ANATOMICAL STUDY
The Evaluation of Morphometry of the Mastoid Process Using Multidetector Computed Tomography in a Living Population Mehmet Tugrul Yilmaz, PhD,* Neslihan Yüzbasioglu, PhD,† Aynur Emine Cicekcibasi, MD,* Muzaffer Seker, PhD,* and Mehmet Emin Sakarya, MD‡ Abstract: The aim of this study was to examine the relationships of the bony landmarks on the lateral surface of the mastoid process (MP). It was also the target of this study to reveal the importance of sexual dimorphism in terms of the mastoid triangle. Our study was performed on 140 (70 women, 70 men) multidetector computed tomography images obtained from patients who underwent radiologic examination at the Department of Radiology of Meram Medical Faculty, Necmettin Erbakan University. The height of the MP was measured using 2 different ways. The distance between the mastoid apex and the midpoint of the distance of the porion and the mastoid notch was measured (mastoid height 1). Then, the distance between the Frankfurt horizontal plane and the mastoid apex was measured (mastoid height 2). The distances between porion– mastoid notch, porion–mastoid apex, porion-asterion, asterion–mastoid apex, articular tubercle–asterion, articular tubercle–mastoid apex, as well as the right and the left MP were also measured. Finally, the angles between porion–mastoid apex–asterion, mastoid apex–asterion– porion, and asterion–porion–mastoid apex were measured. All data were analyzed statistically using the Student’s t-test. According to the results of the measurements, all right and left parameters of the men were higher than the women’s right and left sides except for the angle between asterion–porion–mastoid apex. In addition, all right and left parameters were almost the same in both sexes. Having the knowledge of measurements of the distances between the major landmarks of the temporal bone is essential to avoid possible complications during facial, mastoid, and especially sigmoid sinus surgeries. Key Words: Mastoid process, porion, asterion, MDCT, sexual dimorphism (J Craniofac Surg 2015;26: 259–263)
From the *Department of Anatomy, Meram Faculty of Medicine, Necmettin Erbakan University, Konya; †Department of Anatomy, School of Medicine, İstanbul Medipol University, Istanbul; and ‡Department of Radiology, Meram Faculty of Medicine, Necmettin Erbakan University, Konya, Turkey. Received April 25, 2014. Accepted for publication July 14, 2014. Address correspondence and reprint requests to Aynur Emine Cicekcibasi, MD, Department of Anatomy, Meram Faculty of Medicine, Necmettin Erbakan University, 42080 Meram, Konya, 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.0000000000001216
M
etric analyses are very valuable for the reason that they are more objective compared with nonmetric characteristic features and have greater statistical impact on skeletal sex determination.1 Bone measurements have always been a part of the anthropologic spectrum used for sex determination.2 Previous studies have highlighted the role of the pelvis and the skull on determination of sexual dimorphism. Reliability of sex determination had been reported as 95% in cases that the pelvis solely was used for determination and 92% in cases that the skull solely was used. In addition, it had been reported that reliability had increased up to 98% when sex determination was performed using both the pelvis and the skull.3 The temporal bone is still analyzable even on fragmented or burned skulls because of its localization and endurance. Therefore, it is important for studies of anthropology and forensic medicine.3 Many studies indicate that the mastoid process (MP) is a useful cranial structure on sex determination for forensic purposes. It has been reported that the direction of the MP is more vertical in males and tends to slope toward medial on females and presents sexual dimorphism. Features such as the height, shape, and inclination of the MP are thought to be favorable indicators of sexual dimorphism.1,4,5 The asterion is a craniometric point located on the intersection of the lambdoid, parietomastoid, and occipitomastoid sutures. The mastoid triangle (MT) is a triangular space that happens to be between the mastoid apex, the porion, and the asterion.4 The MT is an area that shows specific features on different populations.1,3 Different localizations of the asterion are important for all posterolateral interventions to the skull base. Therefore, the knowledge of distances between asterion–zygomatic process and asterion-MP would be beneficial for all surgical interventions to the cerebellopontine triangle, the tympanic cavity, the internal auditory meatus, the mastoid antrum, and the membranous labyrinth and for transmastoid cisternoscopies.6,7 In this study, we intended to determine the morphometric relations between the MP and surrounding anthropologic points by using multidetector computed tomography (MDCT) and to emphasize its importance according to sexual dimorphism.
MATERIALS AND METHODS This study was conducted retrospectively in Necmettin Erbakan University, Meram Medical Faculty, Department of Radiology, on MDCT images of patients who presented with clinical manifestations of acute nontraumatic subarachnoid hemorrhage or with suspicions of cerebral aneurysms due to symptoms such as headache and cranial neuropathy. Images of a total of 140 individuals (70 men, 70 women) with no cranial trauma or any cranial operation history and no detectible bone deformities were assessed. The images were obtained with neutral head position without rotation, flexion, or extension to gain standard measurements. Imaging was done with a 64-detector scanner (Somatom Sensation 64, Siemens, Germany). Source images were sent to a Leonardo workstation (Siemens Medical
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12. Mastoid apex right–left (Map right–left): the distance between the right and the left mastoid apex (Fig. 4B)
The data acquired from the radiologic images were computerized and analyzed with the SPSS (13.0 for Windows; Chicago, IL) package program. Lateralization (right-left) and comparison according to sex were done with the Student’s t-test. Summary of the data was stated as mean (SD).
