A Transtibial Prosthetic Socket with Integrated Pneumatic Flexible Matrix Composite Actuators to Accommodate for Volume Change: Proof of Concept

Background: Accommodating for residual limb volume change among lower limb prosthesis users remains a persistent challenge. Pressurizing a pneumatic flexible matrix composite actuator (P-FMC) increases the thickness of the P-FMC. Thus, when a P-FMC is integrated into the interior wall of a prosthetic socket, increasing the P-FMC pressure effectively decreases the volume of the socket and enables accommodation for limb volume change. Importantly, the P-FMCs maintain high stiffness when pressurized, thus retaining stiff interface with the limb. Objective: The aim of this study was to evaluate socket comfort during the use of a transtibial socket with integrated novel P-FMCs. Methods: A single male participant had a custom P-FMC socket fabricated with three integrated P-FMCs for localized volume accommodation. The participant used the P-FMC socket while completing three cycles of a physical activity regimen involving 5 minutes of walking, 5 minutes of sitting, and 10 minutes of standing. During each cycle, a different P-FMC pressure control scheme was used. Cycle 1 involved maintaining the P-FMC pressure at a fixed 20 psi throughout all three activities and served as a baseline. Cycle 2 involved adjusting the P-FMC pressure according to the activity. Cycle 3 involved adjusting the P-FMC pressure according to the participant’s preference. Results: Socket comfort scores improved in Cycles 2 and 3 compared to Cycle 1, suggesting the P-FMC socket’s ability to modulate P-FMC pressure improved socket comfort. Conclusions: These results support further investigation of P-FMCs to accommodate for residual limb volume change. Clinical Relevance: A novel pneumatic composite actuator integrated into the interior wall of a prosthetic socket has the potential to help maintain socket fit and user function despite limb volume change. Key attributes of these actuators are that they maintain a high stiffness when actuated and are amenable to automatic control in future applications.