Update and Literature Review on Basivertebral Nerve Ablation and Vertebrogenic Low Back Pain

Educational Objectives

The goal of this program is to optimize use of basivertebral nerve (BVN) ablation to treat vertebrogenic low back pain (LBP). After hearing and assimilating this program, the clinician will be better able to:

1. Delineate the origin of vertebrogenic LBP.
2. Select ideal candidates for BVN ablation.
3. Achieve proper positioning during BVN ablation.
4. Recognize potential issues that can arise during BVN ablation.
5. Evaluate updates to clinical evidence that demonstrate the efficacy of BVN ablation.

Summary

Low Back Pain

Demographics: low back pain (LBP) affects ≈84% of the United States adult population at some point in their lives; chronic LBP affects ≈15% of the U.S. population; 85% of patients seen in primary care settings will ultimately be diagnosed with nonspecific LBP

Denis classification: anterior column — extends from the anterior longitudinal ligament through two-thirds of the vertebral body and disc; pain worsens with prolonged forward bending or sitting; middle column — includes the area from the posterior third of the vertebral body and disc to the posterior longitudinal ligament (PLL); posterior column — the area posterior to the PLL; pain worsens with, eg, backward bending, twisting, standing

Vertebral endplates: the interface between the vertebral bodies and intervertebral discs; the endplates have to be strong enough to prevent a fracture but porous enough to facilitate transport of nutrients across to the discs, as the lumbar spine carries a significant amount of force and the discs lack a dedicated blood supply; the cartilage component of the endplate consists of collagen fibers aligned parallel to the ends of the vertebral bodies; the bony component of the endplate is a thickened porous layer of trabecular bone

Modic changes: changes to endplates visible on magnetic resonance imaging (MRI) in patients with degenerative disc disease; apparent on sagittal or lateral MRI views as bright or dark areas of the vertebral body just above and below the dark, degenerated disc; type I — characterized by fibrovascular replacement; demonstrate decreased signal on T1 and increased signal on T2 sequences; indicates the presence of vascularized granulation tissue within the adjacent bone marrow; type II — appear bright on T1 and T2 weighted images; represent yellow marrow (ie, fatty replacement); often arise from type I changes over time; type III — represented by decreased signal on T1 and T2 weighted MRIs; represent bony sclerosis, which reflects replacement of the marrow elements with dense bone; association with chronic LBP is unclear

Endplate innervation: endplate changes act as a marker in patients with classic, chronic discogenic back pain; innervation of the intervertebral discs is generally restricted to the outer layer of the annulus via the sinuvertebral nerve; new blood vessels and nerves may develop over time with chronic disc problems, though these are not present at birth; vertebral endplates contain ≈2 times as many nociceptors, compared with the disc; the nociceptors originate from the basivertebral nerve (BVN), which transmits the signals to the spine that the body interprets as pain

Thermal Radiofrequency Ablation of the Basivertebral Nerve

Candidates: ideal candidates include patients with chronic anterior column LBP >6 mo duration (with Modic type I or II changes on MRI) of suspected vertebrogenic origin (pain emanates from the vertebral endplates) who have failed extensive conservative management; the procedure is not recommended for patients with acute disc herniation, spinal stenosis, or advanced facet arthritis

Equipment: the procedure is guided by C-arm fluoroscopy; BVN radiofrequency ablation (RFA) may be performed under monitored anesthesia care or general anesthesia; an introducer cannula (ie, trocar) is used to access the vertebral body via the pedicles and provide a conduit for the RFA probe; needles used include a diamond-tipped introducer needle (preferable to create a straight trajectory), bevel-tipped introducer needle (used if additional maneuvering is required), J-stylet (a fairly long, thin, hooked needle used to create a curved trajectory), and a straight stylet (used to extend the channel)

Location: vertebral endplate disease most commonly occurs at L5-S1, followed by L4-L5 and L3-L4; the procedure is not indicated for ablation above the L3 level, due to increased risk for damage to, eg, the spinal canal (ends at L1)

Technique (for the L5 vertebral level)

Positioning: place the patient in the prone position; initiate anesthesia; start with an anteroposterior (AP) view by placing the C-arms directly above and below the endplates; apply cephalad tilt (typically 10-15° depending on the amount of lumbar lordosis) to achieve alignment

Creation of the angle of trajectory: stay within the pedicle to avoid compromise to any neural structures; stay sufficiently lateral to avoid damage to the spinal canal but sufficiently medial to insert the probe into the middle of the vertebral body without being too deep; obliquely angle the C-arm ipsilateral to the side of the pedicle and maintain this position until the superior articular process bisects the disc; start on the superolateral aspect of the pedicle and use inferomedial aim

Breaching the vertebral body: anesthetize the skin with bupivacaine or lidocaine to prevent postprocedural soreness; make a small stab incision with an 11-blade scalpel and insert the introducer trocar; start with the diamond-tipped needle (better for straight trajectories, compared with the bevel-tipped needle); lightly tap the needle into the superolateral aspect of the pedicle using a mallet weighing 1 to 2 lb; once the pedicle wall has been breached, check the medial and lateral views to ensure safe trajectory; in the medial view, the needle trocar will be visible sitting on the superolateral aspect of the facet/transverse process complex; in the lateral view, the trocar will appear posterior in position with slight breaching of the bony pedicle; alternate between AP and lateral MRI views to ensure appropriate positioning on lateral view (within the posterior one-third to one-half of the vertebral body) and AP view (in the central pedicle); the oblique view is used only to aid with initial alignment