RESULTS The information related to the cases (number of cases, sex, minimum and maximum age) used during the study is presented in Table 1. The mean (SD) age was 58.57 (15.93) years for the men and as 57.72 (14.43) years for the women. All parameters were observed to have statistical differences between sexes except right-left angle 1, 2, and 3 values (P < 0.05) (Table 2). No statistical differences were detected as the result of comparison of right-left side values according to sex (P > 0.05). All parameters were observed as having greater values for the men compared with the women with the exception of angle 3 (Table 3).
DISCUSSION
FIGURE 1. A, MH1: the distance between the midpoint of the distance between porion–mastoid incisura and the mastoid apex. B, MH2: the distance between the FHP and the mastoid apex.
For the approach to the posterior fossa and the skull base, surface landmarks have great importance. Especially, the MP and the asterion are very useful for locating important anatomic structures such as transverse sinus–sigmoid sinus intersection.7 The mastoid area is one of the slowest- and latest-growing areas of the skull, and this type of areas usually presents high sexual
Solutions), and three-dimensional images were created. The images of each case were standardized by adjusting to the Frankfurt horizontal plane (FHP) on lateral aspect to gain standard measurements. After this, the measurement of the parameters described below was done. This study conformed to the Helsinki Declaration. The determined parameters on the three-dimensional volumerendered images are as follows: 1. Mastoid height 1 (MH1): the distance between the midpoint of the distance between porion–mastoid incisura and the mastoid apex (Fig. 1A) 2. Mastoid height 2 (MH2): the distance between the FHP and the mastoid apex (Fig. 1B) 3. Porion–mastoid incisura (Pr-Mi): the distance between the porion and the end point of the mastoid incisura (Fig. 2A) 4. Porion–mastoid apex (Pr-Map): the distance between the porion and the mastoid apex (Fig. 2A) 5. Porion-asterion (Pr-As): the distance between the porion and the asterion (Fig. 2B) 6. Asterion–mastoid apex (As-Map): the distance between the asterion and the mastoid apex (Fig. 2B) 7. Porion–mastoid apex–asterion (Ang 1): the angle presented between the porion, the mastoid apex, and the asterion (Fig. 3A) 8. Mastoid apex–asterion–porion (Ang 2): the angle presented between the mastoid apex, the asterion, and the porion (Fig. 3B) 9. Asterion–porion–mastoid apex (Ang 3): the angle presented between the asterion, the porion, and the mastoid apex (Fig. 3C) 10. Articular tubercle–asterion (At-As): the distance between the articular tubercle and the asterion (Fig. 4A) 11. Articular tubercle–mastoid apex (At-Map): the distance between the articular tubercle and the mastoid apex (Fig. 4A)
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FIGURE 2. A, Porion–mastoid incisura (Pr-Mi): the distance between the porion and the end point of the mastoid incisura, and porion–mastoid apex (Pr-Map): the distance between the porion and the mastoid apex. B, Porion-asterion (Pr-As): the distance between the porion and the asterion, and asterion–mastoid apex (As-Map): the distance between the asterion and the mastoid apex.
© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
The Journal of Craniofacial Surgery • Volume 26, Number 1, January 2015
Evaluation of the MP With MDCT
dimorphism in adulthood.1,5,8 The variable duration of growth in males and females may be the cause of the differences of MP size between sexes. Because males have stronger muscle action from the sternocleidomastoideus, splenius capitis, and longissimus capitis muscles and these muscles are attached to relatively larger areas on males compared with females, MP growth is greater in males.8 The male cranium having well-developed supraorbital ridges, broader plates, thicker zygomatic processes, and larger MPs had been reported on previous studies.4,7,8 It was also stated in various studies that, because of its endurance and well-protected position on the skull, the MP is an important formation on the skull during sex determination.1,3–5,8 With all these, it was demonstrated that environmental and nutritional differences affect the craniofacial growth especially zygomatic progress, mastoid region and occipital bone.8 During the identification of unidentified bodies, sex determination is an
FIGURE 4. A, Articular tubercle–asterion (At-As): the distance between the articular tubercle and the asterion, and articular tubercle–mastoid apex (At-Map): the distance between the articular tubercle and the mastoid apex. B, Mastoid apex right–left (Map right–left): the distance between the right and the left mastoid apex.
important part of the generation process of biologic profile formation. Because sexual dimorphism is greatly population based and shows secular trends, adaptation of morphologic and metric sex determination methods according to specific populations is necessary.9 The sex determination process is important for some disciplines such as osteology, forensic anthropology, paleopathology, and paleodemography and for some cases such as solitary homicides, natural and or manmade disasters, and multiple burials.4,7,8,10 The MT is an alternating area that shows specific characteristic aspects in different populations.1 One of the angles of this triangle is formed by the MP. Saini et al8 had assessed the MT and measured the distances between the asterion and the porion, the mastoid incisura and the porion, the asterion and the mastoid apex, and finally the porion and the mastoid apex. Those results, in compatibility with ours, had indicated the height of the MP as higher in males compared with females. Measured data obtained from our study were greater values than Saini et al.8 Furthermore, it is seen on the study of Saini et al8 that they had done measurements only on the left-side MT and no measurements had been done on the right side. The MT being an important area for sex determination is highlighted in many studies.4,7,8 In addition, it is commonly stated that the knowledge of relations between these anatomic and TABLE 1. Number of Cases, Sex, and Age FIGURE 3. A, Porion–mastoid apex–asterion (Ang 1): the angle presented between the porion, the mastoid apex, and the asterion. B, Mastoid apex– asterion–porion (Ang 2): the angle presented between the mastoid apex, the asterion, and the porion. C, Asterion–porion–mastoid apex (Ang 3): the angle presented between the asterion, the porion, and the mastoid apex.
