Radiofrequency Rhizotomy for Facet Syndrome

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Chapter 14 Radiofrequency Rhizotomy for Facet Syndrome

Chapter Overview

Chapter Synopsis: Neck pain remains among the most difficult pain conditions to accurately diagnose and therefore to successfully treat. Cervical pain can arise from structures including the disci intervertebrales, the vertebrae themselves, the joints, and the ligaments and muscles that surround them. Although trauma and degeneration can be causes of pain, other neck pain syndromes may require investigation. The quality and temporal characteristics of pain as well as concurrent neurological symptoms can lend clues to its source. Anesthetic injections may be used for a diagnostic block. A classification system for “grades” of neck pain has recently been proposed that may help to standardize neck pain diagnoses. Corticosteroid injection, medial branch blocks, and radiofrequency (RF) nerve ablation may all be considered as interventional therapies after more conservative approaches for chronic neck pain have been exhausted. This chapter considers the procedural details associated with these procedures for lumbar facet pain as well as cervical pain.

Important Points:

Clinical Pearls: As in any interventional technique, patients need to be carefully selected prior to offering interventional treatment for pain originating from the zygapophyseal (facet) joints. After treatment, outcome assessment and complication evaluation are mandatory.

Clinical Pitfalls:

Cervical Facet Pain

Establishing the Diagnosis

Background

Neck pain is defined as pain in the area between the base of the skull and the first thoracic vertebra. Pain extending into adjacent regions is defined as radiating neck pain. Pain may radiate into the head (cervicogenic headache), shoulder, or upper arm (radicular or nonradicular pain).1 A distinction is made between trauma-related neck pain (whiplash-associated disorders) and degenerative neck problems. Because the causes of neck pain often are unclear, a distinction is made between the cause and source.2 The following innervated structures in the neck may be sources of pain: vertebrae, discs, uncovertebral (Luschka) joints, ligaments, muscles, and facet (zygapophyseal) joints.

Beside the cervical discus intervertebralis, other structures in the neck, such as facet joints and uncovertebral joints, may also show degenerative signs. A diagnosis is defined as a clinical picture with known etiology and prognosis. A syndrome is a combination of symptoms occurring at a higher frequency in a certain population.

Cervical facet syndrome is defined as a combination of symptoms:

There is a great deal of research into degenerative signs of the cervical vertebral column. In the discus intervertebralis (1) annular tears, (2) discus intervertebralis prolapse, and (3) endplate damage and internal discus intervertebralis disruption have been identified as potential structural discus intervertebralis pathologies.3 Other structures in the neck, such as the facet joints and uncovertebral joints, may also show degenerative signs. The hypothesis that discus intervertebralis degeneration and discus intervertebralis narrowing increase facet joint loading and consequently facet osteoarthritis seems plausible but has yet to be proven. Some researchers claim that the discus intervertebralis and the facet joints can be seen as independent pain generators.4

Compared with research on lumbar facet pain, research on cervical facet dysfunction is relatively recent. In 1988, Bogduk and Marsland5 described the positive effect of injection of local anesthetics close to the facet joints in patients with neck pain. Dwyer et al6 showed that injection of irritating substances into the facet joints results in a specific radiation pattern (Fig. 14-1). The same radiation pattern is seen with mechanical and electrical stimulation. However, because it was later demonstrated that stimulation of the discus intervertebralis produces the same radiation pattern as stimulation of the facet joints, this is probably a segmental phenomenon.

Clinical findings of degenerative signs are mainly based on radiological findings. Spondylosis (disorders of the nonsynovial joints) and osteoarthritis (facet osteoarthritis) are frequent in advanced age. Degenerative disorders are usually seen at the low and midcervical levels (C4-C5, C5-C6, C6-C7). A causal relationship with pain symptoms has not been proven.

