AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 82:73-79 (1990) Anatomical and Developmental Bases for the Ventral Arc of the Human Pubis LINDA C BUDINOFF AND ROBERT G TAGUE Department of Anthropology, Kent State Uniuerszty, Kent, Ohio 44242 (L C B I , Department of Geography and Anthropology, Louisiana State University, Baton Rouge, LouLsiana 70803 ( R G T ) Pelvic anatomy, Pubic length, Sex determination, KEY WORDS Ventral rampart of pubis ABSTRACT The ventral arc of the pubis is frequently used for sexing adult human hip bones. This study addresses the issues of the anatomical and developmental bases for the ventral arc. Dissection of seven adult pelves (four females and three males) demonstrates that the sexes are identical in the muscular and ligamentous attachments to this ridge of bone. The tendons of gracilis and adductor brevis, which are fused for a variable extent, arise from the ridge of bone, and the fibers of the ventral pubic ligament attach to its medial border. Lateral placement of the ventral arc is defined in terms of the minimum distance between the ridge of bone and the inferior border of the symphyseal face of the pubis. The hypothesis that lateral placement of the ventral arc is positively correlated with pubic length was tested using two random samples of adult female hip bones (N = 50 for both whites and blacks) from the Hamann-Todd collection. The correlation between these variables is significant. The results support the argument that lateral placement of the ventral arc is related to the amount of postadolescent growth occurring at the symphyseal border of the pubis. Therefore, the ventral arc should not be considered as an independent criterion from pubic length in sexing adult hip bones. In humans, the hip bone is diagnostic for determining sex from skeletal remains. There have been numerous studies on the anatomical and developmental bases for sexual dimorphism in pubic length, pelvic breadth, shapes of the greater sciatic notch and subpubic arch, and bone resorption adjacent to the pelvic joints; the ventral arc, however, has received little attention. The ventral arc is one of three traits (the other two being the subpubic arch and medial aspect of the ischiopubic ramus) that make up Phenice’s (1969) technique for sexing the adult hip bone. Of the three traits, Phenice (1969:300) regarded the ventral arc as being the “least likely to be ambi OUS” in sex determination (but see Love 1, 1989). Sutherland and Suchey (1987)also found the ventral arc to be reliable in distinguishing between the sexes. Phenice (1969:298) described the ventral arc as “a slightly elevated ridge of bone that extends from the pubic crest and arcs inferiorly across the ventral surface to the lateral Y 0 1990 WILEY-IASS, INC most extension of the subpubic concavity . . . where it blends with the medial border of the ischio-pubicramus.” Sutherland and Suche (1987)agreed with this description and mo ified it only minimally b stating that the definitive arc must be pa pable. Both Phenice (1969)and Sutherland and Suchey (1987) concluded that the corresponding ridge of bone in males generally follows a different course on the ventral aspect of the pubic cor us. Zommentaries on the anatomy of the ventral arc have been few. Todd (1920:311) stated that “the linear prominence appearing on the ventral aspect [of the pubis is] . . . the line of attachment of the acilis muscle.” Cleland (1889, cited in E d d , 1920:292) wrote that “the line in question will always be seen marked by a distinct ridge, with a flattened surface extending inwards from it, covered . . . by the superficial ligament of the B P Received June 10, 1988; accepted June 9, 1989. 