The purpose of this research is to design a high-performance, customized, and rapidly- manufacturable passive prosthetic foot for use in the United States. We are currently testing an early stage prototype and would like user input before pursuing additional clinical testing. Participants will be asked about their current prosthesis type and use, amputation side and cause, and activity level. We will take measurements of height, weight, and length of the participant's residual limb. The participant will be asked to walk in several prosthetic foot conditions in multiple walking activities, and the visit should last approximately four hours.

For each prosthetic foot, a trained prosthetist will fit the foot (either a prototype foot or a commercially available K3/K4 foot) to the prosthesis. The patient will then walk around the room until they feel comfortable. They may initially walk using a gait belt or between parallel bars based on comfort level and an evaluation by the prosthetist. Once they feel comfortable walking on level ground at a normal speed and the prosthetist feels that they will be safe performing more challenging walking activities, the participant will perform different walking activities (such as walking on flat ground at different speeds, walking up/down ramps, and walking up/down stairs). They will then be asked to tell the investigator what they like and dislike about the prosthetic foot.

The purpose of this research is to design a high-performance, customized, and rapidly- manufacturable passive prosthetic foot for use in the United States. We are currently testing an early stage prototype and would like your input before pursuing additional clinical testing. The Global Engineering and Research (GEAR) Laboratory at the Massachusetts Institute of Technology (MIT) has developed a novel design framework for creating high-performance, passive prosthetic feet. By incorporating commercial aesthetic and functional requirements, we hypothesize that we can use this design methodology to create high-performance prosthetic feet that can be customized and provided at scale in the United States.

Participants will be asked about their current prosthesis type and use, amputation side and cause, and activity level. We will take measurements of height, weight, and length of the participant's residual limb. The participant will be asked to walk in several prosthetic foot conditions in multiple walking activities, and the visit should last approximately four hours.

For each prosthetic foot, a trained prosthetist will fit the foot (either a prototype foot or a commercially available K3/K4 foot) to the prosthesis. The patient will then walk around the room until they feel comfortable. They may initially walk using a gait belt or between parallel bars based on comfort level and an evaluation by the prosthetist. Once they feel comfortable walking on level ground at a normal speed and the prosthetist feels that they will be safe performing more challenging walking activities, the participant will perform different walking activities (such as walking on flat ground at different speeds, walking up/down ramps, and walking up/down stairs). They will then be asked to tell the investigator what you like and dislike about the prosthetic foot.

Participants may also be asked to walk while wearing inertial measurement units (IMU's), which are wearable devices similar in size to a pedometer or wrist watch. These devices will record the acceleration of the limbs, which will allow us to understand how people walk in the different prosthetic feet. We will attach the IMU's using their elastic bands, and we will attach necessary wires with hypoallergenic tape. Wearing the IMU's, the participant will walk back and forth in the room while the sensors record information about how you are walking. They may rest at any time.

Inclusion Criteria:

• Unilateral transtibial amputation
• Aged between 18-65 years
• Body mass index between 18.5-29.9 (healthy weight)
• Daily use of their clinically-prescribed prosthesis for ambulation without an assistive device
• Classified as at least a Medicare Functional Classification Level K3 (defined as a patient who is a typical unlimited community ambulator)
• Experience walking with a prosthesis for at least one year
• Residuum and amputated side in good condition (e.g., no adherent scars, lesions, ulcers, or infections)
• Normal or corrected vision
• Ability to walk continuously for 45 minutes without undue fatigue or health risks.

Exclusion Criteria:

• Subjects who weigh more than 200 pounds
• Poor fitting prosthetic socket
• Skin problems on the residual limb
• Co-morbidities or pathologies (other than the amputation) or medications that would affect the sound limb, spine, balance, or stability
• Decision by prosthetists at Hanger that walking on the prototype limb may pose higher than minimal risk for a potential subject.

Subjects with a unilateral transtibial amputation will be recruited through the Hanger Clinic. Subjects will likely be recruited who live in the Salt Lake City, Utah area, where data will be collected. Potential subjects will be screened to ensure that they satisfy the inclusion criteria. Screening will take place during the recruitment process either in person at the clinic or when the subject makes contact with the investigator. Subjects will be asked questions to ensure they meet the study inclusion criteria.

The aggregated data will be kept for several years in order to compare the performance of this prototype with the performance of future prototypes. Data collected will be subjective feedback, information about prosthetic foot alignment, and biomechanical data about walking patterns, none of which is particularly sensitive.

While participant data is not particularly sensitive, it pertains to intellectual property of new prosthetic foot designs, and we will not be making the individual participant data (IPD) available to other researchers.