TECHNICAL NOTE ANTHROPOLOGY Rebecca A. Meeusen, 1 M.S.; Angi M. Christensen, 1,2 Ph.D.; and Joseph T. Hefner, 3 Ph.D. The Use of Femoral Neck Axis Length to Estimate Sex and Ancestry ABSTRACT: Having multiple reliable methods of estimating sex and ancestry from various skeletal features increases the likelihood of iden- tifying skeletal remains. Femoral neck axis length (FNAL), as measured in living individuals, has been shown to vary by sex and ancestry. FNAL has not, however, been previously measured directly from skeletonized remains and investigated for its potential use in forensic anthro- pological applications. This research proposes a method for measuring FNAL from skeletal remains, determines the reliability and repeatability of the measurement, and assesses the validity of FNAL in sex and ancestry estimation. Results showed low interobserver error in the measure- ment of FNAL (TEM = 0.33 mm, R = 0.99). Significant differences in FNAL were found between sexes as well as between American Black, American White, and Native American groups. FNAL can correctly classify sex in ~86% of all cases and is considered valuable to sex estima- tion. The value of FNAL to ancestry estimation, however, is considered limited. KEYWORDS: forensic science, forensic anthropology, proximal femur, femoral neck axis length, ancestry estimation, sex estimation The wide range of skeletal conditions and various levels of skeletal preservation in forensic contexts can challenge the esti- mation of sex and ancestry. Having multiple reliable methods of estimating these aspects of the biological profile increases the likelihood of identifying an unknown individual from skeletal remains. Dimensions of the proximal femur have received some attention in the forensic anthropological literature for their utility as indicators of sex and ancestry. This is due in part to the sur- vivability of this area of the skeleton in forensic contexts and to an appreciable level of quantifiable variation in the proximal femur (e.g., [1–3]). Geometry of the proximal femur, as measured from dual energy X-ray absorptiometry (DXA) scans, is commonly used by bone densitometrists and other skeletal health experts to assess hip fracture risk (e.g., [4,5]). Specifically, hip axis length (HAL), defined as the distance from the base of the greater tro- chanter through the femoral neck axis to the inner pelvic brim (see Fig. 1a), is correlated to hip fracture risk, with greater HAL associated with an increase in fracture risk. This measurement is not related to bone mineral density, but is related to overall fem- oral strength. Both HAL and fracture risk vary by sex and ances- try, and both HAL and fracture risk are sex dependent (4). Femoral neck axis length (FNAL) is HAL excluding the hip component and is defined as the distance from the base of the greater trochanter through the femoral neck axis to the apex of the femoral head (4) (see Fig. 1b). In a recent study, HAL and estimated FNAL obtained from DXA scans of African, Euro- pean, and Asian females and males demonstrated marked varia- tion by sex and ancestry (6). Previously only measured from DXA scans, FNAL can also be measured from skeletonized fem- ora using standard sliding calipers, and potentially used to pre- dict sex and ancestry from skeletal remains. This current study defines the FNAL measurement in this context, determines the reliability and repeatability of the FNAL measurement, and assesses the validity of the FNAL measurement in estimating sex and ancestry from skeletal remains. Materials and Methods Specimens examined included American Blacks and Whites from the Robert J. Terry Anatomical Skeletal Collection at the Smithsonian National Museum of Natural History and the Wil- liam M. Bass Donated Skeletal Collection at the University of Tennessee, Knoxville, as well as Native Americans from the Averbuch Site Skeletal Collection, also at the University of Ten- nessee, Knoxville. Aside from considerable differences in birth dates, all reasonable efforts were made to achieve a uniform sample. The sample size (by sex and ancestry) is provided in Table 1. Measurements collected for all specimens included the FNAL and the maximum femoral length (FEMXLN). For the Native American specimens, maximum femoral head diameter (FEM- HDD) was also collected, and sex was estimated using a FEM- HDD sectioning point derived from Wescott (7). Although pelvic methods of sex estimation were preferred, incomplete remains precluded their use, and measurable FEMHDDs pro- vided an acceptable alternative. All measurements were taken with standard sliding calipers and rounded to the nearest mm. FEMXLN and FEMHDD were collected according to definitions provided by Moore-Jansen et al. (8). 1 Department of Forensic Science, George Mason University, 4400 Univer- sity Drive, Fairfax, VA. 2 Federal Bureau of Investigation Laboratory, 2501 Investigation Parkway, Quantico, VA. 3 Department of Anthropology, College of Social Sciences, Michigan State University, 355 Baker Hall, East Lansing, MI. Received 5 June 2014; and in revised form 27 Aug. 2014; accepted 11 Sept. 2014. 1300 © 2015 American Academy of Forensic Sciences J Forensic Sci, September 2015, Vol. 60, No. 5 doi: 10.1111/1556-4029.12820 Available online at: onlinelibrary.wiley.com