Effects of Design Variants in Lower-Limb Prostheses on Gait Synergy

Area of Science:

• Biomechanics
• Prosthetics and Orthotics
• Rehabilitation Engineering

Background:

• Lower-limb prostheses can cause pain, skin issues, and gait deviations due to pressure and shear forces on the residual limb.
• Improving prosthesis fit, alignment, socket design, and cushioning are direct methods to mitigate these problems.
• Malalignments in prostheses create excessive moments on the residual limb, complicating gait analysis.

Purpose of the Study:

• To investigate the mechanical parameter of prosthetic joints, specifically the moment of resistance/angle of deflection relationship.
• To develop a mathematical model linking residual limb stresses in transtibial amputees to prosthetic ankle joint mechanics.
• To evaluate the impact of prosthetic ankle joint design on reducing stress during critical gait phases.

Main Methods:

• Developed a mathematical model to correlate residual limb stresses with prosthetic ankle moment of resistance during key gait phases.
• Analyzed the model's predictions for stress reduction under different ankle joint characteristics.
• Conducted a gait study comparing an experimental rolling-joint prosthetic foot with a standard SACH foot.

Main Results:

• The mathematical model indicated that a prosthetic ankle moment of resistance similar to a biological ankle joint can substantially decrease residual limb stresses.
• This stress reduction is most significant during the load-bearing stance phase of gait.
• Gait analysis demonstrated that the experimental rolling-joint prosthetic foot provides a more natural gait synergy compared to the SACH foot.

Conclusions:

• Optimizing prosthetic ankle joint mechanics, specifically the moment of resistance, is crucial for reducing residual limb stress in transtibial amputees.
• Prosthetic designs that mimic biological ankle joint behavior can lead to improved patient comfort and functional outcomes.
• The rolling-joint prosthetic foot shows promise in simulating normal gait patterns more effectively than traditional designs.