Sex Differences of the Hip Bone Among Several Populations

Okajimas Folia Anat. Jpn., 58 (4-6) : 265-276, March 1982

KUNIHIKO KIMURA

2nd Department of Anatomy, National Defense Medical College Tokorozawa, 359 Japan

-Received for Publication, August 20, 1981-

Key words : Sexual dimorphism (sex differences) , Hip bone (Os coxae), Ischium-pubis index.

Summary. On the basis of the hip bones (os coxae) of 103 Japanese, 102 American White and 97 American Blacks, sexual dimorphism was ascertained by means of three dimensions (pubic and ischial lengths and iliac width) and three indices (ischium-pubis, ilium-ischium and ilium-pubis) . In relation to sex differences of the hip bone, the shape component seemed to be more important than the size component in each combination of the dimensions, except for a pair of ischial length and iliac width. A pair of pubic and ischial lengths was the most useful relation for sexing the hip bone among all combinations of these dimensions. In the distribution of the ischium-pubis index, the overlap samples between the male and female series were 7.8% in Japanese, 5.9% in American Whites and 7.2% in American Blacks. With the discriminant function of the pudic and ischial lengths, probabilities of misdiagnosis are 3.48% in Japanese, 5.82% in American Whites and 4.50% in American Blacks.

Detailed historical resumes evaluating and interiliac index for sexing the hip sex differences in the pelvis have been bone based on the skeletons of American given by Hoyme (1957), Genoves (1959), Whites and Blacks. According to Derry's Krogman (1962) and Coleman (1969). Ac- and Straus' methods. many studies were cording to Hoyme, the first attempt to reported in Japanese hip bones. For ex- use measurements and indices to deter- ample, based on the pelves of 54 Japanese mine or confirm the sex of pelves was studied by Ikemoto (1929 ab), it seems that made by Matthew and Billings (1891). accurate sexing occurs in 76.2% with the Derry (1923/24) discussed sex and racial chilotic index and 79.4% with the chore- differences of the hip bone by means of matic and interiliac indices each. the chilotic and chorematic indices based On the basis of American White and on English, Egyptian and Derma skele- Black and Bantu pelves, Washburn (1948, tons. Using this method in German pelves, 1949) found that, by means of an ischium- Hdusermann (1925/26) found that misdia- pubis index devised by Schultz (1930), gnosis occured in 16.6% of males and the sex of 93-98% of the skeletons could 54.4% of females. Straus (1927) suggested be determined. With this index, Gaillard

