Patient selection

Selection criteria for patients undergoing radiofrequency ablation (RFA) have long been influenced by protocols set by the Centers for Medicare & Medicaid Services (CMS) and health insurance companies. In this chapter we will discuss patient selection, indications, and contraindications.

When treating classical targets for radiofrequency ablation, such as the medial branch nerves for facet arthropathy, genicular nerves for knee osteoarthritis, and the recently more popular cluneal nerves for cluneal neuralgia, the clinician is responsible for educating the patient as to the process of diagnostic blockade(s) and follow-up rhizotomy. Patients do not always comprehend that a diagnostic block is not necessarily intended to be therapeutic. It must be emphasized that a brief period of analgesia is anticipated, followed by a return of symptoms. Factors such as language barriers, cognitive disorders, and cultural beliefs all may influence the patient’s perception of the diagnostic block and misguide expectations.

It is important to educate both the patient and spouse or caregiver as to the nature of the diagnostic procedure in order to obtain the most accurate feedback. Caregivers may not understand the purpose of the injection and may assume failure when the pain returns. Patients should be evaluated within the time frame of the local anesthetic’s peak effects. It is not always possible or practical for the treating physician to be present during this time period.

The clinical staff, patient, escort, or caregiver should observe the effects of the procedure during the period of the drug’s peak action. They should take note of the pain score upon initial presentation as well as after the injection and record the duration of analgesia. This should be documented at the time of the evaluation to avoid confusion during follow-up visits.

Patients who have a positive response to diagnostic blockade are assumed to have a diagnosis of facet arthropathy, neuralgia, or pain in the territory of the nerve in question and are presumed to be amenable to longer-term therapies such as radio frequency ablation. With an increasing variety of options such as cryotherapy, peripheral nerve stimulation of the medial branch nerve (at the multifidus muscle), steroid injection, or regenerative medicine procedure (platelet-rich plasma, etc.), one must carefully weigh risks, benefits, goals of therapy, as well as insurance coverage to determine the best course of treatment for the patient.

Patient selection is paramount to success. Coexisting diseases such as diabetes mellitus make steroid injections less attractive, and therefore these patients may opt for rhizotomy to achieve longer periods of analgesia. Radiofrequency ablation has been used as a treatment option for more than 40 years, and many patients are familiar with the procedure. As a result, it may be easier for patients to accept this treatment as opposed to using an implantable or temporary peripheral nerve stimulator, which entails the percutaneous implantation of leads.

Selection criteria

Patients should be selected based on the following criteria:

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  have experienced pain at least 3 months and have failed conservative treatment,

  
  
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  have seen relief with diagnostic nerve block(s) of at least 50%, or

  
  
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  have had previous relief of RFA at same location for at least 3 months—but not to be performed more than two times per 12 months.

Indications

Radiofrequency ablation has traditionally been used to treat pain related to osteoarthritis of the facet joints of the spine and knee. In the spine, it is commonly performed in the lumbar and cervical region due to mobility at these levels. The lower weight-bearing levels are more commonly affected and are therefore typically targeted. It is widely accepted that the patient should have failed 3 months of conservative management prior to diagnostic procedures and RFA.

Facet joints

Lumbar medial branch radiofrequency ablation was first introduced in 1975, and utilization of RFA has grown over the last several decades. There are many studies aimed at evaluating the effectiveness and durability of lumbar medial branch nerves, as well as studies utilizing guideline-concordant patient selection and procedural techniques.

Conger et al. described outcomes in patients selected using a guideline-concordant paradigm of ≥80% pain relief with dual comparative medial branch blocks (MBBs). They investigated long-term treatment outcomes for patients selected according to this paradigm and compared the medical records of 111 consecutive patients; 85 met inclusion criteria in a cross-sectional study.

Inclusion criteria consisted of (1) age >18 years, (2) axial low back pain of 3 or more months’ duration, (3) documented ≥80% relief of index pain with dual comparative MBBs before RFA, and (4) willingness to participate in a phone interview.

