| Few publications report on histological differentiation within and between mammalian long bone cortices. Specifically, are osteon populations unique to proximal, midshaft or distal segments? First, this study tests Kerley's (1965) quantification categories, i.e., number of osteons, fragments, and non-Haversian canals and percent circumferential lamellae, to estimate age and second, quantifies those micro-structural differences within and between human femur, tibia and fibula based upon section location. In an identical attempt to understand within-bone differences, i.e., proximal from distal, the same Kerley criteria were qualified and quantified within and between humeral, radial and ulnar diaphyses. However, no age estimation via Kerley was made on the pectoral limb bones, as the method never intended to assess age using these.; Using a Buehler Isomet 1000 saw, three thin sections were made from numerous one-centimeter segments cut from each entire diaphysis. Sections were quantified identical to Kerley's quadrant (anterior, posterior, medical and lateral) using a Leica DMRX light microscope at 16, 50 and 100 magnifications. After video-image capture, morphometric analysis of utilized Image-Pro Express software with a Dell Optiplex GX270 computer.; Quantification of these structures indicates statistically significant within-bone differences, i.e., throughout the shaft, which result in significantly different age estimations. The means for each quantification category were examined independently across the four fields using repeated measures ANOVA at the .05 level. Regression equations for age estimation using Kerley based on the femur, tibia and fibula reveal widely inconsistent age estimations when compared to those derived from midshaft.; Those findings generate two related conclusions: Metabolically and/or mechanically, bone maintenance and remodeling varies greatly within the shaft. Second, fragment location must be identified and existing Kerley and Ubelaker (1978) equations be used only for midshaft. As this research demonstrates, moving proximal or distal from midshaft will result in spurious age estimation particularly pertinent to fragmentary remains. Furthermore, this research underscores that fact that ageing methods developed from fragmentary bone must account for significant difference of microstructural populations throughout the shaft as well as within one thin section. |
