ANATOMICAL STUDY
The Evaluation of Morphometry of Nasal Bone and Pyriform Aperture Using Multidetector Computed Tomography Neslihan Yüzbaşioğlu, PhD,* Mehmet Tuğrul Yilmaz, BVSc, PhD,† Aynur Emine Çicekcibasi, MD,† Muzaffer Şeker, BVSc, PhD,† and Mehmet Emin Sakarya, MD‡ Introduction: The aim of this study was to measure nasal bone (NB) and pyriform aperture (PA), morphometrically. Besides, the different types of NB and PA were classified and determined the sexual differences. Materials and Methods: Our study was performed on 120 (60 women, 60 men) multidetector computed tomography images obtained from patients who underwent radiologic examination in the Department of Radiology of Meram Faculty of Medicine, Necmettin Erbakan University. The right, left, and median heights of NB; the superior and inferior widths of NB; the width of PA; and the distance between rhinion and anterior nasal spine (as the height of PA) were measured. Frontonasal and internasal angles were also determined. All data were analyzed statistically using Student’s t-test. Results: The other data of men were higher than of women except for the superior and inferior widths of NB and the frontonasal angle. We also determined the ratio of the height of PA to the height of NB on median plane and the ratio of the height of PA to the width of PA. They were found less than 2.0 in 64.2% and 100% of the cases, respectively. The NB and PA were classified into 8 and 7 different types, respectively. Conclusions: The knowledge of the morphometric data and different types of the NB and PA is essential for sex determination, all surgical procedures related to this area, and nasal reconstructions. Key Words: Nasal bone, pyriform aperture, MDCT, morphometry, nasal reconstruction (J Craniofac Surg 2014;25: 2214–2219)
T
he nose is an aesthetically important structure located in the center of facial area. Nasal bone (NB) and pyriform aperture (PA) are the contributory main skeletal factors to create the actual shape of nose.1,2 The NB is surrounded by the frontal bone at the top, frontal process of maxilla at the sides, and PA at the bottom. The From the *Department of Anatomy, School of Medicine, İstanbul Medipol University, İstanbul, Turkey; and Departments of †Anatomy and ‡Radiology, Meram Faculty of Medicine, Necmettin Erbakan University, Konya, Turkey. Received January 13, 2014. Accepted for publication April 23, 2014. Address correspondence and reprint requests to Neslihan Yüzbaşioğlu, Department of Anatomy, School of Medicine, İstanbul Medipol University, Atatürk Bulvari, No 27, 34083 Unkapani-Fatih, İstanbul, Turkey; E-mail: [email protected] The authors report no conflicts of interest. Copyright © 2014 by Mutaz B. Habal, MD ISSN: 1049-2275 DOI: 10.1097/SCS.0000000000001063
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PA, which is usually accepted as a pear-shaped opening, is also surrounded by NB at the top, frontal process of maxilla at the sides, and palatine process of maxilla at the bottom.1,2 The variable dimensions and shapes of NB and PA are important parameters on deciding the anthropologic features of a population because of the differences between ethnic groups.1,3–5 The morphometric values and ratios must be known to be successful in rhinoplasty operations and various osteotomies by plastic and reconstructive surgeons.6 The morphometric evaluation of computerized computed tomography (CT) images provides a unique perspective while evaluating craniomaxillofacial skeleton parameters clinically.6 Three-dimensional computer-aided tomography of NB and PA is a perfect technique obtaining quantitative and objective data.1 To know that the CT data obtained with reliable radiologic methods belong to different age, sex, and ethnicity groups will be very important when deciding on the ideal nose shape at rhinoplasty and solving problems such as NB stenosis.1,6,7 Multidetector CT (MDCT), which was used in this study, is a reliable and noninvasive technique displaying the bone formation in detail with the help of high-resolution and multisection images.8 In recent years, this method has started to be used in anatomic studies to obtain reliable morphometric data.9 In this study, we aimed to determine morphometric data and the various types about NB and PA using MDCT.
MATERIALS AND METHODS After receiving approval from the institutional review board (ref, 2012/96), this study was carried out retrospectively on images of the patients with acute nontraumatic subarachnoid hemorrhage or suspected cerebral aneurysm with symptoms such as headache and cranial neuropathy with MDCT in the Radiology Department of Meram Faculty of Medicine, Necmettin Erbakan University, Konya, Turkey. The images of 120 patients (60 men, 60 women) without history of any cranial trauma, rhinoplasty operation, and remarkable bone deformation were assessed. The MDCT scans were provided with a 64-slice CT scanner (Somatom Sensation 64; Siemens Medical Solutions, Forchheim, Germany). The images were obtained in a neutral supine position, without rotation, flexion, or extension, to provide standardized measurements. The images were imported into the Leonardo Workstation (Vitrea 2; Vital Images, Inc, Minneapolis, MN) and were combined to create three-dimensional reconstructions. All the measurements were obtained by visual estimation of the determined points at an approximate window setting and level setting. The dimensions were measured using three-dimensional volume-rendered images and multiplanar reconstruction images. For accuracy, dot cursors were placed in identical positions on corresponding axial, coronal, and sagittal images for measurement on three-dimensional volumerendered images. The start and end points of the linear measurements of the images were determined with the internal digital caliper tool
The Journal of Craniofacial Surgery • Volume 25, Number 6, November 2014
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
The Journal of Craniofacial Surgery • Volume 25, Number 6, November 2014
The Morphometry of NB and PA Using MDCT
FIGURE 3. The angle between the frontal bone and the NBs. FIGURE 1. The height (right, left, median plane) and width (upper, lower) of NB.
included in the Workstation software. The software (syngommwp VE 30A, syngo VE32B) calculated all of the measurements, which were recorded in centimeters. Nasion, rhinion, anterior nasal spine, and gnathion points were passed from the same sagittal plane to obtain standard measurement points for each patient. The determined parameters from the three-dimensional volumerendered images were as follows: 1. The height of the right and left NB (NBH-R, NBH-L): the distance between right-left frontonasal junction and the lower margin of the same side NB (Fig. 1). 2. The height of NB on median plane (NBH-M): the height of internasal suture (the distance between nasion and rhinion) (Fig. 1). 3. The upper width of NB (NBW-S): the distance between the junction points of nasomaxillary suture with frontonasal suture at both sides (Fig. 1). 4. The lower width of NB (NBW-I): the distance between bottom margins of both sides of NB (Fig. 1). 5. The width of PA (PA-W): the widest distance of PA on transverse plane (Fig. 2). 6. The height of PA (R-ANS): the distance between rhinion and anterior nasal spine (Fig. 2).