74 L.C. BUDINOFF AND R.G. TAGUE symphysis.” More recently, Buikstra and Mielke (1985:374)stated that the structures associated with Phenice’s method are “anatomically related to the attachment of the crus penis and crus clitoris.” Bass (1987:201) discussed Phenice’s method under the heading “Attachment of the Arcuate Ligament.” Remarkably, texts on human gross anatomy (for example, Hollinshead, 1974; Moore, 1980; Williams and Warwick, 1980; Woodburne, 1983) fail to mention the sexual dimorphism in the ventral arc and, correspondingly, the tissues that attach to this ridge of bone. However, these anatomical texts are uniform in describing the crura as attaching to the ischiopubic ramus and the arcuate ligament as arching across the inferior aspect of the symphysis pubic to attach to the inferior pubis ramus. Therefore, Buikstra and Mielke’s (1985) and Bass’ (1987) statements on anatomy pertain to the breadth of the ischiopubic ramus and subpubic arch, but not to the ventral arc. Only Todd (1920,1921a)andKerley(1977) have discussed the developmental basis of the arc. Todd (1921a:38) suggested that “the ridge is not marked until after the ventral rampart has been formed.. . [and] the marking out of the line in question is causally related to the growth of bone tissue as a rampart upon the ventral bevelled symphysial area.” Kerley (1977) suggested that sexual dimorphism of the ventral arc results from differential growth at the symphyseal border of the pubis. This study addresses two issues pertaining to the ventral arc. First, the discussion presented above demonstrates that the anatomical relationships of the ventral arc remain unresolved. Moreover, are sexual differences in this ridge of bone accompanied by soft tissue differences? Second, is lateral placement of the ventral arc (symphysis-arc length) positively correlated with pubic length (see Fig. l)?The latter tests the hypothesis that lateral placement of the ventral arc is directly related to pubic growth. MATERIALS AND METHODS Seven cadavers were available to evaluate the anatomy of the ventral arc. All seven specimens (four females and three males) were white and were from individuals older than 50 years of age. To examine the relationship between lateral placement of the ventral arc and pubic length, two random samples of adult female hiD bones (50 whites and 50 blacks) were Fig. 1. Pubic length (A-B): middle of acetabulum to inferior border of symphyseal face of pubis. Symphysisarc length (B-C): minimum distance from inferior border of syrnphyseal face of pubis to ventral arc. Ischial length (A-D): maximum distance from middle of acetabulum to ischial tuberosity. Acetabulum-arc length: pubic length minus symphysis-arc length. Femoral length: maximum length. Ischio-pubic index: pubic length x 100/ischial length. selected from the Hamann-Todd skeletal collection. Only specimens with a complete or virtually complete ventral rampart of the pubis were sampled (see Discussion for significance of the ventral rampart to formation of the ventral arc). The variables analyzed in this study are illustrated and defined in Figure 1. Measurements were taken on the left hip bone and femur whenever possible. This part of the study was restricted to one sex because both variables of interest (symphysis-arc length and pubic length) are sexually dimorphic. A correlational analysis using a mixed-sex sample would obscure the relationship between these variables. RESULTS The dissections show that the sexes are identical in the muscular and ligamentous attachments pertaining to the ventral arc. Both the gracilis and adductor brevis muscles arise from this ridge of bone, adductor brevis from the superior border and gracilis from the inferior border. The inferior portion of the adductor brevis tendon and the superior portion of the gracilis tendon fuse (although the extent of this fusion varies among individuals). and this combined tendon arises from the intermediate section of the ridge (Fig. 2a-c). 