Percutaneous Electrical Nerve Stimulation for Low Back Pain: A Randomized Crossover Study.

Ghoname EA, Craig WF, White PF, et al (Eugene McDermott Center for Pain Management, Departments of Anesthesiology and Pain Management, and Departments of Surgery and Psychiatry, University of Texas Southwestern Medical Center, Dallas, Tex), JAMA. 1999; 281:818-823.

The purpose of this study was to compare the effectiveness of percutaneous electrical nerve stimulation (PENS) with transcutaneous electrical nerve stimulation (TENS) and exercise therapy in patients with long-term back pain secondary to degenerative disk disease. The authors sought to determine the effect of these treatment methods on pain levels, physical activity, quality of sleep, overall sense of well-being, and need for oral analgesic medication.

Sixty patients older than 18 years of age were recruited for the study. The inclusion criteria were: (1) radiologically confirmed degenerative disk disease, (2) low back pain that was maintained at a stable level for at least 3 months with oral non-opioid medications, and (3) no major illnesses. Patients with acute nerve root irritation, history of alcohol or drug abuse, previous use of acupuncture or other nontraditional therapies, or pending medicolegal litigation were excluded.

Patients were randomly assigned to 1 of 4 treatment groups. Each group received 4 different treatments according to 1 of 4 computer-generated sequences: (1) PENS, sham PENS, TENS, and exercise, (2) sham PENS, TENS, exercise, and PENS, (3) TENS, exercise, PENS, and sham PENS, or (4) exercise, PENS, sham PENS, and TENS. Each modality was administered 3 times per week for 3 weeks, with a week off before the next treatment series started.

PENS was administered by insertion of 10 acupuncture-like needles to a depth of 2 to 4 cm in the low back according to the dermatomal distribution of pain. Each pair of needles was connected to an electrical generator which produced a unipolar square wave at 4 Hz with a 0.5-millisecond pulse duration. Stimulation was adjusted to maximum tolerable level without muscle contraction. TENS was administered using four 2.5-cm cutaneous electrodes placed in the dermatomal distribution of pain, with stimulation at 4 Hz and a 0.1-millisecond pulse duration. Exercise therapy consisted of spinal flexion and extension from sitting performed 30 times during a 30-minute session. Sham PENS consisted of placement of 10 needles, in the same distribution as the PENS but without stimulation.

Patients completed the 36-Item Short-Form Health Status Survey (SF-36) before the first treatment and after the final treatment. Pain levels, physical activity levels, and quality of sleep were reported before each treatment, and pain level was reported after each treatment. After the last treatment session, patients were also asked for an overall assessment of the relative effectiveness of each of the 4 modalities.

According to the results, SF-36 scores for physical activity and sense of well-being were significantly improved over pretreatment levels after PENS. TENS and sham PENS produced smaller, but significant, improvements as well. PENS produced significantly greater improvements in overall SF-36 scores when compared with the other modalities. PENS and TENS both produced significant improvements in pain and level of physical activity compared to pretreatment levels, and PENS significantly improved quality of sleep. Comparison of visual analog scale scores for pain, level of physical activity, and quality of sleep for all 4 treatments showed significantly greater improvement produced by PENS. Patients receiving PENS reported a 50% decrease in use of oral analgesics, compared with little or no decrease for the other modalities. The overall assessment of effectiveness of treatment revealed that PENS was the preferred therapy for 91% of the study participants.

The authors concluded that PENS was significantly more effective than TENS or exercise in decreasing pain, improving physical and mental well-being, and decreasing medication use in patients with low back pain. They pointed to enhanced physical activity as the most important outcome and suggested using PENS as part of a comprehensive treatment program for this patient population. They suggested further studies using different stimulation frequencies and stimulation points, and examining the cost benefit of PENS as part of a multimodal treatment approach.

Marilyn Mieras, PT
University of the Pacific
Stockton, Calif