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The clavicle

(collar bone)

Dr M Idris Siddiqui

The clavicle

• The clavicle (collarbone) extends

between the manubrium of the sternum

and the acromion of the scapula.

• It is classed as a long bone , and can be

palpated along its length.

• In thin individuals, it is visible under the

skin.

• It has a slight S-shaped curve.

PECULIARITIES

The peculiar features of the clavicle are as follows:

1. It is the only long bone which lies horizontally.
2. It has absolutely no medullary cavity.
3. It is subcutaneous throughout its extent.
4. It is the 1st bone to start ossifying (somewhere between the fifth and sixth week of intrauterine life) and very last bone to finish its ossification (at 25 years).
5. It is the only long bone which ossifies by two primary centers.
6. It is the only long bone which ossifies in membrane other than its medial end.
7. It might be pierced inside out by cutaneous nerve (intermediate supraclavicular nerve).

Features and Attachments of

the clavicle

• LATERAL END/ACROMIAL END
• It is flattened above downwards. An oval facet on this end articulates using the facet on the medial margin of the acromion to form acromioclavicular joint. The lateral end provides connection to fibrous capsule of acromioclavicular joint.
• MEDIAL END/STERNAL END
• The enlarged medial end has a saddle-shaped articular surface, that articulates using the clavicular notch of manubrium sterni to develop sternoclavicular joint.
• It provides connection to:
  • Fibrous capsule
  • Articular disc
  • Interclavicular ligament.

Features and Attachments of

the clavicle

• Conoid tubercle – attachment point of the conoid ligament (the medial part of the coracoclavicular ligament).
• The conoid tubercle lies on the inferior surface close to the posterior border at the junction of the lateral one- fourth and medial three-fourth of the clavicle.
• Trapezoid line –
• The trapezoid ridge extends forwards and also laterally from conoid tubercle. It is attachment point of the trapezoid ligament( the lateral part of the coracoclavicular ligament). - The coracoclavicular ligament is a very strong structure, effectively suspending the weight of the upper limb from the clavicle.

SHAFT

• The shaft of the clavicle is split into two parts: lateral one-third and medial two-third.
• The medial two-third of shaft is convex forward but lateral one-third is concave forward.
• Lateral One-third It is flattened from above downwards. - It has two surfaces, i.e., superior and inferior, and two borders, i.e., anterior and posterior.
• The shaft of the clavicle acts a point of origin and attachment for several muscles – - Deltoid, trapezius, subclavius, pectoralis major, sternocleidomastoid and sternohyoid

SURFACES

• Anterior surface: It is convex forwards and provides origin to clavicular head of pectoralis major.
• Posterior surface: It is concave backwards and provides origin to sternohyoid muscle close to its medial end. The lateral component of this surface forms the anterior boundary of cervico-axillary canal and relates to the following structures: - Trunks of brachial plexus. - Third part of subclavian artery.

MUSCLES AND LIGAMENTS

CONNECTED TO THE CLAVICLE

Muscles Ligaments Pectoralis major Coracoclavicular Sternocleidomastoid (clavicular head) Costoclavicular Deltoid Interclavicular Trapezius - Subclavius -

Relations of the clavicle

OSSIFICATION

• SUBCLAVIUS OSSIFICATION

• The ossification of clavicle is membrano- cartilaginous. Whole of it ossifies in the membrane with the exception of its medial end which ossifies in the cartilage. The clavicle begins to ossify before some other bone in the body.
• It ossifies by four ossification centres- two primary centres for shaft and two secondary centres, one for each end.

Ossification centers of the Clavicle

Site of appearance Time of appearance Time of fusion Two primary centres (medial and lateral) in the shaft. 5 - 6 weeks of intrauterine life (IUL). 45th day of IUL. Secondary centre at sternal end 19 - 20 years (2 years earlier in female) 25th year Secondary centre at the acromial end (occasional) 20th year Fuses immed

The clavipectoral triangle (also known

as the deltopectoral triangle )

• It is bordered by the following structures:
• Clavicle
• Lateral border of Pectoralis Major muscle
• Medial border of Deltoid muscle
• It contains the cephalic vein, and deltopectoral fascia, which is a layer of deep fascia that invests the three structures that make up the border of the triangle, and also the cephalic vein in the triangle. The deltoid branch of the thoracoacromial artery also passes through this triangle, giving branches to both the deltoid and pectoralis major muscles.
• The subclavian vein and the subclavian artery may be accessed via this triangle, as they are deep to it.

The clavipectoral triangle (also known

as the deltopectoral triangle )