A Prosthetic Foot Test-Drive Strategy for Improving Stability in Veterans With Leg Amputations

Objective/Hypotheses and Specific Aims: The first aim of this proposal is to determine the effects of commercial prosthetic feet of varying stiffness on stability and falls-related outcomes in Veterans with TTA. The second aim is to determine whether a PFE can be used to predict stability and balance-confidence outcomes with corresponding commercial prosthetic feet. The third and final aim is to determine whether a brief trial of commercial prosthetic feet can predict longer-term stability and balance-confidence outcomes in Veterans with TTA.

Study Design: The investigators will use a participant blinded cross-over study with repeated measurements in Veterans and Service members with TTA. Up to 50 participants will be enrolled at each of the two study sites VA Puget Sound and VA Minneapolis. Participants will complete up to 6 visits. After an initial assessment visit, participants will be assigned to the 'high' or 'low' mobility group, and then during visit 2 they will be randomized to use the PFE in three foot modes or the three corresponding actual (commercially available) feet during walking tests on difference surfaces in the laboratory (cross-slopes, inclines, even, and uneven ground). During visit 3 participants will repeat the procedures in the other condition (e.g., PFE if visit 2 included actual feet testing). At the end of visit 3 participants will be fit with one of the actual feet and wear it at home and in the community for approximately one week. At visit 4 participants will be fit with the next actual foot and repeat the 1 week use window. The same process will be followed for the final foot at visit 5, and the study foot will be returned at visit 6.

Using a prosthesis allows many who experience lower leg amputation to regain functional abilities, but walking may be more difficult, and people with limb loss suffer from a wide range of mobility limitations including balance and stability impairments. Selecting an optimal prosthetic foot is an important aspect of maximizing mobility, limiting falls, and the achievement of functional goals for people with lower leg amputation (LLA), however there is limited evidence to guide this process. The current prosthetic prescription process relies on clinician experience and typically does not allow people with a leg amputation to easily try out different prosthetic feet. The investigators have developed a customizable robotic prosthetic foot that can mimic the mechanical properties of commercially available prosthetic feet in the coronal and sagittal planes without physically changing feet. This multiaxial 'prosthetic foot emulator' (PFE) can be attached to the prescribed prosthetic socket and worn like a regular prosthetic foot within the laboratory or clinic, providing people with LLA the opportunity to quickly 'test-drive' many prosthetic foot designs within a single test session. Trial and error with actual commercial prosthetic feet can be inefficient given the time and expense required for the purchasing and fitting of prosthetic feet. The PFE could provide a means to explore a range of feet over uneven, incline, and cross sloped surfaces in a very short period of time. This study aims to optimize stability and balance-related outcomes, to minimize falls, and to optimize vocational and avocational participation and functional quality for life for Veterans with LLA. This study will determine the effects of coronal and sagittal plane commercially-available prosthetic foot stiffness on stability and falls related outcomes and will evaluate the use of a test-drive strategy using a PFE to predict stability and balance-confidence outcomes with corresponding commercial prosthetic feet. Results from this study may contribute to increased understanding of how a patient-centered strategy for optimizing prosthetic prescription can improve patient satisfaction, functional outcomes, and balance confidence for Veterans and others with LLA.

Eligibility Criteria:
Inclusion Criteria:

* has a unilateral (one leg) transtibial (below-knee) amputation
* has used a prosthetic limb for walking for at least six months
* has a comfortably fitting prosthetic socket
* has a removable prosthetic foot attachment (i.e., is not rigidly attached to the back of the socket) so it can be used with study prosthetic feet
* be able to walk with a prosthetic limb sufficiently to participate in the experiment walking trials

Exclusion Criteria:

* contralateral limb or upper limb amputation that would interfere with completion of study activities
* are unable to use more than one of the test feet for any reason (e.g., excessively long residual limb that is not compatible with wearing study prosthetic feet)
* unable to walk under the minimal necessary study walking conditions in order to complete the study procedures without undo stress
* current surgical, neurological, rheumatologic, or lower limb musculoskeletal problem that significantly impairs ambulation (e.g., current ulcer, terminal illness)
* weight greater than 263lbs.
* inadequate cognitive or language function to consent to participate
* currently incarcerated
* impaired decision-making ability or the use of a legally authorized representative