Sex
n
Minimum Age
Maximum Age
Age, Mean (SD)
Male
70 70 140
21 23 21
82 83 83
58.57 (15.93) 57.72 (14.43) 58.15 (15.15)
Female Combined
© 2014 Mutaz B. Habal, MD
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TABLE 2. Comparison of the Data Acquired, Between Sexes According to Lateralization Right
Left
Male Parameters MH1, cm MH2, cm Pr-Mi, cm Pr-Map, cm Pr-As, cm As-Map, cm Ang 1, degrees Ang 2, degrees Ang 3, degrees At-As, cm At-Map, cm Map right–left, cm
Female
Male
Min–Max
Mean (SD)
Min–Max
Mean (SD)
P
Min–Max
1.37–3.51 2.41–4.12 2.56–4.74 2.23–3.95 3.92–6.64 4.13–6.59 58.00–88.40 25.30–50.00 55.30–90.40 5.41–7.63 2.94–4.59 9.26–11.88
2.35 (0.39) 3.39 (0.37) 3.66 (0.48) 3.12 (0.29) 4.93 (0.38) 5.06 (0.46) 70.48 (5.73) 36.54 (4.22) 72.96 (6.93) 6.87 (0.40) 3.84 (0.34) 10.62 (0.61)
1.60–2.46 2.23–3.85 2.60–4.06 2.36–3.26 3.84–5.07 4.21–6.12 58.20–82.10 22.70–46.00 63.10–92.30 5.34–7.14 3.11–4.12 9.01–11.12
1.98 (0.23) 2.94 (0.35) 3.23 (0.34) 2.89 (0.24) 4.61 (0.35) 4.89 (0.32) 69.66 (5.10) 35.32 (3.56) 75.01 (6.06) 6.54 (0.33) 3.61 (0.25) 10.05 (0.41)
0.00 0.00 0.00 0.00 0.00 0.01 0.36 0.06 0.06 0.00 0.00 0.00
1.38–3.13 2.44–4.16 4.71–2.16 2.24–3.94 3.94–6.61 4.15–6.59 58.50–85.40 25.30–50.00 53.80–90.40 5.21–7.59 2.90–4.69
Female Mean (SD)
2.35 3.39 3.65 3.13 4.94 5.07 70.34 36.65 72.99 6.87 3.85
(0.37) (0.37) (0.48) (0.29) (0.38) (0.46) (5.47) (4.48) (6.98) (0.39) (0.33)
Min–Max
Mean (SD)
1.60–2.48 2.21–3.86 2.60–4.01 2.32–3.28 3.88–5.05 4.21–6.14 58.20–82.10 22.70–46.00 63.60–94.90 5.37–7.12 3.01–4.13
1.98 2.94 3.24 2.90 4.60 4.89 69.48 35.49 75.02 6.55 3.61
(0.23) (0.35) (0.33) (0.24) (0.31) (0.32) (5.35) (3.40) (5.97) (0.32) (0.26)
P 0.00 0.00 0.00 0.00 0.00 0.00 0.34 0.08 0.06 0.00 0.00
Max, maximum; Min, minimim.
