Concepts of Pressure in an Ischial Containment Socket: Measurement

Abstract

The goal of this study was to develop a methodology for obtaining and mapping the pressures occurring inside a “comfortable” ischial containment socket during gait for later use in studies of the perception of pressure magnitude. F-Socket (Tekscan, Inc., South Boston, MA) was used to obtain the pressure measurements for a single subject, and pressure maps displaying the dynamics of socket pressure during gait in the muscle compartments and high pressure regions of the socket were developed by windowing regions of the sensor and taking average pressures over five steps during gait. Data for the muscle compartments were plotted as splines using polar coordinates for loading response, midstance, terminal stance, and midswing. Data for regions of higher pressure concentration were plotted as points using polar coordinates. The maps revealed patterns that were in general agreement with those hypothesized by Radcliffe (Radcliffe CW. Prosthetics. In: Rose J, Gamble JG, eds. Human Walking. Baltimore: Williams & Wilkins, 1994:168–173.) to maintain anterior-posterior stability of the knee and medial-lateral stability of the pelvis, but some differences were found. Pressures in the distal compartments are hypothesized to have been influenced by downward movement of the femur and proximal tissues during gait and the morphology of the residual limb, which had fairly mobile adipose tissues distally. Data suggest a “quasi-hydrostatic” form of loading may have occurred distally, which would occur only in a snug-fitting socket. The mappings provided valuable insight into the dynamics of the socket.