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Facet Injection: Intra-Articular Injection, Medial Branch Block, and Radiofrequency Treatment
Intra-articular facet injection has been largely supplanted by radiofrequency treatment techniques for facet-related pain. Clinical experience and a limited number of published observational studies suggest that the intra-articular injection of local anesthetic and steroid leads to relief of facet-related pain that is limited in duration. In contrast, radiofrequency treatment is safe and modestly effective in producing longer term pain relief in the same group of patients (see “Facet Medial Branch Block and Radiofrequency Treatment
”). Nonetheless, an understanding of facet-related pain syndromes and the methods for placing medication directly within the facet joint may still prove useful for those practitioners who are unable to provide radiofrequency treatment.
Osteoarthritis of the spine is ubiquitous and an inevitable part of aging. The cascade that leads to degeneration of the intervertebral discs causes progressive disc dehydration and loss of disc height. Typically first appearing in the third decade of life, disc degeneration leads to increased mobility of adjacent vertebrae and heightened shear forces on the facet joints themselves. This can lead to a pattern of pain over the axis of the spine that increases with movement, particularly with flexion and extension, but produces little or no pain radiating toward the extremities. In the past, the only available treatment for those with debilitating facet-related pain was segmental fusion of the spine to completely arrest motion within the painful portion of the spine.
The majority of patients will have pain that is gradual in onset and can be localized only to a general region of the spinal axis (i.e., high or low cervical spine, high or low thoracic spine, or high or low lumbar spine). However, a subgroup of patients will present with sudden onset of pain, often associated with trauma in the form of sudden flexion or hyperextension of the spine in the affected region. Diagnostic studies are typically unrevealing, either showing no abnormalities or facet arthropathy at multiple levels. In those with pain of sudden onset, it may be possible to isolate one or more facets that are causing the pain. It is in these instances with sudden onset of well-localized pain that intra-articular facet injection with local anesthetic and steroid can prove most beneficial.
The zygapophysial or “facet” joints are paired structures that lie posterolaterally on the bony vertebrae at the junction of the lamina and pedicle medially, and the base of the transverse process laterally. The facet joints are true joints, with opposing cartilaginous surfaces and a true synovial lining, and they are subject to the same inflammatory and degenerative processes that affect other synovial joints throughout the body. The facet joint articular processes are named for the vertebra to which they belong. Thus, each vertebra has a superior articular process and an inferior articular process. This nomenclature can be confusing because the superior articular process of a given vertebra actually forms the inferior portion of each facet joint. The paired facet joints, along with the vertebral bodies and intervertebral discs, form the three weight-bearing support columns that distribute the axial load on the vertebral column while allowing for movement in various planes.
The structure and location of the facet joints is distinct in the cervical, thoracic, and lumbar regions (Fig. 7-1
). The cervical facet joints are oriented nearly parallel to the axial plane where the atlas (C1) articulates with the occiput and become gradually more steeply angulated in a cephalad-to-caudad direction at lower cervical levels. The orientation of the cervical facet joints in a plane close to the axial plane allows for a great degree of rotation of the neck, as well as flexion and extension. The thoracic facet joints become even more steeply angulated, approaching the frontal plane. At midthoracic levels, the inferior articular process of the vertebra forming the superior portion of each thoracic facet joint lies directly posterior to the superior articular process, forming the inferior portion of each joint. This allows for some degree of flexion and extension, but limited rotation of the spinal column in the thorax. The steeply angled cephalad-to-caudad orientation of the thoracic facets also makes intra-articular injection difficult or impossible. The lumbar facet joints are angled with a somewhat oblique orientation, allowing for flexion, extension, and rotation that is greater than that in the thorax but less than in the cervical region. The orientation of the facet joints and the optimal angle of needle insertion for intra-articular facet injection are illustrated in Figure 7-1
Figure 7-1. Anatomy of the facet joints. The plane of orientation of the facet joints varies significantly among cervical, thoracic, and lumbar levels. The axis of the joints and the plane of entry for intra-articular injection are shown for typical cervical, thoracic, and lumbar facet joints.
