Responsiveness of Two Methods for Measuring Foot and Ankle Volume

Abstract

Background: Measurements of volume are taken in the clinical environment to determine the extent of swelling and to evaluate the effects of treatment interventions. In the research setting, volume measurements are taken to determine experimental outcomes. Water displacement and figure-of-eight methods are highly reliable for measuring foot and ankle volumes, but the responsiveness of the two methods has not been compared. This study was designed to investigate effects of manipulating hydrostatic and blood pressures on foot and ankle volume and responsiveness of the two methods to induced changes in foot and ankle volume. Methods: Intervention effects on volume were compared using water displacement and tape (figure-of-eight) methods. Foot and ankle volume was measured in each of the 30 participants while they were supine, sitting, and sitting with a sphygmomanometer cuff inflated around the lower thigh to occlude blood flow into the leg. These variations allowed manipulation of the hydrostatic and blood pressures acting on the foot and ankle. Results: Data from the water displacement method showed that a significant increase in volume of 31 mL (p < 0.002) occurred with the cuff in place, but this was not detected using the figure-of-eight method. No significant difference (p > 0.136) between the sitting and supine positions was detected using either method. Conclusions: Limb dependency while sitting or lying had no effect on measures from either method, but volumetry had a higher responsiveness to changes induced by application of the cuff. This effect was interpreted as arterial leakage past the cuff. Clinical Relevance: The figure-of-eight tape method and the water displacement technique for measuring ankle and foot volume may not be interchangeable. Changes in volume of the ankle and foot are better measured by the water displacement technique, but for measurements of ankle volume alone, the tape method is appropriate. The responsiveness of the tape method to changes in volume is yet to be determined.