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WE ARE LEG UP TRANSTIBIAL PROSTHETICS
(Left to Right): Nick Riccardelli, Darshan Senthil, Saja Jarakji, Kendra Washington, Qing Zou
DESIGNED FOR COMFORT
Amputation can be particularly painful to endure. The inflamation caused by this often results in large swelling (called a “traumatic edema”) in the residual limb. As the time goes, with the use of prosthetic, the residual limb will shrink. This change in size happens regularly in recent transtibial amputees.
Our device is designed to help recent amputees experiencing traumatic oedema to gain more comfort and to create a better fit for their residual limb.
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FEWER REFITTINGS, FEWER PROBLEMS
Our primary users are recent transtibial amputees. Conversations with primary and secondary users indicated that the two components lacking in today’s prosthetics are adjustability and comfort.
Our primary users are in constant need of refittings (due to their constant change in limb size), which puts a large strain on themselves and their prosthetists. In the meantime, they experience great discomfort in their existing prosthetics.
Our device would limit the number of refittings. By doing so, we would provide greater comfort to our users, save prosthetists time and money, and provide agency to a niche group of individuals.
GOALS
Decrease incidence of device rejection by new amputees (% of patients who choose not to use their devices due to dissatisfaction/discomfort).
Decrease frequency of socket refitting following amputation (Mean number refittings during first year).
CONSTRAINTS
Accomodate Varied Limb Geometry.
Adjustable by Patient without use of Extra Tools.
Last at least 1 year (due to reimbursement guidelines).
Not apply excessive pressure to patient limb.
Fit within reimbursement guidelines for medicare/medicaid.
Withstand patient weight up to 300 lbs during use.
CONCEPT GENERATION & SELECTION
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Ever since we began considering the idea of an adjustable socket, inflatables have been key. Our initial tests assumed an inflatable attached to the inside of the prosthetic socket, but then as time went on we decided to follow the model of an inflatable “sock”, which we first made out of neoprene, and then latex.
PROTOTYPING PROCESS
NEOPRENE + PLASTIC FILM SHEET PROTOTYPE
This prototype consisted of a double layered neoprene socks fashioned from sleeves of a wetsuit with a valve placed on the outer layer. The two rims of the socks were sealed with hot glue and was the only way the socks were bound together.
Unfortunately the plastic sheet hot glued to the material made it very rigid around the rim of the inflatable socket. While it enabled us to make outside layer of neoprene airtight, it wouldn’t have allowed for an easy fit over the residual limb. Furthermore, the substitute residual limb did not make an airtight barrier. The inflation failed.
BALLOON PROTOTYPE
This prototype of was constructed with a single neoprene liner and two layers of black latex balloons. Valve attached to outer layer.
While testing, we learned that balloons experience plastic deformation which informed our decision to select a material with a higher yield stress. The inflation succeeded. The airtight barrier was achieved while the elasticity was maintained.
SILICONE. STANDS STRONG UNDER PRESSURE.
A large part of our device design process was choosing the right material, that would both be airtight, and able to withstand pressure due to inflation. Silicone is not only airtight, but boasts a max yield stress of 0.7 MPa, which is 101 times greater than the max stress applied due to inflation (1 psi; rougly 0.0069 MPa).
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HELD TOGETHER WITH LOVE. AND A PIN LOCK.
While the silicone portion of our device is not strong enough to suspend the residual limb, our device does include a pin fitting, which will attach to the bottom of the socket, and keep the limb stable during use.
FINAL DESIGN DETAILS
 Assembly Render.JPG |  Top View Render.JPG |  Valve Render.JPG |
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 Locking Pin Render.JPG | Exploded View.JPG |