Sex determination using maxillary sinus.

BACKGROUND: Individual identification is a subtle concept and often one of the most important priorities in mass disasters, road accidents, air crashes, fires, and even in the investigation of criminal cases. Matching specific features detected on the cadaver with data recorded during the life of an individual is an important aspect in forensics, and can be performed by fingerprint analysis, deoxyribonucleic acid matching, anthropological methods, radiological methods and other techniques which can facilitate age and sex identification. Sinus radiography is one such method that has been used for determination of the sex of an individual. Hence, an attempt is being made to use the different dimensions of the maxillary sinus in the determination of sex using coronal and axial sections of plain computed tomography (CT) scan.
MATERIALS AND METHODS: A total of 30 patients including 17 male and 13 female, visiting the Outpatient Department of the Mamata General Hospital were included as the study subjects. The dimensions of right and left maxillary sinuses of 30 subjects from plain CT were measured using SYNGO software and statistical analysis was done.
RESULTS: Sex determination using height, length, width, and volume of the maxillary sinus on both sides showed statistically significant results with a higher percentage of sexual dimorphism in the case of volume.
CONCLUSION: Volume of the right maxillary sinus can be used as accurate diagnostic parameter for sex determination.

Introduction

Sex determination is one of the important parameters in forensic identification. Gender determination in damaged and mutilated dead bodies or from skeletal remains constitutes the foremost step for identifying in medico-legal examination.[1] Matching specific features detected on the dead bodies with data recorded during the life of an individual is an important aspect in forensics, and can be performed by fingerprint analysis, deoxyribonucleic acid matching, anthropological methods, radiological methods and other techniques which can facilitate age and sex identification.[2]

Determination of gender is done through various body parts, the skull, the pelvis, the long bones with an epiphysis and a metaphysis in skeletons, the mastoid process, the foramen magnum and the paranasal sinuses. In explosions, warfare, and other mass disasters like aircraft crashes, the skull and other bones are badly disfigured, however it has been reported that maxillary sinuses remain intact.[3]

Maxillary sinuses are two spaces, which are filled with air, located in the maxillary bone and can be in various sizes and shapes. Their walls are thin. The apex of the sinuses can extend into the zygomatic process and can occupy the zygomatic bone. The floor formed by the alveolar process, the first, the second and the third molars and the roots of the canines may elevate the sinuses or may perforate their floor.[3]

Sinus radiography has been used for identification of remains and determination of sex and ancestry.[2] Computed tomography (CT) scans are excellent imaging modality used to evaluate the signal-nasal cavities. They provide an accurate assessment of the paranasal sinuses, craniofacial bones, as well as the extent of pneumatization of the sinuses.[4] It provides detailed information that is not available from standard radiographs.[5] CT measurements of maxillary sinuses are useful to support gender determination.

Sexual dimorphism refers to the systemic difference in the form (either in shape or size) between individuals of different sexes in the same species.[1] Maxillary sinuses of various species are known to exhibit sexual dimorphism. The maxillary sinus in males is larger than in females in contemporary human populations.

Based on this background, this study was done to estimate different dimensions of the maxillary sinuses to determine gender of an individual and sexual dimorphism.

Materials and Methods

A total of 30 patients including 17 male and 13 female, visiting the Outpatient Department of the Mamata General Hospital, Khammam, Andhra Pradesh were included as the study subjects. The current study included local patients who had complained of headache without any pathology. The dimensions of right and left maxillary sinuses of 30 subjects from plain CT were measured using SYNGO software. (syngo.via2 3D software)

The following measurements were performed by radiologists:

The right and left side height of the maxillary sinus (height-maximal craniocaudal diameter) [Figure 1]

Figure 1

Axial computed tomography image showing: (a) Right side height (maximal craniocaudal diameter) of maxillary sinus. (b) Left side height (maximal craniocaudal diameter) of maxillary sinus

The right and left side depth of the maxillary sinus (depth-anterioposterior diameter) [Figure 2]

Figure 2

Coronal computed tomography image showing: (c) Right side depth (anterioposterior diameter) of maxillary sinus. (d) Left side depth (anterioposterior diameter) of maxillary sinus

The right and left side width of the maxillary sinus (width-maximal width) [Figure 3]

Figure 3

Coronal computed tomography image showing: (e) Right side width (maximal width) of maxillary sinus. (f) Left side width (maximal width) of maxillary sinus

The height measurement of the maxillary sinus was performed on coronal images, whereas measurements of the depth and width were performed on axial images.

As all three-dimensions of the maxillary sinus were measured, the volume of each maxillary sinus was also calculated using the following equation.[6]

Volume = (height × depth × width × 0.5).

After measuring all dimensions statistical analysis was performed by Mann-Whitney U-test.

