Does a pelvic belt influence sacroiliac joint laxity?

Objective. To evaluate the influence of different positions and tensions of a pelvic belt on sacroiliac joint laxity in healthy young women. Background. Clinical experience has shown that positive effects can be obtained with different positions and tensions of a pelvic belt. A functional approach to the treatment of the unstable pelvic girdle requires an understanding of the effect of a pelvic belt on a normal pelvic girdle. Methods. Sacroiliac joint laxity was assessed with Doppler imaging of vibrations. The influence of two different positions (low: at the level of the symphysis and high: just below the anterior superior iliac spines) and tensions (50 and 100 N) of a pelvic belt was measured in ten healthy subjects, in the prone position. Data were analysed using repeated measures analysis of variance. Results. Tension does not have a significant influence on the amount by which sacroiliac joint laxity with belt differs from sacroiliac joint laxity without belt. A significant effect was found for the position of the pelvic belt. Mean sacroiliac joint laxity value was 2.2 (SD, 0.2) threshold units nearer to the without-belt values when the belt was applied in low position as compared to the case with the belt in high position. Conclusions. A pelvic belt is most effective in a high position, while a tension of 100 N does not reduce laxity more than 50 N.