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3D Design, Visualization and Prototyping. Part 6: Prosthetic Legs

By Mitch,

April 4th 2024

A man walking with two prosthetic legs
A giant step. Prosthetic legs are becoming better by design

So, we've now arrived at part 6 of our series looking at 3D Design, Visualization and Prototyping and we're continuing our look at the medical world. This time though, we'll show you how 3D printing is revolutionizing the field of prosthetic legs in a similar way to what we looked at in our previous article, "3D Design, Visualization and Prototyping. Part 5: Prosthetic Arms".

Firstly then, let's just recap some of the main points we addressed in that article:

  • The term "prosthetic" can cover a vast array of items

  • 3D Design, Visualization and Prototyping covers the physical objects that are in everyday use

  • Other prosthetics and artificial parts are used in surgeries and transplants

  • Functionality is more important than style

There will undoubtedly be some repetition of some of the processes we covered previously with prosthetic arms but we'll try not to repeat things too much!

Let's then take look at some of the things that 3D Design, Visualization and Prototyping are bringing to the world of prosthetic legs.

A New Chapter

As we discussed previously, prosthetic limbs are no longer just cosmetic or a barely functional burden to the user. Major advancements in the technology and design of prosthetics have added both style and substance to artificial legs. It's these advancements that mean that prosthetic users can live their lives in the best way possible and 3D printing is a big part of that.

In order to delve further into the subject, we should again break it down into the three aspects of the design, visualization and prototyping process.

3D Design

This will basically be the same as for prosthetic arms but, of course, with some notable differences.

3D design is the starting point and as with prosthetic arms, the designer can work closely with the user to get the most suitable leg for the individual. Again, there really isn't any room for using a "stock" or "off the peg" leg as this is unlikely to be suitable.

Without aiming to repeat what's been said before. the leg needs to be perfectly tailored to the user in order for them to feel comfortable using it and for its functionality to be optimal. Obviously, there is a basic anatomical template for a human leg but size and orientation (left or right) do come into play at this stage.

3D Visualization

A collection of prosthetic legs lined up beside a swimming pool
The unusual suspects. 3D prototyping is shaping the future for prosthetics

As we've discussed before in this series, 3D visualization and 3D design overlap somewhat as they both involve the beginnings of the design prior to the prototyping stage. However, with something as important and functional as a prosthetic leg, these aspects need to be perfected before moving on.

Visualizing a prosthetic leg should be fairly straightforward as we would all hopefully know what one should look like. In the case of prosthetics though, we're working with the basic human "design" and retro-engineering in a way. Obviously, we're not looking at the complex microbiology involved in a living, flesh and blood leg, but we are looking to replicate its function as closely as possible.

The design and visualization will then be based around these keys factors:

  • Functionality - Does it do what the user needs

  • Design Aesthetics - Is it pleasing to the user and those seeing the prosthetic

  • Comfort and ease of use - This is hopefully self explanatory

  • Practicality - Is the weight, size and functionality appropriate for the user

  • Adaptability - Can the design be modified as the user grows or their needs change

All of these are the things that will need to be considered and discussed between the designer and the user to make sure that everything they need is covered.

3D Prototyping

The final stage before actual production of the prosthetic leg is the prototyping stage.

The design itself has been finalized and both designer and user have visualized the final model using CAD software and 3D rendering. Now is the time to convert the design into a 3D printable model of the actual leg.

This process is a bit easier than that of the prosthetic arm as the leg really only needs to support the user. There are no grip or dexterity functions needed for the leg or foot so yr just needs to be the right size and of sufficient strength to hold the weight of the user.

If you're just looking to prototype the size and look of the leg then it can be printed as one in the first instance to get the general idea.

In 3D printing terms, the prototype could be made using either FDM, SLA or SLS methods or indeed a combination of these. Have a look at our previous article "3D Printing: Comparing, FDM, SLA and SLS* for more insight into each of these methods.

The end goal when prototyping is to produce a fully functional version of the prosthetic leg that can be tried by the user and will perform as well as the final item. The finished product could of course then also be 3D printed but certain components may need to be machine made or indeed already be widely available. The literal nuts and bolts as it were!

The Next Step

A woman running with a prosthetic blade leg
Blade runner. Prosthetics are helping para-athletes achieve their goals

We've covered the processes involved in designing and prototyping a standard prosthetic leg but you will undoubtedly have seen adaptations used in particular by athletes. These are commonly known as "blades" due to their sharp lines and streamlined design. They are also designed to provide a "spring in the step" as it were and enhance the performance of the athlete using it.

These blades are rigorously tested and prototyping is an important part of the research and development that goes into their final design. However, this is where 3D printing can fall behind in the race as it's very difficult at present to 3D print a carbon fiber blade that will withstand the use of a high performance athlete. That's not to say though that the technology won't catch up in the future so keep an eye out for news on the subject.

So there you have our latest article in this series. All the methods mentioned in terms of 3D design, visualization and prototyping can be carried out by our talented technicians here at Politech so please get in contact and we'll be more than happy to assist.

In the meantime, thank you for reading and look out for the next part in this series!



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