Sexual dimorphism is calculated using the following formula.[1]

Percentage of dimorphism = {(Xm /Xf) – 1} × 100

Xm: Mean male maxillary sinus dimension

Xf: Mean female maxillary sinus dimension.

Results

The mean values of the right side maxillary sinus height, length, width, and volume for males is 4, 3.76, 2.63, and 39.93, respectively, and in case of females it was 3.09, 3.12, 2.23, and 21.53. Sex determination using height, length, width and volume of the maxillary sinus on the right side showed statistically significant results with P = 0.00001, 0.00001, 0.00701, and 0.00001 [Table 1 and Figure 4].

Table 1

Comparison of males and females with respect to height, length, width and volume in right side of maxillary sinus by Mann-Whitney U-test

Figure 4

Comparison of males and females with respect to height, length and width in right side of maxillary sinus

The mean values of left side maxillary sinus height, length, width and volume for males is 3.93, 3.73, 2.53, and 37.64, respectively, and in case of females it was 3.07, 3.12, 2.20, and 21.10. Sex determination using height, length, width, and volume of the maxillary sinus on the left side also showed statistically significant results with P = 0.00001, 0.00001, 0.0110, and 0.00001 [Table 2 and Figure 5].

Table 2

Comparison of males and females with respect to height, length, width and volume in left side of maxillary sinus by Mann-Whitney U-test

Figure 5

Comparison of males and females with respect to height, length and width in left side of maxillary sinus

The sexual dimorphism of maxillary sinus right side height, length, width, and volume showed the percentages of 29.44%, 20.51%, 17.937, and 85.46%, respectively [Table 3].

Table 3

Percentage of dimorphism of right side

The sexual dimorphism of maxillary sinus left side height, length, width, and volume showed the percentages of 28.01%, 19.5512%, 15, and 78.38%, respectively [Table 4].

Table 4

Percentage of dimorphism of left side

Discussion

A forensic study is very important in the identification of sex especially when the body of the deceased has been destroyed as a result of physical injury due to weapons, fire or strong chemicals. This becomes more difficult if the bones are compromised by physical insults such as explosive or violence.[7] In that case, maxillary sinus remains intact, therefore maxillary sinuses can be used for sex identification.

In addition to the maxillary sinus, sexual dimorphism can also be done using other skeletal structures such as foramen magnum, occipital bone and frontal bone. In a study done about the gender determination from the foramen magnum, the results demonstrated that sexual dimorphism is present in foramen magnum. Anteroposterior diameter and transverse diameter were higher in male skulls than females (34.04 vs. 31.72 and 28.63 vs. 26.59).[8] In another study gender determination was done using calvarial thickness in different skeletal patterns. They concluded that frontal and occipital bones can be used as important key bones for understanding the calvarial phenotypic description and sexual dimorphism.[9]

In the present study, the dimensions and volume of maxillary sinuses of right and left side were notably larger in males compared with females. They showed statistically significant values with a higher percentage of sexual dimorphism in the case of volume with 85.46% for the right side and 78.38% for the left side.

Kawarai et al. in 1999 did a study on volume quantification of healthy paranasal cavities by three dimensional CT imaging in 20 Japanese subjects and confirmed that paranasal sinuses were individually and on the whole, apparently larger in case of males than females.[10]

Fernandes and Sahlstrand-Johnson et al. stated that the mean value of the maxillary sinus volume was significantly larger in males than in females. In addition to this, Fernandes, found that the European crania had significantly larger maxillary sinus volume than Zulu crania.[611] In case of Egyptians cephalocaudal and size of the left maxillary sinuses are a useful feature in gender determination.[12]

Teke et al. in 2007 studied width, length and the height of the maxillary sinus in 127 adult patients by CT and observed that the measurements of the maxillary sinuses of males are larger than those of females. The mean estimated rate of gender was detected at 69.3%.[3]

Accordingly Uthman et al., maxillary sinus height was the best discriminate parameter that could be used to study sexual dimorphism with overall accuracy of 71.6%.[13] Attia et al. study concluded that maxillary sinus dimension measurements, especially the right height, are valuable in studying the sexual dimorphism with overall accuracy 69.9%.[4]

Vidya et al. in 2013 studied 30 dry skulls of south Indian origin. The height, length, width and volume of maxillary sinuses on each side were determined. The results showed the measurements and volume of maxillary sinus of males were slightly more compared with females. The left width and right sided volume showed statistically significant values.[14]

Conclusion

Gender determination is an important step in identifying in forensic science. The result of the present study showed that the maxillary sinus exhibits anatomic variability between the genders. Maxillary sinus dimensions, especially the right side volume are valuable in studying sexual dimorphism and the CT images could provide adequate measurements for maxillary sinus.