The sensory innervation to the facet joints is anatomically predictable, and the sensory nerves are easily accessible from the dorsal surface of the body. The spinal nerve at each level traverses the intervertebral foramen and divides into anterior and posterior primary rami. The anterior ramus contains the majority of sensory and motor fibers at each vertebral level. The posterior primary ramus, in turn, divides into a lateral branch that provides innervation to the paraspinous musculature and a small, variable sensory branch to the skin overlying the spinous processes; the medial branch of the posterior primary ramus courses over the base of the transverse process where it joins with the superior articular process of the facet joint and courses along the articular process to supply sensation to the joint. Each facet joint receives sensory innervation from the medial branch nerve at the same vertebral level, as well as from a descending branch from the vertebral level above; thus, two medial branch nerves must be blocked to anesthetize each facet joint, for example, medial branch blocks at the base of the L4 and L5 transverse processes are needed to anesthetize the L4/L5 facet joint. The specific course of the medial branch nerves and cannula position for radiofrequency treatment at specific spinal levels is discussed in the following sections.
Patients with facet-related pain are difficult to distinguish from those with other causes of axial spinal pain. Some patients will present with sudden onset of pain following a significant flexion-extension (whiplash) injury, but more common is an insidious onset over months to years. Patients with myofascial or discogenic pain and, in the low back, those with sacroiliac dysfunction present with similar symptoms. Nonetheless, certain features can be helpful in differentiating facet-related pain from other causes of spinal pain. The pain caused by facet arthropathy is most pronounced over the axis of the spine itself and is typically maximal directly in the region of the most affected joints. The pain tends to be exacerbated by movement, particularly extension of the spine, which forces the inflamed articular surfaces of the facet joints together. However, axial spinal pain at rest or worsening with forward flexion or rotation of the spine is also a common feature. The most important historical feature is a predominance of axial spinal pain; those patients who report that the predominance of their pain is in the extremities are more likely to have acute or chronic radicular pain than facet-related pain. The quality of the pain is typically deep and aching, and waxes and wanes with activity. Burning or stabbing qualities suggest neuropathic pain rather than facet arthropathy. Diagnostic studies are often unrevealing. Patients with significant facet-related pain may have unremarkable plain radiographs and/or imaging studies of the spine, or they may have facet arthropathy at multiple levels. Patient selection for facet injection or radiofrequency treatment is empiric and relies on excluding other causes of pain and the presence of a pattern of pain that is consistent with facet-related pain.
The pattern of pain caused by abnormalities in specific facet joints has been established by injecting a mild irritant (usually hypertonic saline) into specific facet joints in healthy volunteers and then recording the pattern of pain produced. This information is shown in Figures 7-2
for the cervical, thoracic, and lumbar regions, respectively. The levels to be treated are chosen by correlating the patient’s report of pain to these pain diagrams. Occasionally, a patient will present with evidence of facet arthropathy and a pattern of pain that corresponds to a single level, but this is uncommon. Most patients will have more diffuse pain that can only be narrowed to a specific region. Treatment should be directed to the joint or joints that most closely match the pattern of referred pain that has been established for each joint and that typically requires treatment at more than one level.
Figure 7-2. Patterns of pain produced by cervical facet joints. Typical pain patterns produced by specific cervical facet joints are illustrated. Data are derived from intra-articular injection in healthy volunteers. (Data from Bogduk N, Marsland A. The cervical zygapophysial joints as a source of neck pain. Spine. 1988;13:615.)
Level of Evidence
Quality of Evidence and Grading of Recommendation
Grade of Recommendation/Description
Benefit vs. Risk and Burdens
Methodological Quality of Supporting Evidence
RECOMMENDATION: Intra-articular facet injections and therapeutic medial branch blocks may be used for symptomatic relief of facet-related pain.
2B/weak recommendation, moderate-quality evidence
Benefits closely balanced with risks and burden
II-2: randomized controlled trials (RCTs) with important limitations (inconsistent results, methodological flaws, indirect, or imprecise) and strong evidence from observational studies
Weak recommendation, best action may differ depending on circumstances or patients’ or societal values
RECOMMENDATION: 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.
1B/strong recommendation, moderate-quality evidence
Benefits clearly outweigh risk and burdens, or vice versa
I: RCTs with important limitations (inconsistent results, methodological flaws, indirect, or imprecise) and strong evidence from observational studies
Strong recommendation, can apply to most patients in most circumstances without reservation
Figure 7-3. Patterns of pain produced by thoracic facet joints. Typical pain patterns produced by specific thoracic facet joints are illustrated. Data are derived from intra-articular injection in healthy volunteers. (Adapted from Dreyfuss P, Tibiletti C, Dreyer S. Thoracic zygapophyseal joint pain patterns. Spine. 1994;19:809, with permission.)
