Background: Lowback pain is an important public health problem that is associated with poor quality of life and disability. Among the electrophysical treatments, the evidence on the use of interferential current (IFC) parameters for decreasing pain remains insufficient. Purpose: Primary: To assess the effects of carrier frequency of interferential current (IFC) on pain in chronic nonspecific low back pain. Secondary: To assess pain during movement, disability, global perceived effect of treatment, the local and segmentar pressure pain threshold, functional performance, the discomfort produced by the current, the consumption of analgesics, and the influence of the treatment on central mechanisms of pain. Methods: A three-arm randomized controlled trial with patient and assessor blinded to the group allocation. One hundred fifty patients with chronic, nonspecific low back pain were randomly allocated into 3 groups (IFC 1 kHz, IFC 4 kHz or Placebo IFC). The interferential current was applied three days per week (30 minutes per session) over four weeks. Ratings of pain intensity, disability, global perceived effect, threshold for pain pressure threshold, functional performance, the discomfort of the current, consumption of analgesics and central pain mechanisms were performed in the immediate effects and after twelve treatment sessions. Follow-up measurements were performed after 4 months. Results: A statistically significant increase in local PPT (lumbar region) (57.5 kPa (difference score) 95% CI 0.0 to 115.0 kPa) and segmental (tibialis anterior) (60.1 kPa (difference score)95%CI 14.6 to 105.6 kPa) with use of interferential current with carrier frequency of 1 kHz was observed when compared to placebo at the end of the treatment. Furthermore, the group 1 kHz was superior to placebo (1,0 (0-10) (difference score) 95% CI 0.0 to 1.9) and group 4 kHz (1.0 (0-10) (difference score) 95% CI 1.0 to 1.9) with respect to the temporal summation after 12 treatment sessions. There was an improvement in all other outcomes in the 3 groups, except in the PPT in the placebo group, with no statistically significant difference between groups. Active groups showed a significant reduction of the consumption of analgesics compared to the placebo group. Pain intensity in the interaction group versus time differed between groups only in the first session 1 kHz group versus the placebo group (0.9 (0-10) (difference score) 95% CI 1 to 1.6) and at the twelfth session 1 groups (-0.8 (0-10) (difference score) 95% CI-1.7 to 0.0) and 4 kHz (0.9 (0-10) (difference score) 95% CI 0.1 to 1.8) versus placebo. Conclusion(s): The carrier frequency of 1 kHz exhibited reduced hyperalgesia of local deep tissue and improves the local and segmentar central sensitization in patients with chronic nonspecific low back pain after 12 treatment sessions. The carrier frequencies of 1 kHz and 4 kHz promoted lower consumption of analgesics in relation to placebo group. Implications: The use of IFC with frequency of 1 kHz can be an adjunct in the treatment of chronic low back pain, both in evaluating aspects of low back pain as the central sensitization, which could provide greater facility in treating these patients.
Corrêa, J., Costa, L., Oliveira, N., Lima, W., Sluka, K., & Liebano, R. (2015). Interferential current on central pain mechanisms in patients with chronic nonspecific low back pain: a randomized placebo-controlled trial. Physiotherapy, 101, e270. https://doi.org/10.1016/j.physio.2015.03.457