Aug 30, 2021 A review of the various approaches used for 3D printing custom fit orthotics and available software solutions.
From bespoke shoe insoles to knee braces and from ski boots to cycling helmets, custom-fit products are becoming increasingly prevalent as they hold various benefits. While it was previously limited to the most exclusive products, mainly those for professional athletes, custom-fit is becoming increasingly democratized and integrated into commercially available products.
For example, the medical practice has recognized the value of personalized care and of making tailor-made medical products such as orthotics and prosthetics shaped to the unique morphology of the patient. This is critical as these devices serve to correct pathology and proper fit is essential.
Fortunately for the patients afflicted, custom products have become far more accessible and affordable over recent years thanks to advances in software and 3D printing. However, there remain major barriers to mass adoption of custom 3D printed solutions and the most cumbersome remain automation and production scaling, which falls mainly to software.
The manufacturing of custom-fit orthotics and prosthetics involves a wide range of professionals, including but not limited to skilled designers, software experts, and additive manufacturing experts. Democratizing mass customization will require that we synchronize and scale the efforts of these professionals, which as in other industries, can be achieved through the development of more streamlined and automated processes.
Approaches to custom-fit
There are several approaches that can be taken to create custom-fit products, and which is used depends on a few factors, principally speed, resources, and optimization capabilities.
A primordial step to creating a custom-fit 3D printed product is the digitization of the body. Subsequently, various approaches can be taken, as described below, to generate a custom-fit product based on the 3D file. Software options are numerous, they include but are not limited to those presented below.
1. Printed Twin approach:
The more rudimentary approach is using the digital file of the patient to 3D print a morphologically identical tangible replica. This can then be used as a copy of the body part around which the final product is shaped, for example using a plastic sheath warmed to become pliable.
This process is used in the manufacturing of bespoke prosthetics as well as custom shoes, the former of which uses a replica known as a “last”. This process holds various benefits over the previous method of using plaster casts to get a negative of the patient, which would then be used to mold the replica of the patient, a process that is often messy, time-consuming, and requires the patient to be on site.
Software options:
2. Augment approach:
Further digitalization of this process involves the virtual augmentation of the 3D file of the patient to create a partial contour of the body part. This outline can then be exported to a 3D printer, resulting in the final product. This approach reduces manual labor compared to the previous method.
The process creates a uniform layer around the limb and can be useful for immobilizing limbs following a fracture, for example. However, the downside to this approach is the fact that the product is often not optimized – a simple uniform layer over the skin surface is created.
Yet, if the technician has enough 3D design experience, the file can be manually edited to improve the design. Additional software, known as Topology Optimization Software, can be used to edit the shape of the outline (filling the volume with a lattice or Voronoi pattern to lightweight the product for example), to create variable thickness throughout the device, or to integrate holes for straps or other features.
Ultimately though, the device is simply an outline of the limb with minimal optimization, which must be manually integrated if the technician has adequate experience with design software.
The augmentation approach and subsequent design optimization steps can be accomplished in two ways: either manually or through automation software. It is important to note though that both are limited in terms of optimization and/or speed. The designer may want to integrate special features which require manual intervention and thus increase the time required; and alternatively, they may want to automate, but are limited in the optimization of function and/or form as the product remains a simple augmentation of the body part surface.
Manual Augmentation Software options:
Automated Augmentation Software options:
Topology Optimization Software options:
- Carbon – Design Engine can be used to add an optimized lattice to a final product
- nTopology – topology optimization software
3. Custom-fit CAD approach:
The most advanced and ideal approach is one that enables optimization of the function and form of the product. It involves the use of CAD software to create an intricate and optimized product – it may include special features such as hinges and even differentiating patterns (ex. logos) to be incorporated in the design.
Custom-fit automation software can then be used to morph the product to the patient’s digital twin. Note that the process of morphing a complex CAD file can be done manually but requires substantial time and expertise due to the need to respect the intricacy of features.
Alternatively, other software can custom-fit the product but would deform the functional and differentiating features.
This is where the most advanced custom-fit automation software comes into play – this branch of software enables all the feature to be kept consistent through the morphing to give a custom-fit product with no compromise to the optimization of form and function.