Figure 7-4. Patterns of pain produced by lumbar facet joints. Typical pain patterns produced by specific lumbar facet joints are illustrated. Data are derived from intra-articular injection in healthy volunteers. (Adapted from Boas RA. Facet joint injections. In: Stanton-Hicks MA, Boas RA, eds. Chronic Low Back Pain. New York: Raven Press; 1982:202, with permission.)
There has been an exponential rise in the use of spinal injections of all kinds during the past decade in the United States, while the prevalence of acute pain associated with various spinal disorders has changed little. The overuse of facet injections, including intra-articular injections and radiofrequency treatment, has been singled out as a significant area of concern. Several organizations have closely examined the scientific literature and made evidence-based guidelines regarding the use of this treatment. The available RCTs examining facet injections and radiofrequency treatment are limited, and we will discuss each in turn.
The American Pain Society (APS) Low Back Pain Guideline Panel published a report in 2009, concluding, “In patients with persistent nonradicular low back pain, facet joint corticosteroid injection… [is] not recommended (strong recommendation, moderate-quality evidence). There is insufficient evidence to adequately evaluate benefits of therapeutic medial branch block [and] radiofrequency denervation…for nonradicular low back pain.” Facet joint injections were not recommended by this group specifically because randomized trials consistently found them to be no more effective than sham therapies.
Subsequently, the American Society of Anesthesiologists (ASA) Task Force on Chronic Pain Management published A 2010 Practice Guideline, offering the following recommendations: (1) “Intra-articular facet joint injections may be used for symptomatic relief of facet-mediated pain.”; (2) “Medial branch blocks may be used for the treatment of facetmediated spine pain.”; and (3) “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…” The ASA Task Force recommendations appear to be at odds with those put forward by the APS Low Back Pain Guideline Panel. The ASA Task Force deliberately included observational studies and expert opinion in its overall analysis. Indeed randomized trials demonstrate little benefit for use of intra-articular injections, while well-conducted observational studies suggest a more significant effect in treating chronic axial low back pain. Observational trials of the use of medial branch blocks with local anesthetic alone, without subsequent radiofrequency treatment, have been encouraging, but randomized trials are lacking. When examining the available trials for use of radiofrequency facet treatment, the ASA Task Force accepted the availability of one or more randomized trial as an acceptable level of evidence to recommend use of this treatment. Nonetheless, the overall level of evidence supporting the efficacy of facet injections and radiofrequency treatment is limited and additional, large-scale clinical trials are desperately needed. Guidance on the optimal frequency for repeating these interventions as well as the efficacy of using multiple repeated treatments over time is lacking entirely.
Intra-articular Facet Injection Versus Radiofrequency Treatment
How to select between intra-articular facet injection and diagnostic medial branch blocks followed by radiofrequency treatment is still a question that is frequently posed by practitioners. Limited outcome studies of intra-articular injection, particularly at the cervical level, have demonstrated only transient pain relief lasting from days to weeks in most patients. In contrast, in those patients who obtain significant pain relief from diagnostic blocks of the medial branch nerves to the facet, radiofrequency treatment can produce significant pain reduction that is somewhat longer lasting (typically 50% or more reduction in pain lasting at least 3 months after treatment). Based on this improved efficacy and a long track record of safety, many practitioners have all but abandoned intra-articular injections in favor of radiofrequency treatment. Intra-articular injection remains of some value in those patients who have had recent onset of pain that is discrete in location and suggests involvement of a single facet joint. Intra-articular injection is also a reasonable alternative when the expertise or equipment for radiofrequency treatment is not available, but it will provide only transient symptomatic relief in those with facet-related pain who have failed conservative treatment. While observational studies have suggested that use of medial branch blocks with local anesthetic alone can provide sustained pain relief in some individuals, transient pain relief lasting only hours to days after injection is more common than not.
