Title

Regression Estimates of Pressure on Transtibial Residual Limbs Using Load Cell Measurements of the Forces and Moments Occurring at the Base of the Socket

Document Type

Article

Abstract

Intrasocket pressures can be a source of tissue trauma or discomfort to amputees. The research goal was to determine if socket-produced pressures at the patella tendon, distal tibia, popliteal, and gastrocnemius regions on the transtibial residual limb could be modeled as a function of the forces and moments occurring at the base of the socket using stepwise linear multiple regression analysis. Sagittal plane forces and moments measured by a load cell attached to the base of the socket were used as the independent variables and force sensing resistor–measured pressure was used as the dependent variable. A convenience sample of two transtibial amputees wearing solid ankle cushioned heel feet provided data for self-selected comfortable speed walking. Regression R2 values ranging from 0.929 to 0.996 were obtained. The models suggested that the force component is a strong predictor of pressure at the distal tibia, gastrocnemius, and popliteal regions throughout stance, whereas the moment component is a strong predictor of pressure at the patella tendon region during forefoot loading. The prosthetic foot was moved anterior and posterior 5 mm to produce load cell measurements that were slightly different from those used to fit the models. The root-mean-square error of the models for the initial alignment increased by as much as 4.6 times when data from the perturbations were used in them, indicating that the values of the regression coefficients seemed to be unique to alignments and subjects. Correlations between sagittal plane resultant force and resultant moment ranged from 0.5140 to 0.7110, indicating colinearity, which could explain the increase in root-mean-square error. Despite the lack of generality in the calibrated models, the approach could provide useful information on the relationship between intrasocket pressures and the force and moment loading at the base of the socket caused by gait, socket interface design, and prosthetic foot design.

Disciplines

Civil and Environmental Engineering | Engineering | Mechanical Engineering | Medicine and Health Sciences | Orthotics and Prosthetics

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