No Longer Smooth: Introducing Striations into Prosthetic Socket Construction to Improve Suspension, Rotation, Fit and Comfort
Abstract
Project Objectives and Rationale: The prosthetic socket is responsible for the comfortable and efficient transfer of weight-bearing forces between the person with amputation and the prosthetic device. Historically prosthetic sockets have had to be smooth in order to be comfortable, and this was especially true when persons with amputation wore rigid sockets directly in contact with the residual limb. However, the introduction of gel liners worn between the residual limb and rigid socket eliminate the need for a totally smooth prosthetic socket. It has been proposed that textured sockets may reduce the tendency for the socket to slip off or rotate on the residual limb by increasing friction between the socket and liner. Texture increases friction by increasing the surface area of the socket. Therefore, the objective of this project is to investigate the effect of different types of texturing on suspension (i.e., the forces that stop the socket from slipping off the residual limb), rotation (i.e., the forces that stop the socket from spinning around with respect to the residual limb), fit (i.e., the degree to which the socket conforms to the shape of the residual limb), and comfort (i.e., as perceived by the person with amputation). We expect that horizontal texturing in the form of striations will improve suspension while vertical striations will help transverse plane rotation. It is possible that with a combination of horizontal and vertical striations both suspension and rotation may be improved. However, striations may vary not only in direction but also in depth and pattern, and it remains unknown what combination of striations might maximize suspension and rotation benefits without compromising fit, comfort, and durability of the socket. Ultimate Applicability and Potential Impact of the Research: The proposed project will explore the effect of different types of texturing on suspension, rotation, fit, and comfort of prosthetic sockets. Texturing of prosthetic sockets can be achieved relatively easily and inexpensively using the SQUIRT-Shape rapid prototyping system previously developed at Northwestern University with funding from the Department of Veterans Affairs and used clinically by our collaborators at Prosthetics Design Inc. SQUIRT-Shape is a form of fused deposition modeling (FDM) where a bead of semi-molten plastic (polypropylene) is extruded onto a platform in a continuous spiral following the digitally conveyed contours of a socket. A single wall socket is created layer by layer as the plastic cools and solidifies, thermally bonding the layers together. SQUIRT-Shape results in a plastic socket with texturing in the form of horizontal striations. Additional patterns of texturing can be programmed. SQUIRT-Shape reduces individual socket fabrication costs by increasing efficiency and reducing waste as it places material only where it is needed (known as additive manufacturing) rather than carving a socket shape from a blank block. SQUIRT-Shape also uses an automated process to acquire each amputee s residual limb shape, resulting in an accurate and precise model in a short time that is also repeatable. Not all of this is possible with current state-of-the-art manual thermoforming or laminating techniques for socket fabrication. While we will explore socket texturing using SQUIRT-Shape sockets, once the concept is demonstrated to have merit, socket texturing could be achieved by any number of alternative automated fabrication methods. Proposed Benefit to Service Members, Veterans, and/or Family Members: Individuals who enter the military are typically young, with excellent premorbid health. Many wounded Soldiers wish to return to pre-injury activity levels, resulting in higher functional expectations. The residual limbs of military persons with amputation tend to be atypical in shape and short in length with damaged soft tissue due to explosive injuries and thus the benefits of sockets wi
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 31, 2017
- Source ID
- W81XWH1610485
Entities
People
- Stefania Fatone
Organizations
- Northwestern University
- United States Army