Quantitative analysis of the relation between soft tissue stiffness palpated from the body surface and tissue...

We investigated the quantitative relation between soft tissue stiffness palpated from the body surface and hemodynamics in the human forearm. We examined the relation between pressures and blood flow in both the main artery and vein measured by magnetic resonance imaging (MRI), the cross-sectional area of forearm measured by MRI and soft tissue stiffness. Six male volunteers participated. Two tourniquet pressures, 120 mmHg and 230 mmHg, were used to induce an occlusion of the proximal portion of the upper arm. Measurements were made at the mid-belly of the brachioradial muscle. The venous outflow ceased at tourniquet pressures of 120 and 230 mmHg. The arterial flow was interrupted at 230 mmHg. Larger increases of the cross-sectional area and soft tissue stiffness were found at 120 mmHg than at 230 mmHg. The increase of the cross-sectional area of muscle was larger than that of the surrounding connective tissue during occlusion. We propose that low-pressure compression occludes venous outflow without restricting arterial inflow and induces an increase of the cross-sectional area that reflects the intramuscular pressure; and changes in this pressure caused by fluid accumulation should be the major factor for change in stiffness.