265 266 K. Kimura

(1961) obtained correct determination in have suggested that, in discriminant func- 93.0%, indetermination in 5.25% and tion analysis, the most significant two misdiagnosis in 1.75% of French skele- values are the total height of the hip bone tons. Hanna and Washburn (1953), using and an index of the diameter of the aceta- the interiliac index, ischial length and bulum to it in 24 variables tested by them. sciatic notch width added to the ischium- They sexed correctly 58 from 59 bones pubis index, obtained accuracy of 99.1% (98.3%) with their function. in the pelves of Alaskan Eskimos. The purpose of this study is to ascertain Sauter and Privat (1952, 1954/55) devised sex differences of the hip bone among a cotylo-sciatic index, on the basis of a several populations by means of three suggestion of Tin (1938). Kimura and simple dimensions to measure : the pubic Kitano (1959) found that accurate diagn- and ischial lengths and iliac width, and osis occured in 78.7% with sciatic notch three indices calcuated from these dimen- index (Bernbeck, 1952), 83.5% with the sions. ischium-pubis index, 81.9% with a revised cotylo-sciatic index and 87.7% with com- Materials and Method bined criteria in 115 Japanese skeletons. Genoves (1959) felt that one index, three The pubic and ischial lengths and the dimensions, and four morphological traits iliac width were measured by the author were basic to determine sex differences with a sliding (length) and a spreading in the pelvis, and found that agreement (width) caliper on the right hip bone of 103 with actual sex was arrived at in 94.5%, Japanese (52 males and 51 females) at the 94.2% and 94.3% of cases by applying Department of Anatomy, Yokohama City the respective metrical, morphological and University School of Medicine, in July, combined criteria. In his study, Genoves 1981, and of 102 American Whites (50 used an index of the distance from the males and 52 females) and 97 American lowest point on the greater sciatic notch Blacks (49 males and 48 females) of the to the pyramidal process to the breadth Terry Collection of the Smithsonian In- of greater sciatic notch. Davivongs (1963) stitution, Washington, in July, 1975. All concluded that the useful sex determinants the individuals were about 20 to 60 years were the ischium-pubis index, greater or adult, and their sexes were known, sciatic notch index (Genoves, 1959) and based on the records attached to the diameter of the acetabulum. In his Aust- skeletons. ralian aborigine material, Davivongs found The pubic length, ischial height (length) that the distribution of the ischium-pubis and iliac height (length) from the point index revealed 17% overlap between the at which they meet in the acetabulum male and female series. may be anatomically a representative di- Hanihara and Kimura (1959) first used mension for each bone of the os coxae. discriminant function analysis in sexing Thieme and Schull (1957) pointed out that the hip bone. With the discriminant func- the landmarks of the pubic and ischial tion of three measurements and the lengths used in the method of Schultz- ischium-pubis index, they obtained the Washburn were somewhat ill-defined and accuracy of 88.9% in sexing Japanese might lead to inaccuracy. In the present skeletons. Howells (1964), obtained the study, following Thieme and Schull (1957), accuracy of 96.5% by means of discrimi- the pubic dimensions was measured from nant function of six measurements of the the nearest border of the acetabulum to hip bone. Day and Pitcher-Wilmott (1975) the superior point of the pubic symphysis, Sex Differences in Hip Bones 267 and the ischial length was measured from Results the far border of the acetabulum to the inferior point of the ischial tuberosity. Table 1 gives the means (5) and stand- Because of the same reasons, instead of ard deviations (s) of the pubic and ischial the iliac height, the iliac width was me- lengths and the iliac width. In the table, asured from the anterior superior spine asterisks show the results of t-test for to the posterior one (Martin and Saller, the differences of the means between 1957). As shown in Figure 1, the pubic sexes in every population. Singificant and ischial lengths and the iliac width differences are found at the 1% level for seem to correspond appoximately to each the pubic and ischial lengths in every to the width, height and depth of the population, but for the iliac width only pelvis at a standing position in man. in American Whites. From multivariate From these dimensions, the ischium- analysis from three dimensions, significant pubis, ilium-ischium and ilium-pubis in sex differences are found at the 1% level dices were calculated. The revised ischi- in every population. In general, all the

- urn-pubis index includes the acetabular three dimensions are greater in the male size, and its value is generally less than than in the female. Significant correla- that of the original index devised by tions are found at the 1% level between Schult-Washburn. With this revised me- two dimensions each in every population thod, Thieme and Schull (1957) have for each sex. obtained the accurcy of 96.5% in sexing Table 2 gives the size and shape dis- of the hip bone. In the present study, in tances and the generalized distances (D2) addition to three indices, the size and for the hip bone between sexes in every shape distances (Penrose, 1953/54), gene- population on the basis of all three di- ralized biological distances (D2) (Mahala- mensions or all pairs of two dimensions. nobis, 1936) and discriminant function In every population, the shape distance is (Fisher, 1936) were calculated from all or apparently greater than the size distance two of three dimensions for sexing the for each combination of the dimensions, hip bone in every population. The calcula except for a pair of the ischial length and tions were proceed by the Cannon BX-1 iliac width. The generalized distances be- system, using BASIC programs. tween the male and the female are greater

Table 1. Means (3-c) and standard deviations(s) of the pubic and ischial lengths and the iliac width in Japanese and American Whites and Blacks.

