Emerging Interventional Treatments for Chronic Back Pain

A perpetual topic of discussion in interventional pain management is the treatment of chronic low back pain. The American Society of Pain and Neuroscience (ASPN) annual meeting, held in July 2022, was no different.

Differential diagnosis of back pain includes disc herniation, lumbar spinal stenosis, degenerative disc disease, sacroiliac joint dysfunction, nerve root compression, plexopathy, and facet joint injury.¹

At the ASPN meeting, physicians were able to experience hands-on training on the latest pain interventions, such as peripheral nerve stimulation (PNS), lateral interspinous fusions, percutaneous image-guided lumbar decompression, spinal cord stimulation (SCS), radiofrequency ablations (RFA), balloon kyphoplasty, allograft for discogenic pain, and dorsal root ganglion stimulation. The purpose of this article is to discuss both novel and commonly used interventions for patients with low back pain.

Lumbar facet pathology is a commonly diagnosed cause of chronic back pain with a prevalence of 4.8% to 50% according to the national low back pain survey.3 The current standard of care for facet disease is RFA of the medial branches – the nerves that provide innervation of the facet joints.

Since 2007, according to the MarketScan commercial claims and encounters databases, lumbar radiofrequency ablations (RFA) have increased 9.7% annually until present day.³ In the last two years, the American Society of Regional Anesthesia and Pain Medicine and the ASPN provided consensus guidelines for the treatment of back pain with lumbar RFA.³˒⁴ Examples of the consensus statements and answers to debated topics about RFA include:³˒⁴

• medial branch blocks (MBBs) should be the prognostic injection of choice before RFA but with certain selectivity
• the orientation of the electrode during RFA should be parallel to nerve being ablated.
• larger lesions may increase nerve capture and ablation effectiveness
• sensory and motor testing improves safety and avoidance of adjacent structures

Recently, chronic low back pain has been correlated to the decreased motor control and fatty infiltration of the multifidus muscle. Since the multifidus muscle plays a significant role in lumbar spine stability and strengthening, better coordinating movement of this muscle using an implantable, restorative neurostimulator has been theorized as a potential treatment.⁵

In the past, motor control exercises were seen as an effective treatment for impaired multifidus muscle function, but long-term effects were limited.⁵ However, restorative medial branch stimulation of the dorsal ramus is a procedure that provides electrical stimulation to the multifidus muscle in hopes of decreasing inhibition and increasing strength of the muscle, thus restoring spinal control and alleviating symptoms.⁵ Permanent restorative multifidus neurostimulation is currently available and has been shown in some studies to improve patient outcomes.

Mitchell et al conducted a 4-year case cohort study with 53 subjects who received permanent restorative medial branch stimulation which helped improve pain and disability by 53% and 50% respectively from baseline.⁶ Gilligan et al completed a double blinded, randomized sham-controlled trial (n = 204) in which patients were randomized to permanent restorative medial branch stimulation v. sham. While treatment superiority was not reached at 120 days, clinically significant improvement was demonstrated when longer outcomes were measured (ie, one year).⁵ Temporary medial branch neurostimulation has also shown promise in small trials and case studies. Larger multicenter trial results will hopefully be available soon.

The efficacy of SCS for all encompassing chronic low back pain continues to be an ongoing topic for discussion in the literature. In 2020, Conger et al completed a systematic review to analyze the efficacy of different SCS technologies for chronic low back pain. It was found that FBSS (failed back surgery syndrome) was the most common clinical diagnosis for patients with back pain who underwent SCS. Based on smaller clinical trials, it was also stated that SCS at 10kHz appeared to be a successful treatment for patients with axial low back pain for more than six months.⁷ The long-term clinical efficacy of SCS for chronic low back pain is currently being studied by several centers utilizing many unique waveforms and frequencies. Results will hopefully be available soon.

BVN Ablation

Basivertebral nerves (BVNs) carry the nociceptive signals from vertebral endplates. Due to variable vascularity, the vertebral endplates are highly susceptible to degeneration, intraosseous edema, fissuring, and inflammatory changes (these are also called Modic changes).⁸

Allografts

Chronic discogenic back pain can also be treated with a viable disc tissue allograft. Beall et al completed a prospective blind RCT for patients who suffered from single level or two-level degenerative disc disease.⁹ Patients were separated into three treatment groups; those injected with allograft, saline, and patients who were continued with nonsurgical management. In 12 months, VASPI and ODI scores in groups that received the allograft and saline both improved, but allograft patients reported the highest improvement.⁹ While these findings are encouraging, it has been theorized by the authors that more significance would have been seen in the VASPI and ODI scores if a different placebo were used instead of saline.⁹

Other etiologies of low back pain also include spinal stenosis. Spinal stenosis occurs when there is narrowing of the spinal canal intervertebral foramina or lateral recesses causing compression of the spinal nerve roots.¹⁰ There are many different causes of spinal stenosis; they include degenerative disease of the spine, hypertrophy of the ligamentum flavum, disc herniations, or osteophytes.

There are various treatment options pain physicians can offer depending on the pathophysiology of the patient. Percutaneous image guided lumbar decompression can be considered when hypertrophy of the ligamentum flavum is the cause of spinal stenosis.¹⁰ For patients who suffer from neurogenic claudication, and their symptoms are relieved by flexion of the spine, an interspinous spacer may be considered.¹⁰ Interspinous-interlaminar fusion may also be offered as an alternative to a larger open fusion technique.¹⁰

Regenerative Medicine

Regenerative medicine continues to be discussed in the field of pain medicine. Percutaneously delivered multipotent mesenchymal stem cell therapy and transplantation of the nucleus pulposus are proposed interventions that can help patients with diagnosed discogenic back pain.¹¹ These new interventions may help with discogenic back pain in three proposed ways: reversal of the catabolic metabolism of the intervertebral disc, rebuilding disc tissue and height, and soothing primary nociceptive disc pain.¹¹ More studies and clinical trials are forthcoming.

It is an exciting time to be in the field of pain medicine. With increased options for back pain, the current challenge is ensuring that we provide the right therapy for the right patient. With continued conversations like the ASPN annual meeting and many other conferences to come in the 2022-2023 academic year, we hope that pain medicine will continue to make strides toward improving quality of care and improving patient outcomes.