Diagnostic Blocks

The working diagnosis of facet pain based on history and clinical examination may be confirmed by performing a diagnostic block. Local anesthetic can be injected intraarticularly or adjacent to the ramus medialis (medial branch) of the ramus dorsalis of the segmental nerve.2,9 Diagnostic medial branch block procedures are performed under fluoroscopy. There is no consensus about the definition of a successful diagnostic block. Some authors claim that 100% pain relief should be achieved.10 But Cohen et al7 showed that there is no difference in outcome of the RF treatment of patients reporting 80% and those reporting more than 50% pain reduction after a diagnostic block. In daily clinical practice, we consider a diagnostic block successful if more than 50% pain reduction is reported.

To minimize the number of false-positive results, a number of researchers have suggested that a second block should be carried out using a local anesthetic with different duration of action (e.g., lidocaine and bupivacaine; comparative double blocks). Only if the patient responds concordantly (longer or shorter pain reduction depending on the duration of action of the local anesthetic) is this indicative of facet joint pain. This is not an etiological but a pharmacological criterion. These researchers suggest that double blocks are the gold standard for the diagnosis of facet pain. A gold standard, however, should be generally accepted and used. The concept of double blocks has theoretical and practical shortcomings. A best evidence synthesis on the assessment of neck pain concluded that diagnostic facet injections have not been validated to identify facet joint pain.11

In summary, on the basis of history and physical examination, a working diagnosis of cervical facet pain is defined. One diagnostic block can be recommended for confirming the clinical working diagnosis of facet pain. A block is considered positive when the patient experiences 50% pain reduction.7

Anatomy

The vertebrae from C2 to S1 articulate with one another at the medial intervertebral joints, or disci intervertebrales between their corpora vertebrae and the lateral intervertebral, zygapophyseal, or facet joints between their processus articulares. The complex of two adjacent vertebrae with their intervertebral joints and ligamentous interconnections is defined as a segment.

The facet joint is located between the processus articularis inferior of a superior vertebra and the processus articularis superior of the adjacent inferior vertebra. It is a synovial joint with joint surfaces, a synovial membrane, and a joint capsule. The bony facets are covered with hyaline cartilage, and the joint capsule is fibrous. The chain of facet joints forms the facet column and permits segmental gliding movements between the vertebrae.

The cervical facet joint capsules are longer and looser than the facet joint capsules in the thoracic and lumbar regions.12 The more or less flat facet joint surfaces from C2 to C7 form an angle of approximately 45 degrees with the longitudinal axis through the cervical spinal column with a large range of intra- and interindividual variability. Compared with the lumbar facet joints, the cervical facet joints have a high density of mechanoreceptors. McLain took twenty-one cervical facet joint capsules and surrounding tissue from three human subjects by block-excision and processed them in a modified gold chloride technique.13 In twenty-five micron serial histological sections he identified, according to the classification of Freeman and Wyke, encapsulated Type I, II, and III mechanoreceptors and non-encapsulated Type IV mechanoreceptors. The Type II receptors were found most frequently, mainly localized in the dens, fibrous joint capsule. Fewer Type I receptors were identified in both the capsule and the areolar, loose connective tissue. Only a handful of Type III receptors were found, at the junction between the capsule and the loose connective, sub-synovial tissue. Unencapsulated, nociceptive Type IV free nerve endings were present throughout the capsule, synovium, and areolar tissue.14

The facet joints from C3 to C7 are innervated by the ramus medialis (medial branch) of the ramus dorsalis of the segmental nerve (Fig. 14-2). Each facet joint is innervated by nerve branches from the upper and lower segments (Fig. 14-3).15

Imaging

In specific cases, plain radiography of the cervical spinal column (two or three directions) can be indicated to exclude tumor or fracture. Plain radiography does not, however, provide information for establishing the diagnosis of facet problems. This examination can help in estimating the degree of degeneration. The anterior spinal column is inspected for narrowing of the discus intervertebralis and anterior and posterior osteophyte formation. The posterior spinal column is inspected for facet osteoarthritis (facet sclerosis and osteophyte formation). In 1963, Kellgren et al16 stated that when degenerative changes are seen on plain radiography, anatomical degeneration has already reached an advanced stage.

