Clavicle

“ When we view the relative position of the subclavian vessels, A B, Plate 11, to the clavicle, R, we can readily understand why a fracture of the middle of this bone through that arch which it forms over the vessels, should interfere with the free circulation of the blood which these vessels supply to the arm. When the clavicle is severed at its middle, the natural arch which the bone forms over the vessels and nerves is lost, and the free moving broken ends of the bone will be acted on in opposing directions by the various muscles attached to its sternal and scapular extremities. ”

“ The depth at which the middle of the subclavian artery lies may be learned by the space which those structures, beneath which it passes, necessarily occupy. The clavicle at its sternal end is round and thick, where it gives attachment to the sterno-cleido-mastoid muscle. The root of the internal jugular vein, when injected, will be seen to occupy considerable space behind the clavicle; and the anterior scalenus muscle is substantial and fleshy. The united spaces occupied by these structures give the depth of the subclavian artery in the middle part of its course. ”

“ The great pectoral muscle in man arises in part from the clavicle; this origin not being possible in animals which have no clavicle, its attachments, as we have already seen, are concentrated on the sternum. The trapezius in man similarly arises in part from the clavicle; for the reasons above indicated its clavicular fasciculi cannot exist in distinct form in the animals which have no clavicle.
The sterno-cleido mastoid, whose inferior attachments we mentioned above, cannot have a clavicular portion. ”

“ Case II. A man luxated the clavicle by falling on the point of his shoulder, and forcing it backward. He was immediately brought to the Hotel-Dieu, where Desault demonstrated to his pupils, that the head of the bone, carried in front of the sternum, was removed nearly an inch from its natural cavity, the ligaments of which were no doubt lacerated.
Here, as in the fracture of the clavicle, the application of the bandage answered the purpose of reduction, and removed the protuberance formed by the extremity of the bone. ”

“ The clavicle or collar bone (h) is strong, and curved nearly as in the human subject; the presence of this bone in the Megatherium, whilst it is wanting in the Elephant, Rhinoceros, and all the large ruminating animals, shows that the fore leg discharged some other office, than that of an organ of locomotion. This clavicle would give a steady and fixed position to the socket, or glenoid cavity of the scapula, admitting of rotatory motion in the fore leg, analogous to that of the human arm. There is in these circumstances a triple accommodation to the form and habits of the Megatherium ”

“ The clavicle is stated by Rathke to be at first continuous with the coraco-scapular plate. It is however soon separated, and ossifies very early, in the human embryo before any other bone. Gegenbaur however shewed that the human clavicle is provided with a central axis of cartilage, and this observation has been confirmed by Kölliker, and extended to other Mammalia by Götte. The mode of ossification is nevertheless in many respects intermediate between that of a true cartilage bone and a membrane bone. ”

“ The acromio-clavicular articulation is also a gliding joint, but allows a swinging or pendulum movement of the scapula on the clavicle. The upper part of the capsule is strongest, and from it hangs down a partial meniscus into the cavity.
Comparative Anatomy.—Bland Sutton regards the interclavicular ligament as a vestige of the interclavicle of Reptiles and Monotremes. The menisci are only found in the Primates, but it must be borne in mind that many Mammals have no clavicle, or a very rudimentary one. ”

“ If an aneurism attack any part of this subclavian arch, it must be in close connexion with some one of these branches. If a ligature is to be applied to any part of the arch, it will seldom happen that it can be placed farther than half an inch from some of these principal collateral branches.
When the shoulder is depressed, the clavicle follows it, and the subclavian artery will be more exposed and more easily reached than if the shoulder be elevated, as this latter movement raises the clavicle over the locality of the vessel. ”

“ While we know that the locality of the main vessels and nerves is that very situation upon which a pad or fulcrum presses, when placed in the axilla for securing the reduction of fractures of the clavicle, the neck of the humerus, or scapula, so should this member of the fracture apparatus be adapted, as well to obviate this pressure upon these structures, as to give the needful support to the limb in reference to the clavicle, &c. ”

“ Origin from the apex and caudal margin of the mastoid process of the temporal bone, by tendon and muscle fibres. The muscle passes caudad, becoming broader and thinner.
Insertion into the lateral four-fifths of the clavicle within the insertion of the clavotrapezius, and into the raphe which continues laterad of the clavicle.
Relations.—Outer or lateral surface at the caudal end with the clavotrapezius (Fig. 65, j) ; further craniad with the depressor conchæ (Fig. 64, b) , the platysma, and the sternomastoid (Fig. 65, g) . ”

“ Being slender and superficial the clavicle is most frequently broken of any bone in the body, generally by indirect violence, as by falling with the hand out, though old people in such a case are apt to get Colles’ fracture at the wrist. The bone generally gives way at the juncture of the outer and middle thirds, with displacement of the parts inward, so that the fracture is seldom compound. Since, however, the main vessels of the upper arm, with their nerves, lie beneath the clavicle, there is danger of their being punctured. ”

“ Luxations of the humeral extremity of the clavicle, take place, according to Petit, in two ways, 1st, under, and 2dly, over the acromion. If we attend to the disposition of the articulating surfaces, the superior of which rests obliquely on the inferior; if we examine, in particular, the relative position of the corocoid apophysis with respect to the clavicle, it will be difficult to conceive how the first kind of luxation can occur, without being accompanied by a fracture. ”

