Endoscopic Radiofrequency Denervation for Treatment of Chronic Low Back Pain

27 Endoscopic Radiofrequency Denervation for Treatment of Chronic Low Back Pain

Won-Suh Choi and Jin-Sung Luke Kim

27.1 Introduction

The lifetime prevalence of low back pain is estimated to be 60 to 80%.1,2 Chronic low back pain (CLBP) that persists for 3 months or more is reported to have a lifetime prevalence of 4 to 10%.³ CLBP can be caused by various sources of pain generation, including intervertebral disk, back musculature, facet joints, and sacroiliac joints. It can also be caused by a combination of these pain generators, and identification of the source of pain is the first step in successful treatment of CLBP.

Low back pain arising from the facet joint, also known as facet joint syndrome (FJS), is a major source of CLBP and is reported to be responsible for 15 to 45% of the total population suffering from CLBP.^4,5 Symptoms can be similar to those of herniated disk, and pain can be exacerbated by back extension after flexion.

The sacroiliac joint (SIJ) complex is also a major, but often overlooked, source of CLBP, accounting for ~ 10 to 33% of CLBP.^1,6,7,8,9,10 The symptoms are nonspecific and can sometimes mimic symptoms of lumbar herniated disk, which makes the diagnosis difficult. SIJ pain can develop as a form of adjacent-segment pathology, especially after fusion surgery.

The current standard treatment for FJS and SIJ pain is steroid injection of the joint itself, the medial branch of the dorsal ramus in the case of FJS^4,11 or lateral sacral nerve branches in the case of SIJ-mediated CLBP.^12,13,14 These procedures can be performed on an outpatient basis, are easy to perform, and have additional diagnostic value. However, patients may experience symptom recurrence due to short duration of effect,¹⁵ and there are always risks of possible local and systemic complications associated with repeated steroid injection.

Fluoroscopy-guided radiofrequency ablation (RFA) of the aforementioned structures provides a longer-lasting effect.^16,17 However, often extensive ablation is required to achieve satisfactory relief of patients’ pain. Extensive ablation can also scar adjacent muscular and ligamentous structures, and the scarring itself can become a source of CLBP. With direct visualization under endoscopic guidance, more precise lesioning and effective neural ablation are possible without damaging nearby structures (Video 27.1).

27.2 Indications and Contraindications

27.2.1 Medial Branch RFA

• A minimum of 2 months of conservative and medical treatment, including analgesics and physical therapy.

• Two diagnostic medial branch blocks performed on separate occasions, with greater than 50% pain reduction after the procedure on both occasions.

• Any patient with CLBP arising from fracture, infection, or pathologic origin, or with issues of possible secondary gain, is excluded.

27.2.2 Sacroiliac Joint RFA

• A minimum of 2 months of conservative and medical treatment, including analgesics and physical therapy.

• Two diagnostic intraarticular and/or periforaminal SIJ blocks performed on separate occasions, with greater than 50% pain reduction after the procedure on both occasions.

• Any patient with CLBP arising from fracture, infection, or pathologic origin, or with issues of possible secondary gain, is excluded.

27.3 Surgical Technique

The patient is placed in the prone position on chest rolls on a radiolucent table. A small dose of intravenous fentanyl and midazolam is administered for light anesthesia. Before the procedure is started, patients are fully informed of all the details of the procedure. Patients are monitored and maintain communication with the surgeon throughout the procedure.

The patient is prepped and draped in a sterile manner. Fluoroscopic equipment, such as the C-arm, is required for confirmation of landmarks and for checking the position of the endoscope (Fig. 27.1).

Fig. 27.1 The patient should be prepped and draped in a sterile manner, as in open surgery. A C-arm is set up to confirm the position of the endoscope at various points during the procedure. An assistant can help hold the cannula or the scope, which can decrease the surgeon’s fatigue.

27.4 Technique

27.4.1 Medial Branch RFA

The facet joint is innervated by the medial branch of the dorsal ramus at the target vertebral level and one level above it (Fig. 27.2).^18,19 Therefore, to successfully treat pain arising from a facet joint, the medial branch one level above the target needs to be ablated as well. The target point for ablation is the junction of the transverse process and the base of the superior articular process (SAP) (Fig. 27.3). After verification of the target level with the C-arm, 0.5% lidocaine is injected at the needle entry site via a 22 G spinal needle. Under fluoroscopic guidance, an 18 G needle is docked on the target point. Next, the skin opening is widened slightly with a No. 11 scalpel, and a K-wire, obturator, and beveled working cannula are serially inserted through the opening (Fig. 27.4). After the correct position of the cannula is verified with C-arm fluoroscopy, the endoscope is advanced through the cannula, and the bipolar electrocoagulator is advanced through the opening in the endoscope.

Continuous irrigation is maintained throughout the procedure to obtain a clear view of the working field, and also to prevent charring of the bipolar tip. We start by ablating soft tissue at the base of the transverse process. Ablating this area should elicit pain, because the medial branch, and sometimes the lateral branch, course through this region. The medial branch is visible in this location with the endoscope (Fig. 27.5), but not in all cases. However, even when the medial branch is not visible, we are able to see the bony landmarks and ablated areas under endoscopic view. Occasionally, the pain elicited during ablation is too much for the patient to bear, and in such cases we inject 0.5 to 1 mL of lidocaine at the target through an 18 G needle prior to ablation. The ablation is done preferably in short bursts of 2 to 3 seconds to prevent excessive charring. The process is continued until stimulation of the previously ablated area does not elicit any significant pain.

Fig. 27.2 The lumbar zygapophysial joint, or facet joint, has dual innervations. It is innervated by the ascending medial branch at the index level, as well as by the descending medial branch from the level above it.

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