Clavicula

Original Editor

Top Contributors - Natalie Patterson, Feride Orman and Kim Jackson

Description

The clavicula (Clavicle) also known as the collar bone, is a sigmoid-shaped long bone[1] that makes up the front part of the shoulder. It sits between the shoulder blade and the sternum. There are 2 clavicles in a person, one on the right and the other one on the left side. It is the only long bone in the body that lies horizontally.

Articulations

Due to the clavicle’s structure, there are only two planar diarthrosis articulations that can be found. This type of articulation is also known as a ‘double plane joint’ – where two joint cavities are separated by a layer of articular cartilage.

The Acromioclavicular joint: The articulation between the clavicle and the Scapula[2]

The Sternoclavicular joint: The articulation between the clavicle and the Manubrium[2]

Acromioclavicular Joint

Acromioclavicular joint (Articulatio acromioclavicularis)

This is articulation between the acromial end of the clavicle and the acromion of the scapula. It enables slight gliding movement about the shoulder region. It is a synovial joint surrounded by a capsule of articular cartilage filled with intra-articular synovium.[3]

Sternoclavicular Joint|Sternoclavicular joint

Sernoclavicular joint (Articulatio sternoclavicularis)

This is the articulation between the sternal end of the clavicle and the manubrium of the sternum. This synovial joint is important as it attaches the clavicle and scapula to the axial skeleton. The joint enables a variety of limited movements of the arm, including:

  • Protraction and retraction
  • Elevation and depression
  • Axial rotation

Muscle attachments

A total of five muscles are attached to the clavicle, found distributed at either the lateral third or medial two thirds of the bone.

Two muscles are attached to the lateral third of the clavicle:

  • The trapezius muscle, which is attached along the posterior surface of the lateral third of the clavicle.
  • The deltoid muscle, where the anterior portion of the muscle is attached to the periosteum at the anterior surface of the bone.

Three muscles are attached to the medial third of the clavicle:

  • The sternocleidomastoid muscle, clavicular head of the muscle attaches to the medial third of the clavicle.
  • The pectoralis major muscle, which is attached to the anterior surface of the bone.
  • The subclavius muscle, which is attached to a groove found in the middle of the bone’s inferior surface. From there, the muscle extends into both lateral and medial areas of the clavicle.[3] It's action is to draw the clavicle downwards and forward[2]

Clinical relevance

The Clavicle plays an essential role in functional movement, serving as the connection between the axial skeleton and the pectoral girdle. This allows the clavicle to act as a brace for the shoulder, allowing weight to be transferred from the upper limbs to the axial skeleton.[3]

Injuries and Treatment

Fractured or broken collar bone, most commonly caused by a fall or blow to the shoulder. It is usually managed with conservative management of wearing a sling and rest. If the fracture results in the bone piercing the skin surgery will be considered to fit a plate with screws.[4]

References

  1. Hyland, S and Varacallo, M. Anatomy, Shoulder and Upper Limb, Clavicle. Available from https://www.researchgate.net/publication/329717390_Anatomy_Shoulder_and_Upper_Limb_Clavicle Accessed 20 July 2020
  2. 2.0 2.1 2.2 The Essential Anatomy 5 App [Mobile application software]. (Version 5.0.8). 3D4Medical (2019). Accessed 20 July 2020
  3. 3.0 3.1 3.2 Kenhub. Clavicle. Available from: https://www.kenhub.com/en/library/anatomy/the-clavicle (Accessed 26 July 2020)
  4. NHS. Broken collarbone. Available from: https://www.nhs.uk/conditions/broken-collarbone/ (accessed 20 July 2020)