In addition, for each patient, the ratio of PA height to NB height on median plane (R-ANS:NBH-M) and the ratio of PA height to PA width (R-ANS:PA-W) have been calculated. Statistical analysis was performed using the Statistical Package for the Social Sciences for Windows, version 13.0 (SPSS, Chicago, IL). Comparisons of the mean data according to sex were analyzed using Student’s t-test. Summary of the data was stated as mean (SD). Statistical significance was defined as P < 0.05.
RESULTS
The determined parameters on the multiplanar reconstruction images were as follows: 1. Frontonasal angle (FN-A): the angle between the frontal bone and NBs on the median plane (Fig. 3). 2. Internasal angle (IN-A): the angle between NBs on the coronal plane after the x and y planes were brought to nasion point (Fig. 4).
In this study, the data (case number, sex, and minimum and maximum age) about the patients were given at Table 1. There were no significant differences between sexes (P > 0.05). We determined differences between sexes for all parameters (P < 0.05) except for NBW-S and R-ANS/NBH-M. In addition, it was observed that the other parameters were higher in men than women except for NBW-S, NBW-I, and FN-A (Table 2). The ratio of R-ANS:NBH-M has been found less than 2.0 on 77 cases (64.2%) and higher than this ratio on 43 cases (35.8%). The ratio of R-ANS: PA-W was also seen below 2.0 on all cases (Table 2). The NBs were classified into 8 categories according to their shapes: Types 1 to 3: an angulation at the lower part of the NB (becoming narrower from sides toward the median plane) and a widening after that (paying attention to the thickness of NB; thick NB is type 1, and thin NB is type 3) (Fig. 5). Types 2 to 6: an angulation at the upper part of the NB (paying attention to the thickness of NB; thick NB is type 2, and thin NB is type 6) (Fig. 5).
FIGURE 2. PA width and height.
FIGURE 4. The angle between NBs.
© 2014 Mutaz B. Habal, MD
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The Journal of Craniofacial Surgery • Volume 25, Number 6, November 2014
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TABLE 1. Number, Sex, and Age of the Patients Sex
n
Age Min
Age Max
Male
60 60 120
15 17 15
82 81 82
Female Combined
Age, Mean (SD) 59.65 (17.21) 56.81 (15.23) 58.23 (16.24)
n, case number; Age Min, age minimum; Age Max, age maximum.
Types 4 to 8: no angulation and nasomaxillary sutures are parallel to each other (paying attention to the thickness of NB; thin NB is type 4, and thick NB is type 8) (Fig. 5). Type 5: an angulation at the midpoint of NB and both NB are thick (Fig. 5). Type 7: no angulation and NB is narrow at the upper part and comes down widening, drawing a triangle (Fig. 5).
The PAs were classified into 7 categories according to their shapes: Pear PA (type 1): wide and round at the lower part, narrowing to the upper part (Fig. 6). Reverse heart PA (type 2): the lower part of PA is below the level of anterior nasal spine (with this feature separated from “drop”) and a continual narrowing to the upper part (with this feature separated from “pear”) (Fig. 7). Rhomboid shape PA (type 3): similar to a rhombus (Fig. 8). Drop PA (type 4): round at the lower part, narrowing gradually coming up to the upper part (with this feature separated from “reverse heart,” as the lower margin does not go down below the level of anterior nasal spine) (with this feature separated from “pear,” as it narrows gradually going to the upper part) (Fig. 9). Oval PA (type 5): pushed inside at the sides and transverse width is almost equal to each other at the upper and lower parts (Fig. 10). Trapezoid PA (type 6): wide lower and narrow upper parts with rectangular shape (Fig. 11). Round PA (type 7): PA is round (Fig. 12). According to the classification of NB types, the most common type was type 2 (26.7%), and the least one was type 7 (3.3%) (Table 3). Types 1 (28.3%) and 2 (26.6%) were the most common types for men and women, respectively. According to the classification of PA types, the most common type was pear type (48.3%), and the least one was trapezoid type (1.6%) (Table 3). The pear type was the most common type for both men (55%) and women (41.6%).
FIGURE 5. The classification of NBs in 8 types according to Lang and Baumeister (1982, obtained from the study of Hwang et al11).
DISCUSSION This study, which was carried out with MDCT, has some crucial advantages such as being applicable on living subjects; being able to classify sexes accurately; the ability to increase the number of subjects; and the evaluation with high-resolution, three-dimensional and multisectional, of all bone structure in detail. In addition, this study is superior to dry bone studies because of accurate sex classification, to cadaver studies because of the minimal tissue draw effect, to panaromic radiographic studies because of realizing the details clearly, and to direct radiographic studies because of the magnification effect. The evaluation of morphometric data and morphologic types of NB and PA is important especially for forensic medicine and forensic dentistry on deciding the sex and ethnical classification. In addition, preoperative evaluation of NB and PA with CT may reveal successful outcomes while planning the maxillofacial procedures by plastic and reconstructive surgeons and otolaryngologists (eg, while choosing the most suitable osteotome in osteotomies).8,11 It is said that the width and shape of PA are major factors in effective nasal breathing.8 It is reported that heating and moisturizing the inhaled air in cold and dry climates can be done with a long nasal passage and a narrow PA. For this reason, the shape of PA is regarded to adapt to geographic region depending on climate conditions.12 The size and shape of NB differ according to racial, sex, and age. In the literature, there were various studies evaluating the differences between races.1,3,10–12 According to Hwang et al,12 NB was almost the same in Korean men compared with German. In Anatolian population, Karadağ et al11 found that the NB height for both sexes was higher than the ones in Korean, German, and black American population. The NB height measured by Karadağ et al11 are higher in Austrian men and lower in women. The NB height measured in our study has been found for both sexes to be lower than in Korean, German, Austrian, and black American populations and also than in Anatolian population in the study of Karadağ et al11 (Table 4). The NB width measured in our study was higher than in Korean population but lower than in German
TABLE 2. Mean Values and SDs of the Parameters for Both Sexes ♂
♀
Combined
Parameters
Min–Max
Mean (SD)
Min–Max
Mean (SD)
Min–Max
NBH-R
1.58–3.45 1.30–2.70 1.56–3.44 0.83–1.64 0.96–2.42 2.01–2.97 2.70–3.92 103°–131° 49°–74° 1.09–2.93 0.95–1.90
2.33 (0.35) 1.87 (0.31) 2.33 (0.36) 1.18 (0.18) 1.43 (0.24) 2.46 (0.21) 3.34 (0.29) 117.93° (5.78°) 60.50° (5.94°) 1.84 (0.38) 1.36 (0.17)
1.59–2.82 1.12 –2.41 1.52–2.79 0.61–1.65 1.01–2.32 1.82–2.91 2.18–3.80 115°–140° 45°–68° 1.16–2.92 0.95–1.87
2.19 (0.28) 1.72 (0.30) 2.18 (0.29) 1.20 (0.19) 1.54 (0.26) 2.33 (0.20) 3.01 (0.30) 124.36° (5.78°) 57° (4.96°) 1.80 (0.40) 1.30 (0.17)
1.58–3.45 1.12–2.70 1.52–3.44 0.61–1.65 0.96–2.42 1.82–2.97 2.18–3.92 103°–140° 45°–74° 1.09–2.93 0.95–1.90
NBH-M NBH-L NBW-S NBW-I PA-W R-ANS FN-A IN-A R-ANS:NBH-M R-ANS:PA-W
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Mean (SD) 2.26 (0.33) 1.80 (0.31) 2.26 (0.33) 1.19 (0.19) 1.48 (0.26) 2.39 (0.22) 3.17 (0.34) 121.15° (6.60°) 58.75° (5.73°) 1.82 (0.39) 1.33 (0.18)
P 0.01 0.01 0.01 0.71 0.02 0.00 0.00 0.00 0.00 0.63 0.04
© 2014 Mutaz B. Habal, MD
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The Journal of Craniofacial Surgery • Volume 25, Number 6, November 2014
FIGURE 6. Pear-type PA.
