Clavicle

Clavicle


Introduction 

• Also called as collar bone.
• Located at the junction of the root of the neck and trunk.
• It is the only bone that lies horizontally on the anterior aspect of the body.
• It is only bony attachment between the trunk and the upper limb.

 

Function 

• It acts as a strut for holding the upper limb far from the trunk so that it can move freely.

• It helps in the transmission of force from the upper limb to the axial skeleton.

 

Peculiarities 

It is only the long bone that lies horizontally.
It has no medullary cavity.
It is subcutaneous throughout its extent.
It is the first bone to ossifying at the age of 5th – 6th week of intrauterine life and last bone to complete ossification at the age of 25 years.
It is the only long bone that has two primary ossification centers. That's why called as modified long bone
It has two types of ossification,
ie. the whole part except medial end is intra-membranous ossification and its medial end is intra-cartilaginous ossification.

 

Parts of Clavicle:

• Medial end
• Lateral end 
• Shaft 

 

Medial end 
• It is enlarged and quadrilateral.

• It articulates with the clavicular notch of manubrium sterni
& form a sternoclavicular joint, which is a saddle type of synovial joint.


Lateral end
Almost Flattened end

• Articulate with medial margin of the acromion process
and form acromioclavicular joint (Plane type of Synovial Joint)


Shaft 

It has two parts 

  1. Lateral one third 
  2. Medial two-third


Lateral 1/3 part of shaft
It is concave forward.

• It has two surface

  1. Superior surface 
  2. Inferior surface 

• It has two border

  1. Anterior border 
  2. posterior border
• Superior surface 
Gives attachment to the deltoid and trapezius.
• Inferior surface 
Conoid tubercle and trapezoid ridge present in this surface which gives attachment to the conoid and trapezoid part of coracoclavicular ligament.
• Anterior border 
Gives origin to the deltoid muscle.
• Posterior border
Provides insertion  to the trapezius muscle

 

Medial 2/3rd part of shaft
It is convex forward.

It has 4 surfaces 

  1. Anterior surface 
  2. Posterior surface 
  3. Superior surface 
  4. Inferior surface
• Anterior surface 
- Gives origin to the clavicular head of pectoralis major.
• Posterior surface 
- Gives origin to the sternohyoid muscle
- Related to the trunk of the brachial plexus and third part of the subclavian artery.
• Superior surface 
- Gives origin to the clavicular head of the sternocleidomastoid muscle.
• Inferior surface 
- Subclavian muscle is inserted into the subclavian groove on this surface.
- Clavipectoral fascia is attached to the margins of the subclavian groove.
- Gives attachment to the costoclavicular ligament.