Measurement of Socket Discomfort -- Part I: Pressure Sensation

Document Type



The purpose of the study was to determine the feasibility of quantifying pressure-related socket discomfort by using psychophysical methods. The first experiment involved the application of known uniform pressure to the residual limbs of three transtibial amputees. Category ratio scales were used to measure sensations of pressure, pain, and perceived discomfort. The second experiment involved altering the geometry at the fibula head and distal tibia of the subjects’ fitted PTB sockets with wafers of varying thickness and use of the same three scales to measure response to the variations in local point-specific pressures. Two of the subjects had more than 32 years of experience with PTB sockets, whereas the third subject had just been fitted with a temporary prosthesis. Results indicated that response functions for global uniform pressure varied among the subjects but were similar for the modifications at specific locations. Both experienced amputees reported constant pressure sensations between 10 and 40 mm Hg of applied uniform global pressure, whereas the inexperienced subject reported a linear increase in pressure sensation over the same range. Pressure and discomfort sensations appeared to be isolated subjectively and assigned different magnitudes among subjects, creating unique response functions for each subject. Possible explanations for unique uniform global pressure response functions could involve years of experience using a PTB socket, residual limb tissue thickness, and morphology or the way in which the amputation surgery was performed. For pressure variations at the fibula head and distal tibia, pressure sensation and perceived discomfort were highly correlated and appeared not to be distinct sensations. Response functions were similar among subjects. Psychophysical measurement could be adapted for use in a clinical setting during the fitting process and offer researchers additional tools for evaluating alternative socket designs and materials. The methods permit the patient to communicate discomfort sensations more precisely and provide the prosthetist with additional insight into the patient’s perception of quality of socket fit.


Biomedical Devices and Instrumentation | Civil and Environmental Engineering | Civil Engineering | Engineering | Orthotics and Prosthetics


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