The Morphometry of NB and PA Using MDCT
FIGURE 10. Oval-type PA.
FIGURE 7. Reverse heart-type PA. FIGURE 11. Trapezoid-type PA.
FIGURE 8. Rhomboid-type PA.
FIGURE 9. Drop-type PA.
population (Table 4). Different from the previous studies, the heigth and width of NB at different parts of the bone were measured in our study. Both right-left heights of NB and height of NB on the median plane were longer in men than in women (Table 2). The upper and lower widths of NB were wider in women than in men (Table 2). According to these results, it can be said that NB was long and narrow in men but short and wide in women. In 2 different studies, it was determined that type 1 was the most common in Brazilian women, men, and Koreans (long and wide NB, narrowing in the center).1,12 Hwang et al12 compared their own study, carried out on Korean subjects, with Lang and Baumeister’s (obtained from the study of Hwang et al12) study on German, which was also carried out without a sex classification. Although the most common NB type was long,wide, and narrowing at the upper part (type 2 in our study) according to Hwang et al,12 it was determined
FIGURE 12. Round-type PA.
© 2014 Mutaz B. Habal, MD
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The Journal of Craniofacial Surgery • Volume 25, Number 6, November 2014
Yüzbaşioğlu et al
TABLE 3. Types and Percentage Distributions of NB and PA Types and Percentages for NB
Sex
Type 1, n (%)
Type 2, n (%)
Type 3, n (%)
Type 4, n (%)
Type 5, n (%)
Types and Percentages for PA Type 6, Type 7, Type 8, n (%) n (%) n (%)
Pear, n (%)
Reverse heart, Rhomboid, Drop, n (%) n (%) n (%)
Male
17 (28.33) 15 (25) 9 (15) 9 (15) 5 (8.33) 2 (3.33) 1 (1.67) 2 (3.33) 33 (55) 6 (10) 1 (1.66) Female 10 (16.67) 16 (26.66) 10 (16.67) 8 (13.33) 6 (10) 3 (5) 3 (5) 4 (6.67) 25 (41.66) 15 (25) 4 (6.66) Combined 27 (22.5) 31 (25.83) 19 (15.83) 17 (14.17) 11 (9.17) 5 (4.17) 4 (3.33) 6 (5) 58 (48.3) 21 (17.5) 5 (4.1)
that the most common was long NB type was narrowing in the center (type 3 in our study) by Lang and Baumeister (obtained from the study of Hwang et al12). The NB was classified into 8 different types in German (Lang and Baumeister, obtained from the study of Hwang et al12). Hwang et al12 have simplified this complex classification method, and NB has been defined under 5 different types. Although type B (types 2 and 6 in our study) was the most common type, type D (type 5 in our study) and type E (types 4 and 8 in our study) have not also been observed in Korean population. Prado et al10 found that type A (types 1 and 3 in our study) in Hwang et al’s12 classification was the most common one in Brazilian population, whereas types D and E were the least observed ones. In our study, NB was classified under 8 categories as in Lang and Baumeister’s (obtained from the study of Hwang et al12). The most common type for NB was type 2, and the least common ones were types 6 and 7. We detected types 2, 1, and 3 mostly and respectively. According to these results, our study bears some resemblance to the studies of both Hwang et al12 and Prado et al.11 In our study, although the R-ANS was larger than in German and Korean populations (Lang and Baumeister, obtained from the study of Hwang et al12), the PA-W was smaller than in Korean population and black race11,13 and larger than in German, Austrian, Anatolian, Korean, white race, and black American populations4,5,12,13 (Lang and Baumeister obtained from the study of Hwang et al12). The PA-W rises 2 times from childhood to adulthood and is said to continue developing even after 20 years old.3 Lang and Baumeister (1982, obtained from the study of Hwang et al12) measured the mean upper width, lower width, and R-ANS, that is, 16.3, 23.6, and 29.1 mm, respectively, in German. In many studies, the upper-lower widths and R-ANS were determined to be wider and higher in men than in women.1,3,5,7,14 However, in male Koreans, the mean upper PA-W was determined to be narrower than in women.12 Hoffman et al13 conducted a race-based evaluation and found out that lower PA-W was wider in blacks.3 In the study of Lopez et al,3 upper PA-W in
Oval, Trapezoid, Round, n (%) n (%) n (%)
7 (11.6) 6 (10) 1 (1.66) 8 (13.33) 3 (5) 1 (1.66) 15 (12.5) 9 (7.5) 2 (1.6)
6 (10) 4 (6.66) 10 (8.3)
blacks has been found meaningfully larger than in white and yellow races. The area of PA has also been reported as an important factor for sex determination.10 In our study, the PA-W was not evaluated in upper and lower parts, and one unique width was measured from the largest level of PA. Both PA-W and R-ANS were significantly larger in men than in women. Although these results were in accordance with the studies of Lee et al1,3, Hommerich and Riegel5, Erdem et al7, and Cantin et al14, it differed from the results of the study of Hwang et al.12 In the study of Ofodile4 on skulls, it was defined that the shape of PA in Western African subjects is oval and in American Indian and Austrian subjects is triangular. In black Americans, a change was observed from triangular to oval. In our study, PA was mostly seen in the pear shape, whereas the trapezoid shape was the rarest one. In addtion, PA types were better classified in detail compared with the previous studies. We determined that the mean FN-A were 117.93° in men and 124.36° in women, and it was consistent with the results of Lang15 (115° in men, 120° in women). The mean FN-A was wider in women than in men. In addition, IN-A was measured in our study different from the previous ones. The mean IN-A was measured as 58.75° (60.50° in men, 57° in women). We think that the data of angles can be used preoperatively. In our study, the R-ANS:NBH-M ratio was detected below 2.0 on 77 cases (64.16%) and over this value on 43 cases (35.83%). The R-ANS:PA-W ratio was detected below 2.0 on all cases. The R-ANS:NBH-M ratio was determined as 1.2 in men and 1.1 in women by Hwang et al11 and 1.2 by Lang and Baumeister (obtained from the study of Hwang et al11) without sex discrimination. The R-ANS: PA-W ratio was measured as 1.2 in men and 1.1 in women by Hwang et al12; as 1.9 in white subjects, 1.8 in black subjects, and 2.0 and 1.9 in men and women of yellow race, respectively, by Lopez et al3; and as 1.2 by Lang and Baumeister (obtained from the study of Hwang