anthropologic points that are located on the lateral surface of the temporal bone and joining the formation of MT (eg, the distances between these points) is highly important for surgical interventions of this area.4,7,8 Therefore, we believe that to achieve more reliable results, bilateral assessment of this region is more important and also necessary. Üçerler and Gövsa7 had also measured the distance between the asterion and the mastoid apex but did not mention the difference between sexes. In our study, the mean values according to sex for both right and left sides are presented and the existence of a statistical difference between the right and the left side within the same sex is also assessed. Therefore, we believe that the data from our study will be more helpful for further studies that would be carried out on this area. The asterion is another point that contributes to the MT and is described as a point that changes location during the aging process continuously.4,7,8 The location of the asterion has importance for all posterolateral approaches to the cranial base.6,11,12 The asterion is considered to be an important landmark for craniotomy and is used to define the location of the transverse-sigmoid junction.11 Nonetheless, the localization of the asterion is variable.7,11 The asterion had been reported as 81% on the transverse-sigmoid junction, 15% on a point below, and 4% above this junction.11 Üçerler and
Gövsa7 had reported these rates as 87%, 11%, and 2%, respectively. The FHP, which was also evaluated during our study, is considered to be an important displayable reference line on the skull for cases in need of craniotomy.7 Adding to these, the squamous part of the temporal bone having some morphologic changes because of some chronic bone diseases must be remembered.7 Currently, CT imaging techniques are used for metric sex analyses, and systematic studies for determination of sex from the skull require CT imaging.9 Morphometric analyses can also be done by the naked eye, but to make this kind of analyses and achieve statistically significant results, studying a great number of samples is required. In addition, for situations in which a sufficient number of skulls do not exist, metric analyses and assessments can be done by using radiologic methods. Multidetector CT, which was used in this study, is a highly advanced radiologic imaging technique. Multidetector CT is a reliable and noninvasive technique that can show the details of bone structures by multislice images and with high resolution.13 Multidetector CT is used in anatomic studies to gain more reliable morphometric data in recent years.14 In addition, this study, conducted with MDCT, is superior to skull studies because of accurate sex determination, cadaver studies because of minimal tissue shrinkage effect, panoramic radiographic studies because of
TABLE 3. Comparison of the Data Acquired, Between Sides According to Sexes Male
Female
Right Parameters MH1, cm MH2, cm Pr-Mi, cm Pr-Map, cm Pr-As, cm As-Map, cm Ang 1, degrees Ang 2, degrees Ang 3, degrees At-As, cm At-Map, cm
Left
Right
Min–Max
Mean (SD)
Min–Max
Mean (SD)
P
Min–Max
1.37–3.51 2.41–4.12 2.56–4.74 2.23–3.95 3.92–6.64 4.13–6.59 58.00–86.40 25.30–50.00 55.30–90.40 5.41–7.63 2.94–4.59
2.35 (0.39) 3.39 (0.37) 3.66 (0.48) 3.12 (0.29) 4.93 (0.38) 5.06 (0.46) 70.49 (5.73) 36.54 (4.22) 72.96 (6.94) 6.87 (0.40) 3.84 (0.34)
1.38–3.13 2.44–4.16 2.55–4.71 2.24–3.94 3.94–6.61 4.15–6.59 58.50–85.40 25.30–50.00 53.80–90.40 5.21–7.59 2.90–4.69
2.35 (0.37) 3.39 (0.37) 3.65 (0.48) 3.13 (0.29) 4.94 (0.38) 5.07 (0.46) 70.34 (5.47) 36.65 (4.48) 72.99 (6.98) 6.87 (0.39) 3.85 (0.33)
0.96 0.98 0.97 0.85 0.88 0.92 0.88 0.87 0.98 0.99 0.86
1.60–2.46 2.23–3.85 2.60–4.06 2.36–3.26 3.84–5.07 4.21–6.12 58.20–82.10 22.70–46.00 63.10–92.30 5.34–7.14 3.11–4.12
Left Mean (SD)
1.98 2.94 3.23 2.89 4.61 4.89 69.66 35.32 75.01 6.54 3.61
(0.23) (0.35) (0.34) (0.24) (0.31) (0.32) (5.10) (3.56) (6.06) (0.33) (0.25)
Min–Max 1.60–2.48 2.21–3.86 2.60–4.01 2.32–3.28 3.88–5.05 4.21–6.14 58.20–82.10 22.70–46.00 63.60–94.90 5.37–7.12 3.01–4.13
Mean (SD) 1.98 2.94 3.24 2.90 4.60 4.89 69.48 35.49 75.02 6.55 3.61
(0.23) (0.35) (0.33) (0.24) (0.31) (0.32) (5.35) (3.40) (5.97) (0.32) (0.26)
P 0.99 0.93 0.95 0.85 0.90 0.97 0.83 0.77 0.99 0.98 0.99
Max, maximum; Min, minimim.
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The Journal of Craniofacial Surgery • Volume 26, Number 1, January 2015
detection and individuation of holes, direct radiographic studies because of magnification factor, as well as ultrasonographic studies because of more accurate data on differentiation of bone structures. In conclusion, we believe that the knowledge of distance measurements of major landmarks of the temporal bone is indispensible to avoid possible complications such as damage to the dura of the medial and the posterior cranial fossa as well as protection of the mastoid parts of the facial nerve and the tympanic chord during surgical interventions to the face, the mastoid area, and especially the sigmoid sinus.
6.
7. 8. 9.
REFERENCES
10.
1. Kemkes A, Gobel T. Metric assessment of the “mastoid triangle” for sex determination: a validation study. J Forensic Sci 2006;51:985–989 2. Wahl J, Graw M. Metric sex differentiation of the pars petrosa ossis temporalis. Int J Legal Med 2001;114:215–223 3. Paiva LAS, Segre M. Sexing the human skull through the mastoid process. Rev Hosp Clin Fac Med Sao Paulo 2003;58:15–20 4. Galdames ICS, Matamala DAZ, Smith RL. Sex determination using mastoid process measurements in Brazilian skulls. Int J Morphol 2008;26:941–944 5. Nagaoka T, Shizushima A, Sawada J, et al. Sex determination using mastoid process measurements: standards for Japanese human skeletons
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12.
