Application of digital technology in nasal reconstruction

Yidan Sun, Zhenmin Zhao, Yang An

Department of Plastic Surgery, Peking University Third Hospital, Beijing 100191, China

Keywords:Nasal reconstruction Digital technology Computer-aided design/manufacturing Three-dimensional printing

ABSTRACT Nasal defects are facial defects caused by trauma,tumors,or congenital diseases that seriously damage a patient’s physical and mental health.Nasal defects, from skin defects to total nasal defects, require surgical repair and reconstruction to restore the appearance and function of the nose, which have always been challenges for rhinoplasty.The development of digital technology has increased the possibility of nasal reconstruction.Digital technology is involved in the preoperative,intraoperative,and postoperative stages of nasal construction and is of great significance in improving the effect of this surgery.This article reviews the application of major digital technologies, including three-dimensional (3D) imaging technology, computer-assisted surgical navigation, and3D printing, in nasal reconstruction and discusses the shortcomings of the current application of digital technology.

1.Introduction

Nasal defects are facial defects caused by trauma, facial tumors, infections, and congenital diseases that seriously affect patients’ appearance.The use of skin grafts and flaps to build a natural nose while preserving the nasal function has always been the focus of and difficulty in rhinoplasty.The discovery of the three-layer structure of the nose—internal lining, structural grafts, and external covering—and the proposal of the nasal esthetic subunit laid the foundation for nasal reconstruction1,2(Fig.1).Based on these theories and practical experience, plastic surgeons have summarized different reconstruction methods for nasal defects of different portions, sizes, and depths3,4(Fig.2).However,the precision of complex nasal reconstruction,such as semi-nasal reconstruction and total nasal reconstruction,especially when cartilage reconstruction is involved, is still technically challenging.The application of digital technology in rhinoplasty has led to new ideas and methods for complex nasal reconstruction surgery.Digital technology can collect different information using certain equipment,convert it into digital information, and then perform calculations and processing to obtain solutions for medical problems.In 1983, Hilger et al.5first used computer image technology for the morphological measurement and structural analysis of rhinoplasty and established an image measurement system for preoperative and postoperative evaluation.Since then, surgeons have gradually explored the wider application possibilities of digital technology in nasal reconstruction.As three-dimensional (3D)printing technology became increasingly widespread in the 1990s,surgeons gradually discovered that 3D printing is an effective technology for preoperative simulations and making personalized prostheses and then applied this technology to nasal reconstruction.According to existing reports, a more precise and personalized nasal reconstruction can be achieved through digital technology.Currently, 3D reconstruction/imaging technology, computer-aided surgical navigation, and 3D printing technology are widely used in nasal reconstruction.In addition,4D technology and artificial intelligence have also been used in preliminary clinical applications.

Fig.1. Nasal esthetic subunits.

Fig.2. Reconstruction methods of different subunits.

2.3D reconstruction/imaging technology

3D reconstruction/imaging technology plays an important role in medical imaging.Image acquisition methods can be divided into contact and noncontact methods.Currently,most image acquisition methods are noncontact ones, mainly including CT 3D reconstruction, stereo photography scanning, and laser scanning.This technology can obtain 3D information that can better reflect the actual situation of a patient’s nose than 2D plane information and then perform measurements and surgical simulation.To date,it has been used in nasal reconstruction for preoperative consultation and evaluation, simulation of visual surgery,postoperative efficacy evaluation and follow-up, and so on.6At present,the main method for obtaining 3D images remains CT reconstruction.CT reconstruction can be used to evaluate a patient’s nasal bone and nasal septum and has become an important part of preoperative evaluation.Graviero et al.7believe that three-dimensional reconstruction (3D-CT)volume-rendering imaging technology can display the morphology of the nasal bone and cartilage and evaluate the structure of the nasal pyramid,which allows for better nasal structure reconstruction at the level of the valve.In addition to morphological evaluation, CT reconstruction can also measure nasal function and provide surgical guidance from other aspects.Rhee et al.8created a digital model using CT images to measure nasal airway resistance during septoplasty.They also measured the improvement in nasal airway resistance through virtual surgery and guided preoperative plans accordingly.Moreover, nasal reconstruction requires external skin reconstruction.Accurate skin reconstruction templates are particularly important,especially for semi-nasal defects or total nasal defects.The application of facial surface 3D scanning technology can help surgeons obtain the 3D stereolithography data of a patient’s nose and establish an intraoperative template.Once an accurate 3D model is obtained,a 2D template can be generated,and the required skin range can be directly outlined on the donor site.9Brower et al.10reported a case of semi-nasal reconstruction using this technology to perform preoperative virtual surgery and designed a cutting guide to facilitate skin flap acquisition.This technique has proven to be applicable to other operations that require complex flap designs to reconstruct anatomical structures.For instance,Zeng et al.11used this technique for total nasal reconstruction and achieved satisfactory clinical results (Fig.3).

