Incidence of sutural bones with special reference to sex--a study in the eastern region of India.
It has been noted that sutural bones are usual in many mammals (4). The association of sutural bones with skull size, development and climatic tolerances of different people have also been suggested (5). Sutural structures have been shown to be genetically determined but environmental factors are responsible for their adult morphology (Oudhof, 1982) (6).
Sutural bones may represent a pre-interparietal element, a true inter-parietal element or some composite (2). One or more pterion ossicles or epipteric bones may appear between the sphenoidal angle of the parietal and the greater wing of the sphenoid (2,7,8). Ossicles as sutural bones have been also observed in coronal, lambdoid and sagittal sutures as well as at asterion, between squamous and mastoid portion of the temporal bone and in the occipito-mastoid suture (7).
Sutural bones are usually normal variants which can be detected prenatally. However some syndromes are associated with it. These are easily remembered by the PORKCHOPS mnemonic (9): P-Pyknodysostosis, O-Osteogenesis Imperfecta, R-Rickets, K-Kinky Hair Syndrome, C-Cleidocranial Dysostosis, H-Hypothyroidism/Hypophosphatasia, O-Otopalatodigital Syndrome, P-Primary Acroosteolysis, S-Syndrome of Downs. It was Wood Jones (1930-1) (10), however, who first proposed that the differing incidences of these minor variants which occurred in different races might be useful in anthropological studies. Laughlin and Jorgensen (1956) (11) put this idea into practice and Berry and Berry (1967) (7) suggested that a wide range of these variants could be used to calculate a distance statistic between population samples.
METHODS AND MATERIALS:
Study design: A cross-sectional observational study was undertaken.
Study type: It is an epidemiological observational type of study.
Scope and delimitation: The research is limited to:
(1) dry adult human crania with no observable craniofacial abnormalities and no teeth,
(2) observations recorded by single person and
(3) crania with all study parameters present prominently.
Study area: The study was conducted at the Department of Anatomy of R G Kar Medical College, Kolkata which is a very old and renowned institute. It receives human skeletal parts from majority of Eastern India.
Study population: One hundred and eleven dry adult human crania were selected from the musea of the study area, according to the following criteria:
(1) crania of macerated dead humans received by the institutions mentioned before,
(2) crania belonging to the late 19th century till death as per records,
(3) crania with no observable craniofacial deformities and
(4) crania with a unique alpha numeric code
These crania were divided into two groups as detailed in Table I Crania were chosen randomly, placed on the cushion in Frankfurt Horizontal and the following noted:
(1) identification number--an alpha numeric code which was made with black paint, eg, XY 20 where XY refers to the institution of origin and 20 the particular number of that cranium.
(2) total number of crania with sutural bones each in male and female
(3) total number of sutural bones each in male and female crania
(4) distribution of different types of sutural bones present bilaterally between male and female crania
(5) distribution of different types of sutural bones present in the midline between male and female crania
The different types of sutural bones studied are depicted in Table II. The sutural bones were subdivided into two groups: 1. Bones present bilaterally--CO, LO, OA, OMB, PNB and PO 2. Bones present in the midline--BO/ OB, OL and SO. Bones in these two groups were studied in both male and female.
Statistical analysis: The results were calculated using Epi Info[TM] statistical software (version 3.4.1 July 3, 2007 for Windows) and a significance level of p<0.05 was considered significant.
RESULTS: 43 male and 34 female crania were found to have sutural bones with an incidence of 38.74% and 30.63% respectively (Table I). The gross incidence of sutural bones was 69.37%. No OB/ BO and OMB were found in the present study. There was a statistically significant difference in the distribution of LO type of sutural bone present bilaterally between male and female crania (Table III).There was no statistically significant difference in the distribution of different types of sutural bones present in the midline between male and female crania (Table IV). LO and CO were the sutural bones with the highest (39.49%) and lowest (0.82%) incidence respectively (Table V).
DISCUSSION: Sutural bones are most common at the borders of the parietal bone (12). The prevalence of sutural bones in the general population varies from 8-15% and males are more affected than females (13). The gross incidence of sutural bones was 69.37% in the present study which is much more than 45% reported by Trivedi et al (2011) (14). However it falls well within the range of 55.56 to 80.32 % reported by Brothwell (1963) (13). Higher number of sutural bones were observed in females (188) compared to males (153). The mean number of sutural bones was 3.56 and 5.53 in males and females respectively. Higher number of sutural bones were recorded on the right (74 in males and 93 in females) than on the left (64 in males and 80 in females). The gross percentages of males and females with sutural bones were 38.74 and 30.63 respectively since a higher number of males (43) with sutural bones were observed than females (34). The higher number observed in females may be due to the hypostotic nature of these traits which represent arrested morphogenesis and are characterized by a slight preference for females and for the right side. The faster growth rate in males either inhibits their formation or speeds up their obliteration (or both) while the slower rate in females produces stress which either encourages their formation or delays their closure (or both) (15). Walulkar et al (16) reported an incidence of 14.90% and 12.50% for males and females respectively with sutural bones. This sharp contrast with the present study further strengthens the view that these are epigenetic variants and vary from one population to another.