Note : **Significant at P<0.01 268 K. Kimura

Ischium—Pubis Index

Ilium—Ischium Index

, Ilium—Pubis Index 0 ,

Text-Fig. 1. Distributions of the ischium-pubis, ilium-ischium and ilium-pubis indices for each sex among three populations. Sex Differences in Hip Bones 269

Table 2. Size and shape distances (Penrose, 1953/54) and generalized distances (Mahalanobis, 1936) for the hip bone between sexes in every population on the basis of all or two of three dimensions.

in the combination of all the three dimen- pair of ischial length and iliac width sions and the pair of the pubic and ischial shows the next best accuracies to the lengths, followed by the pair of the ischial aboves 94.41% in Japanese, 91.00% in length and the iliac width, than the pair of American Whites and 90.82% in American the pubic length and the iliac width in Blacks. On the other hand, from the every population. The intersexual dis- pubic length and the iliac width, the discri- tances are somewhat greater in Japanese, minant function shows only the accuracies followed by American Blacks, than in of 74.22 to 79.11% in each population. American Whites in each combination of Table 4 gives the means (T) and stand- three dimensions of the hip bone, except ard deviations (s) of three indices in every for the pair of the ischial length and the population. Siginificant differences are iliac width. Based on the ischial length found between males and females at the and the iliac width, American Whites 1% level for the means of each index show a slightly greater distance between in every population. At the same time, sexes than American Blacks. as shown in the appendix of the table, Table 3 gives the discriminant func- significant differences are found at the tions, discriminat values and theoretical 1% or 5% level for the means of some probabilities of diagnosis for sexing the indices in each pair of populations for hip bone in every population based on each sex. On the average, the ischium- all or two of three dimensions. The pro- pubis index is greater in American Whites, babilities of sexing is almost the same in followed by Japanese, than in American three populations with discriminant func- Blacks. While, the ilium-ischium and tions based on three dimensions (96.71% the ilium-pubis indices are greater in in Japanese, 94.29% in American Whites Japanese than in American Whites and and 95.60% in American Blacks) and on Blacks. the pubic and ischial lengths (96.52%, Figure 1 shows the distributions of 94.18% and 95.50%, respectively). The three indices in every population for 270 K. Kimura

Table 3. Discriminant functions for the hip bone between sexes in every population on the basis of all or two of three dimensions.

Table 4. Means (R) and standard deviations (s) of the ischium-pubis, ilium-ischium and ilium-pubis indices in Japanese and American White and Blacks.

Note : **Significant at P<0.01 Appendix Results of t-test for the means of three indices between every pair of populations.

Note : ** Significant at P<0.01, * Significant at P<0.05 Sex Differences in Hip Bones 271 each sex separately. Commonly in three difference. Coleman concluded that the populations, the overlap samples between major sex differences resulted from the the male and female series are smaller greater lateral migration of the ischia. for the ischium-pubis index (7.8% in Ja- The results obtained in the present study panes, 5.9% in American Whites and 7.2% seem to agree well to this suggestion. in American Blacks), followed by the However, according to Hugehes and ilium-pubis index (10.7%, 12.4% and 13.7 Tanner (1973), the pelvis shows only the %, respectively), than in the ilium-ischium size difference in rats. index (16.5%, 22.7% and 25.5%, respec- In the present study, the Mahalanobis' tively). Especially, in the ischium-pubis generalised distance between the male index, it may be expected that the hip and the female based on three dimensions bone is divided into the male and the are almost the same with that based on female with a common criterion of 66 in the pubic and ischial lengths. From this three population. With this criterion, 66 fact, it can be confirmed that a relation and more for females, misdiagnosis occurs of the pubic and ischial lengths is certainly in 1 of 52 males (1.9%) and 8 of 51 useful for sexing the hip bone. For the females (15.7%) of Japanese, 4 of 50 males ischium-pubis index, the overlap samples (840%) and 2 of 52 females (3.8%) of between the male and female series are American Whites and in 1 of 49 males about 6-8% in three populations. Divi- (2.0%) and 5 of 48 females (10.3%) of vongs (1963) found 17% overlap of the American Blacks in this series. index between sexes in Australian aborigines. With a common criterion of the Discussion index (66 and more for females), the hip bone was divided into males and females In this study, significant sex differencas in about 91% in Japanese and 94% in are clearly found at the 1% level for American Whites and Blacks in this se- the pubic and ischial lengths and the ries. This accurcy is almost the same ischium-pubis, ilium-ischium and ilium- with that of 93-98% reported by Wash- pubis indices in all the Japanese and burn (1948, 1949), Theime and Schull American Whites and Blacks. On the (1957) and Gaillard (1961) and somewhat size and shape distances, the shape com- greater than the accuracy of 83.5% in ponent seems to be commonly more im- Japanese skeletons (Kimura and Kitano, portant than the size component in the 1959). The accuracy for sexing with the pairs of the pubic and ischial lengths and of index was also almost similar to •the the pubic length and the iliac width, as well probabilities of diagnosis with the discri- as in the combination of all the three dimen- minant function based on the pubic and sions, in relation to the sex differences ischial lengths (94.2-96.5%) or on all of the hip bone. From this fact, it seems three dimensions (94.3-96.7%) in three that the pubic dimension is more impor- populations. However, with the discri- tant to sexual dimorphism among the minant function of the maximum height, dimensions of three bones of the os coxae. the ischial height, the breadth of greater Coleman (1969) divided the superior and sciatic notch and the ischium-pubis index, inferior functional parts of the pelvis for Hanihara and Kimura (1959) obtained only the sex differences. According to him, the accuracy of 88.9% in sexing Japanese while the superior division (ilium and skeletons. sacrum) shows the size difference, the The author (1969) has pointed out a inferior one (ischium and pubis) the shape difference in the sexual dimorphism ob- 272 K. Kimura

