The Clavicle of Newborn Dogs

Abstract

The morphology, topography and structure of the clavicle and its adnexa,forming together the clavicular complex, were investigated in 21 newborndogs of both sexes and various breeds by dissection, radiography andhistological techniques.The reduced clavicle, 1 to 2 mm in size, was oval in most cases.Horseshoe-shaped and annular clavicles were less frequent.The clavicle was located outside the clavicular intersection beinglinked with it by a fascicle of collagenous fibres. A similar fasciclelinked the clavicle with the caudal margin of the scapula. No links ofthe clavicle with the sternum or the perimysium of the pectoral muscleswere observed in the early postnatal period.The histological pattern was typical of desmogenic ossification. Osteoidand osseous trabeculae formed an incoherent cortical surface lamella andthe formation of a cavity was evident in the centre of the clavicle. Theosseous trabeculae aimed radially forming an anastomosing network. Thesurface of the clavicle was covered by a coherent layer of connectivetissue with arranged fascicles of collagenous fibres which, on both endsof the clavicle, passed continuously into fibrous fascicles connectingthe clavicle with the surrounding structures and forming together afunctional unit.An oval basis of an embryonic cartilage, which we considered to be thepreclavium, was observed at the sternal end of the clavicle in more thanone half of the dogs. The function of the markedly reduced canineclavicle in the early postnatal period, in which the formation of theassociated structures is not yet influenced by locomotion, is discussed.We assume that some of the links joining the clavicle with the adjacentstructures develop only after birth in dependence on the locomotion.