Diagnostic Facet Joint Injections
Due to the lack of reliable history, physical exam, or imaging to predict response, providers must rely on facet interventions diagnostic injections given for diagnostic purposes to determine if the facet joint is the source of suspected spinal pain. There is controversy over optimal patient selection for diagnostic injections, which measures successful response and type and number of diagnostic injections performed.
Numerous investigations have been undertaken to correlate symptoms and physical exam findings with facet pathology and have concluded conventional clinical findings are unreliable in identifying facet joint success4,6,7. A 2020 summary of the literature by Cohen et al. “Consensus practice guidelines on interventions for lumbar facet joint pain from a multispecialty, international working group” (2020 Consensus Guidelines) included 21 studies evaluating the association of physical exam findings with facet block results, and conclude there was no historical or physical exam findings that could reliably predict response to facet joint blocks, grade C evidence, low level of certainly4. This is consistent with ASIPP 2020 “Comprehensive Evidence-Based Guidelines for Facet Joint Interventions in the Management of Chronic Spinal Pain: American Society of Interventional Pain Physicians (ASIPP) Guidelines (2020 ASIPP Guidelines) which rated accurate diagnosis of facet joint pain with physical examination and symptoms level IV with a weak strength of recommendation7. 2020 NASS Guidelines reported insufficient evidence to make a recommendation for or against patient -reported reproduction of pain during a facet joint injection as a predictor of response to dual diagnostic blocks with a grade 1 recommendation5,7. A careful medical history and exam remain an important component to the evaluation of other etiologies of low back pain and raise suspicion of facet source7. Physical findings can help identify levels for blocks, and maneuvers can aid in the detection of radicular symptoms4.
Imaging studies have been investigated as a marker of painful lumbar facet joints. While degenerative changes can be found in imaging, they have not been correlated as a reliable predictor of success with facet interventions4,7. Nonetheless, imaging studies often play an important role in the exclusion of other etiologies of back and cervical/thoracic pain. Single-photon emission computed tomography (SPECT), a nuclear medicine imaging technique, can identify active inflammatory markers as seen in facet disease but have not shown consistent results in the prediction of facet joint intervention success. 2020 Consensus Guidelines reported on 12 studies and concluded moderate evidence for SPECT (grade C, moderate certainly) and weak evidence for scintigraphy, MRI, and CT with no to weak supporting evidence4. 2020 ASIPP Guidelines reported level III evidence for SPECT with weak strength of recommendation and level V evidence for other imaging modalities, weak recommendation7.
Conservative treatment, also called medical/interventional treatment, includes integrative treatments (such as acupuncture (see NCD 30.3) or spinal manipulation); physical treatments (physical therapy including exercise, heat and cold modalities, massage), medications (NSAIDS/antidepressants), and lifestyle modifications (weight loss, sleep hygiene, nutrition, smoking cessation) are typically perused before interventional procedures. Facet joint pain is frequently accompanied by other pain etiologies, which may benefit from conservative modalities or combined therapy, and it is well accepted that some back pain will resolve spontaneously or with conservative or non-invasive measures over time. A few studies have had a conservative arm, or investigated combined modalities that support a combined approach, but did not find a conservative approach alone consistently lead to improvement5,8. The Agency for Healthcare Research released a systematic review of noninvasive nonpharmacological treatment for chronic pain, including neck and low back. Two hundred two trials were included which evaluated the spectrum of non-invasive treatment modalities, concluded durable slight to moderate improvement in function and pain for specific chronic pain conditions and support clinical strategies that focus on non-pharmacological and non-invasive therapies9,10. 2015 NASS Guidelines recommend a failure of at least four weeks of non-invasive care11, 2020 Consensus Guidelines recommend a 3-month trial of different non-invasive treatment4, 2020 ASIPP Guidelines rated level of evidence II with a strong recommendation for three months after onset and failure of conservative management7; European Guidelines extend the period to one year12. Chronic pain may lead to stress, anxiety, poor sleep and depression, and other psychological sequalae and treatment beyond the pain symptoms may be necessary. Optimally a biopsychosocial model that promotes a multi-disciplinary team approach addressing physical pain and psychological factors are utilized13. Patients with chronic pain may also benefit from cognitive behavioral therapy, biofeedback, and other psychological interventions14.