TABLE 4. Comparison of Measurements of PA and NB Between our Study and the Previous Ones NB Length
Our study Hwang et al11 (2005) Hoffman et al13 (1991)
Hommerich and Riegel5 (2002) Lang and Baumeister (1982, obtained from the study of Hwang et al11) Karadağ et al10 (2011) Ofodile4 (1994) Lee et al1 (2008)
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NB Width
Method, Origin
Men
Women
Total
Men
MDCT Dried skulls, Korean American White Black
18.7 25.9 — — —
17.2 24.5 — — —
18 — — — —
11.8 9.2 — — —
German
—
—
24.9
CT, Anatolian Dried skulls, Austrian Dried skulls, black American CT, Korean
30.61 — — 22
29.01 — — 17.3
30.2 27.9 —
Women
PA Length
PA Width
Total
Men
Women
Total
Men
Women
Total
12 8.8 — — —
11.9 — — — —
33.4 30.1 — — —
30.1 28 — — —
31.7 — — — —
—
13
—
—
29.1
23.3 25.4 — — — 22.6 —
23.9 — — 23.7 26.7
—
24.6 25.7 — — — 23.6 —
— — — —
— — — —
— — — —
— — — —
— — — —
18.83 — — 24.34
18.19 — — 22.82
— — — —
23.6
— 2.16 2.34 —
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The Journal of Craniofacial Surgery • Volume 25, Number 6, November 2014
et al12) without sex discrimination. As the R-ANS:NBH-M ratio was below 2.0 on most cases in our study, this was consistent with the results of Hwang et al12 and Lang and Baumeister (obtained from the study of Hwang et al12). The R-ANS:PA-W ratio was also consistent with the studies of Hwang et al,12 Lang and Baumeister (obtained from the study of Hwang et al12), and Lopez et al3 except for the result of male individuals of yellow race in the study of Lopez et al.3 Radiographic techniques have been used in the morphometric evaluation of craniofacial anatomic structures.10 In this study, the data were identified on living individuals using computer. We think that the possibility of mistakes was decreased according to dry bones and direct radiographic images. In our study, the more detailed data were gathered about the dimensions and types of NB and PA compared with the previous studies. Especially, we stated some new types that were not mentioned before, concerning IN-A and PA types. We think that the obtained data and detailed classification may be important for surgical interventions and nasal reconstructions in this area.
REFERENCES 1. Lee SH, Yang TY, Han GS, et al. Analysis of the nasal bone and nasal pyramid by three-dimensional computed tomography. Eur Arch Otorhinolaryngol 2008;265:421–424 2. Lee JC, Yang CC, Lee KS, et al. The measurement of congenital nasal pyriform aperture stenosis in infant. Int J Pediatr Otorhinolaryngol 2006;70:1263–1267 3. Lopez MC, Galdames ICS, Matamala DAZ, et al. Sexual dimorphism determination by piriform aperture morphometric analysis in Brazilian human skulls. Int J Morphol 2009;27:327–331
The Morphometry of NB and PA Using MDCT
4. Ofodile FA. Nasal bones and pyriform apertures in blacks. Ann Plast Surg 1994;32:21–26 5. Hommerich CP, Riegel A. Measuring of the piriform aperture in humans with 3D-SSD-CT-reconstructions. Ann Anat 2002;184:455–459 6. Citardi MJ, Hardeman S, Hollenbeak C, et al. Computer aided assessment of bony nasal pyramid dimensions. Arch Otolaryngol Head Neck Surg 2000;126:979–984 7. Erdem T, Ozturan O, Erdem G, et al. Nasal pyriform aperture stenosis in adults. Am J Rhinol 2004;18:57–62 8. Prokop M. Multislice CT angiography. Eur J Radiol 2000;36:86–96 9. Turhan-Haktanir N, Ayçiçek A, Haktanir A, et al. Variations of supraorbital foramina in living subjects evaluated with multidetector computed tomography. Head Neck 2008;30:1211–1215 10. Prado FB, Calda RA, Rossi AC, et al. Piriform aperture morphometry and nasal bones morphology in Brazilian population by postero-anterior Caldwell radiographs. Int J Morphol 2011;29:393–398 11. Karadağ D, Ozdol NC, Beriat K, et al. CT evaluation of the bony nasal pyramid dimensions in Anatolian people. Dentomaxillofac Radiol 2011;40:160–164 12. Hwang TS, Song J, Yoon H, et al. Morphometry of the nasal bones and pyriform apertures in Koreans. Ann Anat 2005;187:411–414 13. Hoffman BE, McConathy DA, Coward M, et al. Relationship between the piriform aperture and interalar nasal widths in adult males. J Forensic Sci 1991;36:1152–1161 14. Cantin L, Suazo GIC, Zavando MDA, et al. Sexual dimorphism determination by piriform aperture morphometric analysis in Brazilian human skulls. Int J Morphol 2009;27:327–331 15. Lang J. Clinical anatomy of the nose, nasal cavity and paranasal sinuses. New York: Thieme Medical Publishers: 1989;25–26
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The Evaluation of Morphometry of Nasal Bone and Pyriform Aperture Using Multidetector Computed Tomography Neslihan Yüzbaşioğlu, PhD,* Mehmet Tuğrul Yilmaz, BVSc, PhD,† Aynur Emine Çicekcibasi, MD,† Muzaffer Şeker, BVSc, PhD,† and Mehmet Emin Sakarya, MD‡ Introduction: The aim of this study was to measure nasal bone (NB) and pyriform aperture (PA), morphometrically. Besides, the different types of NB and PA were classified and determined the sexual differences. Materials and Methods: Our study was performed on 120 (60 women, 60 men) multidetector computed tomography images obtained from patients who underwent radiologic examination in the Department of Radiology of Meram Faculty of Medicine, Necmettin Erbakan University. The right, left, and median heights of NB; the superior and inferior widths of NB; the width of PA; and the distance between rhinion and anterior nasal spine (as the height of PA) were measured. Frontonasal and internasal angles were also determined. All data were analyzed statistically using Student’s t-test. Results: The other data of men were higher than of women except for the superior and inferior widths of NB and the frontonasal angle. We also determined the ratio of the height of PA to the height of NB on median plane and the ratio of the height of PA to the width of PA. They were found less than 2.0 in 64.2% and 100% of the cases, respectively. The NB and PA were classified into 8 and 7 different types, respectively. Conclusions: The knowledge of the morphometric data and different types of the NB and PA is essential for sex determination, all surgical procedures related to this area, and nasal reconstructions. Key Words: Nasal bone, pyriform aperture, MDCT, morphometry, nasal reconstruction (J Craniofac Surg 2014;25: 2214–2219)
