Evaluation of a Modified Running-specific Prosthetic Foot

Amputation of a limb is a life-altering event with profound physical, psychological, and
social implications. To address their functional, vocational, and recreational needs, people
with lower limb amputation (LLA) are often provided with a prosthesis or artificial leg.
While use of a prosthesis can allow an individual to achieve a basic level of functional
mobility, absence of an anatomical foot and ankle still impairs their physical performance.
As a result, people with LLA regularly exhibit decreased walking speeds, diminished
endurance, and restricted ability to participate in desired life situations.

Over the past three decades, increasingly sophisticated prosthetic foot designs have been
developed by the prosthetics industry to replace amputated structures in the leg.
Contemporary, energy storing feet (ESF) employ advanced materials and unique geometric
designs to improve walking performance and endurance of their users. Although prosthetic
limbs with ESF allow people with LLA the potential to return to an active lifestyle, even the
most advanced ESF do not significantly reduce the increased energy demands required for
walking when compared to conventional prosthetic feet.

Commercially-available running-specific feet (RSF) like the Össur Cheetah (Össur, Reykjavik,
Iceland) allow people with LLA to participate in athletic activities and sporting events. RSF
provide significantly enhanced performance, compared to traditional ESF, by extending the
length and increasing the stiffness of the prosthetic keel (forefoot). RSF also do not
include a heel, as they are used only for running activities. Although transtibial runners
with RSF exhibit endurance levels similar to non-amputees, the RSF design does not allow the
biomechanical movements or provide the stability needed to use the foot for walking (over
level or uneven terrain).

A novel modified running-specific foot (mRSF) has been developed to integrate the performance
of a RSF with the utility of an ESF. The mRSF combines the running keel (forefoot) of a RSF
with the walking heel of a ESF. The mRSF can then be used for walking, running, and other
routine daily activities. Preliminary feedback on the mRSF suggests that users experience
improved overall function and high satisfaction with the device. However, empirical evidence
is needed to support prescription of this prosthetic foot at other clinical facilities.

The goal of this study is therefore to evaluate endurance, walking performance, mobility, and
perceived exertion of transtibial prosthesis users (i.e., study participants) walking with a
conventional ESF and the mRSF. Results will be compared to determine if the mRSF provides
superior performance to the ESF, which is commonly prescribed to most active individuals with
LLA.

Inclusion Criteria:

- unilateral or bilateral, transtibial (below-knee) amputation from non-dysvascular
causes

- Medicare functional classification level (K-level) 3 or higher (unlimited community
ambulatory)

- prosthetic user for > 1 year

- scheduled to receive a mRSF prosthesis

- able and willing to participate in the study protocol (e.g., treadmill walking,
overground walking, respond to survey questions, able to read and write English)

Exclusion Criteria:

- contralateral lower or upper limb involvement

- any health condition that would limit participation in the study procedures (e.g.,
skin breakdown, heart disease)