Due to the lack of reliable history, physical exam, or imaging to predict response to facet interventions, diagnostic injections may be given for diagnostic purposes to determine if the facet joint is the source of suspected spinal pain. The response pattern to diagnostic facet joint injections has become the gold standard for diagnosing facet syndrome. Temporary or prolonged abolition of the spinal pain suggests that facet joints were the source of the symptoms1. The possibility of false-positive and false-negative reporting is an inherent risk with facet blocks and challenges identifying the patients most likely to have a positive response to treatment4,7. Intra-articular (IA) and medical branch blocks (MBB) have been evaluated for predictive value for successful RFA. 2020 ASIPP Guidelines reported on ten studies in the lumbar spine and found prevalence rates ranged from 27% to 40% with false-positive rates of 27% to 47%, with ≥ 80% pain relief. They conclude level 1-2 evidence with moderate to strong strength of recommendation of lumbar, diagnostic facet nerve blocks7. While both IA and MBB blocks have been shown in studies to be predictive of success with RFA (2020 Consensus Guidelines grade B recommendation, low level of certainty)4 five studies comparing lumbar MBB to IA injections, including two randomized studies15,16 supports MBB as the preferred modality, largely due to high technical failure rate and pain associated with the IA injections. One randomized trial focusing on younger patients shows IA injection with steroids may play a role in patients in which MBB is contraindicated (Grade C evidence, moderate certainty)4. The Greater Manchester EUR Policy Statement on Facet Injections no longer commissioned IA facet injections and recommended medial branches nerve blocks for diagnostic evaluation for RFA12. The Spinal Intervention Society (SIS) recommended that medial branch blocks replace intra-articular injections as a diagnostic indicator1.
In order to determine if a block is successful, there must be an assessment/measurement of pain and function. There are three points in which pain/function must be evaluated: 1. baseline; 2. after a diagnostic block; and 3. at each follow-up to evaluate long term relief. The definition of success lacks consistency, and there are different cut off values in the literature. Among the Multi-MAC subject matter expert panel, there was an agreement that subjective improvement in pain is a valid measurement of improvement in pain (average voting score of 3.8/5). However, there was not agreement on what the cut-off should be, if a tool should be used, and if so, which tool. There was also a consensus that function is the most important indicator of success. A study assessed the validity of subjective improvement rating improvement after one IA joint injection and compared subjective rating to use of VAS scoring and concluded that validity of pain provocation alone as criterion standards in patients undergoing diagnostic facet injections should be questions with the positive predictive value of 16% for predicating facet joint as a source of pain17. Clinical trials and policy have used multiple standardized tools to measure pain, including the Numerical Rating Scale (NRS) and Visual Analog Score (VAS), with pre-set cut off values in attempt to determine a specific measurement in which patient’s may most benefit from intervention. Studies have evaluated if a specific cut-off value can predict outcomes of RFA and do report a high correlation between verbal rating scales, NRS and VAS score in prediction of outcomes with RFA. However, the panel did not agree on a minimum value that can be used with these tools. The panel did agree that measurement of function can provide valuable clinical input into improvement, such as the ability to stand, walk, and the ability to do activities of daily living and can predict success with future therapeutic procedures. There are multiple tools to measure function including the Pain Disability Assessment Scale (PDAS)18, Oswestry Disability Index (ODI)19, Oswestry Low Back Pain Disability Questionnaire (OSW), Quebec Back Pain Disability Scale (QUE)20, Roland Morris Pain Scale21, Back Pain Functional Scale (BPFS)22,and the easy to use PROMIS profile domains which have been found to correlate well with the ODI scale23.
For the diagnostic block, the pain relief achieved is temporary and used as a predictor of success for subsequent RFA. The objective is to reduce false-positives that would not be predictive of success with RFA and avoid false-negative patients who could benefit but would not be offered treatment. Most studies have used a cut-off of pain relief greater than 80% to consider MBB as positive. Ten studies assessing the prevalence of lumbar facet joint pain using a cut-off value of 80% relief reported with a prevalence rate of 27% to 40% with false-positive rates of 27% to 47% receiving a moderate to strong recommendation from 2020 ASIPP Guidelines 7. One paper reports dual comparative blocks are advocated as a means of identifying true-positive cases and excluding placebo responders and have been shown to have a sensitivity of 100% and a specificity of 65%24.
As stated in the 2020 Consensus Guideline: “the cut-off designating an MBB as positive is one of the most controversial areas in pain medicine”4. Cohen et al in 2013, prospective study to evaluate predictive values and reported no difference in the predictive value of ≥ 50% to <80% pain reduction vs. ≥80% pain reduction25. The guidelines advocate for using ≥50% for clinical trials and clinical practice. The guidelines acknowledge that the existing evidence does not adequately address the 50-80% group and that this cut-off was selected to maximize access to care given the lack of reliable alternative treatment options in this population and potential benefit of treatment in this group4. On the contrary, there are studies that show patients with ≥80% relief are more likely to show a positive response to RFA. 2020 ASPP Guidelines report Level 1 to II evidence based on ten diagnostic accuracy studies (using ≥75% and ≥80% criterion) and offer moderate to strong strength of recommendation. They cite the literature using the 50% cut-off is conflicting due to internal inconsistencies7.
