Radiofrequency Ablation of the Medial Branch Nerves as a Novel Treatment for Vertebral Compression Fractures: A Comprehensive Review
Introduction
Vertebral compression fractures (VCFs) are a significant healthcare challenge, affecting individuals regardless of age or underlying conditions. They are associated with substantial morbidity, mortality, and financial burdens. The cost of treating VCFs, particularly in the United States, is staggering, with estimates reaching 25 billion USD by 2025. The prevalence of VCFs is rising, with approximately 700,000 cases reported annually in the US, and this number is expected to increase with an aging population. VCFs can have a profound impact on an individual's lifestyle, causing severe, debilitating pain that is exacerbated by movement and weight-bearing activities. Osteoporosis significantly increases the risk of VCFs, often from minimal trauma or routine activities, and even after healing, chronic pain can persist, leading to functional limitations and reduced quality of life.
Current treatments for VCFs include physical therapy, non-steroidal anti-inflammatory medications (NSAIDs), and medications that increase bone mass. More invasive approaches, such as percutaneous vertebroplasty or kyphoplasty, have been proposed for acute and symptomatic VCFs, but their efficacy has been questioned. Studies comparing these procedures to conservative treatment have shown mixed results, and two studies in the New England Journal of Medicine in 2009 found no significant benefits of vertebroplasty over a sham procedure. Additionally, vertebroplasty and kyphoplasty are often not indicated or covered by insurance for subacute or chronic VCFs.
A novel strategy for VCFs was proposed by Kim et al. in 2005, involving facet joint blocking before vertebral augmentation to provide patient comfort during vertebroplasty and identify appropriate levels for augmentation in patients with multiple VCFs. The study found that 50% of patients who received radiofrequency ablation (RFA) after facet joint blocking did not report pain recurrence within 6 months, indicating the potential of RFA as an adjunct to vertebroplasty for treating posterior element pain due to VCFs.
Understanding the anatomy and biomechanics of the posterior arch elements of the vertebrae is crucial. These elements consist of bilateral pedicles, an overriding lamina with superior and inferior articular processes, and a posteriorly positioned spinous process. The facet joints, formed by the interdigitation of the superior and inferior articular processes, are surrounded by a dense connective tissue capsule innervated by the medial branch of the dorsal ramus. The joint capsules contain horizontally oriented collagen bundles that facilitate a cephalocaudal rocking motion while resisting rotation and separation.
A biomechanical model by Bogduck et al. implicates the posterior elements in VCF-related pain. Asymmetrical anterior wedging of the vertebral body can displace the adjacent superior vertebral body, causing traction of the IAP of the superior vertebra against the SAP of the fractured vertebra. Joint capsule deformity or pseudo-articulations may occur, becoming significant pain sources. In symmetrical vertebral body collapse, the distance between the pedicle of the damaged vertebra and the vertebra below decreases, forcing the IAP of the damaged vertebra into the SAP of the vertebra below, leading to joint capsule deformity or bony contusions.
Radiographic evidence suggests that the facet joint shows signs of inflammation in patients with VCFs, further supporting the involvement of the posterior elements in pain generation. Preliminary studies indicate that facet-targeted interventions may be effective for managing VCF-associated pain.
A retrospective study by Park et al. reported notable pain relief, functional improvement, and high satisfaction rates in 78.9% of patients who underwent therapeutic medial branch nerve block with local anesthetic and steroid. However, the need for repeated blocks and the short-term duration of pain relief (13.26 weeks) were limitations. Another study by Im et al. found that about 25% of patients with VCFs who underwent facet joint injection before vertebroplasty canceled the procedure due to reduced pain, and 50% experienced notable pain relief. Wang et al.'s prospective randomized trial comparing vertebroplasty to facet blockade showed better short-term pain relief and functionality but no significant differences at one month and 12 months for pain, disability, and quality of life.