“ Behind the base of the clavicle, the sword-shaped post-clavicle (56) extends downward through the muscles behind the base of the pectoral fin. In some fishes, as the stickleback and the trumpet-fish, a pair of flattish or elongate bones called interclavicles (infraclavicles) lie between and behind the lower part of the clavicle. These are not found in most fishes and are wanting in the striped bass. ”

“ Insertion into the clavicle and into a raphe between the clavotrapezius and the clavobrachial (e) muscles. This raphe extends along the clavicle and for some distance laterad of it. The muscle is partly continuous with the clavobrachial (e) .
Relations.—Outer surface with the platysma, and at its craniomedial angle with the levator auris longus. Inner surface with the rhomboideus, splenius, occipitoscapularis, levator scapulæ, cleidomastoid, and supraspinatus. The cranial edge touches the sternomastoid. The caudal border touches the acromiotrapezius near the origin. ”

“ The clavicular artery (Fig. 73, No. 8) accompanies the clavicle to the shoulder-joint.
The acromial artery is given off from the sterno-clavicularis on the ligament near the shoulder-joint.
2. The thoracic artery branches from the subclavian artery (Fig. 70, No. 4) . ”

“ Since, therefore, a clavicle in any degree of development is not essential to a climbing quadruped, we must seek for some other relation and use of that remarkably strong, and perfect bone, as it exists in the Megathere, Megalonyx, and Scelidothere. The absence of ‘dentes primores’ or of anterior or incisive teeth in these quadrupeds at once sets aside any idea of its connection with an action of the fore extremities, very common in the mammals which possess clavicles, viz., that of carrying the food to the mouth, and holding it there to be gnawed by the teeth. ”

“ But if, which rarely happens, the outer part be uppermost, we must not have recourse to this arrangement of the arm. The patient must lie in a supine position, and live upon a spare diet, and if necessary, embrocations and other suitable applications are to be made until the callus is formed. The callus of the clavicle is formed in about twenty days at most. ”

“ In woman it is generally less curved, smoother, and more slender than in man, and as bone is rough when the muscles attached are powerful, the right clavicle, being used more, is generally rougher and thicker than the left. Among the muscles attached are the large neck muscle, the sterno-cleido-mastoid, whose tendons form the presternal notch, the trapezius, the pectoralis major, and the deltoid. ”

“ From Arthur Thomson, Cunningham's Text-Book of 'Anatomy.
Fig. 18. — Ossification of the Clavicle.
known ; its primary centre is the earliest of all in the body to appear, while its sternal epiphysis does not come till the bone is fully grown, and so can have no effect on the growth of the bone. It is probably one of the atavistic class, and is often regarded as the vestige of the precoracoid (see subsection on comparative anatomy) , though it may represent the inter-clavicle, which, as has been pointed out in the article on the axial skeleton, is quite distinct from the episternum. ”

“ Ossification of the Tibia.
clavicle are also largely developed; the scapula too is more bird- like in shape than mammalian. In the higher mammals the scapula develops a spine and usually an acromial process, and has a triangular outline.^ As long as the forelimb is used for support, the vertebral border is the shortest of the three, and the long axis of the bone runs from this border to the glenoid cavity ”

“ Owing to the fore legs frequently presenting a structure different from the rest, adapting them for becoming instruments of prehension, Mr. Kirby thought they made so near an approach to arms, that he applied to them that name. The five portions described above, would, in this view, be regarded as analogous to the clavicle, scapula, humerus, cubitus, and hand. ”

“ The second kind of displacement, that which we constantly find in practice, and which the laws of muscular action render almost inevitable, takes place in such a manner that the shoulder appears to obey the impulse of two powers, one of which draws it downwards, and along with it the external fragment of the clavicle, which is displaced by this power in the direction of its transverse diameter, or thickness. ”

“ The tympanics are annular, and in a rudimentary condition. The centra {524}of the vertebrae tend to become ankylosed in old individuals; the caudals have no processes, but are like those quite at the end of the series in long-tailed animals. The sternum is keeled for the better attachment of the pectoral muscles, the chief muscles of flight. The ribs, which are much flattened, are occasionally ankylosed together by their margins. There is a well-developed clavicle. In the carpus the scaphoid, lunar, and cuneiform are all fused together. In the hind-limb the fibula is rarely fully developed. ”

“ Right Subclavian.—The innominate artery divides into the right subclavian and right carotid exactly behind the sterno-clavicular articulation. The right subclavian extends from this point in an arched form across the neck, between the scalene muscles, over the apex of the pleura, till, passing under cover of the clavicle, it changes its name to axillary at the lower end of the first rib. For convenience of description, the artery is divided into three parts, which have very various anatomical relations, and differ from each other much in their amenability to surgical treatment by ligature. ”

“ The scapula articulates with the coracoid. A pneumatic foramen is located at the base of the acromion process. The anterior part of the scapula is provided with an articular head and is provided with an inner process, called the processus furcularis, which lies near the furcula and coracoid. An outer stronger processus humeralis forms the 44posterior half of the glenoid cavity, or cavitas glenoidalis, in which the humerus articulates and the processus coracoideus.
The Clavicle. Location.—The clavicles, commonly known as the wish bone, are located in the anterior chest region. ”