foot, first and second toe web spaces , lateral aspect of the heel) and muscle strength testing of the affected side (ankle dorsiflexion, ankle plantarflexion, great toe dorsiflexion, great toe plantarflexion). At 24 hours after complete resolution of anesthetic effects following the final SINRB, patients are interviewed for new-onset numbness or discomfort, and the above neurological examinations are repeated. To supervise this key data, video recording will be conducted during inquiry and physical examination, with subsequent quality supervision by third-party senior physicians.	24hs after SINRB
Success rate of SINRB procedure	The SINRB procedure is clinically successful when intraperineural injection is achieved without contrast/drug contamination per fluoroscopic criteria: Drug contamination: Post-lidocaine final radiculography showing contrast extending beyond the target nerve root and spreading along the dura to adjacent nerve roots; otherwise negative.; Definition of successful intraperineural injection The injection is judged as successful when all three fluoroscopic imaging features are satisfied simultaneously: Tubular outline of the nerve root and the linear striated opacification within the nerve root is noted after the contrast material injection;; After lidocaine delivery, the striated opacification around the needle tip is diluted or disappeared;; Re-enhancement of the striated nerve root opacification is observed after supplementary contrast medium reinjection.	immediately post-SINRB

Collaborators and Investigators

• Sponsor: Xi'an Honghui Hospital
• Investigators: Principal Investigator: Lingjiang Li, Attending physician, Xi'an Honghui Hospital, Xi'an, Shaanxi Province, China

Publications and helpful links

General Publications

• Beynon R, Elwenspoek MMC, Sheppard A, Higgins JN, Kolias AG, Laing RJ, Whiting P, Hollingworth W. The utility of diagnostic selective nerve root blocks in the management of patients with lumbar radiculopathy: a systematic review. BMJ Open. 2019 Apr 20;9(4):e025790. doi: 10.1136/bmjopen-2018-025790.
• Sala-Blanch X, Lopez AM, Pomes J, Valls-Sole J, Garcia AI, Hadzic A. No clinical or electrophysiologic evidence of nerve injury after intraneural injection during sciatic popliteal block. Anesthesiology. 2011 Sep;115(3):589-95. doi: 10.1097/ALN.0b013e3182276d10.
• Pfirrmann CW, Oberholzer PA, Zanetti M, Boos N, Trudell DJ, Resnick D, Hodler J. Selective nerve root blocks for the treatment of sciatica: evaluation of injection site and effectiveness--a study with patients and cadavers. Radiology. 2001 Dec;221(3):704-11. doi: 10.1148/radiol.2213001635.

Study record dates

Study Major Dates

• Study Start (Estimated): April 13, 2026
• Primary Completion (Estimated): December 1, 2026
• Study Completion (Estimated): January 1, 2027

Study Registration Dates

• First Submitted: April 5, 2026
• First Submitted That Met QC Criteria: April 11, 2026
• First Posted (Actual): April 15, 2026

Study Record Updates

• Last Update Posted (Actual): April 15, 2026
• Last Update Submitted That Met QC Criteria: April 11, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: lumbosacral radiculopathy; intraperineural; 3D-CT MPVR; diagnostic selective nerve root block
• Additional Relevant MeSH Terms: Bone Diseases; Musculoskeletal Diseases; Pathological Conditions, Anatomical; Spinal Diseases; Hernia; Pathological Conditions, Signs and Symptoms; Intervertebral Disc Displacement
• Other Study ID Numbers: 2025--KY-085-01

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Due to ethical restrictions and patient privacy confidentiality requirements, individual participant data will not be shared

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No