Dang et al.'s study of 198 patients randomized to either vertebroplasty alone or combined with a facet block found that combined therapy resulted in better pain and disability outcomes up to one month later. These studies suggest the potential of facet blocks in conjunction with vertebroplasty for VCF-related pain. A 2022 meta-analysis of seven studies combining facet blocks with vertebral augmentation showed benefits for pain relief and disability up to three months, with little difference between the two interventions.
An alternative to intraarticular facet blocks is radiofrequency ablation (RFA) of the lumbar medial branch nerves, which supply the zygapophysial joint and posterior elements. In the context of limited efficacy and invasiveness of kyphoplasty/vertebroplasty, RFA of the medial branch nerves emerges as a potential long-term therapeutic option for VCF-related pain. A 2024 systematic review and meta-analysis of combination therapy using vertebroplasty and RFA for metastatic spinal tumors demonstrated significant short-term pain reduction with a low complication rate.
Multispecialty experts have reviewed the RFA-MBN procedure and recommended it for well-selected patients with axial back pain from various causes who fail 3 months of conservative management and respond to diagnostic blocks. The procedure is performed under fluoroscopy guidance with electrode placement parallel to the medial branch nerve. RFA-MBN is a safe and effective method for providing lasting relief for facet-mediated pain in up to 60% of patients for up to 12 months.
In the treatment of VCFs, intraarticular facet blocks, often combined with bone cement vertebral augmentation, have been evaluated. However, there is limited information regarding single facet therapy, particularly RFA-MBN, as a standalone treatment for VCFs. While RFA-MBN has shown benefits for chronic axial back pain, its efficacy in VCF pain has not been fully explored. Large-scale studies are needed to assess the long-term effectiveness of RFA-MBN in relieving VCF-associated pain.
Materials and Methods
The study was a 8-year retrospective chart review conducted at a tertiary care academic pain center, University of California, Davis, between August 2014 and June 2022. The study was reviewed by the UC Davis Institutional Review Board and considered exempt. Patient consent was waived due to the retrospective nature of the study. All data were anonymized, and patient confidentiality was maintained. The electronic medical records of 2420 patients who underwent RFA-MBN were reviewed for inclusion criteria, including patients with chronic VCFs and axial back pain who underwent RFA-MBN after achieving greater than 80% pain relief with two diagnostic MBN blocks. Exclusion criteria included patients not receiving at least 2 MBN blocks, under 18 years old, with cervical compression fractures, RFA-MBN for non-compression fracture-related back pain, and lost to follow-up.
The procedures were performed under the supervision of 5 faculty providers during the study period by faculty or fellows in an Accreditation Council for Graduate Medical Education (ACGME) pain medicine training program. Needle probe position was verified by faculty providers before the ablation procedure. The time between repeat ablation procedures was noted if applicable.
Procedure Details
Patients were positioned in a prone position in the fluoroscopy procedure suite, where VCFs and corresponding facet joints were identified. Medial branches innervating the facet joints above and below the compression fracture were localized using bony landmarks. The injection site(s) were prepped aseptically, and the skin and subcutaneous tissue were anesthetized with local anesthetic. Thermal radiofrequency needle probes with ablating tips were advanced to target locations under fluoroscopic guidance. Needles rested on the periosteum, with anterior-posterior, oblique, and lateral views confirming appropriate placement. Motor stimulation was performed to ensure the absence of lower extremity motor fasciculations. Before ablation, a lidocaine or mepivacaine solution was injected at each nerve. After a 3-minute delay, monopolar ablation lesions were performed at 80°C for 90 seconds. Dexamethasone and saline solution were injected post-ablation for neuritis prophylaxis. Needles were removed, and patients were discharged after meeting discharge criteria.
Study Outcomes and Data Collection
The primary outcome was patient-reported percentage and length of pain relief post-RFA-MBN, documented in post-procedure notes. Secondary outcomes included pre- and post-disability index scores and the difference in disability index. Statistical analysis was conducted using R Version 4.1.3, employing univariate linear mixed-effects models to evaluate the association between pain relief and covariates.