T
he nose is an aesthetically important structure located in the center of facial area. Nasal bone (NB) and pyriform aperture (PA) are the contributory main skeletal factors to create the actual shape of nose.1,2 The NB is surrounded by the frontal bone at the top, frontal process of maxilla at the sides, and PA at the bottom. The From the *Department of Anatomy, School of Medicine, İstanbul Medipol University, İstanbul, Turkey; and Departments of †Anatomy and ‡Radiology, Meram Faculty of Medicine, Necmettin Erbakan University, Konya, Turkey. Received January 13, 2014. Accepted for publication April 23, 2014. Address correspondence and reprint requests to Neslihan Yüzbaşioğlu, Department of Anatomy, School of Medicine, İstanbul Medipol University, Atatürk Bulvari, No 27, 34083 Unkapani-Fatih, İstanbul, Turkey; E-mail: [email protected] The authors report no conflicts of interest. Copyright © 2014 by Mutaz B. Habal, MD ISSN: 1049-2275 DOI: 10.1097/SCS.0000000000001063
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PA, which is usually accepted as a pear-shaped opening, is also surrounded by NB at the top, frontal process of maxilla at the sides, and palatine process of maxilla at the bottom.1,2 The variable dimensions and shapes of NB and PA are important parameters on deciding the anthropologic features of a population because of the differences between ethnic groups.1,3–5 The morphometric values and ratios must be known to be successful in rhinoplasty operations and various osteotomies by plastic and reconstructive surgeons.6 The morphometric evaluation of computerized computed tomography (CT) images provides a unique perspective while evaluating craniomaxillofacial skeleton parameters clinically.6 Three-dimensional computer-aided tomography of NB and PA is a perfect technique obtaining quantitative and objective data.1 To know that the CT data obtained with reliable radiologic methods belong to different age, sex, and ethnicity groups will be very important when deciding on the ideal nose shape at rhinoplasty and solving problems such as NB stenosis.1,6,7 Multidetector CT (MDCT), which was used in this study, is a reliable and noninvasive technique displaying the bone formation in detail with the help of high-resolution and multisection images.8 In recent years, this method has started to be used in anatomic studies to obtain reliable morphometric data.9 In this study, we aimed to determine morphometric data and the various types about NB and PA using MDCT.
MATERIALS AND METHODS After receiving approval from the institutional review board (ref, 2012/96), this study was carried out retrospectively on images of the patients with acute nontraumatic subarachnoid hemorrhage or suspected cerebral aneurysm with symptoms such as headache and cranial neuropathy with MDCT in the Radiology Department of Meram Faculty of Medicine, Necmettin Erbakan University, Konya, Turkey. The images of 120 patients (60 men, 60 women) without history of any cranial trauma, rhinoplasty operation, and remarkable bone deformation were assessed. The MDCT scans were provided with a 64-slice CT scanner (Somatom Sensation 64; Siemens Medical Solutions, Forchheim, Germany). The images were obtained in a neutral supine position, without rotation, flexion, or extension, to provide standardized measurements. The images were imported into the Leonardo Workstation (Vitrea 2; Vital Images, Inc, Minneapolis, MN) and were combined to create three-dimensional reconstructions. All the measurements were obtained by visual estimation of the determined points at an approximate window setting and level setting. The dimensions were measured using three-dimensional volume-rendered images and multiplanar reconstruction images. For accuracy, dot cursors were placed in identical positions on corresponding axial, coronal, and sagittal images for measurement on three-dimensional volumerendered images. The start and end points of the linear measurements of the images were determined with the internal digital caliper tool
The Journal of Craniofacial Surgery • Volume 25, Number 6, November 2014
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
The Journal of Craniofacial Surgery • Volume 25, Number 6, November 2014
The Morphometry of NB and PA Using MDCT
FIGURE 3. The angle between the frontal bone and the NBs. FIGURE 1. The height (right, left, median plane) and width (upper, lower) of NB.
included in the Workstation software. The software (syngommwp VE 30A, syngo VE32B) calculated all of the measurements, which were recorded in centimeters. Nasion, rhinion, anterior nasal spine, and gnathion points were passed from the same sagittal plane to obtain standard measurement points for each patient. The determined parameters from the three-dimensional volumerendered images were as follows: 1. The height of the right and left NB (NBH-R, NBH-L): the distance between right-left frontonasal junction and the lower margin of the same side NB (Fig. 1). 2. The height of NB on median plane (NBH-M): the height of internasal suture (the distance between nasion and rhinion) (Fig. 1). 3. The upper width of NB (NBW-S): the distance between the junction points of nasomaxillary suture with frontonasal suture at both sides (Fig. 1). 4. The lower width of NB (NBW-I): the distance between bottom margins of both sides of NB (Fig. 1). 5. The width of PA (PA-W): the widest distance of PA on transverse plane (Fig. 2). 6. The height of PA (R-ANS): the distance between rhinion and anterior nasal spine (Fig. 2).