75 VENTRAL ARC OF THE HUMAN PUBIS a C b d Fig. 2. Ventral pubis dissection. a: Muscles and superficial ventral pubic ligament. Abbreviations: AB, adductor brevis; AL, adductor longus; AM, adductor magnus; GR, gracilis; IL, inguinal ligament; OE, obturator externus; PE, pectineus; PY pyramidalis; RA, rectus abdominis; VPL, ventral pubic ligament. b: Fusion of gracilis and adductor brevis muscles. c: Origin of muscles. d: Ventral pubic ligament: deep layer (top) and deepest layer (bottom). Attached to the medial aspect of the ridge of bone are fibers of the ventral pubic ligament. There are several layers of these ligamentous fibers. The superficial fibers run obliquely and attach to dense connective tissue directly overlying the ridge of bone (Fig. 2a). The deeper fibers run transversely and attach to the medial border of this ridge (Fig. 2d). These transverse fibers cover the interpubic disk, thicken inferiorly, and blend into the arcuate ligament. Phenice (1969) described the ventral arc 76 L.C. BUDINOFF AND R.G. TAGUE as extending from the pubic crest to the ischiopubicramus. As observed in this study, the ridge reached as far as the pubic crest in none of the dissected specimens and in only 25% of those from the Hamann-Todd sample. We surmise that adductor longus has a partial attachment to the ridge in those specimens where the arc does reach the pubic crest (Fig. 2c). The second part of this study tested the hypothesis that lateral placement of the ventral arc (symphysis-arc length) is positively correlated with pubic length. Table 1 presents the summary statistics for the variables. White females have a significantly longer pubis than black females. However, of the two components of pubic length (symphysis-arc length and acetabulum-arc length), whites are significantly different from blacks only in acetabulum-arc length. Also, note that the coefficient of variation is higher for symphysis-arc length than for all other variables. The results of the correlational analysis are presented in Table 2. The correlations between pubic length and symphysis-arc length are significant in whites (r = 0.461, blacks (r = 0.291, and the combined sample (r = 0.39). Symphysis-arc length is significantly correlated with the ischiopubic index in whites (r = 0.44) and the combined sample (r = 0.351, but the correlation is nonsignificant in blacks (r = 0.20). Not surprisingly, acetabulum-arc length (the principal component of pubic length) is positively correlated with pubic length and the ischiopubic index in whites, blacks, and the combined sample. Interestingly, the correlation between symphysis-arc length and acetabulum-arc length is low and nonsignificant in whites (r = 0.091, blacks (r = -0.20), and the combined sample (r = -0.03). Finally, the measures of body size used in this study (femoral length and ischial length) are significantly correlated with pubic length and acetabulum-arc length in whites, blacks, and the combined sample. In contrast, the correlations between symphysis-arc length and measures of body size are low and nonsignificant in whites and blacks; the results for the combined sample are equivocal. DISCUSSION Although males and females generally differ in the course taken by the ridge of bone on the ventral aspect of the pubic corpus, the sexes are identical in the muscular and ligamentous attachments to that ridge. The anatomical observations presented in this study principally are in agreement with those ofTodd (1920)and Cleland (1889, cited in Todd, 1920). Todd (1920) described gracilis as attaching to the ridge of bone, and Cleland (1889, cited in Todd, 1920:292) stated that this ridge was the “inner limit of attachment of the femoral muscles” and that the ridge’s medial surface was “covered. . . by the superficial ligament of the symphysis.” However, the specimens in this study uniformly show that both gracilis and adductor brevis attach to the ridge. The observations in this study differ somewhat from the anatomical descriptions of Hollinshead (19741, Moore (19801, Williams and Warwick (19801,and Woodburne (1983). These anatomists describe adductor brevis as arising from the pubis between gracilis and obturator externus. The specimens in this study show that gracilis and adductor brevis share a common tendinous origin for a variable extent along this ridge of bone. Phenice (1969:300)cautioned that the results of his study were based on observations of adult specimens and that the technique he proposed may not be reliable for subadults in that “there are indications that the ventral TABLE 1. Summary statistics for white and black females, a n d results of Student$ t-tests comparing the means between these groups of females’,2 Pubic length Symphysis-arc length Acetabulum-arc length Ischial length Femoral length Ischiopubic index Whites (N = 50) X SD CV3 X 84.2 10.8 73.4 76.2 413 110.4 5.6 2.1 5.0 3.8 25 5.3 6.68 19.54 6.85 5.01 6.08 4.82 81.5 10.3 71.2 75.3 435 108.3 -.