Results
Of 2420 patients, 68 underwent RFA-MBN for axial back pain due to thoracic and/or lumbar compression fractures. Seven patients were excluded due to missing evaluation information. The study included 61 patients with confirmed thoracic and/or lumbar VCFs who underwent RFA between August 2014 and June 2022. The average age was 72.1 ± 11.5 years, with a majority (44 patients) being female. Regarding VCFs, 33 participants had a single fracture, and 28 had multiple fractures. Most fractures were in the lower lumbar region (18), followed by both lower and upper lumbar regions (12), lower thoracic region (13), and upper lumbar region (18). The main causes were osteoporosis (21), trauma (18), cancer (8), unknown causes (9), and osteopenia (5).
The average pain relief percentage and duration were 56.6% (SD = 28.4) and 36.1 weeks (SD = 35.3), respectively. 41 patients experienced at least 50% pain relief for at least three months, with 29 maintaining at least 50% relief for six months. 7 patients reported the procedure as ineffective. The pre-disability index score was a significant predictor of pain relief percentage (p=0.007), with each increase associated with a 0.64% increase in pain relief. Gender approached significance (p=0.097), with females experiencing 13.28% more pain relief than males. PHQ9 scores, used for depression assessment, showed a positive correlation with pain relief percentage (p=0.12).
Discussion
This study investigated the efficacy of RFA-MBN for managing axial back pain due to thoracic and lumbar VCFs. The retrospective chart review included 61 patients, one of the largest reported cohorts. The procedure provided an average pain relief of 56.6% lasting 36.1 weeks, with 67.2% of patients experiencing ≥50% pain relief for ≥3 months. The pre-disability index score was a significant predictor of therapeutic efficacy, correlating with better post-RFA pain relief percentage. The study highlights the potential of RFA-MBN as a viable long-term therapeutic option for VCF-related pain, especially compared to more invasive procedures.
The clinical relevance is emphasized by the rising incidence of VCFs in aging populations and the controversies surrounding vertebral augmentation procedures. RFA-MBN is an established treatment for facet-mediated pain in degenerative spondylosis, and its role in posterior element pain after VCFs has been underexplored. The study provides evidence for RFA-MBN as a preferred modality for pain relief, reducing posterior element pain by interrupting nociceptive signaling and local inflammation.
The study also demonstrates novelty by reporting a large series of patients with compression fractures from various causes and levels. It fills a gap in the literature, as few large-scale studies have explored RFA-MBN specifically in the VCF population. The procedure's minimally invasive profile, utilizing small gauge electrodes, is advantageous over bone cement procedures, which require larger gauge needles and may cause complications like pulmonary emboli and vascular injury.
RFA-MBN's benefits include its low risk, high yield, and ability to spare medication management in some cases. It is particularly beneficial for complex patients with comorbid disease, who often exhibit high disability and dysfunction. The study shows that RFA-MBN provides greater clinical benefit for these patients, considering their profound baseline disability.
The study has limitations, including its retrospective nature, potential selection bias, and incomplete data collection. Patient-reported pain relief may introduce measurement bias, and the absence of a control group precludes direct comparison with vertebroplasty, kyphoplasty, or conservative options. The study only included monopolar thermal ablation, and future research should explore other RFA techniques. The average duration of relief provides limited information on long-term efficacy, and prospective studies with longer follow-up are needed.
Conclusions
The study describes a nearly 10-year experience with RFA-MBN for VCFs due to various causes, including metastatic cancer and osteoporosis. RFA-MBN could be a low-risk intervention in the treatment algorithm for posterior element pain in VCF patients, especially compared to invasive options. The study shows promising pain relief, with sustained improvement, particularly in patients with higher pre-disability levels. Further research is needed to compare RFA-MBN with cement-based interventions, but this study supports its use as a safe and effective treatment alternative for VCF-related pain.