There is controversy regarding the number of diagnostic blocks needed to ensure an accurate diagnosis before proceeding with RFA. Derby et al. evaluated the correlation of lumbar MMB with diagnostic MMB cutoff values to optimize therapeutic outcomes and a failure of single MMB and conclude with a dual block protocol a 70% cut-off value was acceptable. With a single block, 80% or higher was optimal26,27. Three systematic reviews also showed significantly better improvement with dual MBB with 80% cut off value28-30. Two randomized controlled trials (one in the cervical region) demonstrated positive results with dual blocks31,32. SIS and ASIPP advocate for dual diagnostic blocks, and diagnostic accuracy is reduced if lower cut-off criteria are used. In contrast, the 2020 Consensus Guidelines advocate for single blocks using a 50% cut-off. One RCT compares outcomes of stratified by different prognostic values and reported the success rate in those who underwent RFA in the zero (no block), single and double block groups were 33%, 39%, and 64%, respectively33. Another study reporting on success rates of RFA based on the number of blocks concludes no difference in outcomes based on the number of blocks34. A meta-analysis of five RCT using zero or one block favored RFA35. However, a meta-analysis is challenging given the high heterogenicity of the literature. The 2020 Consensus Guidelines suggest the number of blocks depends on the goals with dual blocks preferable for research where diagnostic accuracy is critical while single (or no) blocks reduce the number of procedures and access to care. Balancing these factors, they recommend a single block reporting moderate evidence that dual blocks result in higher success with RFA, but zero-block results in the highest number of patients with a positive response to RFA4. The result of voting from the Multi-MAC SME Panel was a score of 3.2/5, stating confidence in the clinical literature to support two MMB needed to diagnose facet pain. North American Spine Society (NASS) Guidelines recommend dual MBB blocks on two separate occasions and second block administered only if >80% relief with the first block due to an unacceptably high false-positive rate of single diagnostic injection11. In the 2020 NASS Evidence-Based Clinical Guidelines for Multidisciplinary Spine Care, they state a single diagnostic IA injection with 50% pain relief provides no clinically meaningful improvement at six months (Grade of Recommendation B) and insufficient evidence to make a recommendation for or against the use of RFA (Grade of Recommendation I(Insufficient))5.
The literature and societal guidance report that diagnostic injections should be medial branch blocks, not intraarticular injections. This is agreed upon in the 2020 Consensus Guidelines, 2020 ASIPP Guidelines, and NASS Guidelines. NASS Guidelines state IA facet injections have not been validated for diagnostic use, and the false positive rate is unknown as well as lack of effectiveness studies comparing IA vs. MBB in the cervical spine11. The exceptions in the case of the occipitoatlantal and atlantoaxial joints, since there are no medial branch or other intervention to block readily. In these cases, dual blocks with 80% relief are supported by most guidelines5.
Therapeutic joint injections
Intra-articular injections into the facet joint have been used as a treatment modality for facet related pain and remains controversial. Therapeutic injections typically include a corticosteroid as there would not be anticipated long-acting pain relief from a short-term local anesthetic. Among the Multi-MAC Subject Matter Expert (SME) panel, the average voting was 2.70, with a range from 1-4. There is clinical evidence against the use of IA therapeutic facet joint injection. Lilius et al. conducted an RCT including 109 patients who failed to show a difference between saline, steroids, and anesthetic injected around two facet joints36. Carette et al. conducted an RCT including 101 patients with IA lumbar facet pain showed a non-significant difference between the injection of saline and depo-corticosteroid with 22% in steroid group compared to 5% in saline group reporting benefit at six months37. A small RCT, including 41 patients, reported return of pain in 3 days after IA steroid injection compared to 3.5 days in the control38. Kennedy et al. performed a small RCT comparing IA facet injections with a steroid to saline and did not find a change in need for RFA39. In the FACTS study, a double-blinded RCT, Cohen et al. found no significant difference for pain relief or functional outcome change between lumbar facet IA injection with steroid or anesthetic or MBB with steroid, anesthetic or saline for up to 6 months post-injection. Five patients made it to the 6-month follow-up, of which two had RFA. The FACTS study also found that MBB for anesthetic or steroids did not perform better than saline12.
On the contrary, a systematic review by Manchikanti et al. (2015) using a modified approach to the grading of evidence6 and reported 20 RCT assessed with moderate to high-quality methodological criteria. For therapeutic interventions, the evidence was variable from level II to III, with level II evidence for lumbar facet joint nerve blocks and radiofrequency neurotomy for long-term improvement (greater than six months), and level III evidence for lumbosacral zygapophysial joint injections for short-term improvement only. This review provides evidence for the diagnostic validity of facet joint nerve blocks, and moderate evidence for therapeutic radiofrequency neurotomy and therapeutic facet joint nerve blocks in managing chronic low back pain6. These two studies have been criticized for a high proportion of patients taking opioids and prior back surgery, lack of control groups, and the absence of blinding4. Schneider et al reported in rigorously selected patients, 56% of patients had 100% pain relief at six months40. A systematic review by Engel reported sustained relief of 6 months, and 1/3 had relief at one year29.