- Variables ‘All measurements are reported in millimeters. ‘A two-tail test of significance was used. 1 he Coefficient of variation (CV) is corrected for bias, where CV = (11 *Prob. < 0.05. +‘Prt,b. < 0.001. 3,. Blacks (N = 50) SD cv3 4.6 2.3 4.5 3.9 21 3.4 5.67 22.44 6.35 5.21 4.85 3.16 + 1/4N1 X CVk) X 100 (see Sokal and Rohlf, 1981:S9) t Test * ns * ns ** * 77 VENTRAL. ARC OF THE HUMAN PUBIS TABLE 2. Prodoct-moment correlaiion coefficients for white a n d black females and for the combined samrtle’ Whites (N = 50) Symphysis-arc length Pubic length Symphysis-arc length Acetabulum-arc length 0.46 - - (***) Acetabulum-arc length Ischial length 0.93’ 0.09 (***I (4 0.68 (***) Femoral length 0.38 (**) Ischiopubic index Blacks (N = 50) Syrnphysis-arc length Acetabulum-arc length 0.65 Combined sample (N = 100) Symphysis-arc length 0.29 - - (*I (***) (***) -0.20 (ns) 0.20 (ns) 0.20 ( 4 0.20 (ns) 0.39 - - 0.88 0.83 0.50 0.43 (***) Acetabulum-arc length (**) 0.54 (***) (***) Ischiopubic index 0.34 (***) (***) Femoral length 0.69 (***) (***) (***) Ischial length 0.17 (ns) 0.21 (ns) 0.44 0.9i 0.75 0.41 (**) 0.34 (**) - (***) Ischial length Femoral length Ischiopubic index 0.75 0.72 (***) (***) 0.27 0.23 (**) (9 0.59 0.49 I***) (***I ‘A one-tail test of significance was used. *Prob. < 0.09. **Pmb. < 0.01. ***Prob. < 0,001. arc and the subpubic concavity are not well pubis precedes that of the ventral margin, developed until the female has reached creating the ventral bevel. Following formaabout 20 ears of age.” This caveat was tion of the ventral bevel, there is a build-up of confirmed y Sutherland and Suchey (19871, bone along the ventral margin of the pubis. who observed that the majority of adolescent The bone added along the ventral margin is females do not show an arc. Sutherland and the ventral rampart. Rampart formation Suchey’s results show that a precursor of an may commence in the early part of the third arc (that is, a nonpalpable line) is the modal decade of life, and it is typically completed in morphology among females by age 20, and a the fourth decade (Todd, 1920, 1921a; definite ventral arc (that is, a palpable ridge) Meindl et al., 1985;Brooks and Suchey, n.d.1. Todd (1921~) and Meindl et al. (1985)have is the modal morphology by age 23. We agree with Todd (1920, 1921a) and argued that the ventral rampart is essenKerley (1977)that the ventral arc is related tially a delayed epiphysis. Todd (1921b) t o growth of the pubis at the symphyseal observed that in other mammals the symborder, but, as pubic growth at the symphy- physeal epiphysis of the pubis is a true episis occurs throughout childhood and adoles- physis; it develops as a separate bony elecence, why is the development of the ventral ment that later fuses with its pubic corpus. regarded arc typically delayed until early in the third In humans, however, Todd (1921~) decade of life? Beginning late in the second the epiphysis as “retrogressive”because it is decade of life, there develops an asynchrony not developmentally independent from the in bone growth at the symphyseal border of pubic corpus. Rather, the ventral margin of the pubis. Growth of the dorsal margin of the the symphyseal border of the human pubis t 78 L.C. BUDINOFF AND R.G. TAGUE develops either by the fusion of a series of ossific nodules or by the simple accretion of bone. Evidently, the ventral arc is “displaced” laterally from the symphyseal border of the pubis as a result of late epiphyseal (ventral rampart) formation. “It is the formation of the ventral rampart that causes the muscular attachment to recede from the edge of the pubis”(Todd,1920:325),but why is this ridge of bone not “displaced” until early adulthood? We contend that during early pubic growth the muscles of the ventral pubis have a periosteal attachment, which causes them to retain their same position with respect