For above- and below-the-knee (AK and BK) amputees, experiencing size changes in the residual limb throughout the day is common. Most amputees wear prosthetic shrinkers at night to make fitting into their prosthetic sockets a bit easier in the morning, but as the day progresses, many need to add prosthetic socks to make up for the volume loss.
With many of the recent developments in technology, there must be a way to solve this volume issue. As of this writing, a team of researchers from the Virginia Tech College of Engineering are working on a solution to this dilemma, thanks to a $400,000 research grant from the National Science Foundation in late 2019. For three years, the team will dedicate their time to the study of volume loss and eventually develop smart prosthetic sockets to improve comfort and prosthetic performance.
The team is composed of Michael Philen, an associate professor at the Kevin T. Crofton Department of Aerospace and Ocean Engineering; Michael Madigan, a professor at the Grado Department of Industrial and Systems Engineering; Carson Squibb, an aerospace engineering Ph.D. candidate; Destiny Mason, an aerospace engineering sophomore; and Trevor LeMaster, a mechanical engineering junior, who also happens to be a BK amputee. They will be collaborating with Brian Kaluf from Ability Prosthetics and Orthotics in Charlotte, North Carolina.
For LeMaster, volume or size fluctuation is an everyday occurrence. Just like any other lower-limb amputee, variations in the size of his residual limb can be due to a whole host of factors, including weight change, hydration levels, and physical activity. Unfortunately, these fluctuations or changes in size often lead to discomfort, skin irritations, socket fitting issues, all of which affect any person's quality of life.
Understanding how and why volume changes
The first stage of the research requires developing new techniques to measure the volume change and deformation of an amputee's residual limb throughout the day accurately. Changes in the fit of a prosthetic socket will also need to be measured. For this purpose, an established technique called digital image correlation and a clear diagnostic socket will be used.
Also, a high-precision laser scanning system that is capable of measuring the shape and volume of a limb before and after certain activities is currently in the works.
Developing the technology for smart sockets
Once the team gains a deeper understanding of volume changes in an amputee's residual limb, they will move on to the next phase—developing a prosthetic socket that can adapt to changes.
With Philen's work in the Aerospace Structures and Materials Laboratory, the team is considering using a technology called fluidic flexible matrix composites. The composites are used in aerospace structures, robotics, wave energy conversion systems, and morphing structures. When it is integrated into a prosthesis, this technology can accommodate volume loss as well as maintain a comfortable fit for the user.
The development of the smart prosthetic socket will be highly informed by Madigan's expertise in the dynamics of human movement, as well as LeMaster's unique perspective as a prosthetic user.
LeMaster believes that the development of a smart prosthetic socket will give amputees more control over their comfort and socket fit, especially as their residual limb loses volume towards the end of the day.What do you think of this new development? Please share your thoughts in the comments section below.