The LIMBER UniLeg, a 3D printed single-piece transtibial prosthetic limb, is sufficiently equivalent to traditional passive prosthetic limbs (no motors or sensors), while reducing the cost and time of manufacturing and enabling global reach through the use of digital technologies to solve the worldwide prosthetic accessibility crisis. This is a single-site, Phase I, Clinical Research Study to test the effectiveness and safety of the LIMBER UniLeg. One study group of 30 participants involved for two months using a non-inferiority design in which the participant will be assessed using their normal device (1 month) and the study device (1 month).

Globally, 35-40 million people need prosthetics or other assistive devices, and this number is expected to double by 2050 due to factors including an aging population and the rise in diabetes. However, only 5-15% of people in need have access to prosthetics or other assistive devices, in both underserved and developed countries. The result is that millions of people are denied basic quality of life because they can't walk, take care of themselves, or participate in society. The lack of availability stems from several factors including poor access to clinics and high cost. Prosthetic devices are hand-sculpted and assembled by prosthetists via complex and time-consuming processes. High-cost 3rd party components are used to connect and align the hand-crafted components, leading to an expensive end-product.

Currently, several companies are successfully delivering 3D printed prosthetic sockets, but no one can deliver a fully 3D printed, single piece 'unibody' prosthesis. 3D printed sockets have been shown to provide increased comfort and fit and streamline the manufacturing process, but using traditional pylon, ankle/foot, and connector components lead to many of the same issues as traditional devices. Only 3D printing the socket may improve the outcome for people who could have gotten a traditional device but leaves behind the people in need who don't have access in the first place.

The custom-fit requirements make it difficult to mass-produce affordable devices and a lack of access to proper health care and medical professionals prevents adjustments needed to maintain safe, comfortable, and reliable prosthetic devices. This is critically important during the early recovery period when residual limbs change in shape due to atrophy and scar tissue formation, as well as having nerve endings that may be extra- sensitive. For children who grow quickly and need new devices every few months or years, swift access is both physically and psychologically important. Small imperfections at the prosthesis-limb interface can cause severe discomfort and may be the difference between an amputee wearing their prosthesis or choosing to forgo mobility. To obtain a well-fitted socket, prosthetists take measurements of the residual limb with a fitted liner and then mark anatomical areas on the limb. After assessing the limb, the prosthetist will use plaster bandages to create a cast around the limb. The anatomical marks will transfer to the interior of the mold, such that the prosthetist can attempt to design the socket to consider regions of bone or soft tissue. The prosthetist can manipulate the plaster bandages while they are hardening to adjust its shape. This shaping requires years of experience and will only result in a comfortable, functional socket if the prosthetist is highly skilled. Due to the expensive and time-consuming nature of this traditional process, new solutions are urgently needed.

Clinical Trial Justification:

During this study the study team expects to gather both quantitative and qualitative data that will be used to produce a performance report on the functionality of the LIMBER UniLeg. The goal of this trial is to provide evidence of non-inferiority of the intervention compared to the functional performance of similarly featured passive prosthetic devices, e.g. the patient's existing device.

This clinical trial will quantify the functionality, clinical efficacy, and quality of care of the LIMBER UniLeg and compare it to traditional passive prosthetic devices, referred to as existing prosthetic devices (EPD). This will provide evidence that LIMBER's novel 3D printing, scanning, and digital design workflow produces devices that are not inferior to traditionally manufactured prosthetic limbs.

Inclusion Criteria:

1. Provision of signed and dated informed consent form.
2. Stated willingness to comply with all study procedures and availability for the duration of the study.
3. Persons, aged 18 to 75
4. In good general health as determined by clinical site monitor
5. Weight < 125kg
6. Are not diabetic (self reported)
7. Be a unilateral transtibial amputee of more than 1 year since amputation
8. Have an existing prosthetic device(s) that does not use sensors or motors (is passive)
9. Live in the Southern California region (within 50 miles of UCSD)
10. Has sufficient sensation in residual limb as tested by the clinical site monitor
11. Agreement to adhere to Lifestyle Considerations throughout study duration 11a. Use the testing device (EPD or UniLeg) only during the testing periods. 11b. Walk at least 14,000 steps per week (average of 1 mile per day). 11c. Maintain a similar diet and activity level throughout study duration (no abrupt changes of weight, activity, etc.)

Exclusion Criteria:

1. Not currently using a prosthetic device
2. Prosthetic device with active motors, sensors, etc.
3. Pregnancy (due to fall risk)
4. Diabetic (due to poor limb sensation), self reported
5. No under 18 (due to inability to consent)
6. No over 75 (due to fall risk)
7. Poor proprioception or sensation at the residual limb

Demographic and baseline outcomes will be presented using summary statistics. No individual data will be provided.