Simultaneous changes of leg circumference and interface pressure under different compression bandages

Objectives. To assess the validity of measuring changes of sub bandage pressure and leg circumference in different body positions for an in vivo characterization of the elastic properties of bandage systems. Design. Experimental study. Materials and methods. Different compression bandages were applied on the leg. The variations of interface pressure and leg circumference above the inner ankle (that depends on the elastic property of the bandage) were measured simultaneously by a pressure transducer and by strain-gauge plethysmography in 50 patients. Stiffness is defined as the increase of pressure per increase of circumference. Results. The most consistent parameter to differentiate elastic from inelastic bandages was the pressure-difference between the standing and the lying position corrected for the actual increase of leg circumference (modified static stiffness index, mSSI; sensitivity and specificity 100%). Neglecting the individual changes of the circumference and considering the pressure difference alone allows a differentiation which is slightly less accurate (sensitivity 100%, specificity 88%) but much simpler to use. Conclusions. The static stiffness index is a useful tool to differentiate elastic from inelastic bandage material even without correction for the individual increase of leg circumference.