A standardized telephone survey was used to capture current numeric rating scale (NRS) and Patient Global Impression of Change (PGIC) scores. The primary outcome was the proportion of patients reporting ≥50% reduction of index pain. Binary logistic regression analysis was performed to explore associations between the primary outcome and covariates, including age, duration of pain, presence of scoliosis, degenerative spondylolisthesis, and >75% disc height loss.

The authors that at a minimum of 6 months, 70.6% of patients reported a pain reduction of two or more points (minimally clinically important change), and 54.1% reported a PGIC score consistent with “much improved” or better. Older age and a smaller Cobb angle were associated with a ≥50% pain reduction (P < 0.05).

Dreyfuss et al. studied patients selected for lumbar medial branch RFA (utilizing >80% relief) and found that about 60% of patients experienced 90% pain relief at 12 months and 87% experienced 60% relief. This research sample excluded patients with comorbid depression, hip or knee pain, spinal stenosis, spondylolisthesis, or >75% loss of disc height. It was a small sample size (N=15) and therefore may not be generalizable in clinical practice.

McCormick et al. studied 34 patients after screening for inclusion criteria that included >75% pain relief with one set of diagnostic medial branch blocks. When assessing for measures such as ≥50% improvement in function, ≥50% improvement in pain; change in median NRS pain score, daily morphine equivalent dose (MED), Medication Quantification Scale III (MQS III) score, and procedure complications, researchers found that at a median duration of follow-up at 39 months, patients reported function and pain improved by ≥50% in 58% (CI 45%, 71%) and 53% (CI 40%, 66%) of individuals, respectively. The median reduction in MQS III score was 3.4 points (0, 8.8). No complications occurred in this cohort.

With regard to the cervical medial branch nerves, Engel et al. performed a comprehensive literature search to determine the effectiveness of cervical medial branch thermal radiofrequency neurotomy in the treatment of neck pain or cervicogenic headache based on different selection criteria. A comprehensive literature search was performed, the authors were screened, evaluated, and studied to measure the success rate of the procedure, defined by varying degrees of pain relief following neurotomy, and the data was stratified by the number of diagnostic blocks and degree of pain relief. They found that the data displayed a greater degree of pain relief more often when patients were selected by triple placebo-controlled medial branch blocks or dual comparative medial branch blocks, producing 100% relief of the index pain. The degree of pain relief was similar when triple or dual comparative blocks were used.

MacVicar et al. examined patients suffering from chronic neck pain and performed a prospective outcome study. The goal was to determine the effectiveness of cervical medial branch radiofrequency neurotomy (RFN) performed by two practitioners trained according to rigorous guidelines. Medial branch blocks were performed on patients who presented with neck pain, with or without referred pain to the head or shoulder girdle, and in whom it was suspected that the source of the patient’s pain may be a cervical zygapophysial joint. They found that in the two practices, utilizing rigorous guidelines, 74% and 61% of patients achieved a successful outcome. They noted that relief lasted 17–20 months from the first RFN and 15 months for repeat treatments. Allowing for repeat treatment, patients maintained relief for a median duration of 20–26 months, with some 60% still experiencing relief at follow-up.

Knee

Patients suffering from severe osteoarthritis (OA) report that pain does not reliably respond to conservative therapies and may persist in more than 40% of patients who undergo joint replacement. Radiofrequency ablation to the knee’s nerve supply may be done in the presence of an artificial joint and may be an alternative to surgery or surgical revision.

