Virtual Surgical Planning and Three-Dimensional Printing in Rhinoplasty

Abstract

Recent developments in three-dimensional (3D) imaging technology offer a more comprehensive means of assessing facial features. 3D printing allows for the transition of planning from simply a preoperative tool to an intraoperative device with the use of tools such as 3D-printed cutting guides, marking guides, or positioning guides. With the advent of 3D printing technology, 3D surface images can now be used to generate new medical models, devices, or tools to assist with rhinoplasty during preoperative, intraoperative, and postoperative phases. In the field of rhinoplasty, 3D printing can be applied in three main areas: (1) reference models, (2) surgical guides, and (3) nasal splints. The value of 3D imaging extends far beyond the benefits of “conversion” during a preoperative consultation and has the potential to greatly enhance the overall treatment of rhinoplasty patients with enhanced communication and personalized devices that can be used during surgery and in the postoperative phase.

Photography has played an integral role in the society since it was first invented as a means of documentation for both personal and professional use. Medical photography has played a particularly important role in the field of plastic surgery, serving as a valuable tool for aiding with preoperative planning, postoperative assessment, and patient counseling. ¹ Prior to the development of digitized images, plastic surgeons would simply draw on photographs or other image types (i.e., cephalograms) to help patients visualize surgical possibilities and achieve mutual aesthetic goals. ² Moreover, it has also been common practice for several years for aesthetic surgeons to bring physical copies of photographs to the operating room (OR) to be used as a reference during facial or body procedures.

As result of the digital revolution, conventional film photography has been replaced by digital photography, which now exists in some form in nearly every plastic surgery practice. Whether it be with standard SLR cameras, tablets, or cell phones, two-dimensional (2D) digital photographs can easily be captured and stored to aid at various stages of patient care. Despite the obvious benefit of ease of use, 2D photographs alone provide only a limited amount of data when being applied to facial aesthetics. For example, the face and nose are three-dimensional (3D) structures, with subtle asymmetries and irregularities that can easily be missed by viewing patients in standard 2D views (i.e., frontal, lateral, oblique, and base images of the nose). Moreover, it is quite difficult to obtain true measurements of the nose based on conventional photographs, and requires some form of adjustment to actual size based on measurements of known distances and fixed points on the face, or a ruler incorporated into a life-sized photograph. ¹

Recent developments in 3D imaging technology offer a more comprehensive means of assessing facial features. Unlike standard 2D photography, 3D photographs impart critical information to the surgeon such as contour, geometry, volume, area, and depth. ¹ A major advantage of 3D photography is the technology's ability to take absolute measurements in a life-size manner. With fixed landmarks (manually placed or automated), these 3D images can then be set to a standardized orientation which allows easy comparison with subsequent postoperative images. Additionally, many 3D-capture systems are bundled with computer morphing software, thus providing the additional benefit of being able to simulate results for patients during a consultation. Many surgeons who incorporate 3D simulation into their practice believe that computer simulation improves communication, reduces anxiety, and increases conversion-to-surgery rates.

3D Surface Scanning and Photography

Various types of 3D surface imaging instruments exist, including stereophotogrammetry, Moiré topography, laser scanning, and structured light technology. ³ The earliest form of 3D surface scanning in plastic surgery was applied by Thalmaan using stereophotogrammetry in the 1940s. While the early results from stereophotogrammetry were hard to quantify and did not produce the necessary precision, this work showed potential for 3D surface scanning in the field and its superiority to 2D photography. ¹ The Moiré topography technique was another type of surface scanning system that was used clinically for decades ⁴ but ultimately had limited use in plastic surgery due to its complexity in image processing and user handling. Following this, newer techniques were introduced such as laser scanning, structured light, and others.

