[Pain intensity and power densities of therapeutic ultrasound--a serial, comparative pilot study in patients with low back pain].
BACKGROUND
A pilot study was conducted to provide an indication of the power density (PD) dependent analgesic effect of ultrasound (US) under serial application in patients with low back pain.


METHODS
Thirty patients (n=3 x 10) were randomly assigned to one of three PDs (0.3, 0.7 or 1.0 W/cm(2)). Twelve treatments were applied once a day for 2 weeks. The sonation time per treatment was 10 minutes. Patients were unaware of their grouping. Pain intensity (PI) was assessed using a visual analogue scale for each treatment. The relationship between the different PI profiles was tested by repeated measures by ANOVA.


RESULTS
The averaged duration of pain was over 10 years (chronic low back pain). Twenty-seven (n=3 x 9) patients could be analyzed (three drop-outs). In the medium (0.7 W/cm(2)) and high (1.0 W/cm(2)) PD groups the PI showed a clearly decreasing trend, while in the low (0.3 W/cm(2)) PD group, the PI remained stationary. None of the contrasts showed a locally significant effect (Bonferroni adjustment).


CONCLUSIONS
The observed effect is presumably overestimated. In the low PD group, there were more people out of work, and fewer took analgesic drugs. No conclusive judgement is possible. The concept of the PD-dependent effect of US must be evaluated in trials with greater sample sizes.
Brockow
T
T
Institut für Physiotherapie, Friedrich-Schiller-Universität Jena.
Schreiber
U
U
Smolenski
U
U
Fröhlich
A
A