This is in contrast with another systematic review during the same period that looked at the evidence supporting the use of therapeutic IA facet joint injections for patients with suspected facet joint pain. The review focused on IA facet joint injections with active drug or placebo/inactive injection are more effective in reducing back pain and back pain-related disability than conservative treatment. A total of 391 records were screened, and six trials were included. The trials included were small (range 18-109 participants), and overall in terms of pain and disability outcomes, most were inconclusive. Only two of the trials report any significant between the groups differences in pain or disability outcomes. The authors addressed the limitations and flaws in these trials that were clinically diverse and precluded any meta-analysis. Several methodological issues were identified. The positive results are interpreted with caution and suggest that there is a need for further high-quality work in this area41.
Many societal recommendations that do not support the use of therapeutic facet joint injections include:
- The 2020 Consensus Guidelines developed by a multispecialty international working group recommend against the routine use of therapeutic facet injections giving it a grade D, moderate level of certainty4.
- National Institute for Health and Care Excellence (NICE) guideline on Low back pain and sciatica in over 16s: assessment and management42 recommendations are based on systematic reviews of best available evidence and explicit consideration of cost effectiveness. The NICE recommendation for image-guided facet joint injections “Do not offer spinal injections for managing low back pain. The Guideline Development Group (GDG) agreed that health-related quality of life, pain severity, function, and psychological distress were the outcomes that were critical for decision making. Responder criteria (greater than 30% improvement in pain or function), adverse events, and healthcare utilization were also considered as important. Evidence was reported for all the outcomes except for psychological distress and healthcare utilization. For image-guided facet joint injections, evidence was only available for pain, function, and responder criteria. There was no evidence for any of the other outcomes.” The NICE summary concludes: “Overall, the GDG agreed that there was no consistent good quality evidence to recommend the use of spinal injections for the management of low back pain. There was minimal evidence of benefit from injections, and reason to believe that there was a risk of harm, even if rare. The GDG consequently agreed that it was appropriate to recommend against the use of spinal injections for people with low back pain.”
- The American Association of Neurological Surgeons (AANS) and the Congress of Neurological Surgeons (CNS) 2014 Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine: Part 13: injection therapies, low-back pain, and lumbar fusion. Lumbar intraarticular facet injections are not recommended for the treatment of chronic lower-back pain. The literature does suggest the use of lumbar medial nerve blocks for short-term relief of facet-mediated chronic lower-back pain without radiculopathy43.
- The North American Spine Society (NASS) Evidence-Based Clinical Guidelines for Multidisciplinary Spine Care: Diagnosis and Treatment of Degenerative Lumbar Spondylolisthesis 2nd Edition (2014) reports that there is insufficient evidence to make a recommendation for or against the use of injections for the treatment of degenerative lumbar spondylolisthesis. Grade of Recommendation: I (Insufficient Evidence)11. The 2020 NASS Low Back Pain Guidelines states there is insufficient evidence to make a recommendation for or against the use of steroid injections for suspected facet-mediated pain (Grade 1 Recommendation) nor sufficient evidence for or against the use of 50% reduction in pain following MBB for diagnosis of facet joint pain (Grade 1 Recommendation). The guidelines also state that the outcomes of RFA become more reliable when more stringent diagnostic criteria are used, and relief is durable for at least six months following procedure (Grade B Recommendation)5. NASS Guidelines state while there is some evidence in the literature when compared to RFA, RFA offers longer-term pain relief, and long-term outcomes have not been reported in adequately designed trials. They state that if therapeutic IA injections are used, they should be used in patients whose initial injections resulted in pain relief >50% for at least three months and not be repeated more than three times annually. The guidelines address concern of the majority of research on therapeutic MBBS comes from a single-center, reports on prospective studies and one RCT which had unspecified intervals and cannot determine the true duration of treatment and concern with lack of studies comparing therapeutic MBBs to medical branch RFA5,11.
- Agency for Healthcare Research and Quality (AHRQ) Technology Assessment Program: Pain Management Injection Therapies for Low Back Pain (2015) authors used predefined criteria and selected randomized trials of patients with lumbosacral radiculopathy, spinal stenosis, nonradicular back pain, or chronic postsurgical back pain that compared effectiveness or harms of the epidural, facet joint, or sacroiliac corticosteroid injections versus placebo or other interventions. Also included were randomized trials that compared different injection techniques and large (sample sizes greater than 1000) observational studies of back injections that reported harms. Seventy-eight randomized trials of epidural injections, 13 trials of facet joint injections, and one trial of sacroiliac injections were included. Limited evidence suggested that epidural corticosteroid injections are not effective for spinal stenosis or nonradicular back pain and that facet joint corticosteroid injections are not effective for presumed facet joint pain44.
- A 2009 American Pain Society guideline recommends against the use of corticosteroids into the facet joint14.
Some societal recommendation that supports the use of therapeutic facet join injections include:
- 2020 ASIPP Guidelines7: Therapeutic Facet Joint Interventions in Lumbar Spine states:
- The level of evidence is II with moderate strength of recommendation for therapeutic lumbar facet joint nerve blocks with the inclusion of three relevant randomized controlled trials with long-term improvement.