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Evaluation of the MP With MDCT
of the medieval and early modern periods. Anthropol Sci 2008; 116:105–113 Mwachaka PM, Hassanali J, Odula PO. Anatomic position of the asterion in Kenyans for posterolateral surgical approaches to cranial cavity. Clin Anat 2010;23:30–33 Üçerler H, Gövsa F. Asterion as a surgical landmark for lateral cranial base approaches. J Craniomaxillofac Surg 2006;34:415–420 Saini V, Srivastava R, Rai RK, et al. Sex estimation from the mastoid process among North Indians. J Forensic Sci 2012;57:434–439 Ramsthaler F, Kettner M, Gehl A, et al. Digital forensic osteology: morphological sexing of skeletal remains using volume-rendered cranial CT scans. Forensic Sci Int 2010;195:148–152 Noren A, Lynnerup N, Czarnetzki A, et al. Lateral angle: a method for sexing using the petrous bone. Am J Phys Anthropol 2005;128:318–323 Sheng B, lv F, Xiao Z, et al. Anatomical relationship between cranial surface landmarks and venous sinus in posterior cranial fossa using CT angiography. Surg Radiol Anat 2012;34:701–708 Manolis E, Filippou D, Theocharis S, et al. Anatomical landmarks: dimensions of the mastoid air cell system in the Mediterranean population. Our experience from the anatomy of 298 temporal bones. Anat Sci Int 2007;82:139–146 Prokop M. Multislice CT angiography. Eur J Radiol 2000;36:86–96 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
© 2014 Mutaz B. Habal, MD
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The Evaluation of Morphometry of the Mastoid Process Using Multidetector Computed Tomography in a Living Population Mehmet Tugrul Yilmaz, PhD,* Neslihan Yüzbasioglu, PhD,† Aynur Emine Cicekcibasi, MD,* Muzaffer Seker, PhD,* and Mehmet Emin Sakarya, MD‡ Abstract: The aim of this study was to examine the relationships of the bony landmarks on the lateral surface of the mastoid process (MP). It was also the target of this study to reveal the importance of sexual dimorphism in terms of the mastoid triangle. Our study was performed on 140 (70 women, 70 men) multidetector computed tomography images obtained from patients who underwent radiologic examination at the Department of Radiology of Meram Medical Faculty, Necmettin Erbakan University. The height of the MP was measured using 2 different ways. The distance between the mastoid apex and the midpoint of the distance of the porion and the mastoid notch was measured (mastoid height 1). Then, the distance between the Frankfurt horizontal plane and the mastoid apex was measured (mastoid height 2). The distances between porion– mastoid notch, porion–mastoid apex, porion-asterion, asterion–mastoid apex, articular tubercle–asterion, articular tubercle–mastoid apex, as well as the right and the left MP were also measured. Finally, the angles between porion–mastoid apex–asterion, mastoid apex–asterion– porion, and asterion–porion–mastoid apex were measured. All data were analyzed statistically using the Student’s t-test. According to the results of the measurements, all right and left parameters of the men were higher than the women’s right and left sides except for the angle between asterion–porion–mastoid apex. In addition, all right and left parameters were almost the same in both sexes. Having the knowledge of measurements of the distances between the major landmarks of the temporal bone is essential to avoid possible complications during facial, mastoid, and especially sigmoid sinus surgeries. Key Words: Mastoid process, porion, asterion, MDCT, sexual dimorphism (J Craniofac Surg 2015;26: 259–263)
From the *Department of Anatomy, Meram Faculty of Medicine, Necmettin Erbakan University, Konya; †Department of Anatomy, School of Medicine, İstanbul Medipol University, Istanbul; and ‡Department of Radiology, Meram Faculty of Medicine, Necmettin Erbakan University, Konya, Turkey. Received April 25, 2014. Accepted for publication July 14, 2014. Address correspondence and reprint requests to Aynur Emine Cicekcibasi, MD, Department of Anatomy, Meram Faculty of Medicine, Necmettin Erbakan University, 42080 Meram, Konya, 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.0000000000001216
M
etric analyses are very valuable for the reason that they are more objective compared with nonmetric characteristic features and have greater statistical impact on skeletal sex determination.1 Bone measurements have always been a part of the anthropologic spectrum used for sex determination.2 Previous studies have highlighted the role of the pelvis and the skull on determination of sexual dimorphism. Reliability of sex determination had been reported as 95% in cases that the pelvis solely was used for determination and 92% in cases that the skull solely was used. In addition, it had been reported that reliability had increased up to 98% when sex determination was performed using both the pelvis and the skull.3 The temporal bone is still analyzable even on fragmented or burned skulls because of its localization and endurance. Therefore, it is important for studies of anthropology and forensic medicine.3 Many studies indicate that the mastoid process (MP) is a useful cranial structure on sex determination for forensic purposes. It has been reported that the direction of the MP is more vertical in males and tends to slope toward medial on females and presents sexual dimorphism. Features such as the height, shape, and inclination of the MP are thought to be favorable indicators of sexual dimorphism.1,4,5 The asterion is a craniometric point located on the intersection of the lambdoid, parietomastoid, and occipitomastoid sutures. The mastoid triangle (MT) is a triangular space that happens to be between the mastoid apex, the porion, and the asterion.4 The MT is an area that shows specific features on different populations.1,3 Different localizations of the asterion are important for all posterolateral interventions to the skull base. Therefore, the knowledge of distances between asterion–zygomatic process and asterion-MP would be beneficial for all surgical interventions to the cerebellopontine triangle, the tympanic cavity, the internal auditory meatus, the mastoid antrum, and the membranous labyrinth and for transmastoid cisternoscopies.6,7 In this study, we intended to determine the morphometric relations between the MP and surrounding anthropologic points by using multidetector computed tomography (MDCT) and to emphasize its importance according to sexual dimorphism.
