In a randomized clinical trial, Werners et al.18 applied IFC to cases of chronic low back pain and compared its effect with the effect of massage, among 148 low back pain patients. Both groups underwent six ten-minute sessions, but the selection criterion of how long the patients needed to have had their complaint was not described. There were no significant differences between the groups in relation to the outcomes evaluated. IFC gave rise to a mean pain reduction of 10% immediately after the treatment and 16% after three months. Their findings were not in agreement with those of the present study, in which the mean reduction in VAS was 44.8 mm, thus emphasizing that 54% of the patients were free from pain after IFC treatment.
In a recent randomized study, Solano et al.37 compared 30 minutes of TENS with 30 minutes of IFC among 30 patients with acute low back pain. The TENS equipment was calibrated at a frequency of 100 Hz, with a pulse width of 150 ms, pulses of 2 Hz and four electrodes. The IFC was adjusted to a frequency modulation range of 5 Hz and spectrum of 10 Hz, with vectors. The pain reduction (mean difference) among the patients treated with IFC was 2.18 cm (31.5%) and it was 1.24 cm with TENS (18.4%). Despite the statistically meaningful results obtained, no meaningful differences were found between the groups. Both the results obtained by Solano et al.37 and the results from the current study emphasize that there are no differences between TENS and IFC use for low back pain patients. However, the equipment adjustments used by Solano differed from those of the present study, thus showing that the frequency values for the comparable results from TENS and interferential current were not standardized in Solano's study.
These findings show that the choice of which electric current method to use now depends on the costs of equipment acquisition and maintenance. These factors should be investigated in future studies.
Although it was decided not to implement therapeutic exercises in association with the protocol for the present study, it was found that the electrotherapy protocols even produced significant benefits relating to the patients' functional capability. However, it must be emphasized that ongoing treatment is needed in clinical practice, with exercises, which may make the pain intensity more comfortable.
We therefore suggest that new studies should be carried out with the aim of analyzing what type of equipment is most appropriate with regard to long-term pain relief, taking into account the long-term maintenance costs and the investigation parameters of frequency regulation and pulse width.
CONCLUSIONS
The results from this study showed that TENS and IFC had significant effects in relation to pain intensity reduction, disability improvement and reduction of medication consumption, immediately after each electrotherapy session and after ten sessions, in comparison with the controls. However, no significant differences in these resources in relation to treating patients with nonspecific chronic low back pain were observed.