The Common Patterns of Blood Perfusion in the Fingernail Bed Subject to Fingertip Touch Force and Finger Posture

Abstract

When the human fingertip is pressed against a surface or bent, the hemodynamic state of the fingertip is altered in a way that is common to all people. Normal force, shear force, and finger extension/flexion all result in visibly distinct patterns of blood volume or perfusion beneath the fingernail. These patterns of blood perfusion can be used not only to monitor the state of the finger, but also to understand how the fingernail interacts with the bone and surrounding tissues when various forces or postures are applied. In this paper, photographic techniques are used to catalog the average patterns of fingernail coloration corresponding to various states of applied forces and postures across human subjects of a variety of size, gender, and skin color. Results indicate that there are at least seven different states of force and posture that yield distinct coloration patterns that are statistically significant and common to people in general.