title: Biomechanics of forearm rotation: force and efficiency of pronator teres.
abstract: Biomechanical models are useful to assess the effect of muscular forces on bone structure. Using skeletal remains, we analyze pronator teres rotational efficiency and its force components throughout the entire flexion-extension and pronation-supination ranges by means of a new biomechanical model and 3D imaging techniques, and we explore the relationship between these parameters and skeletal structure. The results show that maximal efficiency is the highest in full elbow flexion and is close to forearm neutral position for each elbow angle. The vertical component of pronator teres force is the highest among all components and is greater in pronation and elbow extension. The radial component becomes negative in pronation and reaches lower values as the elbow flexes. Both components could enhance radial curvature, especially in pronation. The model also enables to calculate efficiency and force components simulating changes in osteometric parameters. An increase of radial curvature improves efficiency and displaces the position where the radial component becomes negative towards the end of pronation. A more proximal location of pronator teres radial enthesis and a larger humeral medial epicondyle increase efficiency and displace the position where this component becomes negative towards forearm neutral position, which enhances radial curvature. Efficiency is also affected by medial epicondylar orientation and carrying angle. Moreover, reaching an object and bringing it close to the face in a close-to-neutral position improve efficiency and entail an equilibrium between the forces affecting the elbow joint stability. When the upper-limb skeleton is used in positions of low efficiency, implying unbalanced force components, it undergoes plastic changes, which improve these parameters. These findings are useful for studies on ergonomics and orthopaedics, and the model could also be applied to fossil primates in order to infer their locomotor form. Moreover, activity patterns in human ancient populations could be deduced from parameters reported here.
authors.affiliation: Unitat d'Antropologia Biològica, Departament de Biologia Animal, Biologia Vegetal i Ecologia, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Catalonia, Spain.
authors.forename: Pere
authors.initials: P
authors.lastname: Ibáñez-Gimeno
authors.affiliation: Centre de Patologia Forense de Collserola, Institut de Medicina Legal de Catalunya, Montcada i Reixach, Barcelona, Catalonia, Spain ; Unitat de Medicina Legal i Forense, Departament de Psiquiatria i de Medicina Legal, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Catalonia, Spain.
authors.forename: Ignasi
authors.initials: I
authors.lastname: Galtés
authors.affiliation: Departament de Paleobiologia, Institut Català de Paleontologia Miquel Crusafont (ICP), Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Catalonia, Spain.
authors.forename: Xavier
authors.initials: X
authors.lastname: Jordana
authors.affiliation: Unitat d'Antropologia Biològica, Departament de Biologia Animal, Biologia Vegetal i Ecologia, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Catalonia, Spain.
authors.forename: Assumpció
authors.initials: A
authors.lastname: Malgosa
authors.affiliation: Unitat de Biofísica, Departament de Bioquímica i de Biologia Molecular, and Centre d'Estudis en Biofísica, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Catalonia, Spain.
authors.forename: Joan
authors.initials: J
authors.lastname: Manyosa
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D004550:Elbow / Q000033:anatomy & histology / Q000502:physiology; D004551:Elbow Joint / Q000033:anatomy & histology / Q000502:physiology; D005542:Forearm / Q000033:anatomy & histology* / Q000502:physiology; D006801:Humans; D008297:Male; D010163:Paleontology; D011403:Pronation / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D012863:Skeleton; D013484:Supination / Q000502:physiology*