Analysis of osteon morphotype scoring schemes for interpreting load history: evaluation in the chimpanzee femur

Abstract

Osteon morphotype scores (MTSs) allow for quantification of mechanically important collagen ⁄ lamellar variations between secondary osteons when viewed in circularly polarized ight (CPL). We recently modified the 6-point MTS method of Martin et al. (Martin RB, Gibson VA, Stover SM, Gibeling JC, Griffin LV (1996a) Osteonal structure in the equine third metacarpus. Bone 19, 165-71) and reported superiority of this modified method in correlating with 'tension' and 'compression' cortices of both chimpanzee proximal femoral diaphyses and diaphyses of other non-anthropoid bones that are loaded in habitual bending (Skedros et al. 2009(Skedros et al. , 2011. In these studies, the 'tension' and 'compression' cortices differed significantly in predominant collagen fiber orientation (CFO) based on weighted-mean gray levels (CFO ⁄ WMGLs) in CPL images. In chimpanzee femora, however, some osteons were difficult to score with the 6-point method; namely, 'hybrids' with peripherally bright 'hoops' and variability in alternating rings within the osteon wall. We hypothesized that some of these hybrids would be more prevalent in regions subject to torsion than bending. In this perspective the present study was aimed at expanding our 6-point scoring method (S-6-MTS) into two 12-point methods with six additional morphotypes that considered these hybrids. Three-and 4-point methods were also evaluated. We hypothesized that at least one of these other methods would out-perform the S-6-MTS in terms of accuracy, reliability, and interpreting torsion vs. bending load histories. Osteon morphotypes were quantified in CPL images from transverse sections of eight adult chimpanzee femora (neck, proximal diaphysis, mid-diaphysis), where the mid-diaphysis and base-and mid-neck locations have relatively more complex loading (e.g. torsion + bending) than the proximal diaphysis, where bending predominates. Correlation coefficients between CFO ⁄ WMGL and MTSs showed that the S-6-MTS method was either stronger or equivalent to the 12-point methods, and typically stronger than the 3-and 4-point methods for all load environments. In nearly all instances the S-6-MTS is more reliable and accurate when it is applied to cases where interpreting load history requires distinguishing habitual bending from torsion. Consequently, in studies of osteonal adaptations for these load histories the 3-and 4-point methods are not stronger correlates, and the extra time required to assign additional scores in the 12-point methods is both unnecessary and can be highly unreliable.

Mechanical properties of porcine femoral cortical bone measured by nanoindentation

“…Martin et al (1996) proposed six osteon morphotypes based on different birefringence patterns. These were generalized by Skedros et al (2011) to 12 different types. These osteon morphotypes depend on anatomical position (regions subjected to torsion versus bending) and may also change with age.…”

Utility of osteon circularity for determining species and interpreting load history in primates and nonprimates

“…By contrast, a series of prior investigations using the same bones examined herein demonstrate that between-or within-bone patterns of predominant CFO and osteon collagen/lamellar "morphotypes" are much stronger correlates in these contexts, and even more strongly than On.N/T.Ar and On.Ar (Skedros, 2012;Skedros and Keenan 2016;Skedros et al, , 2009Skedros et al, , 2011aSkedros et al, , 2011bSkedros et al, , 2013a. In fact, these osteon shape characteristics have little value in terms of predicting load history, even in relatively simply loaded calcanei (none of the calcanei from the three species studied showed all of the expected regional variations).…”

“…The histomorphometric methods used in this study have been described previously (Skedros et al, 2009(Skedros et al, , 2011a Skedros et al 1999Skedros et al , 2012. Modern human fibulae (n 5 11; mean age: 47; age range: 25-65 years; 8 males; 3 females) were also used and the data from these bones have not been published.…”

“…Rows 1-3 and 7 are from prior studies as summarized inSkedros et al (2011a). Rows 1-3 and 7 are from prior studies as summarized inSkedros et al (2011a).…”

Los Estudios De Histología Ósea en Antropología Biológica

“…Comparativamente, una aproximación middle out en la escala del análisis histológico de rasgos microestructurales resulta aún poco explorada. Los datos obtenidos a esta escala permiten obtener información cualitativa y cuantitativa única -que no puede ser obtenida a partir de otras evidencias o resulta difícil de extraer a partir de restos fragmentados-para el abordaje de problemas paleopatológicos (Pfeiffer, 2000;DeBoer et al, 2013), de identificación de especies (Hillier y Bell, 2007), evaluación de la calidad ósea para estudios isotópicos y de ADN antiguo (ADNa), de variación morfológica en estudios ontogenéticos y evolutivos (Bromage, 1989), tafonómicos (Turner-Walker, 2008), paleodemográficos (Robling y Stout, 2008), y biomecánicos (Skedros et al, 2011). Empleados en conjunto, los datos histológicos y los provenientes de otras líneas de evidencia complementaria contribuyen al fortalecimiento de las inferencias realizadas.…”