MATERIALS AND METHODS This study was conducted retrospectively in Necmettin Erbakan University, Meram Medical Faculty, Department of Radiology, on MDCT images of patients who presented with clinical manifestations of acute nontraumatic subarachnoid hemorrhage or with suspicions of cerebral aneurysms due to symptoms such as headache and cranial neuropathy. Images of a total of 140 individuals (70 men, 70 women) with no cranial trauma or any cranial operation history and no detectible bone deformities were assessed. The images were obtained with neutral head position without rotation, flexion, or extension to gain standard measurements. Imaging was done with a 64-detector scanner (Somatom Sensation 64, Siemens, Germany). Source images were sent to a Leonardo workstation (Siemens Medical
The Journal of Craniofacial Surgery • Volume 26, Number 1, January 2015
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The Journal of Craniofacial Surgery • Volume 26, Number 1, January 2015
12. Mastoid apex right–left (Map right–left): the distance between the right and the left mastoid apex (Fig. 4B)
The data acquired from the radiologic images were computerized and analyzed with the SPSS (13.0 for Windows; Chicago, IL) package program. Lateralization (right-left) and comparison according to sex were done with the Student’s t-test. Summary of the data was stated as mean (SD).
RESULTS The information related to the cases (number of cases, sex, minimum and maximum age) used during the study is presented in Table 1. The mean (SD) age was 58.57 (15.93) years for the men and as 57.72 (14.43) years for the women. All parameters were observed to have statistical differences between sexes except right-left angle 1, 2, and 3 values (P < 0.05) (Table 2). No statistical differences were detected as the result of comparison of right-left side values according to sex (P > 0.05). All parameters were observed as having greater values for the men compared with the women with the exception of angle 3 (Table 3).
DISCUSSION
FIGURE 1. A, MH1: the distance between the midpoint of the distance between porion–mastoid incisura and the mastoid apex. B, MH2: the distance between the FHP and the mastoid apex.
For the approach to the posterior fossa and the skull base, surface landmarks have great importance. Especially, the MP and the asterion are very useful for locating important anatomic structures such as transverse sinus–sigmoid sinus intersection.7 The mastoid area is one of the slowest- and latest-growing areas of the skull, and this type of areas usually presents high sexual
Solutions), and three-dimensional images were created. The images of each case were standardized by adjusting to the Frankfurt horizontal plane (FHP) on lateral aspect to gain standard measurements. After this, the measurement of the parameters described below was done. This study conformed to the Helsinki Declaration. The determined parameters on the three-dimensional volumerendered images are as follows: 1. Mastoid height 1 (MH1): the distance between the midpoint of the distance between porion–mastoid incisura and the mastoid apex (Fig. 1A) 2. Mastoid height 2 (MH2): the distance between the FHP and the mastoid apex (Fig. 1B) 3. Porion–mastoid incisura (Pr-Mi): the distance between the porion and the end point of the mastoid incisura (Fig. 2A) 4. Porion–mastoid apex (Pr-Map): the distance between the porion and the mastoid apex (Fig. 2A) 5. Porion-asterion (Pr-As): the distance between the porion and the asterion (Fig. 2B) 6. Asterion–mastoid apex (As-Map): the distance between the asterion and the mastoid apex (Fig. 2B) 7. Porion–mastoid apex–asterion (Ang 1): the angle presented between the porion, the mastoid apex, and the asterion (Fig. 3A) 8. Mastoid apex–asterion–porion (Ang 2): the angle presented between the mastoid apex, the asterion, and the porion (Fig. 3B) 9. Asterion–porion–mastoid apex (Ang 3): the angle presented between the asterion, the porion, and the mastoid apex (Fig. 3C) 10. Articular tubercle–asterion (At-As): the distance between the articular tubercle and the asterion (Fig. 4A) 11. Articular tubercle–mastoid apex (At-Map): the distance between the articular tubercle and the mastoid apex (Fig. 4A)
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FIGURE 2. A, Porion–mastoid incisura (Pr-Mi): the distance between the porion and the end point of the mastoid incisura, and porion–mastoid apex (Pr-Map): the distance between the porion and the mastoid apex. B, Porion-asterion (Pr-As): the distance between the porion and the asterion, and asterion–mastoid apex (As-Map): the distance between the asterion and the mastoid apex.
© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
The Journal of Craniofacial Surgery • Volume 26, Number 1, January 2015
Evaluation of the MP With MDCT
dimorphism in adulthood.1,5,8 The variable duration of growth in males and females may be the cause of the differences of MP size between sexes. Because males have stronger muscle action from the sternocleidomastoideus, splenius capitis, and longissimus capitis muscles and these muscles are attached to relatively larger areas on males compared with females, MP growth is greater in males.8 The male cranium having well-developed supraorbital ridges, broader plates, thicker zygomatic processes, and larger MPs had been reported on previous studies.4,7,8 It was also stated in various studies that, because of its endurance and well-protected position on the skull, the MP is an important formation on the skull during sex determination.1,3–5,8 With all these, it was demonstrated that environmental and nutritional differences affect the craniofacial growth especially zygomatic progress, mastoid region and occipital bone.8 During the identification of unidentified bodies, sex determination is an
FIGURE 4. A, Articular tubercle–asterion (At-As): the distance between the articular tubercle and the asterion, and articular tubercle–mastoid apex (At-Map): the distance between the articular tubercle and the mastoid apex. B, Mastoid apex right–left (Map right–left): the distance between the right and the left mastoid apex.
important part of the generation process of biologic profile formation. Because sexual dimorphism is greatly population based and shows secular trends, adaptation of morphologic and metric sex determination methods according to specific populations is necessary.9 The sex determination process is important for some disciplines such as osteology, forensic anthropology, paleopathology, and paleodemography and for some cases such as solitary homicides, natural and or manmade disasters, and multiple burials.4,7,8,10 The MT is an alternating area that shows specific characteristic aspects in different populations.1 One of the angles of this triangle is formed by the MP. Saini et al8 had assessed the MT and measured the distances between the asterion and the porion, the mastoid incisura and the porion, the asterion and the mastoid apex, and finally the porion and the mastoid apex. Those results, in compatibility with ours, had indicated the height of the MP as higher in males compared with females. Measured data obtained from our study were greater values than Saini et al.8 Furthermore, it is seen on the study of Saini et al8 that they had done measurements only on the left-side MT and no measurements had been done on the right side. The MT being an important area for sex determination is highlighted in many studies.4,7,8 In addition, it is commonly stated that the knowledge of relations between these anatomic and TABLE 1. Number of Cases, Sex, and Age FIGURE 3. A, Porion–mastoid apex–asterion (Ang 1): the angle presented between the porion, the mastoid apex, and the asterion. B, Mastoid apex– asterion–porion (Ang 2): the angle presented between the mastoid apex, the asterion, and the porion. C, Asterion–porion–mastoid apex (Ang 3): the angle presented between the asterion, the porion, and the mastoid apex.
Sex
n
Minimum Age
Maximum Age
Age, Mean (SD)
Male
70 70 140
21 23 21
82 83 83
58.57 (15.93) 57.72 (14.43) 58.15 (15.15)
Female Combined
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Yilmaz et al
TABLE 2. Comparison of the Data Acquired, Between Sexes According to Lateralization Right
Left
Male Parameters MH1, cm MH2, cm Pr-Mi, cm Pr-Map, cm Pr-As, cm As-Map, cm Ang 1, degrees Ang 2, degrees Ang 3, degrees At-As, cm At-Map, cm Map right–left, cm
Female
Male
Min–Max
Mean (SD)
Min–Max
Mean (SD)
P
Min–Max
1.37–3.51 2.41–4.12 2.56–4.74 2.23–3.95 3.92–6.64 4.13–6.59 58.00–88.40 25.30–50.00 55.30–90.40 5.41–7.63 2.94–4.59 9.26–11.88
2.35 (0.39) 3.39 (0.37) 3.66 (0.48) 3.12 (0.29) 4.93 (0.38) 5.06 (0.46) 70.48 (5.73) 36.54 (4.22) 72.96 (6.93) 6.87 (0.40) 3.84 (0.34) 10.62 (0.61)
1.60–2.46 2.23–3.85 2.60–4.06 2.36–3.26 3.84–5.07 4.21–6.12 58.20–82.10 22.70–46.00 63.10–92.30 5.34–7.14 3.11–4.12 9.01–11.12
1.98 (0.23) 2.94 (0.35) 3.23 (0.34) 2.89 (0.24) 4.61 (0.35) 4.89 (0.32) 69.66 (5.10) 35.32 (3.56) 75.01 (6.06) 6.54 (0.33) 3.61 (0.25) 10.05 (0.41)
0.00 0.00 0.00 0.00 0.00 0.01 0.36 0.06 0.06 0.00 0.00 0.00
1.38–3.13 2.44–4.16 4.71–2.16 2.24–3.94 3.94–6.61 4.15–6.59 58.50–85.40 25.30–50.00 53.80–90.40 5.21–7.59 2.90–4.69
Female Mean (SD)
2.35 3.39 3.65 3.13 4.94 5.07 70.34 36.65 72.99 6.87 3.85
(0.37) (0.37) (0.48) (0.29) (0.38) (0.46) (5.47) (4.48) (6.98) (0.39) (0.33)
Min–Max
Mean (SD)
1.60–2.48 2.21–3.86 2.60–4.01 2.32–3.28 3.88–5.05 4.21–6.14 58.20–82.10 22.70–46.00 63.60–94.90 5.37–7.12 3.01–4.13
1.98 2.94 3.24 2.90 4.60 4.89 69.48 35.49 75.02 6.55 3.61
(0.23) (0.35) (0.33) (0.24) (0.31) (0.32) (5.35) (3.40) (5.97) (0.32) (0.26)
P 0.00 0.00 0.00 0.00 0.00 0.00 0.34 0.08 0.06 0.00 0.00
Max, maximum; Min, minimim.