Fig.3. Estimation of the required flap size through virtual surgery technology.First, the patient’s 3D scan information is obtained and matched with the database to construct a 3D model.Thereafter, the 3D model is transformed into a flat 2D model using a dimensionality reduction software.Finally,these models are obtained through 3D printing and placed on the patient’s forehead for comparison.

In addition, 3D imaging technology can assist in surgical effect evaluation,doctor-patient communication,and postoperative follow-up.Based on the preoperative and postoperative 3D imaging results,doctors can measure the esthetic landmark points and the esthetic linear distance and obtain change values before and after surgery.Thus, patients can clearly understand the change in the nasal shape and objectively evaluate the effect of the operation.The development of these tools has provided an accurate and reliable evaluation system for rhinoplasty.12Peters et al.13applied this technique to nasal reconstruction.They evaluated the surgical effect and scar size of forehead flap nasal reconstruction using 3D imaging.This not only promoted better communication between doctors and patients, but also provided a basis for further scientific research.

3.Computer-aided surgical navigation

3D imaging information can not only help in preoperative evaluation,but also help in the construction of a personalized model for precise guidance during surgery.Surgical navigation technology is mainly composed of three parts: imaging diagnosis and the positioning of the device and intraoperative probe, which can transmit spatial position information during the operation and display the position of the lesion.This technology is widely used in rhinoplasty, especially in nasal reconstruction surgery.Since a surgeon needs to accurately restore the multilayered 3D structure of the nose during nasal reconstruction surgery and pay attention to scar contracture and asymmetric healing, an intraoperative anatomical structure reference is often indispensable.Doctors use 3D models to perform virtual osteotomy and design intraoperative guides for nasal reconstruction.Therefore, surgeons can evaluate the nose contour and key anatomical positions continuously during the operation, which can improve the accuracy of the operation and help obtain a satisfactory nasal shape.14,15When encountering lateral wall defects, Yen et al.16used a 3D model to design the forehead flap and cartilage shape, printed the 3D guide, and used it for intraoperative guidance.Indeed,this method has been proven to significantly optimize the symmetry and esthetic structure of the nose.Byrne17first used 3D laser scanning and rapid prototyping technology to construct a nasal structure guide for the repair of rigid cartilage scaffolds for semi-nasal and total nasal reconstructions with more severe damage to the nasal structure.Later, Sultan18also used surface laser 3D data to construct a patient’s nasal prototype guide to evaluate the structure during the operation.Zarrabi et al.19used 3D models to assist in the designing of costal cartilage grafts and nasal guides,which also achieved satisfactory clinical results.According to previous reports, 3D guide technology can assist the surgical incision approach, reduce the operation time, and improve a patient’s treatment effect.However, the surgical guide is designed based on preoperative data and lacks intraoperative real-time data and thus has certain limitations when the intraoperative situation changes.Augmented reality, a technology that superimposes a computer-generated virtual scene on an existing reality scene,can realize real-time guidance of skin flap formation and precise reconstruction of the nasal shape and has broad clinical prospects.20

