What 3D Bioprinting Technology Means For Podiatry

In the 1980s, Charles Hull, an American engineer, developed the first three-dimensional (3D) printer. The printer allowed auto and plane makers to design and print complicated 3D parts that were difficult to construct otherwise. Recently, 3D printers have become much more affordable and several retailers now offer 3D printing services.  

Now 3D printing is starting to revolutionize medicine. Three-dimensional printers have already been printing medical devices such as robotic arms and legs for patients who require prosthetics. Artificial implants such as heart valves, fingers and toes can be useful for patients as well.

In the field of podiatry, the Prophecy Preoperative Navigation Guide (Wright Medical) utilizes 3D printing to print a patient-specific template based on a computed tomography (CT) scan of the patient’s ankle or knee to guide surgeons in positioning an ankle implant. We have found this has not only increased the accuracy and success of the procedure, but it has reduced operating time as well.   

Perhaps most excitingly, researchers and scientists have been developing technology to print living tissue that surgeons can potentially implant into the human body. The technology that is bioprinting is rapidly advancing and eventually, scientists believe they will be able to print an internal organ from the patient’s own cells, allowing organ transplant without needing to wait for an appropriate organ donor. Three-dimensional bioprinting also has the potential ability to restore biological defects caused by trauma, a congenital defect or cancer.¹

Bioprinting begins by harvesting cells from the patient and allowing them to multiply in a lab. These cells then become the “biological ink” and the 3D printer prints on a scaffold and follows a template to arrange the cells into a precise shape. The 3D printer is computer controlled and programmed to assemble precise three-dimensional structures by depositing layers of the biological ink to produce biological and biocompatible materials, called bioconstructs or biostructures, to implant into patients.^2-4 One can also use synthetic polymers in combination with biological polymers to produce the desired structure. The technology has gotten so precise that physicians can deposit a single cell within a complex 3D tissue structure accurately with the help of a laser.²   

Potential Applications Of Bioprinting In Podiatric Surgery
Arthritis is one of the more challenging ailments to treat effectively. One of the reasons for this is because native human hyaline cartilage is so difficult to replace. Some scientists believe that cartilage is one of the first tissue types that can be replicated consistently with a 3D printer. The reason for this is that it is a single cell structure of chondrocytes that is not as complex as internal organs and other tissues. Studies that have looked at bioprinted chondrocytes have shown promising results, showing good cell viability after printing.^5-7

Bioprinting of native hyaline cartilage could help improve our treatment of and possibly be a means of curing osteoarthritis. One can potentially print human cartilage cells onto a scaffold or template of a patient’s arthritic joint obtained from a CT scan or magnetic resonance image (MRI). Surgeons can then implant the biotissue into the joint, allowing them to potentially replace the arthritic joint with viable cartilage.

If bone is able to be printed as well, one could print joint replacements based on the patient’s own anatomy from CT or MRI, and implant the replacements using viable and living bone and cartilage instead of the metal and polymer implants that we have today. As long as the printed bioconstruct is viable and incorporates well into the body, we may theoretically be able to replace arthritic joints with actual new joints made of human tissue, giving new meaning to the term joint replacement. The main benefit would be that these bioconstructs would last longer than traditional metal implants. This appears to be possible as several recent studies have shown the bioprinting of bone to not only have good cell viability and vascularization, but bone-healing properties as well.^5,8-10

There are several other potential applications for bioprinting of bone, including the printing of autografts for surgical application into non-unions after a failed fusion or for injuries such as a Jones fracture that are classically difficult to heal. With 3D printing, there is the potential to obtain autografts without harvesting them from a donor site. There would be less concern regarding the need to obtain a particular size of graft from a donor site and one can potentially fashion the graft to each patient’s anatomical and surgical needs. Printed bone may also fill in defects caused from resection or loss of bone due to osteomyelitis, tumors or trauma.
 
How 3D Printing Can Aid In Wound Care
Another potential application of 3D bioprinting is in wound care. Skin is one of the most complex organs in the body as it consists of various cell types and substructures arranged in a complicated spatial pattern. A fully cellularized skin substitute that compares to native skin has been difficult to create.

However, the advancing technology of 3D printing has allowed various researchers to recreate skin. Several studies have shown that one can bioprint skin by printing fibroblasts and keratinocytes on a stabilizing matrix.^11-12 This advancement would be extremely beneficial in developing autologous grafts for patients with wounds, especially those with large wounds such as burn victims.

Of particular interest in wound healing is the 3D printing of complicated vascular networks that would promote angiogenesis. The research on the printing of vascular networks is promising. Studies have shown the ability for 3D printers to print complex tubular structures with viable cells that would be able to perfuse tissues effectively but this area in particular requires more research going forward.^2,13

In Conclusion
The research that is already being conducted and the possibilities that 3D printing will bring in the future are exciting to multiple fields, including engineering, manufacturing, art, education and, perhaps most of all, medicine.¹⁴ The potential of 3D printers in medicine appears to be limitless and may likely revolutionize medicine as great advances are occurring daily in this fascinating field. The technology in 3D printing is continually developing and improving, and we may soon be able to print complex and functional living tissues that we can use for our patients, especially as 3D printers improve in resolution, printing speed and automation.¹³

As it stands now, more research is necessary to improve the current understanding of the microarchitecture and microenvironment of various tissues and organs as well as the cellular mechanisms to construct tissues. With continued research and development though, we may see the development and printing of quality grafts that one can safely and effectively implant into patients.^3,14

Dr. Yau is a staff member at University Foot and Ankle Institute in Valencia, CA and Simi Valley, CA.

Dr. Baravarian is an Assistant Clinical Professor at the UCLA School of Medicine. He is the Chief of Podiatric Foot and Ankle Surgery at the Santa Monica UCLA Medical Center and Orthopedic Hospital, and is the Director of the University Foot and Ankle Institute in Los Angeles (https://www.footankleinstitute.com/podiatrist/dr-bob-baravarian ).

References

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