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Over 1.6 million people in the United States were living with limb loss in 2005. Below the knee (transtibial) amputations account for 47% of limb loss amputations. Individuals with transtibial amputation are more vulnerable to the risk of falling due to asymmetric kinematics, muscle weakness and other neuro-muscular limitations. Among many other reasons, the absence of ankle plantarflexors chiefly contributes to these issues. The gastrocnemius and soleus muscles are the major ankle plantarflexors. They play an important role in supporting and propelling the body forward. While most plantarflexors are removed (e.g. the soleus) from the traumatic surgery of transtibial amputation, the gastrocnemius muscle is often spared. The distal end of the gastrocnemius is typically wrapped around the distal end of the limb to provide cushioning during walking. Despite this change in apparent function for the gastrocnemius post-amputation, the affected gastrocnemius still spans the knee joint and preserves a similar activation pattern compared to an unimpaired individuals’ gastrocnemius. This suggests the affected gastrocnemius may contribute to generating a redundant knee flexion moment. However, the extent to which the affected gastrocnemius is responsible for generating excessive knee flexion moment is unclear. Additionally, it is unclear the degree to which this destabilizes the limb, leading to increased falls during walking. While many rehabilitation exercises have been developed to reduce the risk of falling, these current rehabilitation exercises are extensive and require a lengthy period, delaying transtibial amputees’ return to their preoperative lifestyle and work. Understanding the role of the affected gastrocnemius will provide insight into the role other muscles play in stable walking and will help in the development of targeted rehabilitation exercises that are more time and cost-efficient. In addition to the development of rehabilitation exercises, identifying the role of affected gastrocnemius can help to develop new surgical methods that allow stable walking.

Not funded

Investigators

Hwan Choi, Ph.D.
Assistant Professor of Mechanical and Aerospace Engineering
[email protected]