Development of a Sensor to Measure Stump/Socket Interfacial Shear Stresses in a Lower-Extremity Amputee

The aim of this study was to develop and validate a sensor to measure interfacial shear forces on the residual limb in the socket of lower-extremity amputees. The sensor consisted of three layers: upper and lower layers made from aluminum, and a middle layer made from polyvinyl chloride. One strain gauge was placed in the middle layer with an elastomer to overcome the nonlinear response properties. In a clinical application, a male transtibial amputee (42 years old, 82 kg, 182 cm) was asked to walk on level ground and on a 5° slope. The interfacial shear force on the stump/socket on the medial and lateral distal residual limb was measured. The shear sensor (28 mm × 16 mm × 3.5 mm), which was validated using weights, showed high linearity and sensitivity (measurement range: –10 to 10 N). A shear force was exerted on the residual limb throughout a gait. Additionally, the vertical shear forces were found to depend on the ground while the horizontal shear forces depended on the prosthetic socket site. In conclusion, a shear sensor of comparable volume may be useful for measuring the interfacial shear force on the stump/socket in lower-extremity amputees.