Build the channel: remove the introducer needle from the trocar and insert the J-stylet; move 1 mm at a time while checking AP and lateral views; do not let the J-stylet move too far medially too quickly (to avoid breaching the medial border of the pedicle or the posterior aspect of the vertebral body); while extremely rare, breach into the spinal canal can occur due to, eg, angles of the C-arms, imperfect lateral views; if some resistance is felt, remove the J-stylet and reinsert the diamond-tipped needle to proceed deeper within the vertebral body; the J-stylet advances in a fairly fluid manner within the vertebral body; ideally, the J-stylet should be visible in the middle of the vertebral body on AP view and in the posterior one-third to one-half of the vertebral body on a lateral view; removal of the J-stylet may cause some bleeding, as the basivertebral vein is adjacent to the BVN

Insertion of the RFA probe: use AP and lateral views to confirm placement; turn on the ablation machine (which will produce an 85°C burn for 15 min)

Preparing for the second level of ablation: trajectory for L3-4 or L4-5 are very similar to one another; S1 level — alignment at S1 requires significant cephalad tilt (20-30°) to square off the sacral endplate; pedicle anatomy can vary and may hinder achievement of ideal positioning within the pedicle (within the superolateral aspect on AP view and within the posterior aspect on lateral view); some providers may obtain an oblique view, which requires 50° to 60° of tilt to achieve optimal positioning (ie, the superior articular process bisects the intervertebral disc); some providers will initiate a stab incision above the iliac crest to help visualize the angle; the J-stylet should be ≈50% through the vertebral body on AP and lateral views, compared with 30% to 50% through the vertebral body at L3-L5; it is ideal to maintain ≥1 cm distance from the most posterior aspect of the vertebral body during ablation to avoid heating elements within the spinal canal

Postprocedure: patients may experience substantial discomfort; check for new weakness or radicular pain in the legs; a variable degree of muscular soreness may be present (usually described as a mild aching sensation), though investigate excessive soreness to rule out radiculopathy; there is no strict recovery period; prescribe nonsteroidal anti-inflammatory drugs, ice, and rest; patients with worse pain tend to be younger in age and have very thick bone requiring additional force to insert the probe; full results may be felt within 2 mo

Potential issues

Medial breach of the pedicle: the largest issue; the needle may enter the spinal canal and cause damage to the cauda equina nerve roots, resulting in radiculitis; typically, radiculitis self-resolves after ≈6 wk; no cases of prolonged radiculopathy or weakness or permanent neurologic pain have been seen

J-stylet: application of excessive force may cause the J-stylet to take a very sharp angle; if the introducer needle retracts while switching to the J-stylet or resistance is felt with the J-stylet, reinsert a thicker needle to ensure appropriate placement within the vertebral body and to reduce the probability of building a channel between the medial border of the pedicle and the spinal canal

Wingnut: rotating the wingnut on the introducer permits appropriate depth of excursion of the J-stylet to the base of the trocar; continued hammering of the J-stylet beyond the appropriate depth can kink the cannula material and cause some of the material from the introducer to dislodge into the vertebral body

Ablation machine switches off: blood from the basivertebral vein may get onto the RFA probe and cause high impedance readings and machine shut-off; remove the RFA probe and wipe off the blood prior to reinsertion; in rare circumstances, a switch in position is necessary

Pearls

Retraction method: can help obtain proper medial positioning of the J-stylet while remaining within the posterior portion of the vertebral body; if resistance is felt, slightly retract the introducer before reinserting the J-stylet to help create a nice trajectory while using the original tract created by the introducer needle

Achievement of positioning at S1: 20° to 45° of cephalad tilt is required to square off the endplate; it is challenging to optimize the lateral view, compared with the AP view; changing the wig-wag is required to achieve an optimal lateral view; wig-wag often provides the same degree of orientation as cephalad tilt

Updates to Clinical Evidence

Fischgrund et al (2018): the Oswestry disability index (ODI) score decreased by an average of 20.5 points 3 mo following BVN RFA, compared with an average decrease of 15.2 points following a sham procedure, for patients with chronic LBP and Modic type I or II changes; thus, both groups met clinical significance for improvement in ODI; 75% of patients in the ablation arm had ≥10 points of improvement in the ODI score, compared with 55.3% of patients in the sham arm; 2-yr follow-up — patients were unblinded after 1 yr; 73% of patients in the sham arm chose to cross over (presumably secondary to overestimation of potential improvements following BVN ablation); 5-yr follow-up — visual analog scale (VAS) pain scores reduced by an average of 4.38 cm; the average initial ODI score of 42.8 points decreased to 16.86 points; 33% of patients were pain-free

Khalil et al (2019): patients with LBP and Modic type I or II changes were randomized to undergo BVN RFA vs standard care (eg, physical therapy); interim analysis demonstrated clear statistical superiority for all primary and secondary patient-reported outcomes following BVN RFA, compared with standard care, and subsequently, study enrollment was halted and early crossover to the ablation arm was offered; 2-yr follow-up (Koreckij et al [2021]) — the mean VAS score decreased from ≈6.8 cm to 2.5 cm, and the mean ODI decreased by 28.5 points; 31% patients were pain-free

Macadaeg et al (2020): mean VAS decreased from 7 cm to 2.5 cm 2 yr following BVN ablation

Conger et al (2021): conclude that there is moderate-quality evidence supporting the efficacy of BVN ablation in reducing pain and disability in patients with chronic vertebrogenic LBP

Readings

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Disclosures

For this program, members of the faculty and planning committee reported nothing relevant to disclose.

Acknowledgements

Dr. Barrette was recorded exclusively for Audio Digest in June 2022. Audio Digest thanks the speaker for their cooperation in the production of this program.

CME/CE INFO

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The Audio- Digest Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The Audio- Digest Foundation designates this enduring material for a maximum of 2.00 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

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Lecture ID:

OR451901

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

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To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

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Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.