The rise of additive manufacturing in prosthetic and orthotic manufacturing

February 17, 2022
9 min

The orthotics and prosthetics market is booming. However, traditional fabrication processes are not a sustainable option to follow its growth. It especially causes material waste and is a time-consuming and laborious process. This is where additive manufacturing (AM), also known as 3D printing, comes into play and facilitates these issues. The 3D printing medical devices market size is projected to grow at a CAGR of 17.5% from 2021 to 2028. However, it also comes with its set of challenges as well. In this article, we will be reviewing the study on the current state of application of AM technologies in prosthesis and orthosis fabrication.

Additive manufacturing versus traditional method

Still today, prefabricated prosthetics and orthotics are available on the market and are much less expensive than custom products. However, tailored prosthetics and orthotics enable a better fit to the patient’s body part, which offers more comfort and better results. The traditional method, which is the most adopted manufacturing method for custom products, involves plaster casting and takes a much longer time because of its manual process.

In the traditional fabrication, a cast mold is obtained by using plaster bandages around the body part and then a positive mold is constructed by pouring plaster into the negative cast. With this method, it is not uncommon to perform multiple adjustments during fitting visits to get the right shape. The whole process results in a waste of materials, time, and high labor costs. Additionally, the quality of the finished product is highly dependent on the skills of the clinician.

On the other hand, with AM, the possibilities are endless. In addition to saving money on material costs (and wasted product), it also allows customization to fulfill unique requirements and consider individual characteristics. The benefits don’t end there; production delays can be avoided due to shortages on specific items needed when making mass produced products.

3D printed hand brace

Studying additive manufacturing in orthoses and prostheses fabrication

With recent advances in materials and decreasing costs, AM technology has been put to the test. Studies have outlined novel O&P manufacturing methods that utilize body scanning technologies like CAD/CAM for accurate 3D acquisition and AM technologies. To create custom foot orthoses, AM technologies have been used to fabricate various types of products and were compared to the traditional fabricated products. These studies concluded that the approach in foot/ankle-foot orthoses can be successful and indicates great potential for clinical use.

Other studies were also performed in prostheses manufacturing where the socket of the transtibial prosthesis was fabricated using CAD and SLS technologies. It showed improved comfort, greater step symmetry, and similar lower extremity joint function compared with the patient’s definitive prosthesis. These studies concluded the feasibility of fused deposition modeling (FDM) in the design and manufacturing of transtibial sockets.

Moreover, with AM, the use of finite element analysis (used to find the stress distribution for complex geometries) has allowed for predictions and optimization in mechanical characteristics as well as functional performance. Topological approaches can be used to optimize material distribution while maintaining design stiffness, which is impossible with traditional procedures. Multi-material technologies, such as SL, FDM, and SLS are used to produce components with multiple materials and complex geometries while adding functionality. One main issue with this technology however is the combination of different materials, due to differences in thermal expansion/contraction and mismatch heat release, which is not a problem in the traditional method. Finite finite-element analysis was introduced in prostheses and orthoses to predict and design an appropriate fit in advance of fabrication. Once again, various studies were conducted to analyze stress distribution in the tissues of the human body and identify biomechanical behaviors.

Framework for additive manufacturing process

These finite-element models have provided valuable information on the prediction of performance. However, these advanced modeling technologies are not yet integrated into clinical practice due to a lack in a mature systematic framework surrounding all aspects including computational analysis. This is why, this study proposes a framework to manage the AM procedure from initial conception through final adaptable products.

This framework reduces time and streamlines production to provide faster customization results with consistent qualities. In the new digital world, AM manufacturing is on its way to becoming a favorite for many companies. However, it has not been widely commercialized and applied in prosthetic or orthotic clinics because of existing limitations on a mature systematic framework.

One main problem is that, in comparison with traditional procedures, the implementation of pre-manufacturing analysis requires extra skills from clinicians. Additionally, this process requires professional software and equipment. The integration of AM technologies into real-life applications is not yet common due to the high costs and time consumption. Also, a better understanding of AM products is yet to be done post-clinical by patient feedback and analysis of long-term effects.

Regardless of the many benefits that AM brings to the market, the adoption is slow in the market as of today and there are still some uncertainties in the industry. In the next few years, it will be interesting to follow the functional long-term outcome of this new technology, the evolution of properly comparing AM with the traditional method, as well as rising debates on intellectual property issues with 3D printing. Are you ready for the rise of additive manufacturing?

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