Appositional long bone growth: Implications for measuring cross‐sectional geometry

Abstract

Objectives As growth at the periosteal and endosteal surfaces varies with age, cross‐sectional geometric (CSG) properties derived from periosteal (“solid”) contours may not produce comparable results to those from endosteal and periosteal contours (“true”), contrary to findings from adults. Error in CSG properties derived from the “solid” sections is compared with “true” sections in a sample of archeologically derived skeletons with estimated dental ages ranging from 1.5 months to 23.5 years. Materials and Methods Cross sections were extracted from 3D surface models, and endosteal contours were located from biplanar radiographs for 56 femora and 59 humeri. Polar second moment of area (J), cross‐sectional shape (Imax/Imin), and polar section modulus (Zp) were calculated from solid and true sections. Relationships between solid and true properties were examined with least squares regression. Multiple regression examined the effect of age and % cortical area on solid section CSG error. Results While correlations were high (R2 = 0.72–0.99, all p < 0.001), the results indicate that solid CSG properties are not within an acceptable error range (%SEE of ≤8.0, and %PE of ≤5.0) of true CSG. Error was most affected by %CA, while estimated age was not correlated with %CA, %PE, or percent difference of true‐solid CSG. Discussion Periosteal contours alone should not be used to calculate CSG properties from individuals during the period of growth and development. Variation in bone growth and/or adaptive responses independent of age may account for the inconsistent age effects.

Asymmetry in linear measurements and cross‐sectional geometry in the humerus during ontogeny

“…However, pooling of samples is necessary to detect ontogenetic trends, and we focused on forager samples, due to a likelihood of high activity, and therefore a potentially clearer signal of bilateral asymmetry. Another limitation arises from the use of solid sections, since altered resorption or deposition at the endosteal surface, and its effect on CSG, could not be captured (Kurki et al, 2022). This would likely most affect the accuracy of CSG asymmetry measures in adolescence, when the endosteal surface becomes most responsive to loading, which may account for the weakening of some trends in the last cohort (Garn, 1970;Goldman et al, 2009;Ruff et al, 1994).…”

“…While CSG locations may differ slightly between fully fused, fusing, and unfused individuals, the sections are still taken in the same region, so considering potential errors of estimating matching section locations; we did not adjust the section location in fused or fusing individuals. CSG properties calculated from periosteal contours alone may differ substantially from CSG calculations based on sections including endosteal dimensions, and deviation from true value increases with a decrease in percent cortical area (Kurki et al, 2022). However, measures still show a strong correlation with values calculated from sections with endosteal contours, and since we deal with intra‐individual asymmetry, errors should be smaller than for inter‐individual comparisons.…”