A Look into 3D-Printed Medical Implants

When we think of 3D printing, the first thing that often comes to mind is creating inanimate objects like toys, tools, furniture, and architectural components using construction materials such as plastics, ceramic, or metal. However, (as we know from our previous two blogs) the uses of 3D printing have evolved way past these applications and additive manufacturing is serving an increasingly important role in healthcare and medical research. With the advancement of 3D printing technology, researchers can form highly complex geometries that imitate human body parts and increase the value of implants without inflating costs or manufacturing time. This blog will look at 3D printed medical implants — devices that are placed inside or on the surface of the body to repair an organ, replace a non-existent part of the body, treat a disease, or supplement a bodily function.

Nonbiological 3D Printing

In our previous blog we covered the topic of bioprinting, an additive manufacturing process that uses cells and biomaterials to produce 3D organ-like structures for transplantation, education, and drug development (read more here). In this blog, we will look at nonbiological 3D printing. Nonbiological 3D printing is most commonly used in dentistry and orthopedics to produce bespoke medical implants using stainless steel, titanium alloys, cobalt-chromium alloys, and ceramics. Titanium is the most common metal material used in 3D printed medical implants today due to its biocompatibility— the body typically accepts this material well which is extremely important when it comes to implants. Using the right material, nonbiological 3D printed implants can even be designed with nearly identical properties to real bone. Similar to bioprinting, the goal of 3D printing nonbiological parts is to print artificial objects that represent some structure of the body and mimic the physical properties of human tissue. However, since nonbiological 3D printed parts are reusable and nonbiological based, they are easier to use and pose less safety concerns than human tissue. Nonbiological 3D printing uses CT or MRI scans of the area of the patient's body where the implant is required to determine precise dimensions and design an implant that fits exactly where it is needed. Nonbiological 3D implants can also be modified to resist infection and filled or coated with growth factors to help repair surrounding tissues.

The Benefits of 3D Printing for Medical Implants

The benefits of 3D printing are multifold, however, in this blog we will discuss 6 significant ways in which additive manufacturing is positively impacting medical implants.

1. The ability to create new kinds of geometries: Additive manufacturing allows researchers to create very complex shapes and new kinds of geometries that would otherwise be extremely difficult to construct manually or with molding. One such example is the ability to produce trabecular lattices. 3D printed lattice structures stimulate the formation of bone within a given implant and mimic native bone properties in order to avoid stress-shielding (a reduction in bone density as a result of an implant removing stress from the bone). With 3D printing, researchers have full control over the properties of the lattice structure and can tailor the material, topology, density, and stiffness of the lattice to meet the needs of the patient. SLM, the selective laser melting process is a widely chosen 3D printing technique to create medical lattice structures.

2. Accelerating the product development process: Not only does additive manufacturing offer the ability to create complex designs and geometries, but it also allows researchers to rapidly prototype these innovative implant designs using the intended manufacturing process. With 3D printing, researchers can accelerate the prototyping process of implants by almost 8 times when compared to traditional device manufacturing. Rapid prototyping means researchers are able to complete tests quickly for early feedback; optimize designs and improve quality for final production; increase certainty and mitigate cost overruns. Once the right design is found and finalized, the implant can go into final production.

3. Improving accessibility to custom Implants: Rapid product development means that custom implants can be developed and produced much more quickly, making patient-tailored implants more widely accessible. 3D printing offers patients access to implants personalized to their precise anatomy, physiology, and needs, resulting in better health outcomes, fewer surgeries, quicker procedures and recovery time, and sometimes even eliminating the need for complicated and invasive procedures.

4. Simplified procedures and less manual work for surgeons: Greater accessibility to custom implants not only offers benefits for patients but also for surgeons. Working with a custom implant made specifically for the patient at hand means simplified procedures and less adjustment and manual work for the surgeon. Additionally, as mentioned in the previous point, custom implants allow procedures to be accomplished faster and less invasively, meaning less time in the operating room for both the surgeon and patient.

5. Provides new opportunities for implant materials: 3D printing offers greater possibilities when choosing materials for medical implants compared to conventional methods as the technology presents new ways of working with traditional implant materials. For example, instead of having synthetic bone graft and bioceramics manually packed by a surgeon, these materials can be 3D printed into precise geometries that fit a patient's specific anatomy. Other common implant materials such as nitinol and polymers can be applied to 3D printing, allowing for more sizes and configurations of implants to be made easily.

