Interface pressures and shear stresses at thirteen socket sites on two persons with transtibial amputation

Abstract—Residual limb/prosthetic socket interface pressures and shear stresses were measured at 13 sites on two subjects with unilateral transtibial amputation (TTA) using total-contact patellar-tendon-bearing prostheses. Maximal interface stresses during stance phase for each of 13 transducer sites were deter-mined, then means for all steps calculated. Maximal pressure and resultant shear stress during stance phase were shown at anterior distal or mid-limb sites and the maxima occurred dur-ing the first 50 % of stance phase. Anterior medial and lateral proximal sites showed their greatest pressure during the second 50%. At lateral mid-limb and popliteal fossa sites, resultant shear stress directions suggest that soft tissue was displaced toward the socket brim during weight-bearing. Results also suggest that skin across the distal tibial crest was in tension at the times of the first and second peaks in the shank axial force-time curve in all sessions. Significant differences (p<0.05) in maximal stresses between sessions conducted>3 weeks apart were apparent for both subjects. Key words: interface mechanics, interface pressures, inter-face stress, lower-limb prosthetics, shear stress, transtibial amputation