PENS for Relief of Low Back Pain
Abstract & Commentary
Synopsis: In this sham-controlled study, PENS was more effective than TENS or exercise therapy in providing short-term pain relief and improved physical function in patients with long-term LBP.
Source: Ghoname EA, et al. JAMA 1999;281:818-823.
Low back pain (lbp) contributes to considerable disability and lost wages in the United States. Commonly used opioid and nonopioid analgesic drugs produce adverse effects and are of limited long-term benefit in the management of this patient population.
The effectiveness of a novel nonpharmacologic pain therapy, percutaneous electrical nerve stimulation (PENS), was compared to transcutaneous electrical nerve stimulation (TENS) and flexion-extension exercise therapies with long-term LBP. We used a randomized, single-blinded sham-controlled crossover design from 3/97-12/97 in an ambulatory pain management center at a university medical center.
Twenty-nine men and 31 women with LBP from degenerative disk disease of at least three months duration were randomized to four administered therapeutic modalities (sham-PENS, PENS, TENS, and exercise therapies) for 30 minutes three times a week for three weeks, with one week off between therapies. PENS was significantly more effective in decreasing visual analog scale (VAS) pain scores after each treatment than sham-PENS, TENS, and exercise therapies.
After treatment, mean +/- SD VAS scores for pain were 3.4/1.4 for sham PENS, 5.5/1.9 for PENS, 5.6/1.9 for TENS, and 6.4/1.9 for exercise therapy. The average +/- SD daily oral intake of nonopioid analgesics (2.6/1.4 pills daily) was decreased to 1.3/1.0 daily with PENS (P < 0.008) compared with 2.5/1.1, 2.2/1.0, and 2.6/1.2 daily with sham-PENS, TENS and exercise, respectively. Compared with the other three modalities, 91% of the patients reported that PENS was the most effective in decreasing their LBP. The PENS therapy was also significantly more effective in improving physical activity, quality of sleep, and sense of well-being (P < 0.05 for each). The SF-36 survey confirmed that PENS improved post-treatment function more than sham-PENS, TENS, and exercise.
In this sham-controlled study, PENS was more effective than TENS or exercise therapy in providing short-term pain relief and improved physical function in patients with long-term LBP.
COMMENT by John La Puma, MD, facp
This well-designed Dallas study has some flaws: the exercise prescribed was a simple spine flexion-extension repeated 30 times in 30 minutes; follow-up was limited to 72 hours; patients using opioids for LBP were excluded; how many patients had radiculopathy, if any, is not stated; and a double-blind design was not possible. Overall, its results are impressive in a notoriously difficult-to-treat population, albeit over the short-term.
PENS produced an acute analgesic effect immediately after each treatment, though it took three to four treatments to change their VAS scores for pain, activity, and sleep, and to decrease the consumption of oral analgesics, significantly beating TENS treatment alone.
PENS combines TENS with electroacupuncture to stimulate peripheral sensory nerves at the dermatomal levels corresponding to the local pathology. Ten 32 gauge stainless steel probes were connected to five bipolar leads connected to a small, non-FDA-approved electrical generator. The probes were placed deliberately into soft tissue or muscle from T12 to S2 and were stimulated at a frequency of 4 Hz for 0.5 milliseconds. In contrast, TENS used 4 one-inch cutaneous electrode pads, stimulated at 4 Hz for 0.1 milliseconds.
A recent randomized controlled trial with two-year follow-up comparison of chiropractic, physiotherapy, and an educational booklet for LBP showed approximately equivalent effectiveness.1 with highest patient satisfaction for chiropractic and least cost for the educational booklet.
A new field of medicine—perhaps called "musculoskeletal medicine"—is emerging from between the cracks of rheumatology, physiatry, orthopedics, sports medicine, and anesthesiology. Physicians seriously interested in these patients approach their diseases from a multimodal rehabilitative perspective rather than a curative one. The main barriers to their success will be the time required to establish a therapeutic alliance.
As part of a multimodal approach to back pain, PENS warrants serious consideration in longer trials to test whether it can improve short- or long-term pain or improve function in a lasting fashion.
Reference
1. N Engl J Med 1998;339:1021-1029.
Which of the following statements is true?
a. PENS produced an acute analgesic effect immediately after each treatment,
b. PENS combines TENS with electroacupuncture to stimulate peripheral sensory nerves at the dermatomal levels corresponding to the local pathology.
c. PENS was more effective than TENS or exercise therapy in providing short-term pain relief
d. All of the above
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