The collarbone (in Latin the clavicula , also Germanized clavicle , old Greek κλείς , genitive κλειδός [Kleidos]) is one of the three original bones of the shoulder girdle in reptiles , birds and mammals . In bony fish , the collarbone is already indicated as ossification of the skin; in amphibians it is missing.
The word collarbone is borrowed from the Latin clavicula , the " little key " as a diminutive of the Latin clavis . According to the etymological dictionary of the German language , the “Kluge”, this reproduces the Greek kleís (“key”, “clavicle”). In ancient Greece, keys were often hook-shaped with which a bolt could be operated.
Some terms are derived from the Greek kleís , the name of the sternocleidomastoid muscle , which connects the sternum and collarbone to the base of the skull , and the gownocranial dysplasia , a malformation of the collarbone and skull.
Other sources interpret the Latin word clavicula as a tendril , which is more reminiscent of the twisted shape of the bone than of a key . Then the Greek term kleís would come from an incorrect transmission. This occurs in anatomy in a similar form in the sphenoid bone .
The resemblance of a wishbone to this “wishbone” leads to the designation double wishbone suspension for the double wishbone axle.
The collarbone, which is about hand-long in humans, has receded (rudimentary) in some mammals. It is well developed in humans , the other primates , generally in climbing animals, but also in rodents and rabbits . In its connection to the sternum ( sternoclavicular joint ) and the shoulder blade, it is the only articulated connection between the upper extremity and the trunk .
A "pit" located above the collarbone can contain a volume simply by keeping the trunk upright and is therefore called a salt barrel .
In domestic cats , it is reduced to a bone embedded in a muscle (cleidocephalicus muscle) and is no longer articulated with the shoulder blade. In many other mammals (e.g. horses , cloven-hoofed animals , dogs ) it has regressed into a tendon strip embedded in this muscle.
In birds , both collarbones are fused to form a V-shaped bone, the fork bone (furcula) , which acts as a tension spring and holds the two shoulder joints apart when flying. In tribal history , the wishbone appears for the first time in theropod dinosaurs . In the English-speaking cultural area, this bone is also known colloquially as the "wishbone". This name comes from the tradition of pinching the dried turkey furcula between the two little fingers of two people sitting opposite and pulling it on the Thanksgiving festival. The one whose bone piece after breaking is the larger, has a desire (wish) free.
In addition to the collarbone, the raven bone (coracoid) and the shoulder blade (scapula) belong to the shoulder girdle . In mammals, including humans, the raven bone is not an independent bone, but an extension of the shoulder blade, which is referred to as the raven beak (coracoid process) .
Human collarbone anatomy
In humans, the collarbone occurs in pairs. A single human collarbone is approximately 12-15 cm long and S-shaped. It has two ends and a middle piece (corpus claviculae) . The (medial) end directed towards the middle of the body is called extremitas sternalis ( pointing towards the sternum) and has a round joint surface, facies articularis sternalis , which is part of the joint between the sternum and clavicle, called articulatio sternoclavicularis . The lateral end, which is referred to as the extremitas acromialis (pointing towards the shoulder level), forms a joint with the shoulder level (acromion) , the shoulder joint (articulatio acromioclavicularis) , which is part of the shoulder blade. The corresponding joint surface, which is flattened like a saddle, is called the facies articularis acromialis .
The deltoid muscle (Musculus deltoideus) attaches to the top of the collarbone . The bone surface is roughened by its strong pull. Medial on the underside there is a depression, impressio ligamenti costoclaviculare , which is caused by pulling a ligament , the ligamentum costoclaviculare .
At the bottom of the middle piece there is a groove laterally, subclavii sulcus musculi through which the subclavian muscle (musculus subclavius) draws. Also on the underside of the center piece is a constantly formed hole, foramen nutricium , through which a blood vessel for supplying the bone with oxygen and nutrients passes. On the underside of the extremitas acromialis there is a roughness, tuberositas ligamenti coracoclavicularis , which can be further divided into a tuberculum conoideum and a linea trapezoidea . The coracoclavicular ligament , which consists of two parts, the conoid ligament and the trapezoid ligament , inserts into these structures . The two clavicles are connected by the interclavicular ligament .
In humans, falls on the shoulder , directly on the collarbone or, rarely, on the outstretched arm, can lead to fractures of the collarbone ( clavicle fracture ) . With around 15% of all bone fractures, the clavicle breaks the second most frequently. Symptoms include a visible and palpable step formation, an apparent extension of the arm and changes in the position of the head.
In the context of congenital diseases there is hypoplasia (underdevelopment) or absence ( aplasia ) of the clavicles, e.g. B. in dressocranial dysplasia , the parietal foramina with dressocranial dysostosis or mandibuloacral dysplasia .
The collarbone can be removed partially (partially) or completely (totally). The partial claviculectomy is sometimes performed at the ends in the area of the shoulder joint or the sternoclavicular joint , mainly in the case of chronic instability or osteoarthritis . Usually only the small section near the joint is removed, while the collarbone is otherwise retained.
In a full claviculectomy, all of the bone is removed, causing instability and moderate loss of function in the shoulder and affected arm. The main causes are malignant bone tumors , mostly osteosarcomas , Ewing sarcomas and primitive neuroectodermal tumors and myelomas , although the collarbone is very rarely affected. Metastases are practically non-existent. Other very rare causes of complete removal are chronic bone infections and complex bone fractures. Removal is difficult and complications are common, as well as local infections and especially injuries to deeper structures, especially the subclavian vein . A reconstruction of the collarbone is rarely undertaken, as this is time-consuming and associated with even higher complication rates, and the removal of the collarbone only causes moderate restrictions in daily life.
In addition, the collarbone can also be removed as a bone substitute and used to reconstruct the humerus , as a clavicula pro humero . After resection of a malignant bone tumor , which has a predilection for the (proximal) humerus near the shoulder, the collarbone on the same side is removed and swiveled into the shoulder socket and after shortening to the correct length with a plate osteosynthesis with the remaining portion of the (distal) near the elbow Upper arm bone connected.
- Elmar Seebold : Kluge: Etymological dictionary of the German language. Walter de Gruyter, Berlin 1995, 23rd edition, page 729.
- Etymology of Abdominal Visceral Terms
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