The percentage incidence of various sutural bones do not vary much from that of Gopinathan et al (17). Trivedi et al (2011) found an incidence of 41.18% and 48.10% in females and males respectively. This might be due to the interplay of similar genetic processes during development in both these populations. However data regarding metric cranial variants are required to further corroborate this view. The mean measure of divergence between these populations can be used to compare relative proximities of the various races. Hence we can have an idea regarding the roots of origin, migration and final settlement of the various human races we observe today.
Berry and Berry (1967) (18) in their study of epigenetic variations of 585 adult crania in humans found lambdoid ossicles (LO) to be most frequent across eight populations. Brunner et al (19) found OA to be significantly correlated with Cranial Module (the latter is used as an index of cranial size). However, no such significance was encountered in the present study. Torgersen (20) and Kjellgren (21) opined that the most consistent factor influencing side differences is the slight retardation of ossification on the right side owing to richer innervation on that side, associated with cerebral hemisphere dominance and mediated, at least in part by the blood supply. The present study indicates a minor role of such innervation and blood supply in the distribution of such bones, instead it appears to be random in nature.
ACKNOWLEDGMENTS: The authors would like to express their sincere gratitude to all faculty members and non teaching staff of our institute for their whole-hearted support for this project.
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(2.) Standring S et al. HEAD Skull and Mandible In: Gray's Anatomy The Anatomical Basis of Clinical Practice Standring S (editor in chief), ELSEVIER Churchill Livingstone Philadelphia USA, 39/e, Chapter 27, 2005;486.
(3.) Dart RA. The Makapansgat proto-human Australopithecus prometheus. Am J Phys Anthrop 1948;6:259-84.
(4.) Joseph J. LOCOMOTOR SYSTEM In: Textbook of HUMAN ANATOMY Late Hamilton WJ (editor), The Macmillan Press Ltd London, 2/e, 1976;71.
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(6.) Oudhof HAJ. Sutural growth. Acta Anat 1982;112:58-68.
(7.) Berry AC, Berry RJ. Epigenetic variation in the human cranium. J Anat 1967;101(2):361-79.
(8.) Ahuja UK, Mukherjee RN, Singh B. PTERION-ITS FORMATION AND VARIATIONS. J Anat Soc India 1971;20(2):103-11.
(9.) Danhert, Wolfgang. Radiology Review Manual. Williams and Wilkins 1999.
(10.) Wood Jones F. The non-metrical morphological characters of the skull as criteria for racial diagnosis. I, II and III. J Anat 1930-31;65:179-95, 368-78, 438-45.
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(13.) Brothwell DR. Digging Up Bones. British Museum of Natural History, London 1963.
(14.) Trivedi GN, Gour KK, Budhiraja V, Rastogi R, Nair S. Incidence of sutural bones in human skulls. Int J Curr Biol and Med Sc 2011;1(4):164-65.
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(17.) Gopinathan K, Dhall U, Chhabra S. Sutural bones in the North Indian Population. J Anat Soc India 1998;47(2):91-6.
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(19.) Brunner E, Averini M, Manzi G. Endocranial traits. Prevalence and distribution in a recent human population. Eur J Anat 2003;7(1):23-33.
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Anirban Sadhu , Rudradev Meyur , Banani Kundu , Abhijit Bhakta , Biplab Goswami , Subhasis Chakraborty , Sharmistha Biswas , Phalguni Srimani 
PARTICULARS OF CONTRIBUTORS:
[1.] Assistant Professor, Department of Anatomy, R G Kar Medical College, 1, Kshudiram Bose Sarani, Kolkata, West Bengal, India.
[2.] Associate Professor, Department of Anatomy, R G Kar Medical College, 1, Kshudiram Bose Sarani, Kolkata, West Bengal, India.
[3.] Assistant Professor, Department of Anatomy, R G Kar Medical College, 1, Kshudiram Bose Sarani, Kolkata, West Bengal, India.
[4.] Associate Professor, Department of Anatomy, NRS Medical College, 138, AJC Bose Road, Kolkata, West Bengal, India.
[5.] Junior Resident, Department of Anatomy, R G Kar Medical College, 1, Kshudiram Bose Sarani, Kolkata, West Bengal, India.
[6.] Junior Resident, Department of Anatomy, R G Kar Medical College, 1, Kshudiram Bose Sarani, Kolkata, West Bengal, India.
[7.] Associate Professor, Department of Anatomy, NRS Medical College, 138, AJC Bose Road, Kolkata, West Bengal, India.
[8.] Junior Resident, Department of Anatomy, R G Kar Medical College, 1, Kshudiram Bose Sarani, Kolkata, West Bengal, India.
