Soft Dynamic Fluidic Cushion for Pressure Sore Management in Transtibial Prosthetics – A Proof-of-Concept Study

Objective: Due to volume fluctuations, bony prominences contacting prosthetic sockets are susceptible to skin breakdown due to constant pressure and shear stresses from lateral and vertical displacements throughout gait. A low-profile unloading cushion that can be controlled with a millisecond response to dynamically provide localized socket fit at the fibular head may offer stress relief during gait. Methods: The study presents a low-profile (<0.5 mm thick) dynamic fluidic cushion that can provide targeted cushioning during gait to mitigate high contact pressures at bony prominences while minimizing duration of pressure and shear. The proof-of-concept study comprised benchtop testing using a residual limb model. Results: The dynamic cushion effectively unloaded high pressure caused by the body weights only during the stance phase at the fibular head for up to 80 kg by mitigating and redistributing contact pressures away from the fibular head to the immediately surrounding soft tissues. Results demonstrated that the fibular head peak contact pressure could be reduced by as much as 94% (98 to 6 kPa) with a response time of 250 milliseconds in benchtop tests, fast enough to turn on during stance and off during swing. Conclusion: The proposed dynamic fluidic cushion has the potential to offer unloading during gait to prevent skin damage at pressure-sensitive spots, notably benefiting individuals with complex limb geometries. Significance: We introduce a new method with the potential to be integrated into prosthetist workflows to locally adjust socket fit (e.g., at the fibular head) using elastomer sheets and a handheld heat press.