In addition, for each patient, the ratio of PA height to NB height on median plane (R-ANS:NBH-M) and the ratio of PA height to PA width (R-ANS:PA-W) have been calculated. Statistical analysis was performed using the Statistical Package for the Social Sciences for Windows, version 13.0 (SPSS, Chicago, IL). Comparisons of the mean data according to sex were analyzed using Student’s t-test. Summary of the data was stated as mean (SD). Statistical significance was defined as P < 0.05.
RESULTS
The determined parameters on the multiplanar reconstruction images were as follows: 1. Frontonasal angle (FN-A): the angle between the frontal bone and NBs on the median plane (Fig. 3). 2. Internasal angle (IN-A): the angle between NBs on the coronal plane after the x and y planes were brought to nasion point (Fig. 4).
In this study, the data (case number, sex, and minimum and maximum age) about the patients were given at Table 1. There were no significant differences between sexes (P > 0.05). We determined differences between sexes for all parameters (P < 0.05) except for NBW-S and R-ANS/NBH-M. In addition, it was observed that the other parameters were higher in men than women except for NBW-S, NBW-I, and FN-A (Table 2). The ratio of R-ANS:NBH-M has been found less than 2.0 on 77 cases (64.2%) and higher than this ratio on 43 cases (35.8%). The ratio of R-ANS: PA-W was also seen below 2.0 on all cases (Table 2). The NBs were classified into 8 categories according to their shapes: Types 1 to 3: an angulation at the lower part of the NB (becoming narrower from sides toward the median plane) and a widening after that (paying attention to the thickness of NB; thick NB is type 1, and thin NB is type 3) (Fig. 5). Types 2 to 6: an angulation at the upper part of the NB (paying attention to the thickness of NB; thick NB is type 2, and thin NB is type 6) (Fig. 5).
FIGURE 2. PA width and height.
FIGURE 4. The angle between NBs.
© 2014 Mutaz B. Habal, MD
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The Journal of Craniofacial Surgery • Volume 25, Number 6, November 2014
Yüzbaşioğlu et al
TABLE 1. Number, Sex, and Age of the Patients Sex
n
Age Min
Age Max
Male
60 60 120
15 17 15
82 81 82
Female Combined
Age, Mean (SD) 59.65 (17.21) 56.81 (15.23) 58.23 (16.24)
n, case number; Age Min, age minimum; Age Max, age maximum.
Types 4 to 8: no angulation and nasomaxillary sutures are parallel to each other (paying attention to the thickness of NB; thin NB is type 4, and thick NB is type 8) (Fig. 5). Type 5: an angulation at the midpoint of NB and both NB are thick (Fig. 5). Type 7: no angulation and NB is narrow at the upper part and comes down widening, drawing a triangle (Fig. 5).
The PAs were classified into 7 categories according to their shapes: Pear PA (type 1): wide and round at the lower part, narrowing to the upper part (Fig. 6). Reverse heart PA (type 2): the lower part of PA is below the level of anterior nasal spine (with this feature separated from “drop”) and a continual narrowing to the upper part (with this feature separated from “pear”) (Fig. 7). Rhomboid shape PA (type 3): similar to a rhombus (Fig. 8). Drop PA (type 4): round at the lower part, narrowing gradually coming up to the upper part (with this feature separated from “reverse heart,” as the lower margin does not go down below the level of anterior nasal spine) (with this feature separated from “pear,” as it narrows gradually going to the upper part) (Fig. 9). Oval PA (type 5): pushed inside at the sides and transverse width is almost equal to each other at the upper and lower parts (Fig. 10). Trapezoid PA (type 6): wide lower and narrow upper parts with rectangular shape (Fig. 11). Round PA (type 7): PA is round (Fig. 12). According to the classification of NB types, the most common type was type 2 (26.7%), and the least one was type 7 (3.3%) (Table 3). Types 1 (28.3%) and 2 (26.6%) were the most common types for men and women, respectively. According to the classification of PA types, the most common type was pear type (48.3%), and the least one was trapezoid type (1.6%) (Table 3). The pear type was the most common type for both men (55%) and women (41.6%).
FIGURE 5. The classification of NBs in 8 types according to Lang and Baumeister (1982, obtained from the study of Hwang et al11).
DISCUSSION This study, which was carried out with MDCT, has some crucial advantages such as being applicable on living subjects; being able to classify sexes accurately; the ability to increase the number of subjects; and the evaluation with high-resolution, three-dimensional and multisectional, of all bone structure in detail. In addition, this study is superior to dry bone studies because of accurate sex classification, to cadaver studies because of the minimal tissue draw effect, to panaromic radiographic studies because of realizing the details clearly, and to direct radiographic studies because of the magnification effect. The evaluation of morphometric data and morphologic types of NB and PA is important especially for forensic medicine and forensic dentistry on deciding the sex and ethnical classification. In addition, preoperative evaluation of NB and PA with CT may reveal successful outcomes while planning the maxillofacial procedures by plastic and reconstructive surgeons and otolaryngologists (eg, while choosing the most suitable osteotome in osteotomies).8,11 It is said that the width and shape of PA are major factors in effective nasal breathing.8 It is reported that heating and moisturizing the inhaled air in cold and dry climates can be done with a long nasal passage and a narrow PA. For this reason, the shape of PA is regarded to adapt to geographic region depending on climate conditions.12 The size and shape of NB differ according to racial, sex, and age. In the literature, there were various studies evaluating the differences between races.1,3,10–12 According to Hwang et al,12 NB was almost the same in Korean men compared with German. In Anatolian population, Karadağ et al11 found that the NB height for both sexes was higher than the ones in Korean, German, and black American population. The NB height measured by Karadağ et al11 are higher in Austrian men and lower in women. The NB height measured in our study has been found for both sexes to be lower than in Korean, German, Austrian, and black American populations and also than in Anatolian population in the study of Karadağ et al11 (Table 4). The NB width measured in our study was higher than in Korean population but lower than in German
TABLE 2. Mean Values and SDs of the Parameters for Both Sexes ♂
♀
Combined
Parameters
Min–Max
Mean (SD)
Min–Max
Mean (SD)
Min–Max
NBH-R
1.58–3.45 1.30–2.70 1.56–3.44 0.83–1.64 0.96–2.42 2.01–2.97 2.70–3.92 103°–131° 49°–74° 1.09–2.93 0.95–1.90
2.33 (0.35) 1.87 (0.31) 2.33 (0.36) 1.18 (0.18) 1.43 (0.24) 2.46 (0.21) 3.34 (0.29) 117.93° (5.78°) 60.50° (5.94°) 1.84 (0.38) 1.36 (0.17)
1.59–2.82 1.12 –2.41 1.52–2.79 0.61–1.65 1.01–2.32 1.82–2.91 2.18–3.80 115°–140° 45°–68° 1.16–2.92 0.95–1.87
2.19 (0.28) 1.72 (0.30) 2.18 (0.29) 1.20 (0.19) 1.54 (0.26) 2.33 (0.20) 3.01 (0.30) 124.36° (5.78°) 57° (4.96°) 1.80 (0.40) 1.30 (0.17)
1.58–3.45 1.12–2.70 1.52–3.44 0.61–1.65 0.96–2.42 1.82–2.97 2.18–3.92 103°–140° 45°–74° 1.09–2.93 0.95–1.90
NBH-M NBH-L NBW-S NBW-I PA-W R-ANS FN-A IN-A R-ANS:NBH-M R-ANS:PA-W
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Mean (SD) 2.26 (0.33) 1.80 (0.31) 2.26 (0.33) 1.19 (0.19) 1.48 (0.26) 2.39 (0.22) 3.17 (0.34) 121.15° (6.60°) 58.75° (5.73°) 1.82 (0.39) 1.33 (0.18)
P 0.01 0.01 0.01 0.71 0.02 0.00 0.00 0.00 0.00 0.63 0.04
© 2014 Mutaz B. Habal, MD
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The Journal of Craniofacial Surgery • Volume 25, Number 6, November 2014
FIGURE 6. Pear-type PA.