- The level of evidence is IV with a weak strength of recommendation for lumbar facet joint intraarticular injections with inclusion of nine relevant randomized controlled trials, with most of them showing lack of effectiveness without the use of local anesthetic.
The American Society of Anesthesiologists (ASA) Task Force on Chronic Pain Management and the American Society of Regional Anesthesia and Pain Medicine (ASRA) Practice Guidelines for Chronic Pain Management (2010)45:
- Recommendations for joint blocks: Randomized controlled trials (RCT) report equivocal findings regarding the efficacy of facet joint steroid injections compared with facet saline injections regarding pain relief for patients with low back pain (LBP). However, studies with observational findings for facet joint injections indicate that pain scores are improved over baseline scores for assessment periods of 1-6 months. Intraarticular facet joint injections may be used for symptomatic relief of facet-mediated pain. Medial branch blocks may be used for the treatment of facet-mediated spine pain.
The American Association of Neurological Surgeons (AANS) and the Congress of Neurological Surgeons (CNS) 2014 Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 13: injection therapies, low-back pain, and lumbar fusion states lumbar intraarticular facet injections are not recommended for the treatment of chronic lower-back pain. The literature does suggest the use of lumbar medial nerve blocks for short-term relief of facet-mediated chronic lower-back pain without radiculopathy43.
Radiofrequency neurotomy is described as radiofrequency lesioning performed utilizing either a heat lesion or pulsed mode radiofrequency. A thermal radiofrequency neurotomy lesion for facet denervation is performed at 80° to 85°C. Clinically, a higher temperature allows for a larger lesion to be made. The size of the lesion is influenced by the vascularity of the surrounding tissue: the greater the vascularity of the tissue, the smaller the lesion. Overall, the mechanism of radiofrequency neurotomy is described as denaturing of the nerves. Consequently, with radiofrequency, the pain returns when the axons regenerate, requiring repetition of the radiofrequency procedure. The pulsed mode radiofrequency is an application of a strong electric field to the tissue that surrounds the electrode, and the temperature of the tissue surrounding the tip of the electrode does not exceed 42°C and heat is dissipated during the silent period7.
The effectiveness of radiofrequency ablation to improve pain and function for facet joint mediated back pain in carefully selected individuals has been explored in the medical literature. Clinical trials report conflicting data on the effectiveness of RFA. Most clinical trials defined success with RFA as 50% pain relief at six months.
A 2015 Cochrane review by Maas et al., including 23 RCTs (n=1309), evaluated patients who had a positive response to diagnostic block and underwent RFA found moderate evidence on the effectiveness of RFA compared to placebo for pain management of facet origin over the short term (mean difference (MD) -1.47, 95% confidence interval (CI) -2.28 to -0.67). Low-quality evidence that facet joint RFA is more effective than placebo for function over the short term (MD -5.3, 95% CI -8.66 to -.20) and over the long term (MD -3.9, 95% CI -6.94 to 0.47). RFA for disc pain did not show effects compared to placebo over the short or long term (MD -1.63, 95% CI -2.58 to -.68). They concluded no high-quality evidence to suggest RFA procedure provides pain relief for patients with chronic low back pain46.
Juch et al. reported on 125 patients in the treatment arm and 126 in the control arm (exercise). Patients had a single diagnostic block with at least 50% or more pain reduction before RFA. The mean difference for the primary outcome pain intensity at three months was −0.18 (95% CI, −0.76 to 0.40). The mean difference for functional status at three months was −2.45 (95% CI, −5.53 to 1.03); the RR for global perceived recovery at three months was 1.35 (95% CI, 0.81 to 2.05). This study has been challenged, stating that the lack of efficacy was due to the treatment arm using the perpendicular technique47. Perpendicular electrode placement has been questioned with concern it may fail to reach the target nerve or only capture a segment, while parallel electrode placement reliably captures the target nerve and does so along a substantial length of the nerve. Those who challenge these studies report there are three studies (1999-2008) that utilized the parallel technique that would result in positive outcomes and report support for RFA from these trials47. There are no recent trials that address this controversy.
Leggett et al. (2014) conducted a systematic review to determine the efficacy of RFA for chronic low back pain associated with lumbar facet joints, sacroiliac joints, discogenic low back pain, and the coccyx. Included articles were sham-controlled randomized controlled trials (RCTs), assessed the efficacy of RFA, reported at least one month of follow-up, and included participants who had experienced back pain for at least three months. Eleven sham controlled RCTs were included: three studies involving discogenic back pain, six studies involving lumbar facet joint pain, and two studies involving sacroiliac joint pain. No studies were identified assessing the coccyx. The evidence supports RFA as an efficacious treatment for lumbar facet joint and sacroiliac joint pain, with five of six and both of the RCTs demonstrating statistically significant pain reductions, respectively. The evidence supporting the RFA for the treatment of discogenic pain is mixed. Future studies should examine the clinical significance of the achieved pain reduction and the long-term efficacy of RFA48.
