3D Models, Cutting Guides and Augmented Reality in Plastic and Maxillofacial Surgery

Since the work of Sushruta in India in the 5th century B.C., facial plastic surgery has always used fabric or paper guides as aids in surgical reconstruction techniques. Later, three-dimensional (3D) molds were used, with a gain in precision. In the last 20 years, thanks to computer-aided technologies, the guides used for craniomaxillofacial bone reconstruction have been improved in terms of precision, anticipation, symmetry, flexibility, speed, reproducibility, etc. Furthermore, over the last five years, 3D printers have become directly accessible in surgery departments, so that today they are part of the landscape. Our department at Henri Mondor Hospital even has a special room dedicated to this technology.
With computer-aided technologies, we can create customized medical devices based on our patients’ radiological data, which become a key part of the surgical procedure. They are used in particular to make cutting guides for free bone flaps. Thanks to these technologies, we can easily transform straight shapes, such as a fibular flap, into complex three-dimensional structures, such as a mandible. They also make it possible to create drilling templates for dental implants required for oral rehabilitation, and for extra-oral implants that are used for attaching facial prostheses, which are themselves computer designed. We can use computer tools for planning the resection margins of invasive bone tumors and for making adapted cutting guides, which enable the surgeon to have a more precise understanding of the extent of the tumors when performing surgery to remove them. Lastly, 3D models allow us to better understand certain complex facial deformations and even simulate difficult surgical interventions – which is useful for staff discussions and to help patients understand the objective of their surgery. All of the above is not easy to accomplish using bi-dimensional (2D) or 3D images on a computer screen. Moreover, when it comes to teaching interns, the educational value of 3D models should not be underestimated. Ultimately, when the time comes to operate, what we will have in our hands is indeed a palpable 3D structure. We essentially possess a kind of tactile memory that it would be a shame not to take advantage of, especially when it can make all the difference in certain difficult cases.
At times, these guides cannot be optimally positioned on a rigid bone surface due to soft tissue fibrosis, or another specific local condition, in which case they are not suited to the task at hand. After plaster molds, followed by digitally generated resin models, we now have a third option: the augmented reality virtual guide. This could be a solution of choice, opening the door to a new sensory world free of the limitations of 3D printing. Although this technology is still in its infancy, it seems promising.