The Morphometry of NB and PA Using MDCT
FIGURE 10. Oval-type PA.
FIGURE 7. Reverse heart-type PA. FIGURE 11. Trapezoid-type PA.
FIGURE 8. Rhomboid-type PA.
FIGURE 9. Drop-type PA.
population (Table 4). Different from the previous studies, the heigth and width of NB at different parts of the bone were measured in our study. Both right-left heights of NB and height of NB on the median plane were longer in men than in women (Table 2). The upper and lower widths of NB were wider in women than in men (Table 2). According to these results, it can be said that NB was long and narrow in men but short and wide in women. In 2 different studies, it was determined that type 1 was the most common in Brazilian women, men, and Koreans (long and wide NB, narrowing in the center).1,12 Hwang et al12 compared their own study, carried out on Korean subjects, with Lang and Baumeister’s (obtained from the study of Hwang et al12) study on German, which was also carried out without a sex classification. Although the most common NB type was long,wide, and narrowing at the upper part (type 2 in our study) according to Hwang et al,12 it was determined
FIGURE 12. Round-type PA.
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The Journal of Craniofacial Surgery • Volume 25, Number 6, November 2014
Yüzbaşioğlu et al
TABLE 3. Types and Percentage Distributions of NB and PA Types and Percentages for NB
Sex
Type 1, n (%)
Type 2, n (%)
Type 3, n (%)
Type 4, n (%)
Type 5, n (%)
Types and Percentages for PA Type 6, Type 7, Type 8, n (%) n (%) n (%)
Pear, n (%)
Reverse heart, Rhomboid, Drop, n (%) n (%) n (%)
Male
17 (28.33) 15 (25) 9 (15) 9 (15) 5 (8.33) 2 (3.33) 1 (1.67) 2 (3.33) 33 (55) 6 (10) 1 (1.66) Female 10 (16.67) 16 (26.66) 10 (16.67) 8 (13.33) 6 (10) 3 (5) 3 (5) 4 (6.67) 25 (41.66) 15 (25) 4 (6.66) Combined 27 (22.5) 31 (25.83) 19 (15.83) 17 (14.17) 11 (9.17) 5 (4.17) 4 (3.33) 6 (5) 58 (48.3) 21 (17.5) 5 (4.1)
that the most common was long NB type was narrowing in the center (type 3 in our study) by Lang and Baumeister (obtained from the study of Hwang et al12). The NB was classified into 8 different types in German (Lang and Baumeister, obtained from the study of Hwang et al12). Hwang et al12 have simplified this complex classification method, and NB has been defined under 5 different types. Although type B (types 2 and 6 in our study) was the most common type, type D (type 5 in our study) and type E (types 4 and 8 in our study) have not also been observed in Korean population. Prado et al10 found that type A (types 1 and 3 in our study) in Hwang et al’s12 classification was the most common one in Brazilian population, whereas types D and E were the least observed ones. In our study, NB was classified under 8 categories as in Lang and Baumeister’s (obtained from the study of Hwang et al12). The most common type for NB was type 2, and the least common ones were types 6 and 7. We detected types 2, 1, and 3 mostly and respectively. According to these results, our study bears some resemblance to the studies of both Hwang et al12 and Prado et al.11 In our study, although the R-ANS was larger than in German and Korean populations (Lang and Baumeister, obtained from the study of Hwang et al12), the PA-W was smaller than in Korean population and black race11,13 and larger than in German, Austrian, Anatolian, Korean, white race, and black American populations4,5,12,13 (Lang and Baumeister obtained from the study of Hwang et al12). The PA-W rises 2 times from childhood to adulthood and is said to continue developing even after 20 years old.3 Lang and Baumeister (1982, obtained from the study of Hwang et al12) measured the mean upper width, lower width, and R-ANS, that is, 16.3, 23.6, and 29.1 mm, respectively, in German. In many studies, the upper-lower widths and R-ANS were determined to be wider and higher in men than in women.1,3,5,7,14 However, in male Koreans, the mean upper PA-W was determined to be narrower than in women.12 Hoffman et al13 conducted a race-based evaluation and found out that lower PA-W was wider in blacks.3 In the study of Lopez et al,3 upper PA-W in
Oval, Trapezoid, Round, n (%) n (%) n (%)
7 (11.6) 6 (10) 1 (1.66) 8 (13.33) 3 (5) 1 (1.66) 15 (12.5) 9 (7.5) 2 (1.6)
6 (10) 4 (6.66) 10 (8.3)
blacks has been found meaningfully larger than in white and yellow races. The area of PA has also been reported as an important factor for sex determination.10 In our study, the PA-W was not evaluated in upper and lower parts, and one unique width was measured from the largest level of PA. Both PA-W and R-ANS were significantly larger in men than in women. Although these results were in accordance with the studies of Lee et al1,3, Hommerich and Riegel5, Erdem et al7, and Cantin et al14, it differed from the results of the study of Hwang et al.12 In the study of Ofodile4 on skulls, it was defined that the shape of PA in Western African subjects is oval and in American Indian and Austrian subjects is triangular. In black Americans, a change was observed from triangular to oval. In our study, PA was mostly seen in the pear shape, whereas the trapezoid shape was the rarest one. In addtion, PA types were better classified in detail compared with the previous studies. We determined that the mean FN-A were 117.93° in men and 124.36° in women, and it was consistent with the results of Lang15 (115° in men, 120° in women). The mean