Patient Selection

Facet-related pain remains a diagnosis of exclusion, supported by reproduction of the pain during arthrography and relief of pain after diagnostic facet injection. In patients with lumbar pain syndromes, facet-related pain is often located in the low back and is described as a deep, dull ache that is difficult to localize. It may be referred to the buttocks or to the posterior leg, and infrequently it extends more distally into the lower leg. The pain is often made worse by lumbar extension, especially with lateral flexion to the affected side because this maneuver opposes the facet joints more forcefully. In cervical facet pain syndromes, the pain remains deep and aching, and the level of the facet involvement dictates the referral pattern of the pain. There are distinct upper, lower, and pancervical neck facet pain syndromes.

Pharmacologic Choice

Diagnostic blocks are most often performed with 1 to 2 mL of local anesthetic, either 1% to 1.5% lidocaine, 0.25% to 0.5% bupivacaine, or 0.2% to 0.5% ropivacaine. Lidocaine is chosen if immediate interpretation is sought, whereas bupivacaine or ropivacaine is used if diagnostic information is sought over a longer interval. For therapeutic injection, the total volume of solution is kept at 1.5 to 2.0 mL, although 20 mg of methylprednisolone is added to the local anesthetic (most often a longer-acting agent for a therapeutic injection). For either diagnostic or therapeutic injection, the needle position is confirmed with 0.25 to 0.5 mL of a radiocontrast agent, Hypaque-M 60% (Sanofi Winthrop, Irving, Tex).

Anatomy

The 33 vertebrae that make up the spinal column are linked by intervertebral disks and longitudinal ligaments anteriorly and through facet joints posteriorly. The posterior facet joints allow flexion, extension, and rotation of the vertebral column while providing a means for the axial nerves to exit the vertebral column on their way to becoming peripheral nerves. The facet joints are synovial joints formed by the inferior articular processes of one vertebra and the superior articular processes of the adjacent caudad vertebra. These articular processes are projections, two superior and two inferior, from the junction of the pedicles and the laminae. In the cervical and lumbar portions of the vertebral column, the facet joints are posterior to the transverse processes, whereas in the thoracic region the facet joints are anterior to the transverse processes (Fig. 44-1). In the cervical vertebrae, the joint surfaces are midway between a coronal and an axial plane, whereas in the lumbar region, the joints (at least the posterior portion) assume an orientation approximately 30 degrees oblique to the sagittal plane (Fig. 44-2).

Figure 44-1. Superior and lateral views of cervical (A), thoracic (B), and lumbar (C) facet joints. Angle of the facet joints in the sagittal plane is indicated in the insets. Transverse processes are highlighted in purple in each image.

Figure 44-2. Facet joint orientation. A, Cervical facet joint orientation is midway between axial and coronal. B, Lumbar facet joint orientation is 30 degrees oblique to the parasagittal plane.

The capsule of a facet joint varies by location relative to the joint. A tough fibrous capsule is present on the posterolateral aspect of the joint, whereas on the anteromedial aspect of the joint, the facet synovial membrane is in direct contact with the ligamentum flavum.

The facet joints are innervated through the segmental sensory nerves that overlap the vertebral levels. Each joint has a dual innervation from the segmental nerve at its vertebral level as well as from the nerve at the level caudad to it. In the lumbar region, the posterior and anterior primary rami of a segmental nerve diverge at the intervertebral foramen (Fig. 44-3A). The posterior ramus, also known as the sinuvertebral nerve of Luschka, passes dorsally and caudally to enter the spine through a foramen in the intertransverse ligament. Almost immediately it divides into medial, lateral, and intermediate branches. The medial branch supplies the lower pole of the facet joint at its own level and the upper pole of the facet joint caudad to it. Each medial branch of the lumbar posterior ramus also supplies paraspinous muscles, such as the multifidus and interspinalis, as well as ligaments and the periosteum of the neural arch (Fig. 44-3B). In the cervical region, the medial branch innervates primarily the facet joint and not the paraspinous musculature. Further, in the cervical region, the nerves of Luschka wrap around the waists of their respective articular pillars and are bound to the periosteum by an investing fascia and held against the articular pillars by tendons of the semispinalis capitis muscle (Fig. 44-4).