In the past two decades, technological developments have made 3D surface imaging more easily integrated into practices through software reengineering and more efficient data analysis. The cost of most 3D imaging systems has significantly decreased over recent years, with current prices closely mimicking those of standard SLR/digital cameras. While computed tomography (CT) and magnetic resonance imaging (MRI) do provide valuable surface data, significant cost and other barriers make their routine use in plastic surgery impractical. The most common, and promising, surface imaging technology used in clinical practice today includes optical-based surface modalities (stereophotogrammetry imaging and structured light imaging systems). The size and cost of these 3D imaging modalities can range greatly, with footprints anywhere from a photo-booth to hand-held cameras, and to an iPad or iPhone. Thus, surgeons interested in incorporating 3D imaging into their practice need to consider various technical aspects such as capture time, ¹ space requirements, accuracy, and validity.

Clinical Applications of 3D Technology for Rhinoplasty

3D Imaging Software

3D Viewing

For decades, 2D computer imaging has been utilized as a means of improving communication during consultations for aesthetic surgery. ⁵ This is particularly relevant for rhinoplasty, which has many unique features such as relatively high patient expectations, increased patient stress, and a wide range of aesthetic “ideals” or goals. The use of 2D photographs during a consultation can be a useful aid to help align patient and surgeon goals. This is true for jointly reviewing the patient's preoperative condition, as well as photos of others (prior patients, or models) to point out unique features, or patient similarities and differences.

The use of 3D images for viewing can offer several distinct advantages relative to conventional 2D images. First, baseline 3D images can be manipulated in real time during a preoperative consultation to highlight various viewpoints. Key landmarks can be identified and discussed, such as the nasolabial angle, nasofrontal angle, the dorsal hump, and the nasal tip. ¹ Notably, these standardized landmarks then allow for distance measurements (surface and direct vector), and also serve as reference points to be able to easily compare results and progression between pre- and postoperative images.

3D Simulation

Presently, 3D morphing is most often applied to the preoperative consultation as a means of increasing patient conversion. However, the inherent value of this technology far exceeds its utility as a simple marketing tool and includes a clinical tool to aid in preoperative planning, intraoperative guidance, and postoperative analysis. Evaluation of rhinoplasty requires multiple key steps in the decision-making process: a well-detailed history, aesthetic assessment, a functional evaluation, and a clear understanding of patient's motivation for surgery. ⁶ Patient morphing software, a tool that simulates the manipulation and deformation of a 3D image, offers unique advantages as a tool for enhanced nasal assessment, operative planning, and patient communication of surgical goals. ⁷

Computer imaging and morphing software can serve as a helpful instrument in patient selection in rhinoplasty. Choosing patients who will be pleased with a particular postoperative outcome relies not only on diagnostic and surgical skills, but also on the ability to effectively communicate clear and credible counseling. The application of morphing software allows the surgeon to clearly delineate the goals and planned results of surgery, the limitations related to surgery, and to illustrate the goals of surgery as improvement over perfection.

An important facet of morphing is the evolution of patients from passive listeners to active contributors by evoking their aesthetic vision and making them actively involved in the rhinoplasty consultation discussion. ⁸ Many patients requesting rhinoplasty desire minor adjustments to their nose rather than a dramatic transformation. ⁹ The desire for minor changes in the nose emphasizes the importance of patient involvement in the decision-making process. The utility of morphing technology extends to the postoperative period by mentally and emotionally preparing the patients with the expected results in advance. ¹⁰ 3D morphing is a sophisticated tool that can reconcile patient and surgeon perspectives.

As computer imaging and morphing software becomes more popular and accessible in practices, potential surgeon concern for usability and technical difficulty is to be expected. Just like any other software tools, a learning curve exists to produce desired, realistic morphed images. However, as the surgeon gains experience in using this technology, the application of this technology can become more seamless. The successful use of morphed simulations in the context of patient consultations requires one to create a realistic and aesthetically pleasing nose, as well as manage patient expectations. In addition to added value to the patient, surgeons themselves can benefit from utilizing morphing software as a means of reviewing their operative plan performing critical self-evaluation. A patient's 3D analysis report, with presumed operative changes and measurements, can easily be made available at the time of surgery as a useful reference. Fig. 1 shows an example of a surgical rhinoplasty report in a preoperative patient.

