Clavicle, a neglected bone: Morphology and relation to arm movements and shoulder architecture in primates

Abstract

In spite of its importance for movements of the upper limbs, the clavicle is an infrequently studied shoulder bone. The present study compares clavicular morphology among different extant primates. Methods have included the assessment of clavicular curvatures projected on two perpendicular planes that can be assessed overall as cranial and dorsal primary curvatures. Results showed that in cranial view, three morphologies can be defined. One group exhibited an external curvature considerably more pronounced than the internal one (Gorilla, Papio); a second group was characterized by an internal curvature much more pronounced than the external one (Hylobates, Ateles); and a third group contained those with the two curvatures equally pronounced (Pan, Homo, Pongo, Procolobus, Colobus). Clavicle curvatures projected on the dorsal plane could be placed into four groups. The first group is characterized by two curvatures, an inferior and a superior (Apes, Spider monkeys). The second included monkeys, whose clavicles have an inferior curvature much more pronounced than the superior one. The third group includes only Hylobates, whose clavicles possess only the superior curvature. The last group includes only modern humans, whose clavicles show only the inferior curvature, which is less pronounced than that which exists in monkeys. Curvatures in cranial view relate information regarding the parameters of arm elevation while those in dorsal view offer insights into the position of the scapula related to the thorax. The use of clavicular curvature analysis offers a new dimension in assessment of the functional morphology of the clavicle and its relationship to the shoulder complex. Anat Rec Part A, 288A: 944-953, 2006. 2006

Evolutionary transformation of the hominin shoulder

“…333x-6/9 is distinct from other hominoids in the orientation of its lateral end (on frontal view) and in the position of the deltoid attachment area, features which he interpreted as evidence of descent of the hominin shoulder by three to four million years ago. However, in his analysis of clavicular shape in primates, Voisin 16 reports that the uniquely low shoulder position in humans is indicated, on dorsal view, by a distinctive curvature of the medial rather than the lateral end of the human clavicle. Although A.L.…”

Morphological study of the anthropoid thoracic cage: scaling of thoracic width and an analysis of rib curvature

“…Understanding the evolutionary process of these features is pivotal for the study of living hominoid evolution. Numerous studies have examined hominoid skeletal morphology in the forelimb, shoulder girdle and vertebral column (Cartmill and Milton 1977;Larson 1988Larson , 1998Rose 1988Rose , 1989Takahashi 1990;Gebo 1993Gebo , 1996Ward 1993;Voisin 2006). However, comparatively fewer morphological studies have been undertaken on the living (Schultz 1956(Schultz , 1961Erikson 1963;Ohman 1986;Gebo 1996;Chan 1997;Preuschoft et al 2003) and fossil (Schultz 1960;Schmid 1983Schmid , 1991Jellema et al 1993;Moyà-Solà et al 2004;Sawyer and Maley 2005) hominoid thoracic region.…”

Mechanical Loadings on Pectoral Pacemaker Implants: Correlation of In-line and Transverse Force of the Pectoralis major

“…One essential, and unique, feature, compared to other laboratory animals, was the presence of a clavicle that enabled movements of the upper limb similar to humans. 24 Furthermore, the pectoral implantation site of the IPM in the baboons compared very well with those of humans. The material density of the Pectoralis major muscle of 1.115 ± 0.055 g/cm 3 of this study, determined on freshly excised tissue, compared well with previously reported values for mammalian muscle tissue of 1.112 ± 0.006 g/cm 3 , measured on muscle tissue after fixation in 4% formaldehyde.…”