Figure 44-3. Lumbar facet joint innervation. A, Cross-sectional view of segmental nerve innervation of facet joint. B, Oblique parasagittal view of overlapping segmental innervation of facet joint.

Figure 44-4. Cervical facet joint innervation. Posterior and oblique parasagittal views of overlapping segmental innervation of facet joint.

Position

Lumbar facet blocks are performed with the patient prone on an imaging table with the hips and lower abdomen supported by a pillow. After the level of the facet joint is identified, the fluoroscopy unit is angled approximately 30 degrees off the parasagittal plane to obtain optimum visualization of the lumbar facet joint (Fig. 44-5). Cervical facet blocks are also performed with the patient prone on an imaging table with the forehead and chest supported by pillows or individual silicone pads (Fig. 44-6A). Again, fluoroscopy is used to identify the facet joint, and after its position has been marked, the fluoroscopy unit is rotated to produce a lateral image of the cervical spine.

Figure 44-5. Lumbar facet joint. A, Position of patient and fluoroscopic imaging unit for optimal visualization of lumbar facet joint. B, Cross-sectional image of lumbar facet joint.

Figure 44-6. Cervical facet joint. A, Position of patient and fluoroscopic imaging unit for optimal visualization of cervical facet joint. B, Oblique posteroanterior image of cervical facet joints, showing cephalad angulation of fluoroscopic unit.

Needle Puncture

The facet joint is often located at the cephalocaudad level of the inferior extent of the more cephalad spinous process of the vertebra contributing to the facet joint. For example, the inferior extent of the spinous process of L3 corresponds to the L3-L4 facet joint. After the level of the facet joint has been marked, the fluoroscopy unit is angled approximately 30 degrees off the parasagittal plane, as described previously (see Fig. 44-5). A mark is then made 5 cm lateral to the vertebral midline at the previously identified facet joint level. After aseptic skin preparation, a 22-gauge, 6- to 10-cm needle is inserted at a slightly medial parasagittal angle. Under fluoroscopic guidance, the needle tip is placed in the facet joint (Fig. 44-7). Then a radiocontrast agent is injected to verify the position of the needle tip (see Fig. 44-6B). Once the needle position is confirmed, the therapeutic or diagnostic injection is performed.

Figure 44-7. Lumbar facet joint injection. Oblique (A) and cross-sectional (B) views of lumbar facet block technique. C, Radiographic image of injection of 1.5 mL of contrast into lumbar facet joint.

Cervical facet blocks are also performed with the patient prone on an imaging table, as described earlier. Fluoroscopy is used to identify the facet joint to be blocked, and its cephalocaudad vertebral level is marked. After the paravertebral cephalocaudad and mediolateral positions of the facet joint have been marked, the fluoroscopy unit is rotated to produce a lateral image of the cervical spine. This allows optimum visualization of the cervical facet joint during needle placement. A needle entry skin mark is made 3 to 4 cm caudad to the facet joint previously identified and approximately 3 cm lateral to the vertebral midline (Fig. 44-8A). After the skin has been aseptically prepared, a 22-gauge, 6- to 8-cm needle is inserted in a cephaloanterior direction and guided with fluoroscopic assistance into the previously identified cervical facet joint (Fig. 44-8B). Radiocontrast medium is then injected to verify the position of the needle tip (Fig. 44-8C). Once the needle position has been confirmed, the therapeutic or diagnostic injection is performed.

Figure 44-8. Cervical facet joint injection. A, Posteroanterior view of needle insertion for a cervical facet block. B, Lateral view of needle insertion for a cervical facet block. C, Radiographic image of injection of 1.0 mL of contrast into C4-C5 cervical facet joint.