The Static Stiffness Index

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Abstract
Background The efficacy of compression therapy depends mainly on the exerted pressure and on the stiffness of the material. Objective To propose a simple method by which pressure and stiffness can be assessed in the individual patient. Material and Methods Using a pressure transducer (Kikuhime small probe, MediTrade, Soro, Denmark) the sub-bandage pressure is measured on the medial aspect of the lower leg at the transition of the gastrocnemius muscle into the Achilles' tendon. The pressure difference between active standing and lying is defined as the static stiffness index (SSI). Results The accuracy and precision of the probe are good. Unna boot bandages (Lohmann-Rauscher, Vienna, Austria) and multilayer short-stretch bandages show a significantly higher SSI than long-stretch bandages and round-knitted class II stockings. The SSI values are lower than 10 mm Hg for elastic, long-stretch material and higher than 10 mm Hg for inelastic, short-stretch material. Conclusion In future compression trials, pressure and stiffness measured in vivo should be declared.