A novel method for determining nasion and pronasale points in preoperative rhinoplasty simulation: Golden triangle

The nose, situated centrally on the face and one of the most prominent facial features, has a significant impact on facial characteristics. Rhinoplasty, the process of reshaping the nose, stands out as one of the most commonly performed procedures in aesthetic surgery due to its substantial effect on facial perception. In rhinoplasty planning, whose preferences should be considered, which points should be focused on, and what methods should be applied during planning and the procedure? These questions have guided the historical development of rhinoplasty and the maturation of rhinoplasty literature. This thesis aims to use the geometric golden triangle in rhinoplasty planning to systematically and comprehensively create a new method primarily through the manipulation of the nasofacial angle. It also seeks to prove the method's compliance with and validity against aesthetic angles and proportions, as well as determine the level of aesthetic appreciation in simulation images. Material and Methods A total of 49 rhinoplasty candidates aged between 18-30 were invited to the study, and after excluding those who met the exclusion criteria, 30 female patients were included in the study. The images were captured in RAW format using an iPhone 15 ProMax (Apple Inc., California, USA) with a 35mm lens and camera flash, positioned at a distance of 30 cm against a black background, with the objective-face distance set at 2 meters from the right profile. The captured images were analyzed using the golden triangle method in the GeoGebra Geometry software (version 6.0.840, International GeoGebra Institute) to determine guide points through manipulation of the nasofacial angle primarily, enabling the identification of pronasale and nasion points. Rhinoplasty simulations were then performed in Adobe Photoshop 2024 (version 25.7.0, Adobe Inc., California, USA) based on these guide points. To assess the success of the method, the pre- and post-simulation satisfaction levels of 30 patients whose images were taken and 20 surgeons who completed the survey (with an annual rhinoplasty case load of 50 or more) were evaluated through survey questions regarding the patients' perspectives on rhinoplasty and planning, as well as technical assessments by the surgeons on vertical radix level, radix height, rotation, and projection in the images. Measurement data covering facial aesthetic angles and ratios in the pre- and post-simulation images were determined using the Geogebra application. These include: total facial convexity angle, facial convexity angle, nasofrontal angle, nasofacial angle, nasomental angle, nazolabial angle, nasal base widening, nasal tip (septodorsal) angle, columella-lobular angle, nasal/midface length ratio, nasal projection/nasal length ratio, Powell-Humphrey ratio, Goode ratio, Crumley-Lanser 1 ratio, and Crumley-Lanser 2 ratio. The collected data were analyzed using the R statistical software (Wenables, Simith, and R Development Core Team, 2002). Throughout the research process, a significance level of p < .05 was adopted. This means that the results obtained were statistically significant with 95% confidence. Results As a result of the study, the average VAS rating scores of patients (n:30) and surgeons (n:20) for pre-simulation images (n:30) with Golden Triangle method in rhinoplasty simulation were evaluated as 41.3 (22.6-64.1) and 32.8 (19.4-45.8) out of 100, respectively. The average VAS rating scores of patients and surgeons for simulation images were evaluated as 81.9 (76.3-89) and 73.2 (63.2 and 78.6) out of 100, respectively. When comparing the rating scores of surgeons and patients, high correlations were observed in both pre-simulation (r:0.86) and simulation (r:0.80) situations. However, it was found that surgeons rated both pre-simulation and simulation images 8.7 and 8.5 points lower out of 100 compared to patients. When the internal consistency of patient and surgeon evaluators was examined, the ICC value for patients was 0.48 and 0.45 for pre-simulation and simulation, respectively; for surgeons, it was determined as 0.54 and 0.72. An increase of 40 points was observed in average rating scores in both evaluator groups after simulation. In technical evaluations by surgeons, common opinions were determined by taking the mode value of the views of 20 surgeons, where vertical radix level 29 out of 30, radix height 28/30, projection 29/30, and rotation 29/30 were observed ideally in simlution images of the patients. When the relationship between the ideal responses and surgeon simulation VAS evaluations was examined in these technical assessments, correlation coefficients of 0.44, 0.67, 