Fig. 1.

Surgical rhinoplasty report in a preoperative patient.

3D Printing and Rhinoplasty

As noted above, data acquisition, viewing capability, data analysis, and surgical simulation that can be performed with 3D photography far exceed those of conventional 2D photography. While these benefits alone highlight the importance of 3D photography, perhaps the most exciting novelty of 3D imaging in rhinoplasty is the potential ability to use such data to develop patient-specific tools or devices that can improve patient care. With the advent of 3D printing technology, 3D surface images can now be used to generate new medical models, devices, or tools to assist with rhinoplasty during preoperative, intraoperative, and postoperative phases.

Historically, the manufacturing industry relied on “subtractive” techniques to build products by carving out from a block of material. 3D printing, a form of additive manufacturing first described by Charles Hull in 1984, is produced by a layer-by-layer technique that enables more detailed designs and a swifter translation into a physical object. ^{11 12} In the 1990s, the 3D printing industry separated into two areas: one focused on high-end printing for complex models (i.e., medical appliances) and the second focused on printers designed for product development which was more economical. ¹¹ In the field of plastic surgery, 3D printing was primarily first utilized as anatomical references for complex craniomaxillofacial surgery. Patient-specific anatomical models are generated from high-resolution images or scans of the patient's body, such as CT and MRI. ^{13 14}

Soon after the implantation of anatomical models, surgeons and engineers began to develop new approaches to marry 3D printing with virtual surgical planning (VSP). VSP involves computer simulation of a surgical plan in a virtual environment, such as could be applied with facial trauma or maxillofacial surgery. For instance, with specialized 3D software, one could simulate osteotomies in the craniofacial skeleton and then manipulate/move these segments into new locations. 3D printing then provided an opportunity to translate a patient's VSP into the OR. 3D printing allows for the transition of planning from simply a preoperative tool into an intraoperative device with the use of tools such as 3D-printed cutting guides, marking guides, or positioning guides. Today, computer-aided design, VSP, and 3D-manufactured technology are impressive tools with applications that extend well beyond orthognathic and craniofacial reconstruction to reconstructions of the head and neck, extremities, and trunk with all bony, soft-tissue, and aesthetic elements in all spatial dimensions. ^{1 15}

The growth and usability of 3D printing and VSP have created a new opportunity for similar applications in aesthetic surgery. In the field of rhinoplasty, 3D printing can be applied in three main areas: (1) reference models, (2) surgical guides, and (3) nasal splints.

Reference Models

Most rhinoplasty surgeons have 2D patient photographs available as a reference during surgery, either as printed copies or displayed on a computer screen. These images can often be helpful to surgeons as they manipulate the nose, so that subtle anatomical features or changes can easily be appreciated. In addition to baseline images, surgeons may also bring simulated results to display in the OR as a surgical reference. For surgeons who find 2D photographs to be a valuable reference, it would only seem logical that 3D data would provide a superior reference given the added information it provides.

Similar to anatomical models in craniofacial surgery, surgeons now have the ability to not only view 3D images on a screen, but rather easily obtain 3D-printed models (or “anatomical nose models”) to be used as a reference during a procedure. These models are true to size and can range from solid uniform colors to true life-like color-matched 3D models. Baseline or simulated models can be manufactured based on the 3D capture and simulation that was performed during the consultation. An example of a full-size color print of a 3D simulation is shown in Fig. 2 .

Fig. 2.

Full-size color print of a 3D simulation. 3D, three-dimensional.