4.3D printing

3D printing is a technology that emerged in the 1970s and has now been widely used in the medical field.Since 1990,the application of 3D printing in rhinoplasty became increasingly extensive.In the field of nasal reconstruction, 3D printing mainly has roles in the following aspects: (1) assisting in preoperative simulation, (2) preparation of personalized grafts, and (3) designing of nasal prostheses.Assistance in preoperative simulation means that 3D printing can help in surgical navigation based on 3D images,as mentioned above.The construction of personalized grafts can be considered to bring new vitality to nasal reconstruction.During nasal reconstruction, especially complex reconstruction, grafts are often required as structural support.Autologous cartilage transplantation remains the primary method of modern rhinoplasty.The residual septal cartilage and ear cartilage can be used for small defects.For larger reconstructions, the costal cartilage is an ideal donor material.The acquisition of the cartilage often causes pain to the patient and may lead to infection, rejection, and complications in the donor site.Customizing personalized artificial or biological grafts through 3D printing can solve this problem well.Practically,these grafts can be used as structural scaffolds for complex nasal defects and have good prospects for septoplasty and nasal reconstruction.21In septoplasty,large (＞2 cm) or irregular perforations are clinically difficult to repair,and the recurrence rate is high.The personalized buttons designed by 3D printing can repair perforations, solve the patient’s clinical symptoms,and have been reported to have good biocompatibility and mechanical properties.22,23For subtotal reconstruction, Walton et al.24created a 3D-printed porous polyethylene scaffold and placed it on the right radial forearm to construct a replacement nose.This method is used to treat subtotal nasal defects after the recurrence of basal cell carcinoma and has obtained good functional and esthetic effects.Ziegler et al.25used 3D printing technology to measure the size of a patient’s nose and constructed a prelaminated paramedian forehead flap for subtotal nasal reconstruction, which improved the patients’ appearance.3D printing-assisted reconstruction has also achieved good results in patients with total nasal defects caused by recurrent infections.Qassemyar et al.26established a 3D model based on the patient’s initial CT results,customized a meshed titanium prosthesis, and transplanted it into the thoracodorsal artery perforator flap for integration.Reconstruction was performed 2 months later,and satisfactory clinical results were achieved.Furthermore, 3D printing has the potential to prevent reconstruction complications.For instance,the absence of mucus secretion in the nasal mucosa can lead to nasal stenosis after reconstruction surgery, and 3D-printed nasal stents have solved this problem well as reported.27The current clinical application examples of 3D printing in nasal reconstruction based on existing reports are summarized in Table 1.

Table 1Reported clinical applications of 3D printing in nasal reconstruction surgery.

To avoid transplantation shortcomings such as tissue absorption and deformation, a variety of medical 3D printing materials have been developed, such as silica gel and tetrafluoroethylene, but adverse reactions such as infection and inflammation still occur.283D printing of the biomimetic nasal cartilage with both biocompatibility and mechanical properties has become a current research hotspot.Researchers have deposited biocompatible materials rich in living cells into a predesigned structure through 3D printing.Antibiotics and growth factors or other factors can also be loaded onto this structure for additional effects.29,30Biocompatible biomimetic nasal cartilage can effectively solve the problems of limited materials, infection, and rejection.Briefly, 3D printing technology and cartilage tissue engineering have an irreplaceable application potential in nasal reconstruction(Fig.4).