to the symphyseal border (cf. Grant, 1978; Grant et al., 1981). However, an osseous attachment for these muscles replaces the periosteal attachment either immediately before or during the period of asynchrony in pubic growth. Further migration of the muscles with continued bone growth is precluded. The subsequent development of the ventral rampart then “displaces”the attachment site for gracilis and adductor brevis from the symph seal border of the pubis. Sutherland and uchey’s (1987) precursor of a ventral arc may be a visualization of the relationship between the attachment site for gracilis and adductor brevis and the developing ventral bevel, and the palpable ventral arc may be a consequence of the osseous attachment of these muscles. The results of this study showing a positive correlation between symphysis-arc length and pubic length support the interpretation that lateral placement of the ventral arc (symphysis-arc length) is a consequence of pubic growth. Although the analysis in this study was restricted to females, we regard the interpretation as applicable to both sexes; there are few differences between the sexes in the sequence in metamorphosis of the symphyseal face of the pubis (Todd, 1920, 1921a; Meindl et al., 1985; Brooks and Suchey, n.d.1. The reason the ridge of bone “sweeps more widely” from the symphyseal border of the pubis in females than males is a sexual difference in the amount of postadolescent growth of the pubis. After age 18 years, significant growth of the pubis continues in females but not in males ( T a p e , 1986). Todd (1920) had also suggested that pubic growth in males ends at approximately age 18 and that “the prominence of the ventral rampart in the female suggests more vigorous growth or a longer $7 period of growth at the symphysis” (Todd, 1921a:38). Finally, results from Coleman’s (1969) study explain why this ridge of bone takes an arc-like path near the inferior border of the pubis. Coleman (1969:141) noted that “at the inferior border of the pubic symphysis . . . there is a larger amount of total growth than . . . [at] the superior border.” As argued, symphysis-arc length (lateral placement of the ventral arc) is derived from ventral rampart formation, The results of this study suggest five implications. First, pubic growth due to ventral rampart formation is markedly variable, as evidenced by the high coefficient of variation for symphysis-arc length (Table 1).Second, the ventral rampart’s contribution to pubic length is not significantly related to measures of body size, such as the lengths of the femur and ischium. In contrast, pubic length and acetabulum-arc length are significantly correlated with these measures of body size (Table 2). Similarly, Moerman (1981) has shown that pubic length is directly related to stature. Third, symphysis-arc length and acetabulum-arc length are independent in their contributions to pubic length, as evidenced by the low and nonsignificant correlations between the two components of pubic length (Table 2). Fourth, white and black females do not differ significantly in symphysis-arc length. Therefore, the difference between the groups in pubic length is due principally to growth unassociated with the ventral rampart (Table 1). Fifth, symphysis-arc length is directly associated with pubic length (Table 2). This result implies that lateral placement of the ventral arc cannot be considered as an independent trait from pubic length in sexing the adult hip bone. Rather, pubic length and the ventral arc provide overlapping information for sex determination. Sutherland and Suchey (1987) observed that 4% of the males in their sample show a morphology that might be interpreted as a ventral arc. We speculate that these males have long pubes. CONCLUSIONS Osteologists regard the ventral arc as diagnostic in sexing adult human hip bones. Although the sexes differ in the course taken by this ridge of bone on the pubic corpus, males and females are identical in the muscular and ligamentous attachments to this ridge. The tendons of gracilis and adductor brevis, which are fused for a variable extent, VENTRAL ARC OF THE HUMAN PUBIS 79 arise from the ridge of bone, and the fibers of Grant PG, Buschang PH, Drolet DW, and Pickerel1 C (1981) The effect of changes in muscle function and the ventral pubic ligament attach to its mebone growth on muscle migration. Am. J. Phys. Andial border. thropol. 