Anirban Sadhu , Rudradev Meyur , Banani Kundu , Abhijit Bhakta , Biplab Goswami , Subhasis Chakraborty , Sharmistha Biswas , Phalguni Srimani 
NAME ADDRESS EMAIL ID OF THE CORRESPONDING AUTHOR:
Dr. Anirban Sadhu, 2, Mahakalitala Lane, PO: Bansberia, Dist: Hooghly, PIN: 712502, West Bengal, India.
Date of Submission: 25/10/2013.
Date of Peer Review: 26/10/2013.
Date of Acceptance: 29/10/2013.
Date of Publishing: 05/11/2013
Table I: Distribution of crania with and without sutural bones in males and females Male (%) Female (%) Crania with sutural bones 43 (38.74) 34 (30.63) Crania without sutural bones 17 (15.32) 17 (15.32) Table II: Description of sutural bones studied Sutural bone Description Bregmatic Ossicle A bone present at the junction (BO)/Ossicle at of the Sagittal suture with the Bregma (OB) Coronal one Coronal Ossicle A bone present in the Coronal (CO) suture. This was scored as COr and COl for right and left sides respectively Lambdoid One or more bones present in ossicle (LO) the Lambdoid suture. This was scored as LOr and LOl for right and left sides respectively Ossicle at A bone present at the Asterion Asterion (OA) which was scored as Oar and OAl for right and left sides respectively Ossicle at A bone at the junction of the Lambda (OL) Sagittal and Lambdoid sutures. No attempt was made to distinguish between a sutural bone in this position, and a 'true ' interparietal or Inca bone formed from the membranous part of the occiput. According to Wood Jones this latter is very rare (10,2) Occipito A sutural bone in the suture Mastoid Bone between Occiput and Mastoid (OMB) bone Parietal Notch Parietal notch is that part of Bone (PNB) the parietal bone that protrudes between the squamous and the mastoid portions of the temporal bone. It may form a separate ossicle which is known as the parietal notch bone. This was also scored as PNBr and PNBl for right and left sides respectively Pterion ossicle A sutural bone (epipteric bone) (PO) inserted between the anterior inferior angle of the parietal bone and the greater wing of the sphenoid. When large it may also articulate with the squamous part of the temporal bone. This was scored as POr and POl for right and left sides respectively Sagittal A bone present in the Sagittal Ossicle (SO) suture Table III: Comparison of the distribution of the different types of sutural bones present bilaterally between male and female crania Type of sutural bone LO PO PNB OA CO %(n) %(n) %(n) %(n) %(n) Male (n=43) 25.58(11) 09.30(4) 16.28(7) 06.98(3) 02.33(1) Female (n=34) 52.94(18) 20.59(7) 17.65(6) 02.94(1) 00.00(0) Z-statistic 2.4600 -1.4060 -0.1590 0.7930 -- P-value 0.0139 * 0.1597 0.8737 0.4278 -- Table IV: Comparison of the distribution of different types of sutural bones present in the midline between male and female crania Type of sutural bone OL SO %(n) %(n) Male (n=43) 20.93(9) 11.63(5) Female (n=34) 29.41(10) 08.82(3) Z-statistic -0.8570 0.4010 P-value 0.3914 0.6884 Table V: Percentage incidence of various sutural bones in the Eastern Region of India and other human populations Population Sample OB SO OL CO size Eastern India 111 0 2.25 3.89 0.82 North India 89 0 1.12 12.40 3.37 Gujarati 284 0 1.05 20.07 0 Punjabi 53 0 0 20.07 1.9 Egyptian 250 0.80 0 14.8 2.6 Palestine 18 0 0 22.2 0 (modern) South American 53 0 0 15.9 1.9 (Peru) Australian 1184 0.3 0 12.9 5.4 (Aborigines) Caucasian 139 0 2.87 10.7 1.43 Black (Negro 182 0 1.09 12.63 0.27 American) Population LO PO OA PNB OMB Eastern India 39.49 8.8 4.3 9.82 0 North India 30.30 6.74 12.4 11.24 5.62 Gujarati 37.40 7.74 13.95 11.26 6.68 Punjabi 32.1 16.9 9.8 7.5 0 Egyptian 32.3 14.4 12.9 7.4 0 Palestine 33.3 6.4 8.3 11.1 0 (modern) South American 45.2 7.5 14.2 11.3 0 (Peru) Australian 47 19.8 17.9 15.4 0 (Aborigines) Caucasian 37 12.94 10.76 11.05 0 Black (Negro 22.5 2.19 7.96 7.14 0 American)
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|Title Annotation:||ORIGINAL ARTICLE|
|Author:||Sadhu, Anirban; Meyur, Rudradev; Kundu, Banani; Bhakta, Abhijit; Goswami, Biplab; Chakraborty, Subha|
|Publication:||Journal of Evolution of Medical and Dental Sciences|
|Date:||Nov 11, 2013|
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