Clinical investigation of the pressure and shear stress on the trans-tibial stump with a prosthesis.

A system for measuring pressures and bi-axial shear stresses at the body support interfaces has been developed. This system has been used, in five unilateral trans-tibial amputees, to investigate the stresses at multiple points on the residual limb and prosthetic socket interface during standing and walking. The subjects investigated regularly used a patellar-tendon-bearing socket. The maximum peak pressure at the measured points was 320 kPa over the popliteal area during walking. The maximum shear stress was 61 kPa over the medial tibia area. Variable wave-forms of stress during walking were observed at the different measured points. The influence of the angular alignment on the stresses was investigated on one subject. It was found that a miss-alignment of +/- 8 degrees produced a change in peak longitudinal shear stress of between 8% and 11.5%.