RADIOLOGICAL MAPPING OF NEPALESE CALVARIA

The present study showed that Mean thickness+_SD of frontal bone were 6.1+_1.8mm; parietal 4.6+_2.2 and occipital 9.5+_3.4. The study also showed that frontal bone had 2.4+_0.8 mm thick outer table; 1.4+_0.6mm inner table and 3.5+_1.3mm diploe. Similarly parietal bone had 1.9+_0.6 mm thick outer table; 1.1+_0.4mm inner table and 0.8+_0.5mm diploe. The occipital bone had 3.5+_1.5 mm thick outer table; 2.2+_0.8mm inner table and 4.3+_1.8mm diploe. Similarly this present study also calculated the mean thickness+_SD of outer table in the calvarium as 2.7+_1.3mm and that of inner table 1.5+_0.9 mm. Thus it concluded that outer table was thicker than inner table.


Introduction
Skull has cranial vault and base.The cranial vault is called as calvarium which roofs the cranial cavity (brain box).Cranial vault consists of frontal, parietal and occipital bones which develops from membranous ossification thus these are called membranous bones.Membranous bones are widely used in bone grafting because of greater acceptability in donor site.While evaluating the donor site, first surgeons should assess the thickness of bone in calvarium with help of Computerized tomography (CT) scan.Knowledge of calvarial thickness is also important for selection of screw length to be used in calvarial bones for fixation.Calvarial bone thickness can be measured with help of CT scan to determine the length of screw that can be used without risk of penetrating the cranial cavity.Total thickness of calvarial bones includes outer

Materials and methods
A hospital based cross-sectional study was carried out with aim to measure the thickness of Nepalese calvarial bones i.e.Frontal, Parietal and Occipital.The CT records of One hundred and fifty adult people, over 20 years age were randomly selected for the study.However those who had history of trauma to skulls and bony pathology of skull bones were excluded in the study.Thicknesses of calvarial bones at various points were measured with the help of CT scan.

Result
CT records of one hundred and fifty adult people were studied.Nine various points on frontal bone, seven on parietal and six on occipital were located and their thickness were measured bilaterally with help of CT scan.

Table 1: Comparison of mean thickness of Frontal, Parietal and Occipital bones (n=150).
There was significant difference among mean thickness of frontal, parietal and occipital bones (p<0.05).models. 2Hemmy DC and Tessier P studied CT of dry skulls with craniofacial deformities and assessed accuracy of three-dimensional reconstruction.In this study dry skulls from patients with Crouzon syndrome or orbital neurofibromatosis were studied using threedimensional reconstruction of computed tomography data.The images were compared with one another and with the actual skulls.It was concluded that the use of dry skulls is helpful in pointing out errors of inclusion or exclusion.
Thinner sections permit more accurate representation.Since reconstructed data do not appear to be significantly enhanced by using overlapping sections, radiation can be reduced by using abutting sections. 3Deborah R.Smith et,al Identified of human skeletal remains by comparision of bony details of the cranium using computerized tomographic(CT) scans.A case was described where a cranium from an unknown individual was identified by comparison of antemortem and postmortem computerized tomographic (CT) images of the bony structure of the skull.Bony details of the frontal and sphenoid sinuses, ethmoid and mastoid air cells, sagittal cranial suture, and the internal occipital protuberance were exactly the same on both CT scans, confirming them as the same person. 4ss MD et.al investigated skull thickness of Black and White races and found that White women have the thickest and White men the thinnest skulls.The skulls of women were statistically significant thicker than those of men in both ethnic groups. 5

Conclusion
The present study studied CT records of one hundred and fifty adult people who had no history of trauma and bony pathology of calvarial bones.Nine various points on frontal bone, seven on parietal and six on occipital were located and their thickness were measured bilaterally with help of CT scan.
table, diploe and inner table.Diploe is made up of spongy bone whereas outer and inner table made up of compact bone.

Parietal bone that were measured bilaterally:
Parietal and Occipital bone as well as among the mean thickness of outer table, inner table and diploe of frontal, parietal and occipital bone.Student's unpaired 't'test was applied to test the significant difference between the mean thickness of outer table and inner table.

Table 2 : Comparison of mean thickness of outer table, inner table and diploe of Frontal, Parietal and Occipital bones (n=150).
There was significant difference among mean thickness of outer table, inner table and diploe offrontal, parietal and occipital bones (p<0.05).

Table 3 : Comparison of overall mean thickness of Outer and Inner tables of calvarium (n=150). Thickness Outer table Inner table P value Mean thickness (mm)+_SD 2.7+_1.3 mm 1.5+_0.9 mm 0.041
Apert patients and 19 with Crouzon syndrome were included in the study.A number of qualitative characteristics of the calvaria and cranial base were recorded and the cranial base angle was measured on the 3-D The study calculated the mean thickness+_SD of outer table in the calvarium as 2.7+_1.3mmand that of inner table 1.5+_0.9mm.Thus it concluded that outer table was thicker than inner table.