6. Enhanced performance and quality: 3D printing medical implants using metal produces implants that are more durable, perform better, and match better for knees, spine, skill and hips. Orthopedic implants created using the electron beam melting 3D manufacturing process, in which metal powder is melted layer by layer by an electron beam, are highly accurate and very closely mimic regular bone tissue due to their spongy structure. As such, metal 3D printed implants increase the chances of osseointegration — the ingrowth of a bone into a metal implant.

Innovative Projects

3D printed solutions often outperform traditional implant methods in a number of aspects, including design, manufacturing time, related costs, patient comfort, and improved patient experience with the implant. The incredible potential of 3D printed implants is increasingly being recognized. So much so that by 2025, additive manufacturing in the field of medical implants is expected to reach $340 million (CAD). The ability of 3D printing to create personalized medical products that meet the specific needs of every patient has made additive manufacturing a revolutionary technology for medical implants. The following list presents some very significant and innovative 3D printed medical implant projects that demonstrate just how hopeful 3D printing is in the medical device industry.

3D Printed Silicone Heart Valves

A team of researchers from ETH Zurich University in Switzerland along with South African company Strait Access Technologies, have teamed up to create 3D printed silicone heart valves, designed according to the heart of each person. Using a CT scan of the patient's aorta, researchers can determine the precise shape and size of the patient's failing heart valve and create a digital model that can then be used to 3D print the artificial valve in only one and a half hours; the result is a personalized valve that is perfectly matched to the patient. The goal of the 3D printed silicone heart valves is to replace failing valves for the aging population and those who lack physical exercise and/or have poor nutrition. Additionally, using 3D printing to create these heart valves has the potential to extend the life of replacement valves from 10 to 15 years — the current lifespan of traditionally manufactured artificial valves in patients before they need to be replaced. Silicone was selected as the material of choice as it is highly compatible with the human body.

3D Printed Carbon Artificial Retina

Dr. Matthew Griffith from the University of Sydney made a breakthrough development when he created a 3D printed artificial retina made out of carbon to help patients see again. After realizing that the human body is essentially a carbon-based semiconductor, he discovered that he could replicate an eye by designing a fully bio-compatible 3D printed carbon device that uses absorbed light to fire neurons and create an electronic charge, just like a human eye, at a low cost. The device is not yet completed and is still in the testing and prototyping stage, but it is expected to enter clinical research in the next three to five years.

3D Printed Orthopedic Implants

Currently, about 2.6 million people worldwide require knee replacement surgery each year, and by the year 2030, research shows that there will be 3.5 million annual total knee replacement procedures, making it one of the most common replacement surgeries. As such, Monogram Orthopedics, an American company, is currently developing a product solution that combines 3D printing and robotics to achieve mass personalization of orthopedic implants. Using a CT scan to obtain a 3D representation of the patient's original bone structure, the company is able to design a 3D printed implant that is as close to the patient's original anatomy as possible, making these implants less painful and reducing the likelihood that the replacement will fail. The implants are designed for maximum cortical contact and stability and 3D printed using a titanium alloy.

Restorative Oral-maxillofacial Implants

AB Dental has innovated the technology and application of Selective Laser Sintering 3D printing in the oral and maxillofacial field. Using SLS technology, the company is able to plan dental and facial restoration treatments with increased precision compared to traditional methods and create patient-tailored restorative 3D printed implants. AB Dental offers patients several 3D printed implant, including sinus roof augmentation, orbital bone repair, and subperiosteal implants for patients with bone resorption.

Hyperplastic Bone Implants

Scientist at Northwestern University in Illinois have successfully developed an innovative 3D printable material known as hyperplastic bone — a synthetic material made from a naturally occurring mineral called hydroxyapatite, combined with a polymer to make it a flexible and consistent substance. The flexibility of the material allows it to be cut, rolled, and easily pressed into areas, making it straightforward and easy to implant during surgery (check out the video below to see the flexibility of the material). Hyperplastic bone is also highly porous and absorbent — allowing the material to act as a scaffold and stimulate the growth and formation of blood vessels and new organic tissues in the surgery area. Additionally, hyperplastic bone is affordable to manufacture, can be 3D printed at room temperature, and has a shelf life of one year, making it a very promising and low cost solution for bone transplants. In 2019, researchers conducted a study in which hyperplastic bone was used on living rats with skull defects. The study showed that hyperplastic bone provided favourable bone regeneration and was very effective when compared to other implants that used the animal's own bone.

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References

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