0.51, 0.49 were determined respectively (p < .0001). When comparing average values of the angle and ratio measurements of patient images before and after simulation, increases were found in nasofacial angle (29°-32°), nasal base angle (99°-106°), nasal projection/nasal length ratio (0.61-0.64), and Goode ratio (0.59-0.61) compared to pre-simulation, which were statistically significant (p<0.05). Decreases were observed in nasofrontal angle (147°-142°), nasal length/midface length ratio (0.69-0.66), Powell Humphrey ratio (3-2.8), Crumley Lanser 1 (3.64-3.45), which were statistically significant (p<0.05). Significant increase was only observed in nasal tip angle (79.5°-82.2°) when examining measurements of 9 patients with the lower and higher average scores in surgeon VAS ratings for simulation images (p<0.05). According to correlation analysis results, Crumley Lanser 2 (r: 0.38, p: 0.038) and total facial convexity angle (r: 0.37, p: 0.041) showed statistically significant positive correlations. A negative and statistically significant correlation was found between nasolabial angle and VAS-A (r: -0.38, p: 0.037). No significant correlations were found in surgeon simulation VAS evaluations. When the surgeon VAS scores and measurement values of the group consisting of 60 images (before and after simulation) were examined, nasofacial angle (r: 0.58, p: 0.000), nasal base angle (r: 0.38, p: 0.003), Goode Ratio (r: 0.37, p: 0.003), nasal projection/nasal length (r: 0.31, p: 0.015) measurements showed statistically significant and positive correlations with VAS, while nasofrontal angle (r: -0.61, p: 0.000), Powell Humphrey (r: -0.39, p: 0.002), nasal length/midface length (r: -0.36, p: 0.004) measurements showed statistically significant and negative correlations with VAS. When examining patient survey data, the average age of participants was 26 (21-30), with an education level of 73% graduate and 23% postgraduate. 53% of patients examine rhinoplasty outcomes very frequently, while 17% do so frequently. They have expectations for both aesthetic appearance (90%) and functionality (92%) from nose surgery. 73.3% agree with the statement "I trust the doctor's sense of aesthetics in planning." and 90% agree with "My own sense of aesthetics is paramount." All patients agree that simulation enhances patient-doctor communication. 90% of patients expect the simulation image to promise a nearly result, while the remaining 10% expect it to promise the exactly same result. When the relationship between survey questions and pre-simulation patient nasal aesthetic satisfaction level (VAS-A) evaluations was examined with logistic regression analysis, for the question "I examine doctors' post-operative results sharing with the idea of having a nose aesthetic surgery" , the effects on VAS scores among the responses "Rarely" (β: 3.354, p < 0.001), "Sometimes" (β: 3.474, p < 0.001), "Often" (β : 4.063, p < 0.001) have continued to increase, and the highest effect was observed in the "Often" responses. In the category "Very Often" (β: 1.024, p: 0.028), a positive effect has shown a decrease. The response "I expect it promises the exactly same result" (β: -1.8761, p < 0.001) for the statement "The result created with pre-surgery simulation is related to my post-surgery result" has shown a negative and significant effect on VAS. Discussion When the differences in correlation levels within the surgeon and patient groups and the differences in VAS ratings between them are examined, it is thought that surgeons give more compatible ratings with their own groups due to their mastery of training and rhinoplasty principles. Surgeons may show lower satisfaction levels in pre-simulation conditions, i.e., in natural images, by detecting deformities better with their professional experience and trained eyes, which may lead to a lower level of satisfaction compared to patients, as they may think that the existing image could be better in simulation images, resulting in lower satisfaction levels. Pre- and post-simulation VAS scores, the increase in VAS scores after simulation, and the level of harmony in the evaluator group support the literature data. In some studies in the literature, unlike our study, the satisfaction level of the surgeon group was found to be higher compared to the patient group. Based on the common views questioned in the surgeon survey, it can be said that this technique provides the ideal level in four parameters (rotation, projection, radix height, and vertical radix level) in at least 93 out of 100 patients in rhinoplasty planning. The Golden Triangle simulation method increases the level of satisfaction and also provides ideal levels in technical parameters. It has been observed that aesthetic perspective and proportions