The importance of the structures in the mastoid part of the temporal bone of the skull has increased due to the increasing use of the transtemporal route for surgical procedures that involve access to structure in the posterior cranial fossa and mastoid air system which are performed by neurosurgeones and otolaryngologists .
The knowledge of mastoid canal and mastoid groove is very important because they contain an arterial branch of occipital artery with its accompanying vien which is liable to injury resulting in sever bleeding.
Since it covers the lateral wall of the mastoid antrum,the suprameatal triangle is generally accepted as a useful anatomical landmark for otologic surgeons during mastoidectomy .
The depth of sigmoid sulcus in relation to suprameatal triangle may be used as a mark that points toward avoidance of bleeding possibility during mastoidectomy.
In this study, hundred human skulls of known sex were conducted to many observations and measurements aimed to describe the anatomical variations of mastoid canal ,suprameatal triangle and suprameatal spine, and to find the sexual dimorphism in the mastoid process and related measurements.
The following measurements had been taken :mastoid length , mastoid breadth ,asterion - mastoidale length ,asterion - porion length , porion – mastoidale length ,bimastoid breadth ,mastoidale-opisthion length (right &left) , prescence or absence of mastoid canal ,unilateral or bilateral mastoid canal ,single or double MC and if both MC &MG are present on same side ,the length of mastoid canal and groove, presence or absence of suprameatal spine; type and size of SMS ,shallow or deep suprameatal triangle ,relation between SMD and SMS relative to shape and size.Measurement of the distance between suprameatal triangle and sigmoid sulcus.
The mastoid canals were present in 28% of total skulls.Among these 28 mastoid canals ;4(4%) were bilateral ,12(12%) were unilateral on the left side ,12(12%) were unilateral on the right side . Both mastoid canals and grooves were found together on the same side in 8 % of total skulls. The mean length of mastoid canal on the right side was 7.5±3.69 mm in male and 6.75±3.33mm in female and it was 6.08±3.64 mm in male and 5.63±3.15 mm in female on the left side with no significant difference between male and female skulls .
Mastoid grooves were present in 24% of total skulls ; 4% were bilateral,12% were unilateral on the left side ,8% were unilateral on the right side . The mean length of mastoid groove was 9.33± 4.79 mm in male and 10.8 ± 4.31mm in female on the right side with no significant difference between both sexes .it was 5.0 ± 0.0 mm in male and 10.53±3.86 mm in female on the left side with a highly significant difference between both sexes .
As regard the types of SMS ,the crest type was present in 20 male skulls (45.5%) and 20 female skulls (35.75%) on the right side,while it was present in 28 male skulls (63.6%) and 24 female skulls (42.9%) on the left side .The triangular type was present in 12 male skulls (27.3%) and in 16 female skulls (28.6%) on the right side. while it was present in 8 male skulls (18.2%) and 16 female skulls (28.6%) on the left side.There were insignificant difference between both sexes and both sides as regard the types of SMS .
As regard the size of SMS,it was small in 16 skulls(16%) on the right side and in 32 skulls (32%) on the left side . The mean size of small SMS was 1.43+_0.11mm in male and 1.17+_0.13mm in female.SMS was of medium size in 28 skulls (28%) of total number on the right side and in 24 skulls (24%) on the left side. The mean size of medium sized SMS was 2.23 ± 0.18 mm in male and 2.22 ± 0.1 mm in female.SMS was large in size in 24 skulls (24%) of total number on the right side and in 20 skulls (20%) of total number on the left side . The mean size of large SMS was in 3.56 ± 0.41 mm male and 2.94 ± 0.11 mm in female. The statistical analysis of these data indicated that there was significant difference between both sexes on the right side while there was highly a significant difference between both sexes on the left side .
Suprmeatal depression or triangle (SMD) was absent in 8 male skulls(18.2%) and 20 female skulls (35.7%) on the right side, while it was absent in 4 male skulls (9.1%) and in 16 female skulls (28.6%) on the left side .It was deep in 24 male skulls (54.5%) and in 16 female skulls (28.6%) on the right side ,while it was deep in 32 male skulls (72.7%) and 20 female skulls (35.7%) on the left side .SMD was shallow in 12 male skulls (27.3%) and in 20 female skulls (35.7%) on the right side while it was shallow in 8 male skulls (18.2%) and in 20 female skulls (35.7%) on the left side. There was a significant difference between both sexes on both sides .
The mean depth of sigmoid sulcus on the right side was 1.13± 0.18 cm in male skulls and 1.11± 0.23 cm in female skulls.The mean depth of sigmoid sulcus on the left side was 1.19 ± 0.18 cm in male skulls and 1.15 ± 0.19 cm in female skulls. There was a highly significant difference between right and left depth in male and in female skulls.
The mean (AST-MS) length on the left side was 5.06± 0.28 cm in male and 4.39± 0.29 cm in female while on the right side , it was 5.22± 0.31 cm in male and 4.44± 0.35 cm in female. The mean (AST-PO) length on the left side was 4.66 ± 0.32 cm in male and 4.26± 0.21 cm in female while on the right side it was 4.65± 0.22 cm in male and 4.23± 0.19 cm in female. The mean( PO-MS) length on the left side was 3.25± 0.12 cm in male and 2.63± 0.27 cm in female while on the right side, it was 3.29± 0.14 cm in male and 2.76± 0.27 cm in female with a highly significant difference between male and female skulls .
The mean length of bimastoid breadth(MS-MS) was 10.29±0.31 cm in male and 9.72± 0.35 cm in female . The mean length of MS-OP on the right side was 5.84±0.20 cm in male and 5.3±0.25 cm in female and it was 5.70±0.29 cm in male and 5.48±0.3 cm in female on the left side with a highly significant difference between male and female skulls.
The mean mastoid length(ML) was 3.70±0.11 cm in male and 3.07±0.38 cm in female while the mean mastoid breadth(MB) was 2.80±0.24 cm in male and 2.31±0.29 cm in female with a highly significant difference between male and female skulls.
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