Irish Manufacturing Research (IMR) undertook a Feasibility Study to determine whether Additive Manufacturing for prosthetic trans-tibial sockets at Atlantic Prosthetic and Orthotic Services (APOS) was commercially feasible. This study investigated a digital manufacturing workflow that consisted of the digital scanning of patient data, clinical rectification of the digital data using design software, subsequent development and the Additive Manufacture (AM) of a Proof of Concept prosthetic socket design.

The Challenge:

APOS had identified a need to explore the benefits of pivoting their manufacturing method from current manufacturing workflow to a more agile virtual or digitised model because:

  • The current workflow is linear with no reliable and repeatable means to iterate
  • Clinical knowledge is not currently integrated with off the shelf solutions
  • An internal skills gap has been identified which may act as a barrier to implement change
  • The most appropriate scanning method has not yet been identified

Additive Manufacturing has been identified as a solution that could bridge the gap between scanning, prototyping, and production while retaining the ability to revise models.

APOS approached IMR with the challenge of examining the feasibility of moving to this model with a view to progressing to a full IPP.

The key goals of the Feasibility study were to show that:

  1. There is a potential method to deal with data translation and integrate this with existing clinical knowledge
  2. Additive Manufacturing has the potential to give the company a global competitive advantage

The Players

Irish Manufacturing Research (IMR)

IMR provides Irish manufacturing companies with the support they need to become ready for the next generation of digital manufacturing. Medical device production is a prevalent industry in Ireland and IMR works with a variety of companies to investigate what can be achieved with 3D printed medical devices.

Atlantic Prosthetic Orthotic Service (APOS)

APOS manufacture:

  • Prosthetics which are external devices fitted to mimic the functionality of a missing limb
  • Orthotics which are external devices used to maintain/alter the position of a joint or body part

APOS are 100% Irish Owned and are the only independent prosthetic and orthotic Irish manufacturer.

The Research

To meet the needs of the Feasibility Study the research was broken up into the following steps:

1. State of the Art Review

The State of the Art (SotA) Review was undertaken to determine the appropriate technologies for commercial manufacture of transtibial prosthetics using a new digital workflow.

Our team needed to identify:

  • A key Additive Manufacturing technology
  • Potential scan partners
  • Potential software solutions

To complete this review:

  • The commercial and clinical motivations for adoption of digital manufacturing technology were identified
  • The manufacturing steps and time burden were captured for the current workflow
  • A digital workflow (and estimated time burden) was proposed
  • The user requirements for the three technologies included in the workflow (scanning, software for rectification of digital patient data, and an Additive Manufacturing (AM) platform) were captured
  • Appropriate solutions for each of the technologies were reviewed based on the User Requirement Specifications (URS) previously developed

Given the high technical capability and the willingness to adapt to new technology demonstrated by APOS, a decision was made to identify individual, best in class technology options to satisfy the digital workflow.

2. Additive Manufacturing Technology Integration
  • Define clinical technological need
  • Skills gap analysis
  • Trial software solution First Pass

The key clinical technical requirements that may act as a barrier to the successful integration of the technology to form a digital manufacturing line are identified and addressed in this report. This report aims to address the unknown elements that may prevent successful research and development of a Proof of Concept (POC).

The research actions identified as required to allow the development of a POC, and the corresponding outcomes are detailed below:

  • Definition of the required skills, and the gap between required and actual skill levels for each step of the digital manufacturing workflow. No significant gaps were identified. IMR was confident that POC work could proceed and that APOS understanding of the steps taken would be sufficient to allow meaningful input and feedback
  • Definition of the repeatability and reliability of the data gathered by the scanner to be used in POC work. Previous research undertaken during the State of the Art (SotA) Report had indicated there are questions around the reliability of data captured using this particular scanner. A Gauge Repeatability and Reliability Study showed that measurements taken by this system show variation well outside that required by APOS per the previously written URS. To mitigate against the potential impact on fitting from this variation, a decision was made to print a range of sizes of sockets for POC work, and to complete the fitting using the best fit socket.
  • Investigation of best practice for software tools and a trial of the digital manufacturing workflow that includes scanning using the Structure Scanner, data rectification in MeshMixe, and printing on the EOS P396. The capability of these technologies to support prototype production and analysis was investigated where required.
3. Transtibial/Below Knee Prosthetic Prototype
  • Patient Scan First Pass
  • 3D Modelling & Clinical Adjustment
  • Draft design
  • Initial single prototype production

A functional prototype trans-tibial socket was produced using the digital design workflow. This prototype fit the patient and was able to be trialed in a controlled environment.

A digital design workflow was developed and shown to work. However, a significant shortcoming of the selected software is that there is no facility for design rollback, requiring duplicates to be saved at key stages in the design process. This relies on a designer to follow a procedure and represents a risk to control of design development.

Previous work had shown that the scanner was not capable of meeting the specified tolerance. Examination of the scan data showed several gross flaws which is taken as evidence to support previous findings. However, a printed part fit the patient and so the Proof of Concept can be taken as successful.

The Results: Is using Additive Manufacturing for Prosthetics commercially feasible?

As Proof of Concept (POC), a prototype trans-tibial socket was successfully developed, manufactured, and tested on a patient. Only one type of prosthesis (transtibial) was investigated for a single patient case.

Following this successful fitting, a Project Gap analysis & Feasibility Review was completed

All assessment criteria identified at the project outset were addressed adequately using predefined key metrics.

Existing technology gaps that must be answered prior to commercial AM of prosthetic sockets were identified.

The most significant gaps are a lack of:

  1. Understanding of the acceptable amount of variation within the manufacturing process that will still allow a socket to fit well
  2. Design review procedures and approved design criteria that allow a formal review of prospective designs
  3. A detailed understanding of the physical properties of materials output from the proposed AM process, and the impact these will have for design and use

A comprehensive project plan for a prospective Innovation Partnership Programme (IPP) based on a New Product Development (NPD) template was detailed to meet all identified gaps. This plan can be tailored to meet the specific needs and resource constraints of APOS (for example, training needs). Furthermore, it can be broken into separate, smaller consecutive projects, or executed as a single comprehensive project.

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