anthropologic points that are located on the lateral surface of the temporal bone and joining the formation of MT (eg, the distances between these points) is highly important for surgical interventions of this area.4,7,8 Therefore, we believe that to achieve more reliable results, bilateral assessment of this region is more important and also necessary. Üçerler and Gövsa7 had also measured the distance between the asterion and the mastoid apex but did not mention the difference between sexes. In our study, the mean values according to sex for both right and left sides are presented and the existence of a statistical difference between the right and the left side within the same sex is also assessed. Therefore, we believe that the data from our study will be more helpful for further studies that would be carried out on this area. The asterion is another point that contributes to the MT and is described as a point that changes location during the aging process continuously.4,7,8 The location of the asterion has importance for all posterolateral approaches to the cranial base.6,11,12 The asterion is considered to be an important landmark for craniotomy and is used to define the location of the transverse-sigmoid junction.11 Nonetheless, the localization of the asterion is variable.7,11 The asterion had been reported as 81% on the transverse-sigmoid junction, 15% on a point below, and 4% above this junction.11 Üçerler and
Gövsa7 had reported these rates as 87%, 11%, and 2%, respectively. The FHP, which was also evaluated during our study, is considered to be an important displayable reference line on the skull for cases in need of craniotomy.7 Adding to these, the squamous part of the temporal bone having some morphologic changes because of some chronic bone diseases must be remembered.7 Currently, CT imaging techniques are used for metric sex analyses, and systematic studies for determination of sex from the skull require CT imaging.9 Morphometric analyses can also be done by the naked eye, but to make this kind of analyses and achieve statistically significant results, studying a great number of samples is required. In addition, for situations in which a sufficient number of skulls do not exist, metric analyses and assessments can be done by using radiologic methods. Multidetector CT, which was used in this study, is a highly advanced radiologic imaging technique. Multidetector CT is a reliable and noninvasive technique that can show the details of bone structures by multislice images and with high resolution.13 Multidetector CT is used in anatomic studies to gain more reliable morphometric data in recent years.14 In addition, this study, conducted with MDCT, is superior to skull studies because of accurate sex determination, cadaver studies because of minimal tissue shrinkage effect, panoramic radiographic studies because of
TABLE 3. Comparison of the Data Acquired, Between Sides According to Sexes Male
Female
Right Parameters MH1, cm MH2, cm Pr-Mi, cm Pr-Map, cm Pr-As, cm As-Map, cm Ang 1, degrees Ang 2, degrees Ang 3, degrees At-As, cm At-Map, cm
Left
Right
Min–Max
Mean (SD)
Min–Max
Mean (SD)
P
Min–Max
1.37–3.51 2.41–4.12 2.56–4.74 2.23–3.95 3.92–6.64 4.13–6.59 58.00–86.40 25.30–50.00 55.30–90.40 5.41–7.63 2.94–4.59
2.35 (0.39) 3.39 (0.37) 3.66 (0.48) 3.12 (0.29) 4.93 (0.38) 5.06 (0.46) 70.49 (5.73) 36.54 (4.22) 72.96 (6.94) 6.87 (0.40) 3.84 (0.34)
1.38–3.13 2.44–4.16 2.55–4.71 2.24–3.94 3.94–6.61 4.15–6.59 58.50–85.40 25.30–50.00 53.80–90.40 5.21–7.59 2.90–4.69
2.35 (0.37) 3.39 (0.37) 3.65 (0.48) 3.13 (0.29) 4.94 (0.38) 5.07 (0.46) 70.34 (5.47) 36.65 (4.48) 72.99 (6.98) 6.87 (0.39) 3.85 (0.33)
0.96 0.98 0.97 0.85 0.88 0.92 0.88 0.87 0.98 0.99 0.86
1.60–2.46 2.23–3.85 2.60–4.06 2.36–3.26 3.84–5.07 4.21–6.12 58.20–82.10 22.70–46.00 63.10–92.30 5.34–7.14 3.11–4.12
Left Mean (SD)
1.98 2.94 3.23 2.89 4.61 4.89 69.66 35.32 75.01 6.54 3.61
(0.23) (0.35) (0.34) (0.24) (0.31) (0.32) (5.10) (3.56) (6.06) (0.33) (0.25)
Min–Max 1.60–2.48 2.21–3.86 2.60–4.01 2.32–3.28 3.88–5.05 4.21–6.14 58.20–82.10 22.70–46.00 63.60–94.90 5.37–7.12 3.01–4.13
Mean (SD) 1.98 2.94 3.24 2.90 4.60 4.89 69.48 35.49 75.02 6.55 3.61
(0.23) (0.35) (0.33) (0.24) (0.31) (0.32) (5.35) (3.40) (5.97) (0.32) (0.26)
P 0.99 0.93 0.95 0.85 0.90 0.97 0.83 0.77 0.99 0.98 0.99
Max, maximum; Min, minimim.
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The Journal of Craniofacial Surgery • Volume 26, Number 1, January 2015
detection and individuation of holes, direct radiographic studies because of magnification factor, as well as ultrasonographic studies because of more accurate data on differentiation of bone structures. In conclusion, we believe that the knowledge of distance measurements of major landmarks of the temporal bone is indispensible to avoid possible complications such as damage to the dura of the medial and the posterior cranial fossa as well as protection of the mastoid parts of the facial nerve and the tympanic chord during surgical interventions to the face, the mastoid area, and especially the sigmoid sinus.
6.
7. 8. 9.
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