Morphometric study of nasal bones and piriform apertures in human skulls

Introduction

The piriform aperture (PA) is the skeletal aperture located in the middle part of the face and limited by the frontal processes of the maxillary bones, the nasal bones, and the anterior nasal spine, palatal process of the maxilla inferiorly. It corresponds to the anterior limit of the skeletal nose, and a major component of the size of the nose and1, 2 the features of the piriform aperture have been reported as classic indicator of sexual differentiation.3 The measurements of PA can be an anatomical landmark used for ethnic differentiation in human identification and provide information for surgical procedures and nasal reconstruction in otolaryngology. There are many variations in nasal bone shape among the different population e.g. the nose is much broader with thickened upper nasal region in East Asians. It is longer and more prominent in Middle Eastern and Southern European populations. Most Egyptian skulls are typically North African Caucasians. The shape of nose in them is broad and lack of a sharp lower border. It is therefore necessary that in cases of unidentified skeletal remains, the ancestry should be estimated.4 The knowledge of the morphometric measures is of immense importance for performing rhinoplasty, osteotomies and plastic reconstructions.5 The respiratory mechanics may be affected due to trauma to the piriform aperture.6 Their form and size may also serve as a basis for anthropological studies. Knowledge of dimensions and shape of the piriform aperture in human skulls, are essential for better understanding of Anatomical structure. With these backgrounds in mind the objective was to study morphological features of nasal bone and piriform aperture.

Materials and Methods

Present study was approved by Institutional Ethical and Research committee [Registration No: PIMS/DR/RMC/2018/251] of a Pravara Institute of Medical Sciences, Loni. Adult human skulls available from collection of dried skulls in the department of Anatomy and from undergraduate students were used for study purpose. Skull bones of unknown age and sex were obtained.

Material

1. Thread

2. Scale

3. Vernier caliper

Following measurements of nasal bone and piriform aperture were noted.

1. Height of piriform aperture: The height of the piriform aperture was measured between the inferior margin of the internasal suture to the anterior nasal spine (Figure 1).

2. Upper width of piriform aperture: Upper width of piriform aperture was measured between the right and left naso-maxillary junction. (Figure 2)

3. Lower width of piriform aperture: Lower width of the piriform apertures was measured between the right and left margin of the anterior surface of the maxilla. (Figure 3)

4. Height of nasal bone: The height of Nasal bones were measured from the nasion to the rhino. (Figure 4)

5. Width of nasal bone: The width of the nasal bones was measured between the upper points of the lateral borders of the nasal bone. (Figure 5)

6. Shape of nasal bone were classified as A, B.C, D and E as mentioned by Hwang et al.1

7. Shape of piriform aperture: The shapes of piriform aperture were classified as long narrow, triangular, triangular to oval and tending to roundness.

Figure 1

Showing measurement of height of Piriform Aperture was measured between the inferior margin of the internasal suture to the anterior nasal spine

Figure 2

Showing measurement of upper width of Piriform Aperture was measured between the right and left naso-maxillary junction

Figure 3

Showing measurement of Lower Width of Piriform Aperture was measured between the right and left margin of the anterior surface of the maxilla

Figure 4

Showing measurement of height of nasal bone were measured from the nasion to the rhino

Figure 5

Shapes of nasal bone were classified as A, B.C,D and E as mentioned by Hwang et al

Results

It is evident from Table 1 that height, upper width and lower width of piriform aperture were greater in male as compared to female. This difference was not statistically significant for upper width of piriform aperture (p=0.49) and for lower width of piriform aperture (p= 0.65) while the difference in height of piriform aperture was statistically significant. (p <0.0001).

Differences in Height and width of nasal bone were not statistically significant among male and female nasal bones.(Table 2)

Shapes of nasal bone were classified as A, B.C,D and E as mentioned by Hwang et al. Most common shape of nasal bone observed was Type A followed by Type B and C. (Table 3)

It is evident from Table 4 that most common shape of piriform aperture was triangular to oval (50.00) in both the gender followed by tending to roundness (31.48).