The perceived downside to this approach is the need for CAD design skills or high cost of having it outsourced to a design firm. It is important to note that among the two most advanced processes, although you can optimize the product using the Augment approach, the modifications must be repeated manually for each file.
An improvement to this is having a single, highly optimized file, that is then pushed through a custom-fit software that automates the morphing while respecting the intricacies of the design.
Software options:
Key metrics comparison
There are various reasons why an orthotist or prosthetist would use a particular approach. Digital transformation is often a gradual process, and incremental adoption of technologies can be a wise decision when resources are limited.
Nonetheless, as per the table below, the Custom-fit CAD approach is quickest, creates the most optimized products, and does not require substantially more resources than other techniques, although it requires the acquisition of new equipment and training to use it.
| Production speed | Design optimization | Resources required | |
| Printed twin | X (slowest) | X | X (most resources) |
| Augmentation | XX | XX | XX |
| Custom-fit CAD | XXX | XXX | XXX |
It is quickest at it displaces the time requirements to product development, after which the product is custom-fitted automatically per patient.
It is most optimal as it can integrate complex functional and aesthetic features most consistently from patient to patient. While the features can be integrated using the augmentation strategy, consistency may lack.
Lastly, it is least resource intensive as it, again, displaces the time and cost commitment to when the initial product is designed. Furthermore, the manufacturing of the end-product can often be out-sourced due to the cost of the additive manufacturing equipment required.
Augmentation is ranked as requiring more resources as a trained technician is required for each device to be generated, whereas for the custom-fit approach, only quality control by said technician is needed. This rating assumes the medical professional has not yet acquired equipment for another customization approach (ex. is starting their career).
Important considerations
Regulations:
There are several important regulatory considerations to be taken when developing orthotics and prosthetics. While the tools used to create these devices is not regulated or standardized, there are efforts underway by associations like the Association for Orthotics and Prosthetics of America (AOPA) to develop guidelines/standards. In the meantime, it is important to acknowledge the importance of having an appropriately certified/licensed medical professional prescribing and overviewing the care of the patients, as recommended by the American Association for Orthotists and Prosthetists (AAOP).
Orthotics and prosthetics are ultimately medical products that can cause considerable harm if not prescribed, distributed, and/or used properly – proper training is key to mitigating risks. Although 3D printing is indeed democratizing access to these life-changing devices, it is essential that this democratization be done by those with the required training and experience.
Furthermore, there are several regulations in place to ensure the safety of the data being handled. Compliance to the General Data Protection Regulation (GDPR) in Europe and the Health Insurance Portability and Accountability Act (HIPAA) are required.
CAD training:
It is important to note that there are considerable learning curves associated with a change in the approach taken to create custom-fit products. Not only is new equipment required, but new skills as well.
While a growing number of educational institutions are adopting curricula that introduce students to 3D design, there remains a need to fine-tune design skills over time. As mentioned above, the most optimized process requires the development of a product CAD file. This is a laborious process that requires substantial knowledge and time.
It is recommended that orthotics and prosthetists learn to use design tools, yet not all have the time and resources to do so. While the educational system continues to adapt curricula, design services are available to clinicians interested in designing their own product(s).
While these services may be associated with a cost, the benefit (patient wellbeing, business viability, etc.) of a fully optimized and just-in-time product should motivate practitioners to strive for this approach. It is primordial that patient care is optimized, but so is business viability.
Conflict of interest disclosure: The author of this article declares that they receive monetary compensation from Shapeshift 3D.
About the Author:
Jacob Lavigne is a Ph.D. graduate from the program of Experimental Surgery at McGill University. His research interests include orthopedics and associated technologies (algorithm development, 3D printing/additive manufacturing, simulation, and targeted drug delivery) as well as innovation management and marketing practices. Lavigne currently holds the position of community engagement manager at Shapeshift 3D, a software development firm empowering orthotists and prosthetists to create optimized products through the use of AI and 3D technologies. He also works as an independent innovation consultant working to facilitate the adoption of various technologies and the paradigm shift to personalized medicine. He achieves this through knowledge development and dissemination, partnership development, advocacy/lobbying, and product development.
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