Enhancing functional interpretations of shoulder morphology: an investigation of the range of motion and biomechanical capacity of the hominoid shoulder complex

导论.猿类（不包括人类）的肩胛骨（肩胛骨）与人类的肩胛骨相比显示出相当大的形态差异。这些长期以来已知的差异是有据可查的。传统上，猿特有的肩胛骨形态被理解为对树栖栖息地（攀爬和悬挂运动）的适应，这在人类进化过程中消失了。然而，这种理解仅仅是基于相似的肩胛骨形态和运动行为的相关性，而猿肩胛骨的功能优势的证据是缺失的。因此，目前对肩胛骨（化石）的功能解释是基于假设的;基于证据的解释工具是不存在的。目标.该项目的目的是确定不同的肩膀形态对前肢功能的影响在Hominoidea（人类和猿类），这将提供洞察肩膀的适应不同的运动行为。在人类中，充分记录的肩部机制包括手臂抬起和放下期间所有关节的复杂相互作用。然而，在猿类中，单个关节的贡献目前尚不清楚。关于肩胛胸运动（肩胛骨在胸部滑动）的缺失信息尤其成问题，因为不知道哪些肩胛运动是猿抬起手臂所必需的，因此不可能调查不同肩部解剖结构的生物力学特性。工作方案。作为第一步，本项目将调查两种树栖猿（长臂猿和黑猩猩）的肩部机制和肩带中单个关节的运动范围。这是解决使用国家的最先进的标记为基础的录像。实验是在死后进行的;猿类的上臂被动地移动，通过它们的整个运动范围，而单个骨骼的位置则通过标记记录下来。标记数据用于研究各个元件的运动范围以及每个关节对整个肩部机制的贡献。作为第二步，将使用肌肉骨骼建模研究解剖学上不同肩部的生物力学特性。首先，将开发一个肩关节和黑猩猩的肩膀模型。与现有的大猩猩和人类模型一起，这些模型将用于评估和比较肩部肌肉的生物力学能力。不同物种的能力的比较，以及物种特异性的肩关节机制的知识，将使我们能够提高我们的理解不同的肩关节解剖结构的生物力学效应。

Introduction. The scapulae (shoulder blades) of apes (excluding humans) display considerable morphological differences compared to those of humans. These long known differences are well documented. Traditionally, ape-specific scapular morphology is understood as an adaptation to the arboreal habitat (climbing and suspensory locomotion), which was lost during the course of human evolution. However, this understanding is based on mere correlations of similar scapular morphologies and locomotor behaviours, while evidence for the functional advantage of the ape scapula is missing. As a result, current functional interpretations of (fossil) scapulae are based on assumptions; a tool for evidence-based interpretation is non-existent. Objectives. The aim of this project is to determine the effect of different shoulder morphologies on forelimb function within the Hominoidea (humans and apes), which will provide insight into the adaptation of the shoulder to different locomotor behaviours. In humans, the well-documented shoulder mechanism consists of a complicated interaction of all joints during arm raising and lowering. However, in apes, the contribution of the individual joints is currently unknown. The missing information on scapulothoracic movement (the gliding of the scapula across the thorax) is particularly problematic, as without knowing which scapular movements are necessary for apes to lift their arm, an investigation of the biomechanical properties of different shoulder anatomies is impossible. Work programme. As a first step, this project will investigate the shoulder mechanism and the range of motion of the individual joints in the shoulder girdle of two arboreal apes (gibbons and chimpanzees). This is addressed using state-of-the-art marker-based videography. The experiments take place post mortem; the upper arms of the apes are passively moved through their full range of motion, while the position of the individual bones is recorded via the markers. The marker data is used to investigate the range of motion of the individual elements and the contribution of each joint towards the overall shoulder mechanism. As a second step, the biomechanical properties of anatomically different shoulders will be investigated using musculoskeletal modelling. Firstly, a gibbon and a chimpanzee shoulder model will be developed. Together with already existing models of a gorilla and a human, these models will be used to evaluate and compare the biomechanical capacities of the shoulder muscles. The comparison of the capacities of different species together with the knowledge of the species-specific shoulder mechanism will allow us to enhance our understanding of the biomechanical effect of different shoulder anatomies.