in post-simulation images conform more to the reference ranges in the literature, and the measurement intervals have decreased compared to pre-simulation. This increase in conformity and decrease in variations and approaching ideal values suggest that the method shows similar success in individuals with different facial angles and proportions. The Nasolabial Angle close to or exceeding the upper limit of the reference range of 95°-115° indicates that noses with excessive rotation receive lower VAS-A scores, while images closer to the upper limit in the evaluation of total facial convexity (134.5°-143.5°) are associated with higher VAS scores. As Nose Projection increases relative to glabella and pogonion, the Total Facial Convexity Angle decreases, so it can be assumed that noses that are closer to or excessively projected towards the upper limit are evaluated with lower satisfaction. A positive and statistically significant correlation was found between Crumley Lanser 2 and VAS-A, indicating that surgeons rate images with less nasal over-projection based on preoperative patient assessment of midface and lower face length and the vertical position of the alar crease (i.e., based on midface projection) with higher satisfaction levels. These analyses have shown that in the pre-simulation images in our research group, as rotation and projection ideal values approach the upper limits, the surgeon's satisfaction level naturally decreases. In our research, we found that the Nasal Tip Angle was approximately 82° in simulated images with higher VAS-B scores, ranging from 78° to 85°. Therefore, it may be beneficial to set the Nasal Tip Angle during rhinoplasty planning closer to the upper end of the Farkas reference range (73°-81°), around 82°, to potentially enhance pleasantness. When the relationships between 60 images (pre-simulation and simulation images together) and surgeon VAS scores were examined; it was more likely to observe higher VAS scores for nasofacial angle (32°-35°), nasal base inclination angle (105°-110°), and Goode ratio at upper reference values (in the range of 0.6-0.63). As the Nasofrontal Angle approaches 140° and the Powell Humphrey ratio decreases towards 2.8-2.7, it contributes to achieving high VAS scores. The lower limit of the nasofrontal angle observed in the literature in the Turkish population is 136°-149 degrees, accordingly, noses characterized by a clear radix depth, which enhances midface depth like in "High Ramp Concept ", are considered to have higher levels of attractiveness. Although ideal values of 2.8-3 levels have been shown in the literature when examining Powell-Humphrey data, noses with projection ratios lower than the upper lip, such as the suggested 2.8 level by Powell Humphrey and noses with values close to the lower end, are evaluated with higher levels of attractiveness. When looking at the relationship between the frequency of following rhinoplasty surgeons after surgery shares, it was observed that while the VAS rating scores increased in the 'rarely'-'often'-'sometimes' responses, in individuals who follow 'very often', the rating score levels decreased acutely compared to other categories Based on this, it can be said that the visual exposure beyond a certain level in following shares increases selectivity and detail in perception, creating negative effects on the pleasantness. Participants who expect the exactly same result of the simulation image from the surgeon were observed to be lower VAS raters than others. These participants may score the pre-simulation images lower due to being more perfectionist with higher expectations. Conclusion The rhinoplasty simulation using the "Golden Triangle" method ensures a significant increase in pre- and post-simulation visual appeal for young female rhinoplasty candidates with different facial types and facial angles-proportions, consistent with the literature. Similarly, a high increase in appeal is observed in the surgeon evaluator group.It is a low-cost, consistent, and reliable method for planning rhinoplasty surgeries that achieves the ideal reference values of facial and nasal angles-proportions defined in the literature and provides the common ideal perspective of surgical technical evaluations regarding the radix-tip. This method offers an easy and comprehensive rhinoplasty planning technique for inexperienced young surgeons. By adopting a holistic approach to the face, this study provides a valuable contribution to the literature in compiling and interpreting the harmony and proportions that are prominent in the technical assessment and planning of rhinoplasty. Keywords: Rhinoplasty Planning; Nasion; Pronasale; Golden Triangle; Preoperative Rhinoplasty Simulation; Visual Analog Scale; Nose Beauty İdeal Nose.