Biomechanical Evaluation on the Bilateral Asymmetry of Complete Humeral Diaphysis in Chinese Archaeological Populations

Yuhao Zhao,Mi Zhou,Pianpian Wei,Jianing He,Haijun Li,Song Xing

doi:10.3390/sym13101843

Abstract

Diaphyseal cross-sectional geometry (CSG) is an effective indicator of humeral bilateral asymmetry. However, previous studies primarily focused on CSG properties from limited locations to represent the overall bilateral biomechanical performance of humeral diaphysis. In this study, the complete humeral diaphyses of 40 pairs of humeri from three Chinese archaeological populations were scanned using high-resolution micro-CT, and their biomechanical asymmetries were quantified by morphometric mapping. Patterns of humeral asymmetry were compared between sub-groups defined by sex and population, and the representativeness of torsional rigidity asymmetry at the 35% and 50% cross-sections (J35 and J50 asymmetry) was testified. Inter-group differences were observed on the mean morphometric maps, but were not statistically significant. Analogous distribution patterns of highly asymmetrical regions, which correspond to major muscle attachments, were observed across nearly all the sexes and populations. The diaphyseal regions with high variability of bilateral asymmetry tended to present a low asymmetrical level. The J35 and J50 asymmetry were related to the overall humeral asymmetry, but the correlation was moderate and they could not reflect localized asymmetrical features across the diaphysis. This study suggests that the overall asymmetry pattern of humeral diaphysis is more complicated than previously revealed by individual sections.

Highlights

Humeral bilateral asymmetry has been extensively studied in orthopedics, forensics, and paleo/archaeological anthropology [1,2,3]
This study evaluated humeral biomechanical asymmetry across complete humeral diaphysis based on high-resolution micro-CT, and by quantifiable visualization and statistical methods
Using specimens from three Chinese archaeological populations that varied in geographic location, chronological age, and subsistence pattern, the pattern of humeral asymmetry in East Asian modern humans was investigated

Summary

Introduction

Humeral bilateral asymmetry has been extensively studied in orthopedics, forensics, and paleo/archaeological anthropology [1,2,3]. A combined study of endocranial and humeral asymmetry can shed light on how the human body responds to dependent asymmetrical stimuli across biologically independent anatomical regions [10] These applications make humeral bilateral asymmetry an effective approach for reconstructing the behaviors of past human populations [11,12,13,14,15,16]. Long bone diaphyses show great plasticity to remodel in response to mechanical loadings across a lifetime, especially prior to sexual maturity [17,18,19,20,21] This remodeling makes diaphyseal cross-sectional geometry (CSG) a more effective indicator of bilateral upper-limb use and asymmetry compared to other linear measurements, such as articular breath or bone length [13,20,22,23,24]

Objectives

Methods

Results

Discussion

Conclusion