The systematic review (2015) by Manchikanti et al. looked at both therapeutic injections, and RFA in lumbar, cervical and thoracic regions evaluated 21 RCTs and five observational trials, using a modified approach to the grading of evidence3, reported Level II evidence2 for RFA in the lumbar and cervical spine, and level IV in the thoracic region28. A systematic review by Engel et al. 2016, which serves as the basis for NASS recommendations, “The Effectiveness and Risks of Fluoroscopically-Guided Cervical Medial Branch Thermal Radiofrequency Neurotomy: A Systematic Review with Comprehensive Analysis of the Published Data” using the GRADE system for rating. They conclude the majority of patients were pain-free at six months and over a third pain-free at one year29. In 2017, Lee et al. conducted a meta-analysis that included seven trials with 454 patients comparing RFA (n=231) to sham or epidural (n=223) and reported greater improvement in the RFA group35.
2020 ASIPP consensus guidelines7 Table 22 reports on 11 studies on RFA effectiveness and concludes:
Lumbar Spine: The level of evidence is II with moderate strength of recommendation for lumbar radiofrequency ablation with the inclusion of 11 relevant randomized controlled trials (RCTs) with two negative studies and four studies with long-term improvement.
The American Society of Anesthesiologists (ASA) Task Force on Chronic Pain Management and the American Society of Regional Anesthesia and Pain Medicine (ASRA) Practice Guidelines for Chronic Pain Management (2010) Recommendations for Ablative Techniques45: The Task Force notes that other treatment modalities should be attempted before consideration of the use of ablative techniques.
- Chemical denervation: Chemical denervation (e.g., alcohol, phenol, or high-concentration local anesthetics) should not be used in the routine care of patients with chronic non-cancer pain.
- Cryoablation: Cryoablation may be used in the care of selected patients (e.g., post-thoracotomy pain syndrome, low back pain (medial branch), and peripheral nerve pain).
- Radiofrequency ablation: Conventional (e.g., 80°C) or thermal (e.g., 67°C) radiofrequency ablation of the medial branch nerves to the facet joint should be performed for low back (medial branch) pain when previous diagnostic or therapeutic injections of the joint or medial branch nerve have provided temporary relief. Conventional radiofrequency ablation may be performed for neck pain. Conventional or thermal radiofrequency ablation of the dorsal root ganglion should not be routinely used for the treatment of lumbar radicular pain.
National Institute for Health and Care Excellence (NICE) guideline on Low back pain and sciatica in over 16s: assessment and management (2016) Evidence Statement49:
- Radiofrequency denervation compared with placebo/sham for low back pain: Evidence from four studies demonstrated clinical benefit in pain for radiofrequency denervation compared to placebo/sham at both the short and long-term follow-ups of less than and greater than four months (low to moderate quality, n=160). In contrast, there was no difference in function between treatments at any time point. Conflicting evidence from one study for quality of life at less than four months follow-up showed clinical benefit for radiofrequency denervation compared to placebo/sham for the SF-36 domains of general health and vitality. Radiofrequency denervation was inferior to sham for the domains of mental health, pain, and social function. There was no difference between treatments for the physical domain (low quality, n= 81).
Evidence from a single study reporting adverse events at less than four months follow-up demonstrated an increase in adverse effects for radiofrequency denervation in terms of the number of patients with moderate or severe treatment- related pain (low quality, n = 79). There was no difference in other adverse events (change of sensibility and loss of motor function) at short term follow-up when radiofrequency denervation was compared to placebo/sham in the same study (very low quality). Additionally, when compared with placebo/sham, a benefit for radiofrequency denervation in responders to pain reduction measured by global perceived effect was demonstrated by two studies at both the less than and greater than four months follow-up time points. However, this was not seen for pain reduction measured by visual analog scale (VAS) at less than four months reported by a single study (low quality, n equal to 111).
Radiofrequency denervation versus medial branch block:
Evidence from a single study demonstrated clinical benefit in terms of pain for radiofrequency denervation compared to medial branch blocks at both the short- and long-term follow-ups of less than and greater than 4 months (very low quality, n = 100). Radiofrequency denervation has evolved as a treatment for spinal pain over the last 40 years and is a minimally invasive and percutaneous procedure performed under local anesthesia or light intravenous sedation. Radiofrequency energy is delivered along an insulated needle in contact with the target nerves. This focused electrical energy heats and denatures the nerve. This process may allow axons to regenerate with time, requiring the repetition of the radiofrequency procedure.
The duration of pain relief following radiofrequency denervation is uncertain. Data from randomized controlled trials suggests relief is maintained for at least 6-12 months, but no study has reported longer-term outcomes. Pain relief for more than 2 years would not be an unreasonable clinical expectation.
- The de novo economic model undertaken for this guideline for radiofrequency denervation suggested that the treatment is likely to be cost-effective, provided the duration of effect exceeds 16 months.
