With wide spread of facial plastic reconstructive surgery, normative anthropometric database plays an important role in diagnosis such as determining the location, size, and the extent of deformity. It also provides essential information in determining a treatment plan, and playing an important role in showing the difference between pre- and post-operative data.(7, 8) Conventionally, the nasal profile is measured through a photograph, which is done manually by landmarks. Therefore, there might be errors in the repeated measurement. In addition, it is a time-consuming work.(7) It also has limitation in illustrating 3D structures because a 2D form cannot evaluate facial depth or shape.(9) 2D photographs have another limitation in that results may vary depending on head position or changes of setting.(2) To overcome these limitations, various techniques with a 3D anthropometric approach have been introduced. For the rhinoplasty, 3D imaging technique plays an important role, and is widely used by plastic surgeons. However, there has been no universally accepted platform, nowadays.(2, 10)
There have been several studies about three-dimensional imaging. Van Heerbeek et al. have evaluated whether 3D imaging is capable of and useful for measuring and objectifying rhinoplasty results.(11) According to Zogheib et al., 3D imaging could enable angular measurement of human face as much as a photograph.(12) Through these current studies, 3D imaging could be used to study whether surgical techniques have the desired effect on the nose.
In this study, we investigated reproducibility of conventional 2D photography and 3D imaging techniques based on their inter- and intra-rater reliability for four angular parameters. Results of this study revealed that all inter- and intra-rater reliability of both imaging techniques showed intraclass correlation coefficient values higher than 0.75, meaning that both 2D photograph and 3D imaging had excellent reproducibility. Hence, both conventional 2D photography and 3D imaging are feasible anthropometric methods for measuring external nasal angles.
The authors also compared reliability of both imaging methods. Comparing the reliability of nasal angular parameters, we found that 2D photography showed significantly higher reliability than 3D imaging for the nasofacial angular parameter. For the other three angular parameters, they showed no significant difference. we infer that error occurs when setting and correcting the landmarks on 3D images because correcting landmarks on 3D structure were more complicated than 2D image. Because, landmarks can be placed at more various locations in the 3D image, than in 2D photograph. Errors are more likely to occur when the landmarks are set by an unexperienced researcher. The nasofacial angle is set through the intersection with a glabella-pogonion line as well as a nasion-pronasale line. The pogonion is more planar structure than other landmarks, which suggests that errors can occur more when correcting the pogonion in a 3D image than in a 2D image.(13)
Aside from this point, 3D assessment of facial anthropometry still has its own advantages. Lekakis et al. have described several advantage of 3D imaging, stating that 3D images offer an excellent patient teaching tool.(1) Additionally, Honrado and Larrabee et al. have mentioned that 3D imaging will help surgeons perform surgical planning and assess the outcome with increased understanding of structures.(9)
As a limitation of this study, we didn’t take into account the experience of the researcher in setting or correcting the landmark, which means if experienced researchers performed this procedure, the reliability might be different. Another limitation was that our study was designed only as an angular study of external nose because there was no comparable value of real nasal anthropometric parameter.
In summary, 2D and 3D imaging showed high reliability for all angular parameters, which did not show a significant difference in reliability except for the nasofacial angle. The authors thought that there might be technical errors in the assessment of nasofacial angular parameter of 3D imaging. However, 3D imaging has its own advantages that is easy to explain the images to the patients and is easy to get the its anthropometric results repeatedly. The authors suggest that both 2D photography and 3D imaging in anthropometric technique for nasal angles are reliable and complementary each other. Further studies and technological development are needed to improve the accuracy and reliability of the results.