Does She or Doesn’t She: Change in Osteon Size with Age and Sex. M.A. Streeter 1 , J. Purcell 1 , L. Larson 1 , B. Jumonville 1 , L. McCormick 2 , J. Goliath 2 , M.T.J. Cosgriff‐Hernandez 3 , E. Dubie 1 , T. Schroeder 1 , K. Brown 1 , M. Drapeau 4 , R. Lazenby 5 . 1 Department of Anthropology, Boise State University, 2 Department of Anthropology, The Ohio State University, 3 Joint POW/MIA AccounYng Command‐Central IdenYficaYon Laboratory, 4 Départment d’‐anthropologie, Université de Montréal, 5 Department of Anthropology, University of North BriYsh Columbia. IntroducYon: Studies invesYgaYng pa]erns of change in mean osteon size (On.Ar) have produced varied results. While some researchers have reported a decrease in On.Ar with age (Currey, 1964; Barer and Jowsey, 1967; Burr et al. 1990) others have reported no age associated change in size (Takahashi et al., 1965; Jowsey, 1966; Landeros and Frost, 1964; Ha]ner et al., 1965; Takahashi et al., 1965; Yoshino et al., 1994; Pfeiffer et al., 2006; Denny, 2010)Yet other studies (Black et. al, 1974; Burr et al., 1990)found an increase in On.Ar with increasing age. These studies have focused on various bones, ribs, femurs, humerus, Ybias and the second metacarpal in diverse populaYons including modern and archaeological samples. Most studies did not consider sex differences however, Burr et al. (1990) analyzing femoral samples from Pecos Pueblo, and found that On.Ar decreased with age in males but not in females. Pfeiffer et al. (2006) reported no sex or age effects on On.Ar. Measures of variaYon in osteon size have been used to infer age and the rate of bone metabolic processes. The purpose of this study is to calculate On.Ar in mulYple elements to determine if there is a change in On.Ar associated with age and sex. Methods: • Point count method was used to determine mean osteon size (200X) • Some samples were analyzed using a computer program (SPOT) • Wafers of the cross‐secYons of five bones (2 nd metacarpals, ribs, clavicles, femurs and Ybias) were mounted on microscope slides • Data was entered into excel to calculate, mean, max, min, standard deviaYon used to create sca]er plots from which linear regression, coefficient of determinaYon, correlaYon coefficient were determined Materials: 2 nd Metacarpals  Two sources, the Sadlermiut Inuit, an East arcYc foraging group (1289‐1903 A.D.)(Merbs, 1983; Lazenby, 1998), and 2 nd metacarpals originaYng from St Thomas Anglican Church, Bellville, Ontario a 19 th century Euro‐Canadian sample (Lazenby, 1998; Saunders et al, 2002) Ribs  Modern samples prepared for previous research originaYng from Missouri Medical Examiners offices and forensic cases  Archaeological ribs from the archaeological sample Chiribaya (900AD – 1350 AD) an archaeological agriculturalists group from Peru (Buikstra,1998) Clavicles  Composed of modern samples originaYng from cadavers, and autopsies from Missouri Medical Examiner’s office and archaeological samples from Chiribaya, Peru Femurs  Modern samples are derived from Missouri Medical Examiner’s offices and a cadaver series from the University of Missouri department of Anthropology Tibias  A sample of modern bones from the same cadaver series and Missouri Medical Examiner’s office Results: Analysis of age changes in On.Ar • In the 2 nd metacarpals no age associated change in On.Ar was observed (r=0) • In ribs there was a negaYve correlaYon between On.Ar and age (r=.5) • In the clavicles there was no correlaYon between age and On.Ar (r=0) • The femurs showed the strongest negaYve correlaYon between age and On.Ar (r=. 72) • In Ybias there was a slight negaYve correlaYon between age and On.Ar (r=.32) Analysis of age changes in On.Ar by sex • The correlaYon between age and On.Ar in females by bone were; 2 nd metacarpals no correlaYon (r=0), ribs negaYve correlaYon (r=.63), clavicles negaYve correlaYon (r=.12), femurs strongly negaYve correlaYon (r=.79) and Ybias negaYve (r=.57) • The correlaYon between age and On.Ar in males by bone were; 2 nd metacarpals no correlaYon (r=.05), ribs negaYve correlaYon (r=.44), clavicles slightly posiYve correlaYon (r=.18), femurs strong negaYve correlaYon (r=.67) and Ybias moderate negaYve correlaYon (r=.35) • Females showed the strongest negaYve correlaYon between age and On.Ar in ribs, Ybia and femurs but in the 2 nd metacarpals and clavicles there was virtually no correlaYon. Conclusions: • An age associated decline in On.Ar appears to be bone specific • The weight bearing bones, the Ybia and femur did show an age associated change in On.Ar . • 2 nd metacarpals and clavicles are non‐weight bearing bones and there was no change in On.Ar with age. • Ribs are also non‐weight bearing bones but they did show a decrease in osteon area with age. Similar to the Ybia and femur • We suggest that the mechanical strain incurred by weight bearing bones and ribs during respiraYon provides sufficient sYmulaYon to affect a change in On.Ar with age. • This might suggest that unlike the case in weight bearing bones, which experience fluctuaYon in strain level, the more constant mechanical strain of non‐weight bearing bones results in an On.Ar that does not change with age. References: Barer M, Jowsey J. 1967. Bone FormaYon and ResorpYon in Normal Human Rib. Clin Ortho and Rel Res 52:241‐247. Black J, Ma]son R, Korostoff E. 1974. 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