This paper presents the results of experiments conducted on a batch of additively manufactured customized prosthetic sockets for upper limbs, made of thermoplastics and designed automatically on the basis of a 3D-scanned limb of a 3-year-old patient. The aim of this work was to compare sockets made of two different materials—rigid PLA and elastic TPE. Two distinct socket designs with various mounting systems were prepared. To find a reliable set of parameters for cheap and stable manufacturing of usable prostheses using 3D printers, realizing the fused deposition modeling (FDM) process, sets of sockets were manufactured with various process parameters. This paper presents the methodology of the design, the plan of the experiments and the obtained results in terms of process stability, fit and assessment by patient, as well as strength of the obtained sockets and their measured surface roughness. The results are promising, as most of the obtained products fulfil the strength criteria, although not all of them meet the fitting and use comfort criteria. As a result, recommendations of materials and process parameters were determined. These parameters were included in a prototype of the automated design and production system developed by the authors, and prostheses for several other patients were manufactured.

Study on Properties of Automatically Designed 3D-Printed Customized Prosthetic Sockets

Capturing patient anatomy for designing and manufacturing personalized prostheses.

Risk analysis of personalized medical devices, such as prostheses, is challenging due to the complexity of technological and geometrical issues. The paper undertakes a process of risk analysis for upper limb prostheses for adult patients, individualized by 3D scanning and produced by additive manufacturing. The analysis was performed to systematize the process and its steps and diagnose specific problems to achieve future devices with correct fit and function, produced in as few iterations as possible. The Failure Mode and Effect Analysis of Process (PFMEA) method was used. The results identified main process risks: the problems are primarily caused in stages, where the operator’s decision or activity is to be performed, regarding socket length, offset, and suitable lining. The primary prevention activities were determined – human involvement in the decision process should be minimal, and the intelligent models should be adjustable to as many patient cases as possible. Consequently, future steps for process optimization were determined – a more extensive base of patient cases is necessary to acquire and study, to gather data for model and process improvement.

/pdf/risk-assessment-of-individualized-3d-printed-prostheses-12oclvuc.pdf

Risk Assessment of Individualized 3D Printed Prostheses Using Failure Mode and Effect Analysis

Prosthetic sockets are still routinely designed without the aid of quantitative measurement, relying instead on the experience and skill of clinicians. Sockets remain the most common cause for complaint regarding the suitability of a prosthesis, and poor pressure distribution is implicated in many forms of unacceptable care outcomes.

Monitoring pressure distribution has been effectively restricted to laboratory settings, and only limited work has examined conditions other than flat walking. In this work, a transtibial amputee completed static and dynamic tasks on flat ground, on slopes and with changes to prosthetic materials and alignment. This was achieved using a set of wireless measurement nodes and custom LabView and MATLAB code, using external strain measurements and a neural network to understand the internal pressure distribution.

Future work will focus on modifying the software to be more user-friendly for a clinical operator, and in simplifying the required hardware. Although the system in its current form facilitated the desired measurements effectively, it required engineering support to function accurately. Improving the reliability and stability of the system will be necessary before routine use is possible.

Monitoring the suitability of the fit of a lower-limb prosthetic socket using artificial neural network in commonly encountered walking conditions

The common manufacturing process of prosthetic sockets is usually a time- and labor consuming activity. This project’s purpose was to look for alternative manufacturing methods that could speed up the process and enhance the experience for the patient for example make some personal design or make the socket lighter. The main goal was to investigate which properties could be achieved by applying Electron Beam Melting as an alternative manufacturing process for prosthetic sockets by applying an earlier developed methodology. An investigation of earlier scientific works with the keywords (additive manufacturing, free form fabrication, orthopedic, prosthetic sockets and rapid manufacturing) was done as well as gathering knowledge how to operate and handle the machines necessary to carry out the project. An updated version of the methodology was developed where the design was verified using finite element analysis. With the updated version the methodology contained nine steps, which in short was as follows. First apprehend an inner socket from an orthopedic clinic with a pattern drawn up on it, the pattern is then transferred to a computer environment and manipulated to the desired shape and thickness. A compressive strength test, both virtual and experimental, was designed by a modified version of the ISO-10328 standard and the virtual design was verified before the socket was manufactured in the Electron Beam Melting machine. The manufactured socket was tested in the experimental set-up to verify the virtual one. The result was a personal designed socket of Ti6Al4V including the male pyramid for connection and a suspension system, which consisted of an inner socket and a one-way valve. It was concluded that Electron Beam Melting could be used as an alternative manufacturing process of prosthetic sockets.

Prosthetic socket in Titanium : An outer shell prosthetic socket for a lower-leg amputee manufactured in Ti6Al4V by Electron Beam Melting

—Recent trends in
the field of prosthetic technology are shifting towards all-digital approaches.
These digital technologies have the potential to augment the current models of
clinical healthcare and reach more amputees than currently possible.
Unfortunately, most of the equipment needed to design and build digitally
shaped prostheses is expensive or requires a high level of expertise. Objective:
This paper developed several methods to enable the digital fabrication of
prostheses using only low cost tools that do not require extensive specialized training.
Methods: The authors built a cell phone application in Android Studio
that enables automated collection of image data which can be rendered into
accurate 3D-models using photogrammetry on a remote server. They then developed
a new protocol to shape these residual limb models into functional prosthetic
sockets using the freely available software Autodesk Meshmixer. Results:
Finally, the authors ran a case study where they rectified a prosthetic socket for
an amputee and compared this model to a socket built by a clinician. Conclusion:
This case study showed that these new methods can successfully create accurate
and functional prosthetic sockets. Significance: By leveraging
ubiquitous low cost smartphone technology, the authors believe that amputees in
underserved areas, who currently face large barriers both in cost and physical
access to proper care, could soon be able to obtain affordable prosthetic limbs.

/pdf/smartphone-telemedicine-a-novel-workflow-for-creating-1l5qcdix8z.pdf

Smartphone Telemedicine: A Novel Workflow for Creating Prosthetic Sockets Using Semi-automated Photogrammetry

Additive manufacturing is one of the most promising emerging technologies for building prosthetic sockets. However, there is no reliable way to estimate the factor of safety and the lifetime of 3D printed prosthetic sockets. Here, we explore 360° 3D digital image correlation (DIC) and discover how this new tool can increase our understanding of prosthetic structural failures. We establish that this new technology can dramatically improve the prosthetic design cycle by identifying local strain concentrations and by highlighting limitations in current simulated models. Overall, 360° 3D DIC technology empowers prosthetic engineers to characterize the performance of new materials and create innovative designs that are both safe and affordable.

/pdf/seeing-the-big-picture-improving-the-prosthetic-design-cycle-83p6ms20j4.pdf

Joseph Martin

Papers

Smartphone Telemedicine: A Novel Workflow for Creating Prosthetic Sockets Using Semi-automated Photogrammetry

Seeing the Big Picture: Improving The Prosthetic Design Cycle Using 360° 3D Digital Image Correlation