The human skull is a complex anatomical structure that serves as the protective casing for the brain and supports the facial features. Its shape and dimensions have been the subject of interest in various scientific fields, including anthropology, forensics, and archaeology. Cranial morphometry, the measurement and analysis of the skull's shape, is a pivotal tool for understanding human variation, ethnic differences, and biological evolution. ^[1]

Cranial indices—ratios of specific cranial measurements—have been developed to classify skulls into different types based on their proportional characteristics. These indices help researchers understand the diversity in cranial shapes across populations, genders, and even within individuals from different age groups. The study of cranial morphometry and indices plays a significant role in forensic identification, determination of ancestry, and even the study of developmental and pathological conditions. ^[2]

Cranial anthropometry has become an increasingly significant field for anatomists, anthropologists, and plastic surgeons. In addition to metric measurements of the cranium, cranial indexes offer valuable insights into cranial morphology. The calculation of the cranial index is a method used to categorize human populations. ^[3] The cephalic index, introduced by Swedish professor of Anatomy Anders Retzius (1796–1860), was initially employed in physical anthropology to classify ancient human remains discovered in Europe. ^[4] The cranium, comprising twenty-two bones interconnected to form the head skeleton, expands to twenty-nine with the inclusion of one hyoid bone and three pairs of ear ossicles. It is classified into two main divisions based on its surrounding structures: the neurocranium, encasing the brain, and the splanchnocranium (viscerocranium), enveloping the oral and nasal cavities. ^[5]

The neurocranium comprises eight bones, while the splanchnocranium consists of fourteen bones, all belonging to the flat and irregular bone groups. These bones, excluding the mandible, are linked via immobile joints termed sutures. Cranial anthropometry holds increasing significance for anatomists, anthropologists, and plastic surgeons, facilitating detailed analysis and understanding of cranial structures and their variations. ^[6] The cephalic index is now widely used to describe individuals’ appearances and to estimate the age of fetuses for legal and obstetrical purposes. As a result, it has broad applications in various forensic investigations. ^[7]

The study was conducted using a sample of 100 dry human skulls, obtained from an anatomical collection. The skulls were selected to represent various age groups, genders, and ethnic backgrounds to provide a comprehensive dataset. The following parameters were measured using standard anthropometric instruments:

1. Maximum Cranial Length (MCL): The greatest distance from the glabella to the opisthocranion.
2. Maximum Cranial Breadth (MCB): The maximum width of the cranium, measured at the parietal eminences.
3. Biparietal Diameter (BPD): The distance between the parietal bones, measured horizontally.
4. Frontal Breadth (FB): The distance between the most lateral points of the frontal bone.
5. Nasion-Prosthion Distance (N-PD): The distance between the nasion and prosthion (the point where the maxilla meets the upper incisor).
6. Height of the Cranium (HOC): The vertical distance from the glabella to the vertex of the skull.

Cranial Indices Calculated:

1. Cephalic Index: The ratio of maximum cranial breadth (MCB) to maximum cranial length (MCL), multiplied by 100.

Cephalic Index=(MCBMCL)×100\text{Cephalic Index} = \left( \frac{\text{MCB}}{\text{MCL}} \right) \times 100Cephalic Index=(MCLMCB​)×100

This index helps classify skulls as dolichocephalic (long and narrow), mesocephalic (intermediate), or brachycephalic (short and broad).

1. Cranial Index: The ratio of the biparietal diameter (BPD) to the height of the cranium (HOC), multiplied by 100.

Cranial Index=(BPDHOC)×100\text{Cranial Index} = \left( \frac{\text{BPD}}{\text{HOC}} \right) \times 100Cranial Index=(HOCBPD​)×100

1. Frontal Index: The ratio of the frontal breadth (FB) to the maximum cranial breadth (MCB), multiplied by 100.

Frontal Index=(FBMCB)×100\text{Frontal Index} = \left( \frac{\text{FB}}{\text{MCB}} \right) \times 100Frontal Index=(MCBFB​)×100

The analysis revealed significant variation in cranial measurements and indices across different demographic groups. The cephalic index was found to differ notably between genders, with males exhibiting a higher incidence of mesocephalic and brachycephalic skulls, while females showed a higher proportion of dolichocephalic skulls. Ethnic differences were also evident, with individuals from Caucasian populations predominantly having mesocephalic skulls, while those of African and Asian descent exhibited a greater variety of cranial types. inherited traits. In anthropology, the cephalic index serves as a useful metric for distinguishing samples or individuals by race, sex, or personal identity

Cephalic Index Findings:

• Dolichocephalic: 25% (mean index < 75)
• Mesocephalic: 50% (mean index 75-80)
• Brachycephalic: 25% (mean index > 80)

Cranial Index Findings:

• The cranial index varied between 70 and 90 for most individuals, with a slight gender variation—males tending to have a higher cranial index than females.

Frontal Index Findings:

• The frontal index was found to be higher in individuals with brachycephalic skulls, indicating a broader frontal region compared to the more narrow frontal region of dolichocephalic skulls.

Table 1: Cranial Measurements (Mean ± Standard Deviation)

Table 2: Cephalic Index Distribution

Table 3: Cranial Index Distribution

Table 4: Frontal Index Distribution

Table 5: Gender Distribution by Cranial Type (Based on Cephalic Index)

Table 6: Comparison of Cranial Indices by Ethnicity

The morphometric data from this study provides a detailed understanding of cranial diversity within the studied sample. The findings corroborate previous studies that have demonstrated sex and ethnic differences in cranial shape. ^[8] Males generally exhibit broader and shorter skulls compared to females, which is consistent with sexual dimorphism observed in human skulls. Ethnically, individuals of African descent often display a broader skull, while those of Asian descent typically have a more rounded skull shape. ^[9]

The cranial indices calculated in this study are valuable in forensic anthropology for identifying ancestry, age, and sex of skeletal remains. These indices are particularly useful when soft tissue is absent, allowing forensic experts to make inferences about the biological characteristics of an individual. ^[10]

Morphometric parameters of orbit are important in ophthalmology, oral maxillofacial surgery and neurosurgery. Orbital index has been employed to determine the sex of a person in forensic medicine. The orbital index which determines the shape of the face differs in different population groups. This means that the orbits with larger widths than height will have smaller orbital indices while those with larger orbital indices will have narrow faces. ^[11] This index varies with race, regions within the same race and periods in evolution. The present study aimed to compare the orbital index of the South Indian population with available data from other populations of the world Normal values of orbital indices are vital measurements in the evaluation, and diagnosis of craniofacial syndromes and post traumatic deformities, and knowledge of the normal values for a particular region can be used to treat abnormalities to produce the best aesthetics and functional result. ^[12] For these purposes, standards based on local data are desirable, since these standards reflect the different patterns of craniofacial growth resulting from racial, ethnic, social and dietary differences. ^[13,14]

Cranial morphometry and the use of cranial indices provide valuable insights into the variability and diversity of human populations. This study highlights the role of cranial measurements in forensic and anthropological investigations, emphasizing the importance of understanding cranial diversity for identification purposes. Future studies with larger and more diverse sample sizes, including a broader range of ethnic groups, will further refine our understanding of cranial variation across populations.

The continued application of cranial morphometry, combined with advancements in technology and statistical methods, holds the potential to significantly enhance our understanding of human evolution, forensic identification, and medical applications related to cranial development and pathology.

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