Early ontogeny of the human femoral bicondylar angle.
The presence of a femoral bicondylar angle consistently and significantly greater than 0 degrees has been a hallmark of hominid bipedality, but its pattern of development has not been documented. We have therefore compiled cross-sectional data on the development of the articular bicondylar angle for a clinical sample of modern humans and of the metaphyseal bicondylar angle for two Recent human skeletal samples, one predominantly European in origin and the other Amerindian. All three samples exhibit a pattern of a bicondylar angle of 0 degrees at birth and then a steady average increase in the angle from late in the first year postnatal, through infancy; and into the juvenile years. The two skeletal samples reach low adult values by approximately 4 years postnatal, whereas the clinical sample with a lowered activity level appears to attain consistent adult values slightly later (approximately 6 years postnatal). In addition, two modern human individuals, one nonambulatory and the other minimally ambulatory, show no and little development, respectively, of a bicondylar angle. These data, in conjunction with clinical and experimental observations on the potential and form of angular changes during epiphyseal growth, establish a high degree of potential for plasticity in the development of the human bicondylar angle and the direct association of a bipedal locomotion and (especially) posture with the developmental emergence of a human femoral bicondylar angle.
Tardieu
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UA 1137 du C.N.R.S., Laboratoire d'Anatomie Comparée, Muséum, National d'Histoire Naturelle, Paris, France.
Trinkaus
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D000293:Adolescent; D000818:Animals; D002648:Child; D002675:Child, Preschool; D005260:Female; D005269:Femur / Q000033:anatomy & histology*; D005684:Gait; D015186:Hominidae / Q000033:anatomy & histology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007719:Knee Joint / Q000033:anatomy & histology*; D016018:Least-Squares Analysis; D008297:Male; D009024:Morphogenesis; D011187:Posture; D012737:Sex Factors