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The clavicle, collarbone, or keybone is a slender, S-shaped long bone approximately 6 inches (15 cm) long [1] that serves as a strut between the shoulder blade and the sternum (breastbone). There are two clavicles, one on each side of the body. The clavicle is the only long bone in the body that lies horizontally. [2]
Cleidocranial dysostosis (CCD), also called cleidocranial dysplasia, is a birth defect that mostly affects the bones and teeth. [1] The collarbones are typically either poorly developed or absent, which allows the shoulders to be brought close together. [1]
The shoulder girdle or pectoral girdle is the set of bones in the appendicular skeleton which connects to the arm on each side. In humans, it consists of the clavicle and scapula; in those species with three bones in the shoulder, it consists of the clavicle, scapula, and coracoid.
White hyaline cartilage on the ends of the bones (called articular cartilage) allows the bones to glide and move on each other, and the joint space is surrounded by a synovial membrane. Around the joint space are muscles - the rotator cuff, which directly surrounds and attaches to the shoulder joint - and other muscles that help provide ...
It is composed of 270 bones at the time of birth, [2] but later decreases to 206: 80 bones in the axial skeleton and 126 bones in the appendicular skeleton. 172 of 206 bones are part of a pair and the remaining 34 are unpaired. [3] Many small accessory bones, such as sesamoid bones, are not included in this.
The joint is formed by the sternal end of the clavicle, the clavicular notch of the sternum, and (the superior surface of) the costal cartilage of the first rib. [1] The articular surface of the clavicle is larger than that of the sternum, and is invested with a layer of cartilage, which is considerably thicker than that of the sternum. [1]
The shoulder joint is made up of three bones: the shoulder blade (scapula), the collarbone (clavicle) and the upper arm bone (humerus). The acromion is a bony process at the end of the scapula The shoulder is a complex mechanism involving bones, ligaments , joints , muscles , and tendons .
However, in between 1% and 15% of cases, this osseous union fails and the acromion remains separate as an accessory bone. This condition is referred to as os acromiale , but rarely causes pain. Earlier estimates of its prevalence were as low as 1.4%, and this higher estimate was made by Sammarco in the year 2000, based on radiographic and ...