Doctors and surgeons can use 3D printed organ or bone models to explain to patients or students the details of a surgery or to practice the surgery itself. Other surgeons are actually designing their own prototypes of new surgical tools or bone replacement options.
The challenge, historically, is that 3D printing can be expensive and difficult to complete.
As a mechanical engineer, I began my career in automation design and robotics, but moved into the medical industry in 1990 when I was hired by an orthopedic knee replacement company. They asked me to utilize my experience to automate the process for finishing knee implants. It was a three-year project and the result was a new process that produced a knee implant in minutes instead of hours.
During that process, I saw the opportunity that surgeons have to develop new techniques and tools to enhance surgical procedures, but they lacked the resources to turn their ideas into a reality. Now, in my spare time I work with the doctors and surgeons to brainstorm a design based on their idea and 3D print it so that they can pitch to companies for production.
So, how does it all work?
An orthopedic surgeon comes up with an idea and it is then modeled using computer-aided design (CAD) software. The design is then printed using a desktop ABS 3D printer to fabricate the first conceptual models and get the surgeon to a point where they are happy with the design and are confident the part will be functional.
Up to this point, it’s fairly easy to manage time and expenses. However, when it comes time for a real functional prototype, that means working with metal and that’s when the costs start to increase. As the surgeons are often doing this on their own time and paying for it from their own pocket, it’s important that costs are managed.
Historically, the key to managing project costs has been to design parts with the prototyping or end manufacturing process in mind. This used to require thinking about manufacturability at every step so that the product design did not end up so complex and complicated that it couldn’t be manufactured. Up until 3D printing was capable of fabricating high-quality metal parts, this meant designing each part with machining in mind. Unfortunately, this significantly limited the complexity of the surgeons’ designs as well as the dimensions and shapes of the parts. Now, metal 3D printing has evolved to the point that it can be considered as the end manufacturing process. As a result, the surgeons can design streamlined, more complex parts with fine details that would be too hard to machine.
One example is implant designs that need to be porous to encourage bone growth. Adding porosity is very difficult in a machining application, because it relies on a laser taking material away from a solid part or a secondary material being applied. But with 3D printing, porosity can be built into the design and accurately output by the printer.
All things considered, designing for manufacturability has been massively aided by advancements in metal 3D printing.
Enhancing Hip Implants
Recently, one orthopedic surgeon I work with—Dr. Brian G. Burnikel, M.D.—had an idea to overcome the debilitation that comes when a patient with a hip implant gets an infection. The current process is to remove the implant and fill the void with antibiotic cement. This cement hardens, but it can’t provide function and stability like the previous hip prosthesis. Thus, the patient has limited mobility and persistent pain.
Dr. Burnikel’s idea was for a temporary implant that provides a scaffold framework inside of the bone cement. This can be used with the antibiotic bone cement to provide a solution that both eliminates the infection and offers the patient much more mobility. The design of the implant features an adjustable neck angle and certain other features to make it easier to implant and remove after the infection is gone.
After designing the part and 3D printing it on a desktop 3D printer, it was time to get a part printed using a metal 3D printer. Since metal 3D printers start in the tens of thousands of dollars, I outsource that production step.
In Dr. Burnikel’s case, we used 3Diligent, a rapid manufacturing services provider, to 3D print the part in stainless steel. 3Diligent uses data science to analyze my request for quote and identify the optimal suppliers in its network of qualified providers for my project. I used to do this process of gathering quotes manually, but they are experts in metal printing and this expedites the process quite a bit.
After receiving the 3D printed part within a couple of weeks, Dr. Burnikel tried the part out in a cadaver lab and the implantation was a great success. Dr. Burnikel has begun engaging orthopedic device manufacturing companies to see about selling his idea for broader use.
Accessing the universe of cutting edge 3D printing has never been so easy and the process has opened the door for innovators to enhance surgical procedures and tools. As newer printers and materials become available, the opportunities for surgeons to innovate will be plenty.
Jody Stallings is a mechanical engineer in Palm City, Florida.