3D printing in orthopedics. Part 2

By 20 June 2016Medicine

So far we discussed only the “out of OR” use of 3D printing, now it is time to get our hands dirty.

Surgical instruments

The most common application of rapid prototyping for surgical instruments is guides creation. A surgeon facing complex procedure or one that requires high precision would first accurately measure patient’s anatomy and design a tool on it based on a 3D reconstruction. Such instrument will be patient specific and easy to position. It will guide other surgical instruments like drills or saws in a way that will assure a surgeon sticks to a plan. There are a few demonstrations of such procedures online. One of those is a story of a woman with a complex fracture of her fore-arm. She regains full mobility after her doctor performed surgery with customized guides what otherwise would not be possible. OptiNav faced the idea of employing rapid prototyping in guides creation. Our software Bone Extractor and Guider Creator are dedicated for orthopedists to plan hip resurfacing. The first module allows extracting bone tissue from a CT scan with the possibility to separate a femur from a pelvis. The obtained model could be printed for procedure planning or loaded to the second module for digital estimation of correct drill axis. A guide will then be automatically generated and printed. It will assure proper drill through a femur neck. The first module is already available for testing.

In maxillofacial surgery, such guides are often used to constrain operative placement to a particular area. Such guides are already typical approach with mandibular reconstruction where they assure correct fibula resection and positioning[1]

Use of 3D printed guides, compared to conventional instruments, resulted in better-positioned implants. This, in turn, can lead to increased implant longevity and less side effects for patients.

Another approach is to print single use standard surgical instruments. The goal here is to provide access to cheap tools, which would not require sterilization, and could be used in places where providing them is restricted. A perfect example here is a recent research in how to provide surgical equipment on long-duration space missions. Another studied purpose is to provide surgical instruments to underserved or less developed parts of the world. Important factor examined was per tool price, sterilization requirements and durability. As they found out, such approach may reduce the cost to 1/10 of standard price, and production conditions assure the sterile state of created tools[2].

Implants and prosthesis

Now, we have reached the most promising application of 3D printing in medicine.

Nowadays, the market offers a wide range of prosthetics and implanted devices that have for their purpose to replace, support or enhance biological structures functionality. Most treatments may be conducted with use of standard implants or prosthesis, but there are cases when such approach is impossible. For those cases, patient specific solutions are required, e.g. a patient in Hampshire is given a customized 3D printed hip implant. In cranioplastic surgery, patient specific plates for facial reconstruction are created based on CT imaging. It provides well-fitting and more aesthetic implants that retain patient’s anatomy. With a patient’s consult, the shape of the prosthesis can be digitally manipulated, printed and fitted onto a patient so that final result meets expectation[3].

Rapid prototyping may also assist surgeons when trying to treat conditions that have no standard treatment assigned. Such case occurred when a few month old baby with a rare condition (tracheomalacia) got a chance of survival by the outstanding invention of his doctor who designed and printed a specific for him bioresorbable implant allowing the baby to breathe freely.

More futuristic vision is that about printing entire organs with true living cells. Although this technology is still under development some amazing use cases are already published including:

  • 3D cell printing with introducing modifications to a standard HP inkjet[4],

  • a transplantable kidney 3D printed[5],

  • a successfully implanted 3D printed bladder[6],

  • skin grafts[7].

Some of these cases are generated using actual deposition of bioink (stem cells) by a printer onto thermosensitive, biodegradable matrices (inkjet print)[8]. Others require laser assistance or extrusion methods that are elaborately described by Christian Mandrycky et al.[4]. There is also method of organ “printing” created by applying cells to 3D printed biodegradable scaffolds[9]. Although no successful organ print was found concerning orthopedics, these methods have applications beyond those most exciting products mentioned above beginning with vessels cardiac valves, neuronal tissues, ending with bone, cartilage and muscles which potentially have an impact on orthopedics[4]. There also is scope for using the technology in scaffold construction impregnated with antibiotics to function as drug delivery system (DDS) i.e. in spinal tuberculosis[10]. Such solutions can increase efficacy and decrease risk of adverse reactions by making drug delivery patient-customized.

Conclusion

Rapid prototyping offers a broad range of applications in orthopedics. As the subject is broad, there is no possibility to discuss deeply all aspects of this technology used in medicine. For everyone who already caught the spark of interest in the subject there are a few videos to start your personal search.

Bibliography

  1. Levine, J.P. et al., (2012), “Computer-Aided Design and Manufacturing in Craniomaxillofacial Surgery: The New State of the Art”, Journal of Craniofacial Surgery, 23(1), pp. 288-293

  2. Rankin T.M. et al., (2015), “Three-Dimensional Printing Surgical Instruments: Are We There yet?”, Journal of Surgical Research, 189(2), pp.193-197

  3. Bum-Joon, K. et al., (2012), “Customized Cranioplasty Implants Using Three-Dimensional Printers and Polymethyl-Methacrylate Casting.” Journal of Korean Neurosurgical Society 52(6), pp. 541–546

  4. Mandrycky, Ch. Et al, (2015), “3D Bioprinting for Engineering Complex Tissues”, Biotechnology Advances

  5. Atala, A., (2011), Printing A Human Kidney , Available from: https://www.ted.com/talks/anthony_atala_printing_a_human_kidney?language=en, (accessed: 27/04/16)

  6. 3D Printer and 3d Printing News, (2012), Future of Medicine: 3D-Printing New 0rgans, Available from: http://www.3ders.org/articles/20120629-future-of-medicine-3d-printing-new-organs.html, (accessed: 27/04/16)

  7. Maynard, J., (2016), 3D-Printed Human Skin Could Revolutionize Medicine and Cosmetics, Available from: http://www.techtimes.com/articles/63678/20150625/human-skin-produced-3d-printers-revolutionize-medicine-cosmetics.htm, (accessed: 27/04/16)

  8. Boland, T. et al., (2003), “Cell and Organ Printing 2: Fusion of Cell Aggregates in Three-Dimensional Gels”, Anat Rec A Discov Mol Cell Evol Biol, 272(2), pp. 497-502

  9. Cox, S.C. et al., (2015), “3D printing of Porous Hydroxyapatite Scaffolds Intended for Use in Bone Tissue Tngineering Applications”, Materials Science and Engineering, 47(1), pp. 237–247

  10. Dong, J. et al, (2014), “Novel Alternative Therapy for Spinal Tuberculosis During Surgery: Reconstructing with Anti-Tuberculosis Bioactivity Implants”, Expert Opinion on Drug Delivery, 11(3), pp. 299-305


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