Discussion

Adult human skulls were used for morphometric study of nasal bone and piriform aperture. It is evident from Table 1 that height, upper width and lower width of piriform aperture were greater in male as compared to female. The difference in height of piriform aperture was statistically significant. (<0.0001).Height of piriform aperture in a study by Durga Devi et al8 on south Indian population was 31.2 ± 1.3mm in male 27.2 ±1.3 mm in female while in a study done by Cantin et al on Brazilian dry skull was 50.82 mm in male 47.53mm in female.3 Moredduet al studied on 3D computerized tomography scan (C.T. scan), the values were 32.54mm in females and 36.35mm in males.6 In a study by Hwang et al on Korean population piriform aperture height was 30.1mm and 28mm in males and females respectively.1 Yüzbaşioğlu et al studied skull CT on Turkish population 33.4mm and 30.1mm males and females respectively.9 In present study PA height was 32.4±1.7mm in males and 28.1±1.6mm in females. In a study done by Asghar et al7 on North Indian the mean Height of PA was 29.57±3.28mm in females and 31.16±3.58mm in males which corresponds with present study. Upper width of piriform aperture was 15.6 ± 2.4 mm in male 16.6 ± 2.8 mm in female in a study conducted by Durga Devi et al on south Indian population.8 Hwang et al1 showed upper width of PA 16.8±2.6mm in male 17.0±2.0 mm in female but in the present study upper width of PA was 16.1±2.2mm in male and 15.7±2.1mm in female, (Table 1) which was in concordance with observations by Durga et al.8 In present study, upper width of piriform aperture was greater in male as compared to female. This difference was not statistically significant for upper width of piriform aperture (p=0.49). Hwang et al reported lower width of PA 25.7±1.7mm in males and 25.4±2.1 in females.1 Durga Devi et al observed lower width of PA in male 24.03 ±1.4 mm and 24.4 ± 2.3mm in female.8 In present study, lower width of piriform aperture was 24.8±1.3mm in male and24.6±1.9mm in female. It is evident from Table 1 that lower width of piriform aperture was greater in male as compared to female and this difference was not statistically significant (p= 0.65).

Height of Nasal bone in present study is 16.8±2.1 mm in male and 16.4±1.3 in female. (Table 2) In a study of Turkish population by Yüzbasioglu N et al, height of nasal bone was 18.7mm in male and 17.2 mm in female. 10 Hwang et al reported height of nasal bone 25.9 mm in male and 24.5 mm in female.1 Karadag D et al in a study carried out in Antolian population observed that height of nasal bone was 30.61 mm in male and 29.01 mm in female. 10 Baek et al in a study carried out study in Korean population and that height of nasal bone was 22 mm in male and 17.3 in females.11 In a South Indian population study by Durga et al reported that nasal bone height was 16.3±1.9 mm in male and 17.4 ±2.3 mm in female, values of which correlates with present study. In a study carried out by Asghar et al height of nasal bone was 17.76 mm in male and 17.25 mm in female.7

In present study width of nasal bone was 10.7±1.4 mm in male and 10.4±1.6mm in female. (Table 2). In a study by Yüzbasioglu et al width of nasal bone was 11.8 mm in male and 12 mm in female. 9] while in North Indian population width of nasal bone was 12.6mm in male and 11.8 mm in female.7 In a study by Durga et al width of nasal bone was 11.3±1.6 in males and in female it was 12.05±1.7 mm in south Indian population.8

In present study shapes of nasal bone were classified as A, B, C, D and E as mentioned by Hwang et al.1 Most common shape of nasal bone observed was Type A (42.59%)followed by Type B (18.51%) and C(16.66%) and Type D(12.96%) and Type E (09.25) (Table 3). In a study carried out in Korean population by Hwang, commonest shape of nasal bone were Type B (52.3%) next Type A,[43.2%] followed by Type C(4.5%) while Type D and Type E were not found.1 In a study carried out in South Indian population in relation to the shape of nasal bone, Type A was 35.2%, Type B 19.6%, Type C 17.6%, Type D 15.6% and Type E 11.7%.8

In present study shape of piriform aperture was Triangular to Oval in 50% followed by tending to roundness 31.48%, Triangular 14.81% and Long and Narrow 3.70%. (Table 4) In a study by Durga Devi et al shape of piriform aperture was triangular to oval 45.09% and tending to roundness in 39.21%.8 Asghar et al observed shape of piriform aperture triangular to oval 83.5% tending to roundness in 15%.7

Conclusion

Height, upper width and lower width of piriform aperture were greater in male as compared to female but only the difference in height of piriform aperture was statistically significant. Differences in Height and width of nasal bone were not statistically significant among male and female nasal bones. Most common shape of nasal bone observed was Type A followed by Type B and C. Most common shape of piriform aperture was triangular to oval in both the gender. Majority finding of the present study were in concordance with North and south Indian population studies while significant differences have been noted in comparison to the morphometric measurements of Turkish, Korean, Brazilian and Anatolian population. These variations might be because of differences in ethnicity.

Source of Funding

None.

Conflict of Interest

The authors declare no conflict of interest.