served in the androgyny scale (Tanner, Naturw. Diss., 1952. (cited from Martin, 1951) between Japanese and English stu- R. and Saller, K. : Lehrebuch der dents. With this scale, misdiagnosis in Anthropologie. p. 556. Gustav Fischer sexing was somewhat greater in the Verlag, Stuttgart, 1957. 2) Coleman, W. H. : Sex differences in the Japanese students (14.9%) than in the English (10.8%). Recently, Hanihara (1978) growth of the human bony pelvis. Am. J. Phys. Anthrop., 31 : 125-152, 1969. has observed that, in dental morphology, 3) Davivongs, V.: The pelvic girdle of the the intersexual distances are more than Australian aborigine ; sex differences and twice as large in Caucasians, Pimas and sex determination. Am. J. Phys. Anterop., American Blacks as in Japanese and 21 : 443-455, 1963. Australian aborigines. According to Ki- 4) Day, M. H. and Pitcher-Wilmott, R. W. : mura and Kitano (1959) and Hanihara Sexual differentiation in the innominate and Kimura (1959), the sexual dimorphism bone studied by multivariate analysis. in the hip bone seemed to be less strongly Annals of Human Biology, 2: 143-151, manifested in Japanese than in other 1975. 5) Derry, D. E.: On the sexual and racial populations. However, in the present characters of the ilium. J. Anat., 58: study, it appears that the sex differences 71-83, 1923/24. are slightly greater in Japanese, followed 6) Fisher, R. A.: The use of multiple by American Blacks, than in American measurements in taxonomic problems. Whites. True reasons of these differnces Ann. Eugenics, 7: 179-188, 1936. between the results of both studies in 7) Gaillard, J.: Valeru de l'indice ischio- Japanese hip bones are uncertain. pubien pour la determination sexuelle de l'os coxal. Bull. et Mem. de la Soc. d'Anthro. de Paris, 11-2 : 92-108, 1961. Acknowledgements 8) Genoves, S. T.: Differencias sexuales en el hueso coxal. U. Nacional Autonoma The author is grateful to Dr. L. St. de Mexico. Public. del Inst. de Hist. Hoyme, Division of Physical Anthropology, Primera serie, Num 49, Mexico City, National Museum of Natural History, D. F., 1959. Washington, and Dr. A. Ichikawa, Depart- 9) Hanna, R. E. and Washburn, S. L.: The ment of Anatomy, Yokohama City Uni- determination of the sex of skeletons, as versity School of Medicine, for their illustrated by a study of the Eskimo kindness in providing every facility for pelvis. Hum. Biol., 25: 21-27, 1953. the study of skeletons, to Dr. R. Singer, 10) Hanihara, K.: Differences in sexual Department of Anatomy, University of dimorphism in dental morphology among Chicago, for his kind advice on the pre- several human population. In : Butler, P. M. and Joysey, K. A. (eds.) : Develop- paration of the English manuscripts, and ment, function and evolution of teeth. also to Mr. M. Konishi, Department of pp. 127-133, Academic Press, London, Anatomy, National Defense Medical Col- 1978. lege, for his assistance in calculation of 11) Hanihara, K. and Kimura, K.: Sexual the data. diagnosis of Japanese hip bones by means of discriminat function. Proc. 14th Ref erences Joint Meet., Anthrop. Soc. Nippon and Jap. Soc. Ethnol., 1959: 174-175, 1960. 1) Bernbeck, R.: Vergleichend-anatomische (in Japanese) Untersuchungen zum problem des auf- 12) Hausermann, E.: Zur Bestimmung von rechten Ganges und des spezifischen Geschlechts-und Rassen-unterscheiden am Geburtsmechanismus beim Menschen. menschlichen Os ilium. Z. Morph. Sex Differences in Hip Bones 273