Intra-articular Facet Injection
Cervical Intra-articular Facet Injection
The patient lies prone, facing the table with a small headrest under the forehead to allow for air flow between the table and the patient’s nose and mouth (Fig. 7-5
). The C-arm is rotated 25 to 35 degrees caudally from the axial plane without any oblique angulation. This brings the axis of the x-rays in line with the axis of the facet joints and allows for visualization of the joints (Fig. 7-6
). Although the cervical facet joints can also be entered from a lateral approach with the patient lying on his or her side, advancing a needle using radiographic guidance in the anterior-posterior (AP) plane allows the operator to directly see the position of the spinal canal at all times and avoid medial needle deviation that could lead to spinal cord injury (Figs. 7-7
The skin and subcutaneous tissues overlying the facet joint where the block is to be carried out are anesthetized with 1 to 2mL of 1% lidocaine. The cervical level is easily identified by counting upward from the T1 level, where the vertebra is distinguished by the presence of a large transverse process that articulates with the first rib (see Fig. 7-6
). A 22- or 25-gauge, 3.5-inch spinal needle is placed through the skin and advanced until it is seated in the tissues in a plane that is coaxial with the axis of the x-ray path (see Fig. 7-6
). The needle is adjusted to remain coaxial and advanced toward the joint space using repeat images after every 2 to 4 mm of needle advancement. Once the surface of the joint space is contacted, a lateral radiograph is obtained (Fig. 7-9
), and the needle is advanced just slightly to penetrate the posterior joint capsule. The needle should not be advanced into the joint between articular surfaces; this serves no purpose and is likely to abrade the articular surfaces and lead to worsened pain once the local anesthetic block subsides. Although intra-articular location of the needle tip can be confirmed with radiographic contrast, this is unnecessary if the needle location is correct in both AP and lateral planes. The facet joint itself holds only limited volume (typically ∽0.5mL), and thus, placing contrast in the joint limits the ability to place local anesthetic and steroid within the joint. Once needle position has been confirmed, a solution containing steroid and local anesthetic is placed. A total dose of 80 mg of methylprednisolone acetate or the equivalent should be divided over all the joints to be injected, but more than 40 mg per joint is probably unnecessary. Using concentrated steroid (40 or 80 mg per mL) allows 1:1 mixture with local anesthetic (0.5% bupivacaine) to provide some immediate pain relief.
Figure 7-5. Position for intra-articular cervical facet joint injection. The patient is placed prone with a small headrest under the forehead to allow for air flow between the table and the patient’s nose and mouth. The C-arm is angled 25 to 35 degrees caudally from the axial plane.
Figure 7-6. A: Bony anatomy relevant to cervical intra-articular facet injection. Three-dimensional reconstruction computed tomography of the cervical spine as viewed from the posterior approach used for cervical intra-articular facet injection. Inset matches the anatomic area in the radiographs shown in (B) and (C). (Cont.)
Figure 7-6. (Continued) B: AP radiograph of the cervical spine during intra-articular cervical facet injection. A 22-gauge spinal needle is in position in the left C3/C4 facet joint. C: Labeled image.
Figure 7-7. Position and angle of needle entry for intra-articular cervical facet injection. A 22-gauge spinal needle is advanced in the sagittal plane overlying the facet joint with 25 to 35 degrees of caudad angulation from the axial plane.
Atlantoaxial (C1/C2) Facet Injection
Degenerative joint disease involving the atlantoaxial joint is not uncommon, and techniques to inject this
joint are well described. However, there is no evidence that injection of the atlantoaxial joint can produce anything more than modest, short-term pain reduction. At the same time, recent reports of massive stroke following intra-arterial injection of particulate steroid during the conduct of atlantoaxial injection have appeared (see Fig. 4-4
). Thus many practitioners have abandoned the use of this technique entirely.
The technique is discussed here briefly to make readers aware of the relevant anatomy that makes intra-articular injection of the atlantoaxial joint particularly hazardous. The vertebral artery lies in close apposition to the lateral aspect of the atlantoaxial joint, while the dorsal root ganglion and spinal nerve of C2 lie directly over the medial and midportion of the joint (Fig. 7-10A
). Block of the atlantoaxial joint is performed in a manner similar to that described for intraarticular injection of more inferior cervical facet joints. The patient in positioned prone with the head in a neutral position and the mouth opened as far as possible to allow good visualization of the lateral elements of C1 and C2 in the anteroposterior projection (Fig. 7-10B
and C). To avoid contact with the C2 spinal nerve medially and penetration of the vertebral artery laterally, the needle is directed to the lateral third of the joint in the AP projection. Once the surface of the joint space is contacted, a lateral radiograph is obtained (Fig. 7-10D
and E), and the needle is advanced just slightly to penetrate the posterior joint capsule. It is imperative that intra-arterial location of the needle tip is identified before injection of steroid, thus injection of a small volume of radiographic contrast under live fluoroscopy with or without digital subtraction is essential, for example, 0.5 to 1 mL of iopamidol 41%. There is no published evidence regarding efficacy of particulate versus nonparticulate steroid for atlantoaxial joint injection. Nonetheless, given the close proximity of the vertebral artery and the potentially catastrophic consequences of intra-arterial injection, strong consideration of use of nonparticulate steroid should be given, for example, 4 mg of dexamethasone sodium phosphate.
