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Brown: Atlas of Regional Anesthesia, 3rd ed., Copyright © 2006 Saunders, An Imprint of Elsevier
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PLACEMENT

Anatomy.

The 33 vertebrae that make up the spinal column are linked by intervertebral discs 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 of exit from the vertebral column for the axial nerves 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. 39-1 ). 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. 39-2 ).

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Figure 39-1  Superior and lateral views of cervical (A), thoracic (B), and lumbar (C) facet joints. The angle of the facet joints in the sagittal plane is indicated in the insets. Transverse processes are highlighted in purple in each image.


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Figure 39-2  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.

Innervation of the facet joints occurs 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. 39-3 A ). 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 (see Fig. 39-3 B ). In the cervical region, the medial branch innervates primarily the facet joint and not the paraspinous musculature. Furthermore, 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. 39-4 ).

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Figure 39-3  Lumbar facet joint innervation. A, Cross-sectional view of segmental nerve innervation of the facet joint. B, Oblique parasagittal view of overlapping segmental innervation of the facet joint.


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Figure 39-4  Cervical facet joint innervation. Posterior and oblique parasagittal views of overlapping segmental innervation of the facet joint.


Position.

Lumbar facet blocks are performed with the patient prone on an image table, with the hips and lower abdomen supported by a pillow. After identifying the level of the facet joint, the fluoroscopy unit is angled approximately 30 degrees off the parasagittal plane to obtain optimum visualization of the lumbar facet joint ( Fig. 39-5 ). Cervical facet blocks are also performed with the patient prone on an image table, with the forehead and chest supported by pillows or individual silicone pads ( Fig. 39-6 A). 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.

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Figure 39-5  Lumbar facet joint. A, Position of the patient and fluoroscopy unit for optimal visualization of the lumbar facet joint. B, Cross-sectional image of a lumbar facet block.


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Figure 39-6  Cervical facet joint. A, Position of the patient and fluoroscopy unit for optimal visualization of the cervical facet joint. B, Oblique posteroanterior image of cervical facet joints, showing cephalad angulation of the fluoroscopic imaging 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 L3–4 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. 39-5 ). A mark is then made 5 cm lateral to the vertebral midline at the previously identified facet joint level. After aseptic skin preparation has been completed, a 22-gauge, 6- to 10-cm needle is inserted at a slightly medial parasagittal angle. The needle tip is placed in the facet joint under fluoroscopic guidance ( Fig. 39-7 ). A radiocontrast agent is then injected to verify the position of the needle tip (see Fig. 39-6 B ). Once the needle position is confirmed, a therapeutic or diagnostic injection is performed.

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Figure 39-7  Lumbar facet joint injection. A, Cross-sectional and oblique views of the lumbar facet block technique. B, Radiographic image of the injection of 1.5 mL of contrast into the lumbar facet joint.


Cervical facet blocks are also performed with the patient prone on an image 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. 39-8 A ). After the skin has been aseptically prepared, a 22-gauge, 6- to 8-cm needle is inserted cephaloanteriorly; it is guided with fluoroscopic assistance into the previously identified cervical facet joint (see Fig. 39-8 B ). Then radiocontrast medium is injected to verify the position of the needle tip (see Fig. 39-8 C ). Once the needle position has been confirmed, the therapeutic or diagnostic injection is performed.

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Figure 39-8a  Cervical facet joint injection. A, Posteroanterior view of needle insertion for a cervical facet block.


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Figure 39-8b  B, Lateral view of needle insertion for a cervical facet block. C, Radiographic image of injection of 1.0 mL of contrast material into the C4–5 cervical facet joint.


Potential Problems.

As with any other regional block, facet injections should be avoided if the patient has a coagulopathy or infection at the site of the injection. Because these injections are administered near the neuraxis, epidural or intrathecal effects are possible, as is injection of the vertebral artery in the cervical region.

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