With progressing age, degenerative changes are more frequently seen: 25% at the age of 50 years up to 75% at the age of 70 years.17 An age-related prevalence study concerning facet joint involvement in chronic neck pain indicates a comparable prevalence among all age groups.18

Degenerative changes of the cervical spinal column are present in asymptomatic patients, indicating that degenerative changes do not always cause pain. However, the conclusion that there is no relation between degeneration and pain cannot be drawn. There are studies indicating a relationship between degenerative changes and pain symptoms.17,19

In summary, a relationship between radiologic identification of degenerative changes and pain symptoms is not proven. If neurological etiology of the pain symptoms is suspected, magnetic resonance imaging (MRI) or computed tomography (CT) is indicated.

Technique

Percutaneous Facet Denervation

The (postero-)lateral approach in the supine position is described below (Fig. 14-5). The advantage of this technique is that it is possible to maintain eye contact with the patient. Sedation is rarely required.

The patient is placed in the supine position with the head slightly extended on a small cushion. The C-arm is placed in an oblique position (±30 degrees). In this position, the beam runs parallel with the exiting nerve root that runs somewhat caudofrontal. Also in this position, the pedicles from the contralateral side are projected on the anterior half of the vertebral body. In the frontal plane (anteroposterior [AP] direction), the C-arm is positioned in a small angle with respect to the transverse plane. In this position, the discus intervertebralis space and neuroforamen are visible (Fig. 14-6). The ramus medialis (medial branch) of the ramus dorsalis runs over the base of the processus articularis superior. The injection point is marked on the skin, slightly posterior and caudal to the end point of the needle that is dorsal to the posterior boundary of the facet column. The first needle is introduced in a horizontal plane, slightly cranially so the tip of the needle points in the direction of the end point. It is important to understand that this is not a “tunnel-view” technique. The needle is slowly advanced anteriorly and cranially until bony contact with the facet column occurs. The farther the needle is advanced, the more difficult it becomes to change the direction. Therefore, the position of the needle needs to be checked frequently. If the needle points too much in the direction of the neuroforamen without contacting bone, the direction needs to be corrected to be more posterior. If there is no bone contact in the posterior direction, there is a risk that the needle will enter the spinal canal between the laminae. To prevent this, the needle position can be checked in the AP direction. The final position of the needle in the AP direction is in the concave “waist” of the facet column. After placement of the first needle, the other needles are introduced in the same way. The first needle acts as a guide to direction and depth.

The same technique is used for the facet joints of C3-C4 to C6-C7. For the facet joint of C2-C3, a different end point for the needle is used, just beneath the C2-C3 joint.23

After an optimal anatomical localization is reached and controlled using fluoroscopy, the position of the needle tip at the ramus medialis (medial branch) of the dorsal ramus is confirmed using electrical stimulation. The stimulation threshold is determined: an electrical stimulation of 50 Hz must give a reaction (tingling) in the neck at less than 0.5 V. Then stimulation is carried out at 2 Hz. Contractions of the paraspinal muscles can occur. Muscle contractions in the arm indicate a position close to the exiting segmental nerve. The needle should then be placed more posterior. After the correct position has been determined, 0.5 to 1 mL local anesthetic (1% or 2% lidocaine) is given. A RF lesion at 80° C for 60 seconds is carried out.

Outcomes Evidence

The recently published Evidence-Based Practice Guidelines based on clinical diagnoses based the recommendations on the “grading strength of recommendations and quality of evidence in clinical guidelines” described by Guyatt et al24 and adapted by van Kleef et al25 in an editorial in Pain Practice (Table 14-2).

Table 14-2 Summary of Evidence Scores and Implications for Recommendation

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Score Description Implication
1A+ Effectiveness demonstrated in various RCTs of good quality. The benefits clearly outweigh the risks and burdens. } Positive recommendation
1B+ One RCT or more RCTs with methodological weaknesses demonstrate effectiveness. The benefits clearly outweigh the risks and burdens.
2B+ One or more RCTs with methodological weaknesses demonstrate effectiveness. The benefits are closely balanced with the risks and burdens.
2B±