Austrian study shows improvement; IDE clinical trial under way in United States
A minimally invasive technique involving ablation of the basivertebral nerve may provide relief to patients with chronic lower back pain, according to an Austrian study presented at the annual meeting of the North American Spine Society (NASS).
Stephen W. Becker, MD, of the Institute of Musculoskeletal Analysis, Research, and Therapy, in Vienna, Austria, described the technique, in which a radiofrequency device is used to ablate the nerves within the vertebral bone that transmit pain signals produced at vertebral endplates adjacent to degenerated disks. In a small pilot clinical study, the procedure resulted in improved patient Oswestry Disability Index (ODI) scores and Visual Analogue Pain Scale (VAS) values, which were sustained at 1 year.
The rationale for the procedure is based on studies indicating that the basivertebral nerve conducts pain receptive signals from intraosseous sources. Previous researchers had described consistent reports of a severe “deep boring pain” when the bony endplate was directly stimulated during surgical procedures performed on nonanesthetized patients. Pathologic changes (including edema and inflammation), within the bone adjacent to degenerating lumbar disks and noted on magnetic resonance images, suggest that clinical pain could be addressed by ablatement of the intraosseous nerves within the anatomic area where these nerves enter the bone.
Fig. 1 (A) In the Intracept procedure (not approved for use in the United States), C-arm fluoroscopy is used to navigate the radiofrequency (RF) probe to the terminus of the basivertebral foramen. (B) Temperature-controlled bipolar RF energy is delivered to create a well-defined lesion.
“There was some evidence that an efferent nerve was causing some mechanical actual pain,” Dr. Becker said. “So it was logical to explore that further and develop a treatment method.”
Although most research in basivertebral nerve ablation has been performed in animal systems, Dr. Becker and colleagues treated 16 human patients with chronic (greater than 6 months) isolated lower back pain who were unresponsive to at least 3 months of nonsurgical conservative care. Patients were an average of 47.6 years old and had undergone an average of 32.4 months of conservative treatment. Participating patients all had ODI scores greater than 30 and either pathologic changes or positive provocative discography at the targeted degenerated disk level.
Using conventional MRI imaging, researchers visualized and mapped the intraosseous course of the basivertebral foramen for the targeted vertebral bodies. Treatment was performed using intraoperative fluoroscopy and a transpedicular approach (Fig. 1). A bipolar radiofrequency probe with a curved obturator, inserted through a bone biopsy needle, was guided to the target. Then, bipolar radiofrequency energy was used to ablate the basivertebral nerve in a controlled manner. Treatment was limited to L3, L4, L5, and S1 vertebrae. Two- and three-level intraosseous ablatements were performed, always at adjacent levels; 12 patients were treated at L4-L5, 2 at L3 through L5, and 2 at L5-S1.
Radiographs found no fractures during the follow-up period, and no remodeling of bone was seen.
“Profound and immediate relief” was reported by 13 of the 16 patients, Dr. Becker said. ODI scores were significantly improved at 6 weeks, 3 months, 6 months, and 12 months. The mean decrease in ODI scores at 1 year was 31 points. Similarly, VAS values decreased from a preoperative average of 61.1 to an average of 45.6 at 12-month follow-up. No device-related serious adverse events were reported.
The researchers concluded that basivertebral nerve ablation is a safe, simple procedure that is applicable during the early stages of treatment for patients with disabling back pain.
“Ideally, lower back pain can be managed with simple measures like targeted exercise, behavioral therapy, and mild pain medications,” Dr. Becker said. “For patients with chronic pain, conservative treatment is simply not enough, and a minimally invasive treatment is the next logical step. This method is minimally invasive and tissue-sparing, and preserves essentially all other therapeutic options and surgical interventions should they be required in the future.”
Describing the discoveries and treatment developments involving ablation of the basivertebral nerve as among “the most important in the past 10 years” for low back pain, Dr. Becker said, “I think this may be the missing link between conservative treatment and more aggressive treatment such as fusion and disc replacement.”
Although these results are promising, this was a small uncontrolled study, and thus additional investigation is warranted. A randomized, sham-controlled double-blind IDE study of 200 patients at 20 leading U.S. medical centers is currently under way to evaluate this therapy.
Coauthors of “Ablation of the Basivertebral Nerve for the Treatment of Back Pain: A Pilot Clinical Study” are Alexander Hadjipavlou, MD; Guy Danielson III, MD; Aaron K. Calodney, MD; Allen L. Carl, MD; and Mark Belza, MD. Disclosure information: Dr. Becker—Medtronic, Kyphon, Benvenue Medical, Relievant Medsystems, Skeltex; Dr. Hadjupavlou—Journal of Bone and Joint Surgery–British; Dr. Carl—Trans1, K2M, K Spine, Highgate Orthopedics, Intrinsic Orthopedics, Replication Medical, CardioMEMS, DePuy, Musculoskeletal Transplant Foundation, The Spine Journal, Dr.Belza—Relievant, Medtronic. Drs. Danielson and Calodney reported no conflicts.
- Evidence collectively supports the theory that mechanical back pain is a result of stimulation of pain receptive fibers within the vertebral body.
- Endplates of patients with “discogenic” pain are touch-sensitive and show more pain receptors than those in patients without pain.
- In this small, prospective study without a control group, ablation of the basi-vertebral nerve provided substantial relief of symptoms in patients with chronic lower back pain.
- Although this procedure is not yet cleared for use in the United States, a randomized, sham-controlled double-blind IDE study is currently under way to evaluate this therapy.
January 2012 Issue
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