Segment velocities in normal and transtibial amputees: prosthetic design implications

Area of Science:

• Biomechanics
• Prosthetics
• Gait Analysis

Background:

• Dynamic elastic response prosthetic feet offer improvements over conventional designs for transtibial amputees.
• Despite advancements, transtibial amputees exhibit higher energy expenditure and altered gait patterns compared to non-amputees.

Purpose of the Study:

• To quantify prosthetic mobility by measuring segment velocities in transtibial amputees using different prosthetic foot designs.
• To compare the gait characteristics of transtibial amputees with different prosthetic feet to normal, non-amputee controls.

Main Methods:

• Measured foot, shank, and thigh velocities in nine transtibial amputees wearing Single Axis (SA), Seattle Lite (SL), and Flex Foot (FF) prostheses.
• Compared segment velocities and timing of early stance events between prosthetic users and normal (NA) controls using Dunnett's test.

Main Results:

• Transtibial amputees walked slower with shorter stride lengths regardless of prosthetic foot type.
• Peak foot and shank velocities were reduced in early stance for SL and FF designs compared to NA controls.
• Delays in peak shank velocity, ankle plantarflexion, and knee flexion compromised stability; SA offered uncontrolled foot/shank mobility, while FF/SL restricted ankle mobility.

Conclusions:

• Current prosthetic feet do not fully replicate normal dynamic stability and forward progression during the early stance phase.
• Future prosthetic designs should focus on improving ankle mobility to better emulate the natural articulation between foot and shank segments.
• Enhanced prosthetic ankle dynamics are crucial for reducing energy expenditure and improving gait in transtibial amputees.