Background

There are over 57 million people worldwide living with trauma-related limb loss, yet these amputations make up only 22% of the amputee demographic in the United States [1-2]. Since the Covid-19 pandemic, amputation rates have risen significantly due to the formation of dangerous blood clots, making the need for a prosthetic device more prevalent than ever [3]. It is currently estimated that one in every 190 Americans is an amputee [4]. Despite the growing need for prosthetic limbs worldwide, nearly one-third of lower limb prosthetic users with reject their prosthetic device due to extreme discomfort and another 20% will experience reamputation from pressure ulcer due to a poorly fitted socket due to volume loss [5].

The importance of socket fit is not only imperative to keep the prosthetic connected to the residual limb, but if the fit is flawed, then it can lead to complications such as redness, pressure ulcers, reduced regional blood flow, sores, tissue death, gangrene, and even complications as extreme as reamputation [6-7]. Understanding the residual limb-to-prosthetic socket interface is essential for creating a near-perfect fit that reduces tissue damage and incidences such as the ones listed above [7]. 

In the 80 days post-amputation, residual limb volume decreases by over 9% and does not begin to level out until nearly 160 days after amputation [8]. Because of this, amputees generally do not fit with a prosthetic limb until their residual limb volume remains steady, as the rigid socket is unable to account for these changes. This is ultimately detrimental to the amputee as studies have shown that early prosthetic fitting improves gait, increases independence, decreases maturation time, increases physical activity, and increases adaptation of definitive sockets [8]. Once fit for a definitive socket, the residual limb will continue to change in volume depending on the time of day, activity, temperature, weight loss, weight gain, salt intake, and numerous other biological and environmental factors. 

An amputee must constantly adjust the volume of their socket, by adding or removing prosthetic socks, to maintain proper fit and decrease complications. However, many amputees don't know when or how to do this or find it inconvenient to do so [6]. Ultimately, sockets today are unable to adjust for the daily volume fluctuations of the residual limb and it is vital to account for volume changes for the health of the limb and the well-being of the patient.