Craniometry Patterns of Nigerians and its Correlation with Chronological age

Vidona WB^1*, Oviosun A¹ and David LK^2
*Correspondence: Vidona WB, Department of Anatomy, Edo University Iyamho, Edo State, Nigeria, Tel: +2348038690470, Email:

Keywords

Craniometry • Anthropometry • Cranial vault • Cranium • Encranial • Sex • Age variations

Abbreviations

SS: Sum of Squares; MSS: Mean Sum of Squares; TRT = Treatment; F-ratio: Mean sum of squares of treatment/mean sum of square of error, N: Number of sample; K: Total number for each treatment, DF: Degree of freedom

Introduction

Craniometry being the scientific study and measurement of the skull has been useful in anthropometry for the morphometric and non-morphometric identification of the sex and age and in forensic practice when cranial remains are compared with living photographs. Cranial dimensions and cranial indices are considered as simplest and most efficient way to indicate facial differences and age variations. For instance, cranial volume expresses several aspects of growth and development and permits critical evaluation of unusually large or smallcrania [1]. Through skull morphology, population differentiation has been explored by recent studies [2-5], showing that not only vault features but also various facial characteristics are responsible for both inter and intra-regional differences within a region. These cranial index variations between and within population have been attributed to a complex interaction between genetic and environmental factors. There are several skeletal indicators that are used to estimate age at death for adults such as Cranial suture closure or suture synostosis of which Nawrocki (1998) introduced 14 regression equations for determining age at death using these sutures and as Acsadi and Nemeskeri (1970) opined in an attempt to create an age estimation method using endocrinal suture closure while examining 285 symmetrically closing crania suggest that as age increases so does mean suture closure [6,7].

The aim of the study is to investigate the craniometric patterns in the Nigerian population based on three dimensional computed tomographic data with the objectives of determining the age of individuals in the eastern part of Nigeria as well as determining if the skull of individual varies with age using computed tomography since it enables 3-D reconstruction and assesses the cranium data both inner and outer anatomical landmark for the craniometric study.

Methodology

Methodology Involve a descriptive study design with age was determined using standard ageing techniques, as specified in Scheuer and Black (2000a; 2000b) and Cox (2000) [8]. Normally, the practice consists of taking precise measurements using ‘anatomical landmarks’ on the skull. The inclusion criteria include individuals within ages 25 to 60 with no incidence of head trauma or abnormality, no loss of teeth from the maxilla and no chronic illness that might affect the cranium. The exclusive criteria include individuals with anatomical deformities and children. The data was collected from a CT SCAN’s radiological department in Abia state Diagnostic center, Umuahia and Union diagnostic center, Port Harcourt Rivers State. Patients were scanned in the radiology department and the CT data were processed in a computer workstation at the department. A spiral computed tomography scanner (SIEMEN) was used to obtain data from 150 crania. The CT scan acquisition was performed with 1.5mm slice thickness and reconstruction was done with 1.0m 2m slice thickness. All the CT data were recorded using DICOM 3.0 as a medical image file format into CD-ROM and subsequently will be imported to the medical imaging software (MIMICKS). The segmentation techniques will be used to identify the region of interest of the computed tomography image based on Hounsfield unit. The selected region was calculated into 3-D modem which enabled determination of the 3-D Craniometric data. During each scanning, each subject was placed in a supine position. Axial scanogram was obtained from the setting that the tube voltage is 120KVP and tube current be 52 mA, with 0.58 rotation time and 1mm slice thickness, the CT scan lateral view 300 applications present in the machine so as to avoid problem of magnification. To determine the craniometric data in the present study, the first step was to define the anatomical landmarks which can be classified as median and bilateral types. All landmarks used in the present study were based on the traditional definition with the modification into 3-D model. The most prominent anatomy in 2-D/3-D views were selected to state the proper position of each anatomical landmark. The second step was to calculate the craniometric parameters, which were derived from the two and three coordinate points for linear and angular measurements respectively. The measurement data were typed in Microsoft Excel and then exported to SPSS version 20.0 for the statistical analysis.

The anatomical landmarks in craniometric study are categorized into median and bilateral landmarks [9].