Choi et al. compared genicular nerve RFA to sham RFA. Nerves targeted in this trial were the SM (superior medial), IM (inferior medial), and SL (superior lateral) genicular branches. Inclusion criteria were (1) age between 50 and 80 years, (2) presence of refractory knee pain of at least 3 months duration, and (3) at least grade 2 radiographic evidence of OA on the 5-point Kellgren–Lawrence scale. They found that RFA significantly lowered the visual analogue scale (VAS) at all time periods compared to sham, but both groups showed similar improvement at 1 week, suggesting a temporary improvement with local anesthetic nerve block. ^,

Shen et al. compared RFA with platelet-rich plasma (PRP) and sodium hyaluronic acid (HA) to PRP and HA alone. Inclusion criteria consisted of patients suffering from refractory pain of at least 3 months duration due to OA and pain level of at least 6 on a 0–10 VAS. Both groups received intraarticular injections of PRP and HA weekly for 5 weeks, but the treatment group also received RFA at 70°C. The study failed to mention timing of treatment as well as label the precise nerves, nor did it specify whether image guidance was used. Twenty-seven patients were randomized to each group and follow-up was obtained at the completion of intraarticular injections and 3 months. Outcome measures included pain intensity as measured on a VAS, life quality as measured on the 36-item Short-Form Health Survey, and function via the American Knee Society Score. Both groups showed improvement in pain and function. The RFA group had gains that were statistically superior at all time periods. The RFA group also demonstrated significant improvement in quality of life at 3 months, while the control group did not.

Davis et al. performed the largest study to perform CRFA (cooled radio frequency ablation). One hundred and fifty patients met the criteria and were randomized to receive either CRFA or intraarticular steroid injection. The SM, LS, and IM genicular nerves were targeted. Patients who had at least grade 2 Kellgren–Lawrence radiographic OA, refractory knee pain of at least 6 months duration, pain 6 out of 10 on the NURS, Oxford Knee Score (OKS) of at least 35, and at least 50% improvement with genicular nerve blocks were included. They found that function and global perception were superior in the CRFA cohort but that there was no difference between total opioid consumption between groups. The authors noted that the longer duration of relief with CRFA may be related to a larger legion size.

Contraindications

Radiofrequency procedures are safe, but there are a few absolute contraindications including patient refusal, local infection, and pregnancy. Relative contraindications do not prevent these procedures, but special precautions and considerations may have to be undertaken prior to each procedure. Anticoagulation is a relative contraindication. Lumbar medial branch RFA, thoracic medial branch RFA, and genicular nerve RFA are considered low-risk procedures according to Narouze et al.

According to these guidelines, in most situations the anticoagulation medication should not be held but a consultation with the patient and prescribing physician should be performed. Cervical medial branch RFA is considered a moderate risk procedure, and each anticoagulation should be held according to the guidelines. Coagulation studies also should be reviewed as appropriate. The recent Spine Intervention Society’s Fact Finder for Patient Safety article on RFN for patients who have PPM/AICD (permanent pacemaker/automatic implantable cardioverter-defribrillator) by Clark et al. recommends patient education on risks of the procedure with the device, follow-up with cardiologist or electrophysiologist, and to follow their recommendations including but not limited to magnet placement, external defibrillator/pacing pads, or day-of-procedure support. Cohen et al. recommend a consultation with the healthcare team managing the implanted device prior to the RFA procedure. A discussion should be had with the patient about possible device damage. There was a recent care report of an epidural abscess after lumbar medial branch blocks in patients on disease modifying antirheumatic drugs and corticosteroids by Onyima et al. Patients who are on immunosuppressants, including DMARDs and steroids should be counseled about the relative risks.

Absolute contraindications include:

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  patient refusal,

  
  
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  local infection,

  
  
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  pregnancy, and

  
  
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  inadequate pain relief with diagnostic injections

Relative contraindications include:

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  anticoagulation (lumbar medial branch, thoracic medial branch, and genicular nerve RFA are considered low-risk procedures; cervical medial branch RFA is considered a high-risk procedure),

  
  
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  PPM/AICD,

  
  
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  neurostimulator devices,

  
  
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  immunosuppression,

  
  
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  uncooperative patient, and

  
  
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  bacteremia