Sunday, August 1, 2010

Destroy Nerves to Relieve Arthritic Back Pain?

New research suggests that adhering to common interventional approaches for diagnosing arthritis-related back pain may result in excessive tests, delays in pain relief, and wasteful spending. A recommended course is to skip diagnostic nerve blocks altogether and move straight to denervation (nerve destroying) treatments when arthritis is suspected as causing nonspecific back pain… but there are some reservations.

Lumbar JointsCurrent estimates are that about 10% to 15% of patients with spinal (axial) low-back pain have arthritis of the vertebral facet joints. However, this condition is difficult to precisely diagnose because findings on x-rays or MRIs often do not correspond with the degree of back pain. This has led to routinely performing temporary diagnostic nerve blocks (by injecting numbing agents) to establish the arthritis connection before recommending radiofrequency denervation, which essentially stems pain signals by burning the nerves serving affected facet joints [see illustration]. Facet-joint interventions are the second most frequently performed procedures in pain clinics across the United States and, according to new research, it may be appropriate in many cases and more cost-effective to go directly to denervation without first performing diagnostic nerve-blocks to confirm the root cause of the problem.

Writing in the August 2010 edition of Anesthesiology, researchers report a randomized, multicenter study that enrolled 151 adult patients with nonspecific low back pain suspected of originating from lumbar facet joints, and who had failed to respond to more conservative therapies for at least 3 months [Cohen et al. 2010]. The investigators compared 3 outpatient treatment approaches: A) Group 0 immediately received radiofrequency denervation based solely on clinical inference of facet-joint arthritis; B) Group 1 underwent denervation contingent on a positive response to single diagnostic nerve blocks; and C) Group 2 proceeded to denervation only if they had positive responses to comparative blocks done with both lidocaine and bupivacaine. A positive outcome was predesignated as ≥50% pain relief coupled with a positive global perceived effect persisting for 3 months. Overall, in Group 0 (without screening procedures), 17 patients (33%) obtained a successful outcome at 3 months versus 8 (16%) in Group 1 and 11 (22%) in Group 2. The cost per each successful treatment was only $6,286 in Group 0, compared with roughly $15,000 to $17,000 in the other two Groups.

COMMENTARY: The authors conclude that proceeding to radiofrequency denervation without diagnostic screening is the most cost-effective treatment paradigm. Patients in Group 0 visited the clinic just once, were treated immediately, and lost no extra and costly days of work to undergo repeated diagnostic tests. However, while first having the diagnostic-screening blocks resulted in fewer patients qualifying for radiofrequency denervation procedures, percentage-wise, their favorable outcomes at 3-month were greater: 79% (11/14) of Group 2 patients who underwent denervation procedures had successful outcomes, compared with 42% (8/19) in Group 1 and 33% (17/51) in Group 0. In other words, many patients undergoing denervation procedures without adequate prescreening did not actually have lumbar facet-joint arthropathies that would benefit from denervation.

However, it must be considered that diagnostic-screening nerve blocks may be more art than science. A related editorial in the same edition of the journal noted that there currently is no definitive standard on how to perform the blocks, which results in variations in technique, agents used and their dose, procedural protocols, and the interpretation of results [Van Zundert et al. 2010]. Consequently, the proportion of patients ultimately selected for radiofrequency ablation procedures ranges widely from 10% to 92%, which is inconsistent with the estimated prevalence of facet-joint arthropathy (10-15%). However, Cohen and colleagues [2010] contend that many patients may needlessly endure long delays and multiple procedures before finally getting lasting pain relief, and some may be denied appropriate radiofrequency-denervation treatment because of false-negative results associated with inaccurate diagnostic blocks. They assert that denervation is not considered dangerous for those without arthritis; although, there can be complications due to infection with either diagnostic blocks or radiofrequency denervation [and, presumably, a mismanaged procedure might incur harm].

While pain relief can last many months and sometimes years following denervation, the procedure often must be repeated when pain returns. And, some might question whether all patients who “may qualify” should undergo an invasive nerve-destroying procedure with the foreknowledge that only some, but not all, would benefit. Another drawback of the approach seems that it views interventional procedures in isolation as a primary solution, without taking into account the possible contributions of noninvasive integrated strategies for helping to achieve more long-term pain relief, such as exercise, physical therapy, dietary supplements (including vitamin D), clinical massage, and other modalities.

> Cohen SP, Williams KA, Kurihara C, et al. Multicenter, Randomized, Comparative Cost-effectiveness Study Comparing 0, 1, and 2 Diagnostic Medial Branch (Facet Joint Nerve) Block Treatment Paradigms before Lumbar Facet Radiofrequency Denervation. Anesthesiology. 2010(Aug);113(2):395-405 [
access article here].
> Van Zundert J, Mekhall N, Vanelderson P, van Kleef M. Diagnostic Medial Branch Blocks Before Lumbar Radiofrequency Zygapophysial (Facet) Joint Denervation: Benefit or Burden? Anesthesiology. 2010(Aug);113(2):276-278 [
access article here].