Bone macromorphology at muscle attachment sites: its relationship with the microarchitecture of the underlying bone and possible implications for the reconstruction of habitual physical activities of past populations

Abstract

Background: The term “enthesis” is usually used to mark the sites of muscle attachments, as well as attachments of ligaments and joint capsules to bones. In the last three decades, studies concerning entheses in human skeletal remains have attempted to reconstruct the habitual physical activities of past populations. The evaluation of entheseal morphological appearance was suggested for the identification of gross workload patterns, which could be used in the interpretation of labour division on a gender, age or social basis in ancient populations. There have been four major research streams in literature with regard to entheses and entheseal changes (EC). The first group of studies mainly focused on the analysis of the histological structure of the attachment site. The second group of studies focused of visual scoring methods based on the macromorphological features of the attachment surface with the aim of evaluating the degree of muscle use. The third group included studies dealing with the relationship between EC and the biomechanical properties of long bones, while a fourth group of studies was aimed at reconstructing the habitual physical activities of past populations, using visual scoring methods. Regardless of the fact that habitual physical activities or stress patterns of past populations are frequently reconstructed based on EC, there is no direct experimental evidence for the relationship between muscular activity and particular macroscopic entheseal scores. Although entheses were investigated from macroscopic, histological and biomechanical aspects, it is surprising that microarchitectural studies of the underlying bone are still lacking, despite the well-known potential of bone microarchitecture to reflect mechanical loading. It is widely accepted that the bone adapts its structure to changes in its mechanical environment, and a number of studies have reported the relationship between bone microarchitecture and loading patterns in different skeletal sites. However, despite numerous studies reporting that bone morphology is affected by mechanical loads and that bone has a self-optimising capability, there is no comprehensive study dealing with this issue in the region of the entheses...