Effects of prosthesis alignment on pressure distribution at the stump/socket interface in transtibial amputees during unsupported stance and gait

Objective: To assess the effects of antero-posterior realignment of the prosthesis on pressure distribution at the stump/socket interface in unilateral transtibial amputees during unsupported stance and gait. Design: Cross-sectional group study. Setting: Outpatient rehabilitation clinic. Subjects: Seventeen unilateral transtibial amputees. Intervention: Antero-posterior prosthesis realignment using 0.5 cm heel or forefoot wedging. Measures: Pressure distribution changes at several sites at the stump/socket interface, expressed as peak pressure, peak pressure time, sustained submaximal load (MP80+) and time period of MP80+ (TP80+). Results: During stance, heel wedging led to a 30.4% decrease in mean pressure near the patella tendon and a 40.0% increase near the distal tibia site, whereas forefoot wedging led to a 30.0% decrease in pressure in the tibial end region. Antero-posterior ankle realignment did not lead to significant changes near the fibular head. During gait only heel wedging led to a 11.5% increase in peak pressure in the tibia end region. Mean peak pressure time increased 22.7% using heel wedging and decreased 8.8% using forefoot wedging. MP80+ increased 23.8% in the tibia end region during heel wedging and 17.0% in the subpatellar region during forefoot wedging. Conclusions: Antero-posterior realignment of the ankle joint led to an inverse loading and unloading of the subpatellar region versus tibial end region. However, results indicate that stump/socket interface pressure during stance seems not to be highly predictive as to pressure behaviour during gait. Ankle joint realignment led to significant differences in temporal sequences of tissue (un-)loading in the subpatellar area during gait.