3D simulation and 3D printing can not only assist in the surgical process, but can also directly help in the design and manufacturing of nasal prostheses.When reconstruction of the nasal cavity is limited by insufficient residual tissue and vascular damage, the prosthesis is a feasible alternative to repair facial defects.Digital technology has reportedly been applied to prosthesis simulation, design, and manufacturing.35Significantly, compared with the traditional manufacturing process, a digitally designed nasal prosthesis showed a better fit and esthetic effect to a certain extent.The participation of digital technology has improved the acceptability of the prosthesis in patients and may make the prosthesis an effective treatment option for the treatment of nasal absence.36,37

5.4D technology and artificial intelligence

With the further development of technology, doctors have also explored the application prospects of advanced technologies such as 4D technology and artificial intelligence in rhinoplasty.In nasal reconstruction, traditional nasal prostheses are mostly fabricated based on static models.The edges of the prosthesis fit poorly with the facial expressions.Yoshioka et al.38established a 4D expression model and created a prosthesis by analyzing the facial expression changes in patients with nasal defects.The prosthesis can maintain marginal sealing when the face changes dynamically.Artificial intelligence has been applied in preoperative simulations.By establishing artificial intelligence modeling, the postoperative effect can be displayed according to the surgeon’s surgical style and esthetic standards, which can obtain more realistic visualization effects.The application of this advanced technique plays a significant role in preoperative evaluation and face-to-face communication between doctors and patients and achieve a more precise and detailed nasal reconstruction surgery.39

In the past few decades,the development of digital technology and 3D printing has provided new ideas for medical progress.Computer-aided technology has been increasingly applied in craniofacial plastic surgery.Nasal reconstruction is crucial for facial esthetics and functional recovery.In summary, the use of digital technology has increased the possibility of nasal reconstruction, enabling surgeons to obtain a virtual design before surgery, guide operations during surgery, and improve surgical accuracy.In addition, the application of digital technology has also increased patient participation in medical treatment and optimized doctor-patient communication.However, as the development of technology brings convenience to medical treatment, corresponding problems also arise: (1) Equipment and facilities are insufficient.Both 3D scanning imaging and CT 3D reconstruction require large-scale equipment, which is time-consuming to operate and leads to large scanning costs, cumbersome procedures, and possible radiation exposure.These shortcomings are not conducive to the efficiency of patients’ medical treatment and limit the popularization of 3D scanning.(2)Accuracy must be improved.Regardless of the postoperative shape simulated by 3D imaging or the 3D printed model, ideal postoperative shapes were simulated based on preoperative images.However, because of the complex nasal structure and the effects of soft tissue deformation, scar healing,and other factors,the accuracy of the postoperative morphologyof the 3D simulation is reduced.40(3) The 3D information database has an insufficient sample size.Many medical institutions have applied digital technology to rhinoplasty and have established a 3D information database.However, the current sample size is still small, and the information sharing of regional databases is insufficient, which reduces the matching accuracy of the nasal shape.Online sharing of databases from various regions can have a more positive impact on the treatment and research of nasal reconstruction in the future.In conclusion, these problems need to be addressed through further technological development and research,and there is still a long way to go for the application of digital technology in nasal reconstruction.

Fig.4. 3D bioprinting of the nasal structure support.Biocompatible materials such as hydrogels and polymers are printed as a scaffold based on the 3D model.Autologous nasal chondrocytes are injected into the scaffold;antibiotics or growth factors can also be added.The 3D biological scaffold is cultured in vitro,and then the biomimetic nasal scaffold can be obtained.

6.Conclusion

In recent years,digital technology has been involved in every aspect of medical treatment and medical research.With regard to the field of rhinoplasty, the application of digital technology meets the goals of esthetics, precision, and individualization required in plastic surgery and improves the efficiency of communication between plastic surgeons and patients.Even though the current digital technology still has some shortcomings, we believe that with the development of science and technology,emerging digital technologies can be applied in personalized nasal reconstruction, which will achieve the perfect restoration of nasal function and shape.

Ethics declarations

Ethics approval and consent to participate

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Authors’contributions

An Y: Conceptualization, Methodology, Writing-Reviewing.Sun Y:Data curation,Writing-Original draft preparation.Zhao Z: Supervision.

Acknowledgments

This study was supported by the Clinical Key Project of the Peking University Third Hospital(grant no.BYSYFY2021005).