Anthrop., 25 : 465-474, 1925/26. Museum at Washington. 7th Memoir, 13) Howells, W. W.: Determination du sexe 6, Nat. Acad. Sci. : 139-286, 1891. du bassin par fonction discriminate : 23) Penrose, L. S.: Distance, size and shape. etude de materiel du docteur Gaillard. Ann. Eugenics, 18: 337-343, 1953/54. Bull. et Mem. de la Soc. d'Anthro. de 24) Sauter, M. R. and Privat, F.: Une Paris, 11-7 : 95-105, 1964. nouvelle methode de determination 14) Hoyme, L. E.: The earliest use of indices sexuelle de l'os coxal : l'indico cotylo- for sexing pelves. Am. J. Phys. Anthrop., sciatique. Bull. Schweize Gesellsch. f. 15: 537-546, 1957. Anthrop. et Ethnol., 28: 12-13, 1952. 15) Hughes, P. C. R. and Tanner, J. M.: A 25) Sauter, M. R. and Privat, F.: Sur une radiographic study of the growth of the nouveau procede matrique de determi- growth of the rat pelvis. J. Anat., 114: nation sexuelle du bassin osseux. Bull. 439-448, 1973. Soc. suisse d'Anthro. et d'Ethno., 31: 16) Ikemoto, S.: Anthropological observation 60-84, 1954/55. on Japanese ilium. Acta Anat. Nippon., 26) Schultz, A. H.: The skeleton of the 1: 496-510, 1929. (in Japanese) trunk and limbs of higher primates. 17) Ikemoto, S.: Anthropological observation Hum. Biol., 2: 303-438, 1930. on Japanese ilium. Acta Anat. Nippon., 27) Straus, W. L.: The human ilium : sex 2: 83-104, 1929. (in Japanese) and stock. Am. J. Phys. Anthrop., 11: 18) Kimura, K.: Androgyny score in the 1-28, 1927. Japanese. Bull. Faculty Phys. Educ. 28) Tanner, J. M.: Current advances in the Tokyo Univ. Educ., 8: 121-124, 1969. study of physique. Photogrametric (in Japanese with English summary) anthropometry and an androgyny scale. 19) Kimura, K. and Kitano, S.: Sexual Lancet, 1: 574-579, 1951. diagnosis of Japanese coxae by indices. 29) Thieme, F. P. and Schull, W. J.: Sex J. Med. Soc. Toho., 6: 415-417, 1959. (in determination from the skeleton. Hum. Japanese with English summary) Biol., 29 : 242-273, 1957. 20) Krogman, W. W.: The human skeleton 30) Tin, Ngueyen-van Recherches sur le in forensic medicine. pp. 122-142. Charles bassin de la femme annamite. These C Thomas, Springfield, 1962. medicine, Hanoi, pp. 87, 1938. 21) Mahalanobis, P. C.: On the generalized 31) Washburn, S. L.: Sex differences in the distance in statistics. Proc. Nat. Sci. pubic bone. Am. J. Phys. Anthrop., 6: India, 2: 49-55, 1936. 199-208, 1948. 22) Matthews, W. and Billings, J. S.: The 32) Washburn, S. L.: Sex differences in the human bones of the Hemenway Collection pubic bone of Bantu and Bushman. Am. in the United States Army Medical J. Phys. Anthrop., 7: 425-532, 1949. ....1tv A.-

Explanation of Figure

Plate I

Fig. 1. Measurements of the hip bone. .-t co Left, cranial aspect ; middle, ventral aspect ; right, right lateral aspect. P, pubic length ; S, ischial length ; I, iliac width. 275 Plate I

K. Kimura