The manufacturing process of ankle-foot orthosis: traditional vs. 3D printed

By
December 20, 2021

3D printing technology is increasingly becoming a part of any clinical practice, including the manufacturing of ankle-foot orthosis (AFO). You might be wondering if you should embrace it in your practice?

There is no straightforward answer to this. The technology might be getting better each day, but you might still want to take into account the efficiency, process, and results of both the traditional or manually-made AFO and the one that is 3D printed. 

This is why we decided to put the traditional clinical practice of making orthoses side by side with the 3D digital workflow. We will compare the time, flow, materials, and tools used in both processes. We will also discuss what each of them means for your practice.

Here is a quick overview:

Table comparing traditional vs 3D printing process of making AFOs
Traditional vs. 3D printing process of making AFOs

Conventional orthosis manufacturing 

Let us take a look at the typical process of making orthosis manually:

1. Measuring

The process starts with orthopaedic technicians isolating the limb using Vaseline or saran wrap to preserve the body hair when later removing the impression. Taking measurements of the body part is the most important step. Yet, this alone can take up to half an hour, including setting up and cleaning. 

2. Placing markers

Next, the technician indicates the bony markers with a pencil on the patient’s skin. Then they tape the tube to the patient’s limb to be used as cutting space later in the process. 

3.  Molding 

Now comes the molding process. For complicated orthoses, this can take up to ten hours. Shaping the impression involves closing up the cutting line with plaster bandages and isolating the negative mould.

4. Positive mold and drying

After this, the technician places a long steel rod in the middle of the orthosis to ensure stability while filling in the negative impression with liquid plaster. Now we have a positive mold. Once again, the imprint has to dry, which takes between two and forty-eight hours. 

5.  Correcting and polishing

The next step is to correct and polish the positive mould. This can be a risky process that can decrease the accuracy of the mould and potentially break it. Yet, it’s a crucial step in the preparation of making the orthoses. 

6.  Removing negative mold

Once the positive form is dry and smooth, the orthopaedic technician can start removing the negative mold. The Plastazote or plastaform foam is then stapled over the model, and the thermoplastic is pulled over. 

7.  Heating thermoplastic

The thermoplastic is then heated in the oven. The oven makes the PP, PE, or Copolymer material flexible so that the orthopaedic technician can mould it over the model. 

8.  Removing mold

Finally, the technician removes the mold from the model and smooths out the rough edges. 

9.  Initial fitting

This is when we are finally ready for the initial fitting of the orthosis. Usually, some adjustments are necessary, which can take up some time. When adjustments needed are numerous, it can result in the need for a whole new orthosis. In those cases, the technician might have to start the process all over again.

Traditional process of making AFOs
Traditional making of AFOs is a long and delicate process

Time to compare that with the 3D digital workflow.

3D printed orthosis workflow

The digital workflow process consists of only four steps: scanning, modelling, printing, and cleaning. 

Here is a closer look:

1.  Scanning

The process starts by scanning the pathological limb. This involves positioning the limb and taking the scan. The technician adds the landmarks while rectifying the scan, which usually doesn’t take more than a few minutes. For complicated orthoses or limbs with multiple markers, it may take some time longer. However, the 3D scanning solution enables more exact measurement without the challenges of traditional molds. 

2.   Modelling and modifying

There is no need for plaster, positive or negative molds. There is also no drying process, meaning that the technician spends less time waiting. Instead, they can move right into the modelling and modification of the scan. Positioning and sculpting don’t take more than three minutes. Padding or foam can be added accordingly.

3.   Printing

Next up is the printing process. A series of rapid infrared rays determine the outline of the limb, on which a model for the orthosis can be built, using a portable scanner and a tablet. The printing process can take between 2 and 24 hours. This might be long and is perhaps longer than preferable. Yet, 3D printing technology is developing quickly and we may expect printing to take less and less time in the future.

4.   Cleaning

Lastly, cleaning up after printing takes up about ten minutes. Velcro straps can also be added using the loops through the belt loops. 

What does this all mean in practice?

Limitations of manual orthosis making

The manual manufacturing process can take up to 2 days, including drying. The technician needs to spend most of that time working on the orthosis, taking the time away from the work with patients and other aspects of their work.

Traditional manufacturing also requires several different materials, such as plaster, a plastaform foam, and thermoplastic, as well as a variety of measurement and shaping tools. Unfortunately, regardless of the expertise and experience of the orthopaedic technicians, manual manufacturing is prone to errors. When it comes to more complex cases, the process might have to start all over again.

In addition to all of this, producing multiple customized orthoses with the same quality is challenging. For the technician, this can mean a long and messy process that needs a lot of planning and preparation.

The 3D workflow is designed to answer this. 

How 3D technology changes the orthosis making

In practice, 3D printing offers a more simplified and streamlined process for orthopaedic technicians. The technicians can skip the manually intensive step of molding plaster and spend their time focusing on other tasks. This also means that, in the long run, there is less need for a big workplace to house the machinery, tools, and all the orthosis models. 

Another important change is that 3D scanning is a far more precise and accurate measuring method. Inaccuracies made by the 3D printer are rare. Moreover, digital storage allows the orthopaedic technician to find, modify and reuse all the information about their patients’ orthosis, all the while taking up zero space and reducing the amount of waste significantly. If a change or multiple customized orthoses are needed, the technician can easily access the stored data and make a new model by simply pressing the button. 

Finally, a 3D printing solution can drastically reduce the time spent on manual and repetitive tasks. For the orthopaedic technicians, this means more time to focus on each patient, easier communication, and high chances to produce orthoses that fit perfectly.

 

3D printing process of making AFOs
3D printing process reduces time spent on repetitive and manual tasks

3D printed AFOs

The technology has already proven to bring major value to the field of orthopaedics, including AFOs. In particular, studies like the one by Cha, Yong Ho, et al. show a great potential of 3D-printed AFO both for the practitioners and the patients. Another study, by Dal Maso, Alberto, and Francesca Cosmi, discussed the procedure for designing a fully-customized 3D-printed AFO. The study concluded that the process can be easily automated, further reducing the lead time and costs of the whole process, while delivering AFO that is comfortable and practical for the patient.

Perhaps the biggest concern with the 3D printing workflow is the time. It takes up to 24 hours to print the orthosis, which may seem long. Yet, once launched, the printer works autonomously, without the need of an operator. On average, only 10 minutes is needed to model the AFO. In the 24-hour long process, this means that only 0.5% of the production requires actual human interference.

While the merge of 3D technology with orthopaedics may seem daunting for the orthopaedic technician, there are many advantages. The purpose of this technology is not to substitute the work and expertise of the technicians but rather to make their work more meaningful and efficient. It is giving them more time to focus on the patients and develop solutions for them, rather than spending time on repetitive tasks or administration.

At Spentys, we have recently released a new feature as a part of our software, tailored specifically for the designing and making of AFO. You don’t need any previous technical knowledge to use our platform and we will guide you through the entire process, making sure that it fits your regular workflow. 

Start by booking your call with a specialist today.

References

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