Introduction
One of the most common health conditions worldwide is chronic low back pain (CLBP). In fact, the point prevalence of low back pain is noted to be around 12% to 33% in the general population. In addition to the pain burden, back pain also is one of the leading causes of disability in the world, affecting over 600 million patients, and is one of the primary leading causes of financial burden on the health care system. In order to treat back pain, a stepwise approach is typically taken. Initially, nonpharmacological methods such as education, increased activity, and improvement of posture are all methods that are initiated. , In addition to education, the use of pharmacological therapies such as analgesic medication are first-line therapy. If conservative measures fail, interventional approaches to the treatment of back pain can be done, such as the use of spinal cord stimulation (SCS) and spinal surgery for patients who may qualify. Many clinical theories exist regarding the source of low back pain. Initially, many theories postulated that over time, as vertebral discs degenerate, the nociceptors in the annulus fibrosus are the primary contributing factor of low back pain. Although for many years this was the prevailing theory, new research has theorized that the basivertebral nerve (BVN) may play a role in carrying nociceptive signals from vertebral end plates that are damaged and result in CLBP. Given the potential for the BVN to result in chronic back pain, effectively localizing and targeting the BVN and conducting a BVN ablation can lead to the resolution of chronic back pain.
Anatomical considerations
The innervation of the vertebral body by the BVN has been extensively studied by Antonacci et al. and Fras et al. , In the study, 69 vertebral bodies were stained for substance P in addition to the nerves innervating the vertebral bodies. The BVN is a branch of the sinuvertebral nerve, which arises from the dorsal root ganglion (DRG). Specifically, the sinuvertebral nerve arises from the ventral ramus of the spinal nerves bilaterally and enters the spinal canal through the basivertebral foramen. In the basivertebral foramen, both BVN and basivertebral plexus travel through the foramen to reach the vertebral end plates. In Fig. 9.1 , the BVN can be seen traveling through the basivertebral foramen and innervating the vertebral body. In Fig. 9.2 , the sinuvertebral nerve is branching out into the BVN, which innervates the vertebral body.
Patient selection and indications
Various patients may qualify to undergo BVN ablation for the treatment of CLBP. First, CLBP as a result of vertebrogenic causes is the number one indication for BVN ablation. As explained earlier, the BVN has been studied as the nerve that innervates the vertebral body. Prior to the conduction of the procedure, other causes of CLBP—such as musculoskeletal conditions, facet joint conditions, and annulus fibrosus trauma must be ruled out. All patients undergoing the procedure must have had CLBP for longer than 6 months that was nonresponsive to at least 3 months of conservative medical care. Additionally, all patients undergoing the procedure must have no spinal stenosis present and have Type 1 or type 2 Modic changes present on magnetic resonance imaging (MRI). Type 1 and type 2 Modic changes on imaging refers to hypotensive on T1WI and hyperintense on T2WI and hyperintense on T1WI and isointense or slightly hyperintense on T2WI, respectively ( Fig. 9.3 ).
Contraindications
Various contraindications exist that may exclude a patient from undergoing a BVN ablation. In general, patients that have any signs of infection—both systemic and spinal—are typically contraindicated to undergo an interventional spine procedure such as BVN ablation. Other conditions that are contraindications to undergoing this procedure include patients with a spinal malignancy, metastatic malignancy, increased risk of bleeding, pregnancy, and implanted cardiac devices, such as pacemakers. , ,
Description of procedure
The BVN ablation procedure is typically performed in an outpatient setting. First, the patient should be positioned prone on the operating table. Patients undergo the procedure under general anesthesia or monitored anesthesia care (MAC) with continuous monitoring. After the patient is placed in a prone position and under anesthesia, the area is prepped in a sterile fashion with the target pedicle and area of entry marked. In general, 1% lidocaine anesthetic is used at the site of entry and an incision is made with the use of a scalpel. Next, an introducer trocar cannula is advanced through the pedicle to enter the posterior vertebral wall, as seen in Fig. 9.4 . As the trocar is introduced into the posterior vertebral wall with the use of a mallet, various anteroposterior and C-arm views are obtained to ensure the proper trajectory of the trocar. After ensuring proper trajectory, the introducer trocar is replaced with a curved nitinol stylet probe which allows for the facilitation of a curved path from the posterior vertebral wall to the BVN terminus in the vertebral body, as seen in Fig. 9.5 . After fluoroscopic imaging has confirmed the location of the curved stylet, the stylet is replaced with a bipolar radiofrequency probe that is positioned similarly at the terminus of the BVN in the vertebral body as seen in Fig. 9.5 . The target zone of the probe placement is typically 30% to 50% across the vertebral body width, as seen in Fig. 9.6 . After proper placement is confirmed, the radiofrequency probe is activated for 15 minutes at a temperature of 85° C until the creation of a 1-cm lesion in the vertebral body, as seen in Fig. 9.7 . After proper ablation, the radiofrequency probe is removed from the vertebral body and the skin is sutured in a sterile fashion.
