Fig. 7.1
Oblique fluoroscopy view (“Scottie dog” projection): Facet joint consists of the inferior articular process of the upper vertebra (forming the joint’s medial part – white line) and the superior articular process of the lower vertebra (forming the joint’s lateral part – red line)
In the posterior part of the joint’s superior articular process, the mamillary process is located where multifidus muscle is inserted. In the dorsal surface of the transverse process, the accessory process is located varying in length and shape; the longissimus muscle is attached to the accessory process. Both mamillary and accessory processes are the attachment locations of the mamillo-accessory ligament which along with the superior articulate and the transverse process form a tunnel within which runs the medial branch of the posterior primary ramus [9] (Fig. 7.2).
Fig. 7.2
Oblique fluoroscopy view (“Scottie dog” projection): The mamillo-accessory ligament (purple lines) along with the superior articulate (red asterisk) and the transverse (black asterisk) process form a tunnel within which runs the medial branch of the posterior primary ramus (yellow curved line)
The junction of ventral and dorsal spinal cord roots forms the lumbar spine nerves which run in the intervertebral foramen; in their course outside the foramen (shortly after exiting), the spinal nerves are separated into anterior and posterior primary rami, with the posterior ramus being divided into medial and lateral branches. The medial branch runs in a groove located at the junction of superior articulate and the transverse process under the mamillo-accessory ligament [9]. Exception is the L5 posterior primary ramus which is much longer and runs caudally towards the dorsal side of the sacral ala inside a groove formed by the ala and the sacral superior articular process. Each medial branch in the lumbar spine is divided into an ascending and a descending articular branch; each facet joint in the lumbar spine is innervated by two medial branch nerves, one from the joint’s level and one from the above level. For example, the L3–L4 facet joint is innervated by the L2 and L3 median branch and therefore in case of denervation the ablation process must be performed in both L2–L3 and L3–L4 levels.
7.3 Procedure
7.3.1 Pre-procedural Care
Radiofrequency denervation of lumbar facet joints is an outpatient procedure performed under local anaesthesia and imaging guidance. The latter ensures the correct needle placement which is a key factor for safety and efficacy. Facet joint denervation should be performed at least 48 h post the diagnostic infiltration in order to ensure that all the local anaesthetic effect has been cleared and motor or sensory stimulation will not be affected. For the same reasons, no opioid medication is administered the day of the procedure. Patient fastens 6 h prior to the technique. In case of anticoagulants, administration these is discontinued; the discontinuation period depends on the type of the anticoagulant. Although the technique is performed under local anaesthesia, an IV access should be established in all cases.
Each patient undergoes physical examination and coagulation laboratory tests at least 24 h prior to the radiofrequency denervation session. Consulting with the patient and explaining potential benefits, outcomes and complications is pre-requisite; patient is additionally advised to be accompanied by an adult capable of driving for the return home. An informed consent is obtained just prior to the session.
7.3.2 Technique
Imaging is a key factor for safety and efficacy of RF facet joint denervation in the lumbar spine; fluoroscopy is the most commonly used imaging guidance method. Patient is placed in prone position with a pillow under the head for comfort. Depending on an operator’s preference, a second pillow can be placed under the lower abdomen in order to flatten lumbar lordosis. Under fluoroscopic guidance, the technique is similar for all facet joints from L1–L2 till L4–L5 levels.
Starting the session, the operator defines the level of interest; on A-P projection, the spinous process should be on the midline and the endplates of the vertebral bodies aligned; occasionally this will require medial-to-lateral and cranio-caudal beam angulation. Once a true A-P projection is obtained, the beam is angulated 25–45° to obtain the “Scottie dog” projection (oblique projection). In this projection the snout of the dog is the transverse process, the ear is the superior articulating process, the front leg is the anterior articulating process, and the dog’s body is the lamina of the vertebra. The target point is the junction of the transverse process and the superior articulating process where the median branch nerve runs to innervate the facet joint (i.e. the junction of the dog’s nose and ear) (Fig. 7.3). Needle is advanced parallel to the beam angulation (“gun barrel view”) until bone contact is made at the dorsal and superior part of the transverse process in the junction with the superior articulating process. Specifically for the L5-S1 facet joint, one needle is placed in the L4–L5 level with the aforementioned technique and a second needle is located at the junction of the dorsal side of the sacral ala and the sacral superior articular process (Fig. 7.4).
