Diagnostic cervical facet joint injections are useful in the diagnosis and treatment of axial neck pain. The C1-2 joint is a source of headaches, often in patients with a history of trauma. The C2-3 third occipital nerve is often used to treat cervicogenic headaches. The C3-4 and C4-5 cervical facet joints refer pain to the neck, while the C5-6 and C6-7 cervical facets refer to the shoulder and upper back.
Positioning the patient is crucial to the safe and successful procedure. An uncomfortably positioned patient will continue to move on the table, resulting in repeated repositioning of the fluoroscope, and danger posed to the patient with needles in position near the spine. While patients can be placed supine or lateral for this procedure, most commonly patients are in the prone position.First, placing a pillow under the chest allows the patient to flex the neck, while opening the facet joints. Second, the arms should be placed at the side, not up over the head, to allow for the fluoroscope to obtain a lateral view. This should be done before beginning the procedure. One should avoid repositioning the arms after the needles have been placed. Third, turning the head to the contralateral side to be injected, with the chin tucked in (flexed) accomplishes two important goals. The mandible with possible radiopaque dental work (see Image 1) is now no longer in view obscuring the cervical spine (see Image 2). Also, this maneuver opens up the cervical facet joints on the ipsilateral side to be injected (see Image 3).
Positioning the fluoroscope is the next step in sequence. First, the C-arm should be placed in the AP view so that the spinous processes are in the midline (see Image 1). By rotating the head to the contralateral side, the spine will rotate, so the C-arm should not be assumed to be a straight AP to the spine (see Image 2). Second, the fluoroscope should be positioned with the image intensifier toward the feet until the facet joint space is clearly visualized (see Image 3). In this view, the joint is now in the same parallel orientation as the waist of the articular pillars where the medial branch nerve lies. Thus this view allows the practitioner to adequately perform either an intra-articular facet joint injection, or extra-articular medial branch nerve block.
Positioning the needle is the final step. For an intra-articular injection, a 25 gauge spinal needle is often necessary, as the commonly used 22 gauge spinal needle is too large to access the joint space. However, the 25 gauge needle is more difficult to steer, and using the gun of the barrel technique is required. Aim for the middle of the joint space. A medial direction can result in a subarachnoid placement. Once contact is made with the joint, a lateral view will confirm proper needle depth. For extra-articular injection, using either a 22 or 25 gauge spinal needle is possible. A curved tip allows one to steer the needle. Aim for the lateral border of the articular pillar waist. A medial to lateral approach with the needle will result in the needle tip moving away from the medial branch nerve as the tip is advanced off the os of the posterior pillar. By using a very slight lateral to medial approach with the needle, the tip may be advanced after contact with the os of the posterior pillar, and still remain in contact with the waist and presence of the medial branch nerve. Again, a lateral view will confirm proper depth of the needle tip, which should be at the midpoint of the pillar.
Since this is a diagnostic procedure, only local anesthetic is necessary. In some cases, such as acute injury with motor vehicle accidents, use of intra-articular steroids may be therapeutic. There is no indication for steroid in the extra-articular injection. A positive diagnostic block should demonstrate at least a 50% reduction in pain. The procedure should be repeated at least one additional time for verification before proceeding with denervation of the joint.
Edward Chen, MD
Clearwater Pain Management Associates