Bone Abstracts

Habitual physical activities of past populations are frequently reconstructed based on musculoskeletal markers (MSM) in human skeletal remains, i.e. particular morphological features of muscles attachment sites. However, the relationship between muscular activity and bone microstructure at the site of muscle attachments is unexplored. Therefore, this study aimed at analyzing bone microstructural characteristics of the muscles attachments sites and correlating these features with MSM macroscopic scores. The hypothesis is that bones with macroscopically pronounced muscle attachment sites also reveal distinct micro-structural patterns caused by persistent biomechanical stress. Our sample consisted of two groups of Ancient Avar individuals: 30 riders (buried with horses) and 30 farmers (engaged in daily life activities). We analyzed the attachments of leg muscles that are active during a horse riding (adductor muscles of the thigh) using an MSM scoring system proposed by Villote (2006). The bone samples were cut from distal femoral diaphysis at adductor tubercle (insertion site of adductor magnus muscle) enthesis in two individuals of the same age and sex but different macroscopic expression of this muscular insertion. The cortical and trabecular microarchitecture were assessed using micro-computed tomography (Scanco μCT40, Scanco Medical). The sample with macroscopically well-expressed adductor tubercle displayed remarkably higher cortical thickness (1.48 vs 0.79 mm) and denser trabecular network (BV/TV: 47 vs 31%; Tb.N: 1.89 vs 1.38/mm; Tb.Th: 0.29 vs 0.24 mm; Tb.Sp: 0.58 vs 0.70 mm) along with improved trabecular connectivity (Conn.D: 6.16 vs 4.44/mm³). Beyond the hypothesis that macroscopic appearance of muscle insertion sites is related to muscle strength/activity, our study reveals similar relationship at micro-structure level (increased cortical thickness and improved trabecular architecture to further distribute the repeated load). Our findings add micro-architectural data to the morphological analysis of MSM on bones from archaeological context, which potentially may help in classifying and grading these phenomena in human bones.