The mean landmarks are approximately located on sagittal plane. The landmarks are:

Glabella (GL) - the most anterior point of frontal bone between supraorbital in the sagittal plane. Bregma (BR) - the crossing of the coronal and sagittal sutures on the top of the skull. Opisthocranium (OPC) - the most posterior point in midline of inion bone which length of the skull is maximum when measure from Glabella point.

Nasion (NA) - the intersection point of the internasal and frontonasal sutures in the sagittal plane. Basion (BA) - the most anterior point of the great foramen magnum in the sagittal plane.

Each of the three-dimensional models of skull is used to determine the anatomical landmark. Only one investigator locates the entire landmarks in every skull to avoid uncertainty of intra-observer. The measurements are interpreted using statistical analysis and reported in form of comparism of the mean values and mean difference, standard deviation, and confidence interval in respect to the various landmarks. In order to distinguish Craniometric parameters of each age, analysis of variance was utilized for analysis. A p-value 0.005 alpha level of significant that was used to determine the difference. 150 dry adult human skulls cases (male and female both) constituted the material for the present study between age group of 25 - 60 years. In this study,we considered only complete union of the glabella occiput length, basionnasion length, basionbregma height, nasionbregma cord, bregma lambda cord, lambda opisthion length, basionprosthion length sutures instead of taking into account other scoring system of suture closure and compared with standard data mentioned in different previous studies.

Results

Result of the study shows that the total number of sample for each landmark group in table 1.1 is 1050 which covers the range value of 6 with a minimum number 1 and maximum number 7. The total sum of all Landmarks d is 4,200. The mean statistics of the seven groups is 4.00 with standard error of 0.62. The total number of length is 1050 with range of 119. The length attracts the minimum and maximum value of 80 and 199 with total sum of 132282. The mean statistics is 125.98 with standard error of 0.740.Table1.4 describes the data in terms of the mean, standard deviation, standard error and the confidence interval for the mean. The total for each group mean, standard deviation, standard error and confidence interval (CI) can be seen at the columns of the Table 1.

Table 1.2 describes the confidence interval for the mean (upper bound), minimum value and maximum value of the length for each group. LOL has the least value with a cumulative mean of 99.89 and it is considered as the group minimum number of mean (xmin). BNL has the second least value with the cumulative mean of 115.26 and is considered as second minimum number of mean (x2min). BLC is the third minimum with the cumulative mean of 117.34 (x3min). BBH is the fourth minimum with the cumulative mean of 123.25 (x4min). BPL is the fifth minimum with the cumulative mean of 124.53 (x5min). NBC is the sixth minimum with the cumulative mean of 128.14 (x6min) and GOL has the maximum cranium length value with the cumulative mean of 173.46 and is considered as the group with maximum number of mean (xmax) Tables 2 & 3.

From the distribution of means among the various group. We notice that the difference between each group is not large but rather each group differences from another group b a few number which ranges from 1 to at least 50 Tables 4 & 5.

Decision Rule: If F-ratio value is less than or equal to 0.05 alpha level of significance then the test is statistically significant.

The between group has sum of squares of error 470793.851, the degree of freedom (df) is 6, the mean square error 78465.642, F-ration of 617.463 and significant value 0.00. The within groups has sum of squares of error 132541.840, degree of freedom 1043 and mean square error 127.078. The total sum of squares of error is 603335.691, the total degree of freedom I 1049.

From Table 1.1 the alpha (α) level of significance used was 0.05. The confidence interval for each group was displayed in each column. The significance value or p-value was 0.00. In this research work the significance value is 0.00 which means that the researcher is 90% confident that the results are accurate.Therefore, the test is statistically significant which means that the cranium results have an acceptable amount of error. The confidence interval for each group is given as LOL=99.89, BNL=115.26, BLC=117.34, BBH=123.25, BPL=124.53, NBC=128.14, GOL=173.46. with p-value or significance values in each rows 1.00, 0.684, 0.958, 0.85 and 1.000.Since all the p-value are less than or equal to 1.00 therefore we are 90% confident that the result is accurate and the research work is statistically significance, the aim of the craniometric research is achieved.

Conclusion

can be drawn that the craniometric data of Nigerians age have statistical significant differences in their mean values. Age of the cranium skulls suture of glabelloocciput length, basionnasion length, basionbregma height, nasionbregma cord, brema lambda cord, lambda opisthion length, basionprosthion length suture was matching with standard data given in the table that was analyzed.

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