- If radiofrequency denervation is repeated, we do not know whether the outcomes and duration of these outcomes are like the initial treatment. If repeated radiofrequency denervation is to be offered, we need to be more certain that this intervention is both effective and cost effective.
NASS Guidelines state that therapeutic medial branch RFA is a validated treatment for facet mediated pain, and repeat procedures are equally successful if the response to the initial RFA lasted at least three months. These guidelines advocate dual diagnostic MBB with ≥80% relief of the primary (index pain), and the onset, and minimum duration of relief is consistent with the agent employed. Also, RFA should be performed at the same level no more than twice annually, and only if the initial radiofrequency lesion results in significant pain relief (> 50%) for at least six months. In those situations, a repeat procedure in that year is appropriate15. 2020 NASS Low Back Pain Guidelines states there is insufficient evidence to make recommendations for or against the use of cryodenervation for treatment of zygapophyseal (facet) joint pain5.
The American Association of Neurological Surgeons (AANS) and the Congress of Neurological Surgeons (CNS) 2014 Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 13: injection therapies, low-back pain, and lumbar fusion. Lumbar intraarticular facet injections are not recommended for the treatment of chronic lower-back pain. The literature does suggest the use of lumbar medial nerve blocks for short-term relief of facet-mediated chronic lower-back pain without radiculopathy. Lumbar medial nerve ablation is suggested for 3–6 months of relief for chronic lower-back pain without radiculopathy. Diagnostic medial nerve blocks by the double-injection technique with an 80% improvement threshold are an option to predict a favorable response to medial nerve ablation for facet-mediated chronic lower-back pain without radiculopathy. Still there is no evidence to support the use of diagnostic medial nerve blocks to predict the outcomes in these same patients with lumbar fusion43.
Cervical and Thoracic Spine
Most of the literature focuses on the lumbar region regarding interventional facet joint diagnosis, and the 2020 Consensus Guidelines are specific for the lumbar region. The 2020 ASIPP Guidelines include the cervical and thoracic regions. The 2020 ASIPP Guidelines report level I-II with moderate to strong strength of recommendation for lumbar, diagnostic blocks report ten diagnostic accuracy studies to support the recommendation. ASIPP report level II evidence for the cervical spine with moderate strength or recommendation citing ten diagnostic accuracy studies. Two systematic reviews support reliance on dual diagnostic blocks with 100% relief of the index pain to select patients for the procedure reporting more than 60% selected using this stringent criterion had 100% relief of index pain. They were pain-free at six months and nearly 40% pain free at one year with functional improvement in neck pain29,30.
ASIPP (2020)7Therapeutic Facet Joint Intervention Cervical Spine:
- The level of evidence is II with moderate strength of recommendation for therapeutic cervical facet joint nerve blocks with the inclusion of one relevant randomized controlled trial and three observational studies, with long-term improvement.
- The level of evidence is V with weak strength of recommendation for cervical intraarticular facet joint injections with the inclusion of three relevant randomized controlled trials, with two observational studies, the majority showing lack of effectiveness. In contrast, one study with a six-month follow-up showed a lack of long-term improvement.
- The level of evidence is II with moderate strength of recommendation for cervical radiofrequency ablation with the inclusion of one randomized controlled trial with positive results and two observational studies with long-term improvement.
ASIPP (2020)7 Therapeutic Facet Joint Interventions Thoracic Spine:
Evidence to support use in the thoracic region is sparse. ASIPP reports level II evidence with moderate strength recommendation for thoracic spine, citing three diagnostic accuracy studies.
- The level of evidence is II with moderate strength of recommendation for thoracic therapeutic facet joint nerve blocks with the inclusion of two randomized controlled trials and one observational study with long-term improvement.
- The level of evidence is III with weak to moderate strength of recommendation for thoracic intraarticular facet joint injections with the inclusion of one randomized controlled trial with a six-month follow-up, with emerging evidence.
- Thoracic Spine: The level of evidence is III with weak to moderate strength of recommendation with emerging evidence for thoracic radiofrequency ablation with the inclusion of one relevant randomized controlled trial and three observational studies.
Evidence to support use in thoracic region is further supported by one 2012 systematic review report evidence for diagnostic accuracy of the thoracic facet joint injection, and one 2018 study comparing thoracic IA vs. MBB reporting significant pain relief with thoracic joint injection50,51. NASS guidelines state the lack of supporting literature for the use of IA injections for thoracic pain, however, states the lack of other effective alternative therapies11.
Image guidance has become standard care for facet blocks and RFA procedures, allowing accurate needle placement, monitor contrast and anesthetic spread, and improve safety by direct visualization of bony elements and avoiding surrounding structure. Studies dating back to the 1980s comparing “blind” injections to image-guided concluded that the procedure should not be performed without radiographical imaging. Fluoroscopy is considered the gold standard for facet block procedures, and most studies were conducted with fluoroscopic guidance and consistent with societal recommendations. The US Department of Health and Human Services OIG report in 2008 asserted radiographic guidance is recommended52. One cadaveric study showed improved accuracy with fluoroscopy over CT53. 2020 Consensus Guidelines recommend CT or preferably fluoroscopy for lumbar MBB (grade B recommendation), CT scanning for IA placement (grade C recommendation), and fluoroscopy for medial branch RFA (grade B recommendation, low level of evidence). The Guidelines state fluoroscopy is preferred to CT due to lower cost, faster times, and less radiation exposure than CT4.