FN-A was wider in women than in men. In addition, IN-A was measured in our study different from the previous ones. The mean IN-A was measured as 58.75° (60.50° in men, 57° in women). We think that the data of angles can be used preoperatively. In our study, the R-ANS:NBH-M ratio was detected below 2.0 on 77 cases (64.16%) and over this value on 43 cases (35.83%). The R-ANS:PA-W ratio was detected below 2.0 on all cases. The R-ANS:NBH-M ratio was determined as 1.2 in men and 1.1 in women by Hwang et al11 and 1.2 by Lang and Baumeister (obtained from the study of Hwang et al11) without sex discrimination. The R-ANS: PA-W ratio was measured as 1.2 in men and 1.1 in women by Hwang et al12; as 1.9 in white subjects, 1.8 in black subjects, and 2.0 and 1.9 in men and women of yellow race, respectively, by Lopez et al3; and as 1.2 by Lang and Baumeister (obtained from the study of Hwang
TABLE 4. Comparison of Measurements of PA and NB Between our Study and the Previous Ones NB Length
Our study Hwang et al11 (2005) Hoffman et al13 (1991)
Hommerich and Riegel5 (2002) Lang and Baumeister (1982, obtained from the study of Hwang et al11) Karadağ et al10 (2011) Ofodile4 (1994) Lee et al1 (2008)
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NB Width
Method, Origin
Men
Women
Total
Men
MDCT Dried skulls, Korean American White Black
18.7 25.9 — — —
17.2 24.5 — — —
18 — — — —
11.8 9.2 — — —
German
—
—
24.9
CT, Anatolian Dried skulls, Austrian Dried skulls, black American CT, Korean
30.61 — — 22
29.01 — — 17.3
30.2 27.9 —
Women
PA Length
PA Width
Total
Men
Women
Total
Men
Women
Total
12 8.8 — — —
11.9 — — — —
33.4 30.1 — — —
30.1 28 — — —
31.7 — — — —
—
13
—
—
29.1
23.3 25.4 — — — 22.6 —
23.9 — — 23.7 26.7
—
24.6 25.7 — — — 23.6 —
— — — —
— — — —
— — — —
— — — —
— — — —
18.83 — — 24.34
18.19 — — 22.82
— — — —
23.6
— 2.16 2.34 —
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The Journal of Craniofacial Surgery • Volume 25, Number 6, November 2014
et al12) without sex discrimination. As the R-ANS:NBH-M ratio was below 2.0 on most cases in our study, this was consistent with the results of Hwang et al12 and Lang and Baumeister (obtained from the study of Hwang et al12). The R-ANS:PA-W ratio was also consistent with the studies of Hwang et al,12 Lang and Baumeister (obtained from the study of Hwang et al12), and Lopez et al3 except for the result of male individuals of yellow race in the study of Lopez et al.3 Radiographic techniques have been used in the morphometric evaluation of craniofacial anatomic structures.10 In this study, the data were identified on living individuals using computer. We think that the possibility of mistakes was decreased according to dry bones and direct radiographic images. In our study, the more detailed data were gathered about the dimensions and types of NB and PA compared with the previous studies. Especially, we stated some new types that were not mentioned before, concerning IN-A and PA types. We think that the obtained data and detailed classification may be important for surgical interventions and nasal reconstructions in this area.
REFERENCES 1. Lee SH, Yang TY, Han GS, et al. Analysis of the nasal bone and nasal pyramid by three-dimensional computed tomography. Eur Arch Otorhinolaryngol 2008;265:421–424 2. Lee JC, Yang CC, Lee KS, et al. The measurement of congenital nasal pyriform aperture stenosis in infant. Int J Pediatr Otorhinolaryngol 2006;70:1263–1267 3. Lopez MC, Galdames ICS, Matamala DAZ, et al. Sexual dimorphism determination by piriform aperture morphometric analysis in Brazilian human skulls. Int J Morphol 2009;27:327–331
The Morphometry of NB and PA Using MDCT
4. Ofodile FA. Nasal bones and pyriform apertures in blacks. Ann Plast Surg 1994;32:21–26 5. Hommerich CP, Riegel A. Measuring of the piriform aperture in humans with 3D-SSD-CT-reconstructions. Ann Anat 2002;184:455–459 6. Citardi MJ, Hardeman S, Hollenbeak C, et al. Computer aided assessment of bony nasal pyramid dimensions. Arch Otolaryngol Head Neck Surg 2000;126:979–984 7. Erdem T, Ozturan O, Erdem G, et al. Nasal pyriform aperture stenosis in adults. Am J Rhinol 2004;18:57–62 8. Prokop M. Multislice CT angiography. Eur J Radiol 2000;36:86–96 9. Turhan-Haktanir N, Ayçiçek A, Haktanir A, et al. Variations of supraorbital foramina in living subjects evaluated with multidetector computed tomography. Head Neck 2008;30:1211–1215 10. Prado FB, Calda RA, Rossi AC, et al. Piriform aperture morphometry and nasal bones morphology in Brazilian population by postero-anterior Caldwell radiographs. Int J Morphol 2011;29:393–398 11. Karadağ D, Ozdol NC, Beriat K, et al. CT evaluation of the bony nasal pyramid dimensions in Anatolian people. Dentomaxillofac Radiol 2011;40:160–164 12. Hwang TS, Song J, Yoon H, et al. Morphometry of the nasal bones and pyriform apertures in Koreans. Ann Anat 2005;187:411–414 13. Hoffman BE, McConathy DA, Coward M, et al. Relationship between the piriform aperture and interalar nasal widths in adult males. J Forensic Sci 1991;36:1152–1161 14. Cantin L, Suazo GIC, Zavando MDA, et al. Sexual dimorphism determination by piriform aperture morphometric analysis in Brazilian human skulls. Int J Morphol 2009;27:327–331 15. Lang J. Clinical anatomy of the nose, nasal cavity and paranasal sinuses. New York: Thieme Medical Publishers: 1989;25–26
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