Introduction
Radiofrequency ablation (RFA) is a procedure utilizing electric current to create a thermal lesion that results in ablating a specified target. For facetogenic joint pain, the targeted lesion is the medial branch of the dorsal ramus of spinal nerves. Medial branch lesioning interrupts nociceptive nerve transmission from the facet joint. Utilization of electric current and heat introduces a set of possible complications involving interaction with existing hardware in the patient. This chapter will discuss radiofrequency ablation of the medial branches in the presence of implanted patient devices.
Procedure
Radiofrequency ablation (RFA) for facetogenic pain is performed by image-guided (commonly fluoroscopy) insertion of a small-diameter needle to the medial branch of the dorsal ramus of spinal nerves. This location is typically inferred by local landmarks such as the junction of the superior articular process and transverse process of the vertebra adjacent to the target nerve, or the “eye” of the “Scotty Dog” radiographic landmark ( Fig. 17.1 ). A controlled lesion is then generated with the tip of the RFA needle by introducing an electrical current. Lesioning is typically obtained by heating the tip of the probe to 80°C to 90°C for a duration of 1 to 3 min. This process is repeated at various vertebral levels, depending on the source of the patient’s pain. See Fig. 17.2 for the radiographic views of RFA needles in place for L3 and L4 medial branch neurotomy.
Complications and management
RFA should be used with caution in certain patients with implanted hardware. Implantable medical devices such as cardioverter-defibrillators, deep brain stimulators (DBS), spinal cord stimulators, and implantable spinal hardware such as pedicle screws pose a theoretical risk with introduction of electrical current into the body.
RFA probes can utilize either monopolar or bipolar electrical current to create ablative heat. While monopolar RFA creates electrical current flowing from one cannula to a grounding pad on the patient’s body, bipolar RFA involves the current leaving one electrode and entering another electrode in the same location. This conduction of electricity creates an electromagnetic field that can theoretically interfere with implanted electrical devices such as brain or spinal cord stimulators. It is thought that bipolar RFA is potentially safer than monopolar RFA due to the creation of a smaller electromagnetic field and localization of current. Support for this concept has been demonstrated in a case report with two patients with automatic implantable cardiac defibrillator (AICD) devices receiving successful RFA treatments utilizing a bipolar technique.
Placement of the grounding pad on the patient can affect the risk of interference as well. With monopolar RFA, placement of the grounding pad closer to the site of ablation decreases the risk of affecting implanted electronics. However, reducing the distance between the probe and the pads increases the risk of thermal tissue injury because there is less physical space for the current to dissipate.
It is important to work as a team with all the healthcare providers responsible for any implantable device to assess risks and benefits of an RFA procedure. The patient should be involved in these discussions in order to make an informed decision as to whether or not to continue. Electrical devices should be turned off with an output of zero if possible, and neurostimulators should subsequently be reprogrammed to their original settings after the procedure. The primary physician managing the device, as well as the maker of the device, should be consulted for recommendations before following through with the procedure. Finally, the use of minimal sedation should be sought to ensure proper communication with the patient, as well as early detection of any new-onset deficits that could be related to the procedure.
RFA in the presence of pacemakers and implantable cardioverter-defibrillators
Pacemaker-dependent patients with implantable cardioverter-defibrillators (ICDs) can and do have successful courses of RFA, but there are at least two documented anecdotal instances of defibrillator discharge despite adherence to the precaution. However, a systematic review of the literature in 2021 found no complications or malfunctions in cardiac implantable electronic devices (CIED) with 71 bipolar RFA treatments of 33 patients. The authors provided the following guidelines for safe use of RF in CIED patients:
- 1.
Maintain thorough communication between pain physician and treating cardiologist.
- 2.
Consider having cardiac device manufacturer support prepared onsite during the procedure for potential reprogramming if needed. Implantable cardiac device should be interrogated prior to and after RFA procedure.
- 4.
Keep RFA application as brief as possible.
- 5.
RFA application should be as remote as possible from CIED (5 cm or more).
Additionally, the American Society of Anesthesiology recommends placing the grounding pad at least 15 cm away from the pacing leads for implantable cardiac defibrillators and pacemakers.
RFA in the presence of deep brain stimulators
Reversible neurologic deficits have been documented in a patient with a DBS receiving diathermy treatments. Diathermy is a procedure involving the use of targeted RF energy into biological tissues to increase heat and blood flow to generate a therapeutic effect. While this procedure is contraindicated in patients with DBS implantations, there is evidence of successful medial branch RFA in patients with deep brain stimulators.
RFA in the presence of spinal cord stimulators
An additional modality for treatment of refractory chronic pain is an implantable spinal cord stimulator (SCS). These neuromodulatory devices share the risk of interference from RFA. A case has been documented of occipital nerve RFA leading to activation of a cervical SCS device and subsequent pain to the patient. Neither patient nor device experienced long-term effects. However, a retrospective analysis of 20 patients receiving 44 separate RFA treatments in the presence of SCS devices showed no problems regarding the devices during or after the procedure. These physicians used precautions by checking the devices before and after each procedure, utilizing only local anesthesia and instructing the patient to mention any unusual sensations.
RFA in the presence of peripheral nerve stimulators
Just as the spinal cord can be electrically stimulated to modulate pain, so too can the peripheral nervous system. Peripheral nerve stimulators are similar to spinal cord stimulators in that a generator uses an electrode to administer targeted current to a nerve. A report of two cases demonstrated instances of two-needle monopolar lumbar RFA interfering with dorsal root ganglion stimulation (DRG-S) systems. When ablation was started, muscular contraction was noted in both patients in an S1 distribution. This finding was repeated. However, it was elucidated that the DRG-S devices were in the “on” position, that when turned to the “off” position, no muscular contraction occurred, and that the procedure was completed successfully. Neither patient nor device experienced long-term effects.
RFA in the presence of spinal hardware
While there has been concern for thermal injury raised for the use of RFA for the medial branch in patients with metal spinal fixation hardware, a 2018 study including 44 ablations at the lumbar level in such patients demonstrated no serious complications. Though demonstrably uncommon, this complication should remain a concern. Care should be taken to confirm the RFA probe is not in contact with any spinal hardware via multiplanar fluoroscopic imaging.
Another study by Abd-Elsayed et al. compared patients who received RFA next to hardware versus patients who received RFA at the same sites in the absence of hardware, and the efficacy was not different.
As with the devices described, the safe use of RFA should additionally be considered in patients with gastric pacers, vagal nerve stimulators, intrathecal pumps, and other implantable devices. However, guidelines for these devices have not been published.
References
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