54547-553. Lateral placement of the ventral arc (sym- Hollinshead WH (1974) Textbook of Anatomy. Hagersphysis-arc length) is directly related to pubic town, MD: Harper and Row. length. This association results from epiphy- Kerley ER (1977) Forensic anthropology. In CG Tedeschi, WG Eckert, and LG Tedeschi (eds.): Forensic seal (ventral rampart) formation at the symMedicine: A Study in Trauma and Environmental physeal border of the pubis. Therefore, the Hazards: Vol. 11. Physical Trauma. Philadelphia: W.B. ventral arc and pubic length cannot be conSaunders Co., pp. 1101-1115. sidered as independent traits for purposes of Love11 NC (1989) Test of Phenice’s technique for determining sex from the 0s pubis. Am J Phys Anthropol sexing adult hip bones. ACKNOWLEDGMENTS We thank Bruce Latimer and the Cleveland Museum of Natural History for allowing us to study skeletal material in their care. Discussions with Douglas Bailey, Bruce Latimer, Owen Lovejoy, Richard Meindl, Judy Suchey, and Steven Ward were helpful in the preparation of this manuscript. Portions of this paper were presented at the 57th Annual Meeting of the American Association of Physical Anthropologists (1988). LITERATURE CITED Bass WM (1987) Human Osteology: A Laboratory and Field Manual, 3rd ed. Columbia, MO: Missouri Archaeological Society (Special Publication No. 2). Brooks S, and Suchey JM (n.d.1Skeletal age determination based on the 0s pubis: A comparison of the AcsadiNemeskeri and Suchey-Brooks methods. Manuscript in possession of authors. Buikstra J E , and Mielke J H (1985) Demography, diet, and health. In RI Gilbert Jr, and H J Mielke (eds.):The Analysis of Prehistoric Diets. New York: Academic Press, pp. 359-422. Cleland J (1889)On certain distinctions of form hitherto unnoticed in the human pelvis, characteristic of sex, age and race. Memoirs Memoranda Anat. 1:95-103. Coleman WH (1969) Sex differences in the growth of the human bony pelvis. Am. J . Phys. Anthropol. 31:125-152. Grant PG (1978)The effect of position on the migration of muscle. J. Anat. 127t157-162. 79:117-120. Meindl RS, Lovejo CO, Mensforth RP, and Walker RA (1985) A revisedrmethod of age determination using the 0s pubis, with a review and tests of accuracy of other current methods of pubic symphyseal aging. Am. J . Phys. Anthropol. 68:29-45. Moerman ML (1981)A Longitudinal Study of Growth in Relation to Body Size and Sexual Dimorphism in the Human Pelvis. Ph.D. dissertation, Ann Arbor, University of Michigan. Moore KL. (1980) Clinically Oriented Anatomy. Baltimore: Williams and Wilkins Co. Phenice TW (1969) A newly developed visual method of sexing the 0s pubis. Am. J. Phys. Anthropol. 30:297302. Sokal RR, and Rohlf FJ (1981)Biometry. San Francisco: W.H. Freeman and Co. Sutherland LD, and Suchey J M (1987)Use of the ventral arc in sex determination of the 0s pubis. Poster presentation, 39th Annual Meeting of the American Academy of Forensic Sciences, Physical Anthropology Section, San Diego, CA. Tague RG (1986) Obstetric Adaptations of the Human Bony Pelvis. Ph.D. dissertation, Kent, Ohio, Kent State University. Todd TW (1920) Age changes in the ubic bone I The male White pubis. Am. J . Phys. Antlropol. 3:2851334. Todd TW (1921a)Age changes in the pubic bone: 11. The pubis ofthe male Negro-White hybrid; 111: The pubis of the White female. IV.The pubis of the female NegroWhite hybrid. Am. J. Phys. Anthropol. 4:l-70. Todd TW (1921b) Age changes in the pubic bone: V. Mammalian pubic metamorphosis. Am. J. Phys. Anthropol. 4:333406. Todd TW (1921c)Age changes in the pubic bone: VI. The interpretation of variations in the symphysial area. Am. J . Phys. Anthropol. 4:407-424. Williams PL, and Warwick R (1980) Gray’s Anatomy, British Edition. Philadelphia: W.B. Saunders Co. Woodburne RT (1983) Essentials of Human Anatomy. New York: Oxford University Press.