The use of ultrasound has been explored as an alternative imaging modality. Cadaveric, retrospective studies, and review of RCT and non-RCT suggest that there is little difference between ultrasound and fluoroscopy guided procedures, however, there are no well-designed studies to report the safety of this approach. Limitations for ultrasound guidance include reduced visibility in obese patients, more challenging to target the proper segment, and not being able to visualize facet joint4. NASS Guidelines state insufficient evidence to support use of ultrasound guidance11. Subject matter experts score low confidence that the facet joint procedures can be performed under ultrasound guidance (score 1.7/5).
Facet Joint Cyst Rupture
Facet joint cysts have been found to have a prevalence of 6.5% and are thought to play a role in facet mediated pain. In these cases, nerve root compression or irritation is associated with radicular pain like other neuro-compressive lesions. Rupture of the cyst has been associated with pain improvement and may potentially avoid more invasive open surgical procedures. In these cases, IA injection is used and often with TFESI to treat radicular pain11 . A systematic review of 870 patients report cyst resolution to be 58% for the percutaneous procedure, and 90% for decompressive procedures concluding advantage of surgical intervention as compared to percutaneous procedures and pain relief with surgical management is estimated 83.5%. Shuang et al. systematic review of 29 studies reported overall the satisfactory results (after short- or long-term follow-up) were achieved in 55.8% [49.5, 62.08] (pooled mean and 95% CI) of the 544 patients subjected to percutaneous lumbar facet joint cyst resolution procedures. 38.67% [33.3, 43.95] of this population underwent surgery subsequently to achieve durable relief54. However, the analysis consisted largely of small retrospective studies and case reports with low-quality evidence. In one prospective, non-randomized study, 120 patient’s satisfaction was reported as 75%, with 25% requiring repeat surgery55. NASS Guidelines address the concern of cyst reoccurrence, which occurs about 50% of the time and does not recommend repeating the procedure more than once and only if the first procure produces satisfactory results, which they define as 50% improvement for at least three months11. The subject matter expert panel voted 3.9/5 in support of facet joint cyst rupture for pain relief.
Centralized Pain Syndrome
Facet procedures by nature treat a local pain condition, while a centralized pain syndrome, such as fibromyalgia, is a generalized pain condition. Patients with centralized pain syndromes are thought to have alternations in central neurotransmission. A prospective study with 548 patients diagnosed with primary spine pain were also evaluated for fibromyalgia criteria before spinal interventions. 42% of the patients meet diagnostic criteria for fibromyalgia. They determined a profound phenotypic difference in those with fibromyalgia as compared to those with spinal pain alone associated with more neuropathic pain descriptors, anxiety, greater pain interference and lower physical function. The authors concluded that the phenotypical factors found in the fibromyalgia group may be predictive of poor outcomes in spine intervention procedures56. Exploration of factors associated with poor outcomes from lumbar RFA and long duration pain was correlated with treatment failure57. There is insufficient literature that addresses if facet joint procedures are beneficial for centralized pain conditions.
Intrafacet implants have been proposed as an alternative technique to surgical fusion. They involve the placement of an allograft dowel made from bone (from femur or tibia) and placed surgically or via the minimally invasive procedure. The allograft, which is processed by licensed tissue banks, which must be compliant with FDA requirements for tissue processing, are not subject to FDA 510K clearance and can be marketed. There are no clinical trials that address the efficacy and safety of these implants. The report on six cases did not indicate efficacy58.
Several alternatives to percutaneous radiofrequency denervation have been proposed, including pulsed radiofrequency, cryoablation, laser ablation, and chemical ablation, in which a neurolytic substance (e.g., alcohol, phenol, glycerol) is injected into the affected nerve root. An alternative method of denervation using an endoscopic approach (i.e., endoscopic dorsal ramus rhizotomy) has also been proposed59. The literature on these modalities is largely limited to case reports or small series with mixed results60-63. One RCT (n=80) comparing pulsed radiofrequency ablation to steroid injections concluded it may be more effective than steroids64. A RCT (n=50) compared study of continuous to pulsed radiofrequency ablation and did not report significant differences65. Long term safety and efficacy data is lacking. The American Society of Anesthesiologists (ASA) Task Force on Chronic Pain Management and the American Society of Regional Anesthesia and Pain Medicine (ASRA) Practice Guidelines for Chronic Pain Management (2010) Recommendations for Ablative Techniques: The Task Force notes that other treatment modalities should be attempted before consideration of the use of ablative techniques45.