Surgical Guides

In addition to anatomical reference models (baseline, simulation, etc.) 3D printing affords the opportunity to manufacture guides that can help carry out a surgical plan. Indeed, much of the excitement and adoption of VSP in reconstructive surgery was based on the ability to translate an operative plan in the OR using 3D printing. For instance, with various craniomaxillofacial procedures, surgeons may utilize a 3D-printed guide for “marking” a planned osteotomy, or a “positioning” guide to aid in fixating/establishing new anatomical bony locations.

Currently, similar applications of this technology are being applied for rhinoplasty with the use of marking guides and positioning guides. Of note, these devices can be sterilized and therefore easily utilized throughout the case. Marking guides can be applied to the nose at the start of the procedure to delineate the extent of dorsal reduction that was planned. This marking guide is typically based off of the simulation and, if the markers are left in place, can help surgeons achieve this new dorsal height during the procedure. In addition, the guides can be applied throughout the case and provides a window to compare the new intraoperative dorsal height to the desired height.

Positioning guides have also been described that can be applied during surgery as changes to the nose are performed. Similar to the marking guide, this guide can be continuously referred to, and applied during the cases, to help achieve the simulated result. While various design types have been described for this, the senior author prefers a guide which begins as a transverse “T” at the forehead and extends to the columellar–labial junction. If significant changes to the noses are proposed, the positioning guide will not align with the nose at the start of the case. Only after the desired results are neared during the procedure, will this guide fit properly into position on the noses. An example of positioning guide is shown in place at the start of the case ( Fig. 3 ), as well as at the conclusion of the case after a new tip position was established ( Fig. 4 ). In this patient example, we were aiming for a moderate reduction in dorsal height, with significant de-rotation of her tip position. Of note, our group has found positioning guides to be especially helpful in cases like this where significant changes to tip rotation and projection are desired but can be difficult to assess on table. Interestingly, some rhinoplasty surgeons have relied on devices such as a projectometer to perform these types of measurements to document changes in tip position during a procedure. Relative to a projectometer, 3D-printed guides offer a much easier, more accurate, and patient-specific approach that is linked to the desired, simulated outcome.

Fig. 3.

Positioning guide at start of case.

Fig. 4.

Positioning guide at conclusion of case after new tip position was established.

Nasal Splints

Postoperative edema after rhinoplasty is a common sequalae that can last for several months to years. This can be a significant contributor to patient dissatisfaction due to the delayed visualization of the final aesthetic result. Currently, there is no standard of care for interventions in the postoperative period of rhinoplasty to reduce edema. Surgeons have implemented the use of various approaches including allopathic/homeopathic medications, direct steroid injections, and postsurgical taping to reduce postoperative swelling. One potentially exciting application of 3D printing in rhinoplasty is customized 3D-printed nasal splints. Such splints can be based on either simulated results or postoperative photographs, which can be designed to fit the patient's nose with specific treatment goal in mind. Typically, this splint can be placed immediately following surgery, or during an early postoperative visit after a thermoplastic splint is removed ( Fig. 5 ). A range of nasal splints can also be designed which are progressively smaller and can accommodate (and even expedite) the resolution of edema. The patient's long-term results are shown in Fig. 6 .

Fig. 5.

Postoperative splint.

Fig. 6.

Preoperative and postoperative lateral photographs.

It is also worth noting that 3D-printed nasal splints may provide an opportunity to “mold” the nose in the early postoperative period. Anecdotally, our group has utilized splints in this manner during the early postoperative phase to address early concerns of tip asymmetry/deviation. Future studies are certainly needed to determine the value of 3D splints to achieve successful postoperative molding.

Conclusion

Although 3D imaging has been commonplace for many plastic surgery offices, VSP and 3D printing are novel advancements in our field. 3D technology has revolutionized reconstructive plastic surgery and offers the same opportunity to make a significant impact in the field of cosmetic rhinoplasty. The value of 3D imaging extends far beyond the benefits of “conversion” during a preoperative consultation and has the potential to greatly enhance the overall treatment of rhinoplasty patients with enhanced communication and personalized devices that can be used during surgery and in the postoperative phase.