Abstract

Abstract A prosthetic socket is the critical interface between a person and their prosthetic device. Pressure, shear, and friction experienced by the residual limb from wearing a socket can damage soft tissue. While Compression Release Stabilized (CRS) style sockets are beneficial for enhancing prosthesis stability, range of motion, and control, the abrupt differences in compression throughout the socket present risks for tissue damage to the residual limb. A socket design that enables clinicians to control a progressive decrease in firmness in the transition areas between compression and release could mitigate such undesirable effects. Density-graded lattice structures designed and produced with 3D printing technologies may allow this capability by providing gradual transitions in magnitudes of compression throughout modified CRS sockets. The primary aims of this study are to determine which features of lattice unit cells can produce lattice structures that can serve as compression and release areas within CRS style sockets, provide spatially variable compressibility to minimize the risk for tissue damage to the residuum, and print accurately without support structures on benchtop fused filament fabrication (FFF) 3D printers. These aims guide the following research questions which will be explored throughout this dissertation. RQ1: Can a single type of 3D printable lattice structure meet the requirements to serve as both compression and release areas of a modified transhumeral CRS style socket when its density is altered? RQ2: Is it possible to create a lattice model that linearly increases the compressibility magnitudes of a single lattice structure from the compression area requirements to release area requirements over a prescribed distance? RQ3: Which features of lattice unit cells are most associated with lattice structure printability on desktop fused filament fabrication (FFF) 3D printers? Two initial lattice structures comprised of selected unit cell types were compression tested to determine if they could produce the desired compressibility properties suitable for compression and release areas in a modified CRS socket. Because the research was primarily, though not exclusively, intended for prostheses production and use in the low-resource area of Haiti, factors that impact manufacturing time and materials cost were also explored. While these factors may be of interest in any area in the world, in Haiti, margins of feasibility for production are narrow due to such complexities as limited economic, healthcare, and electrical infrastructure. Compression testing revealed unit cells that provided adequate compression levels, but not suitable release levels. Both materials cost and print time were lower when using the Offset Diamond lattice type. It was demonstrated that density-graded lattice structures could be printed with compressibility values that could be varied over a definable distance. A procedure for assessing which characteristics affect lattice print accuracy and the need for support structures, here termed “lattice printability,” was carried out on 29 additional lattice types. Printability testing indicated that lattice unit cell geometry and beam/wall thickness had significant impacts on lattice printability scores. Interactions between the cell type and beam thickness and the cell type and cell size were also noted. Procedures to characterize the compressibility and printability of 3D printed lattice structures were developed and executed. Evaluation of the feasibility of producing density-graded lattice structures suitable for incorporation in a novel CRS socket design concept was conducted. These procedures form the basis of the potential for producing customizable CRS sockets that consider the tissue properties of a residual limb.

Library of Congress Subject Headings

Prosthesis--Design and construction; Artificial joints--Design and construction; Three-dimensional printing

Publication Date

12-20-2023

Document Type

Dissertation

Student Type

Graduate

Degree Name

Mechanical and Industrial Engineering (Ph.D)

Department, Program, or Center

Mechanical Engineering

College

Kate Gleason College of Engineering

Advisor

Daniel Phillips

Advisor/Committee Member

Denis Cormier

Advisor/Committee Member

Kathleen Lamkin-Kennard

Campus

RIT – Main Campus

Plan Codes

MIE-PHD

Download

Share

COinS