Figure 7-8. Axial diagram of intra-articular cervical facet injection. The needle is advanced in the sagittal plane to enter the posterior aspect of the facet joint. Although the cervical facet joint can be entered from a lateral approach, using the posterior approach and radiographic guidance allows the operator to directly visualize the position of the spinal canal at all times. If the needle strays medially, the direction can be immediately corrected before dural puncture or injury to the spinal cord. When a needle is placed using a lateral approach, anterior deviation can also lead to penetration of the vertebral artery; the vertebral artery is protected by the facet column when a posterior approach is used.
Figure 7-9. A: Bony anatomy relevant to cervical intra-articular facet injection. Three-dimensional reconstruction computed tomography of the cervical spine as viewed in the lateral projection. Inset matches the anatomic area in the radiographs shown in (B) and (C). B: Lateral radiograph of the cervical spine during intra-articular cervical facet injection. A 22-gauge spinal needle is in place in the posterior aspect of the C3/C4 facet joint. C: Labeled image.
Figure 7-10. A: Bony anatomy relevant to cervical intra-articular facet injection of the atlantoaxial (C1/C2) facet joint. Three-dimensional reconstruction computed tomography of the cervical spine as viewed in the oblique projection. Inset illustrates the position of the vertebral artery; the approximate position of the C2 dorsal root ganglion and spinal nerve is shown. B: AP radiograph of the cervical spine during intra-articular atlantoaxial (C1/C2) facet injection. A 22-gauge spinal needle is in position in the lateral third of the left atlantoaxial facet joint. C: Labeled AP image showing the approximate position of the vertebral artery and the C2 dorsal root ganglion and spinal nerve. (Cont.)
Thoracic Intra-articular Facet Injection
Thoracic intra-articular facet injection is not commonly employed. The plane of the thoracic facet joints is steeply angled, nearing the frontal plane. Even with steep angulation of the C-arm, the joint space cannot be visualized directly, but rather it must be inferred from the position of adjacent structures. The patient is positioned prone with the head turned to one side. The C-arm is angled 50 to 60 degrees in a caudad direction from the axial plane (Fig. 7-11
). The plane of the mid- and lower thoracic facet joints lies at an angle of 60 to 70 degrees from the axial plane, but further angulation of the C-arm is impractical without the image intensifier resting against the patient’s back. This angle allows visualization of structures adjacent to the facet joint from which the position of the joint can be inferred (Fig. 7-12
). The inferior articular process (superior aspect of the joint) lies posteriorly, directly over the superior articular process (inferior aspect of the joint). The needle tip is advanced toward the inferior aspect of the joint (Figs. 7-12
Figure 7-10. (Continued) D:
Lateral radiograph of the cervical spine during intra-articular atlantoaxial (C1/C2) facet injection. A 22-gauge spinal needle is in position in the posterior atlantoaxial facet joint. E:
Labeled lateral image showing the approximate position of the vertebral artery. (Radiographs in Fig. 7-10 (B-E)
are reproduced with permission from Aprill C, Axinn MJ, Bogduk N. Occipital headaches stemming from the lateral atlanto-axial (C1-C2) joint. Cephalalgia.
Figure 7-11. Position for intra-articular thoracic facet joint injection. The patient is placed prone with the head turned to one side. The C-arm is angled 50 to 60 degrees caudally from the axial plane.
Figure 7-12. A: Bony anatomy relevant to thoracic intra-articular facet injection. Three-dimensional reconstruction computed tomography of the thoracic spine as viewed from the posterior approach used for thoracic intra-articular facet injection. Inset matches the anatomic area in the radiographs shown in (B) and (C). B: AP radiograph of the thoracic spine. Because of their steep angle, the thoracic facet joints cannot be seen directly but must be inferred from the position of adjacent structures. The superior aspect of each joint (inferior articular process) lies posteriorly (arrows), directly over the inferior aspect of the joint (superior articular process). This position can be inferred by following the inferior margin of the lamina from the spinous process laterally. C: Labeled image.
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