Clavicle Flashcards
List 2 fn of clavicle.
- Supports shoulder so that the arm can swing clearly away from the trunk.
- Transmits wt. of the limb to sternum.
Clavicle is composed of how many parts? Name them.
3 parts. Curved part, shaft + 2 ends, lateral and medial.
List side determining characters of clavicle.
- Lateral end- flat
- Medial end- large & quadrilateral (quadrangular)
- Shaft- slightly curved such that it is convex forwards in medial 2/3rd and concave forwards in lateral 1/3rd
- Inferior surface- grooved longitudinally in its middle 1/3rd
List 7 pecularities of clavicle.
- Only long bone which has 2 1° centres of ossificatn
- First bone to start ossificatn
- Only long bone which undergoes membranous ossification
- Only long bone which lies horizontally
- No medullary cavity
- Subcutaneous throughout
- Occasionally pierced by middle supraclavicular nerve
Shaft is divisible into which regions
Lateral one third
Medial two thirds
List 3 key points on the lateral one third of shaft.
- Lateral one third is flat from above downwards
- It has 2 borders- anterior and posterior. Anterior border is concave forwards. Posterior is convex backwards.
- It has 2 surfaces- superior and inferior. Superior surface is subcutaneous. Inferior presents an elevation called conoid tubercle and a ridge called trapezoid ridge.
List 7 key points on the medial two thirds of shaft.
- Rounded and has 4 surfaces
- Anterior- convex forwards
- Posterior- smooth
- Superior- rough in its medial part
- Inferior- oval impression for costolavicular ligament, at the medial end
- Lateral- longitudinal subclavian groove
- Nutrient foramen lies at the lateral end of the groove
Write short notes on :
i) acromial end
ii) sternal end
i) acromial end is also called lateral end. It is flattened above downwards. It bears a facet that articulates w acromion process of scapula to form acromioclavicular joint.
ii) sternal end is also called medial end. It is large and quadrangular. It articulates w clavicular notch of manubrium sterni to form sternoclavicular jt. The articular surface extends to the inferior for articulation w first costal cartilage.
LAQ : attachments of the clavicle
- At the lateral end, the margin of the articular surface for the acromioclavicular joint gives attachment to the joint capsule.
- At the medial end, the margin of the articular surface for the sternum gives attachment to:
a) fibrous capsule of sternoclavicular joint all around
b) articular disc posterosuperiorly
c) interclavicular ligament superiorly - Lateral one third of shaft
a) anterior border gives origin to the deltoid muscle
b) posterior border gives insertn to trapezius muscle
c) conoid tubercle and trapezoid ridge give attachment to the conoid and trapezoid parts of the coracoclavicular ligament - Medial two thirds of the shaft
a) most of the anterior surface gives origin to pectoralis major
b) half of the rough superior surface gives origin to clavicular head of sternocleidomastoid
c) oval impression on the inferior surface gives attachment to costoclavicular ligament
d) the subclavian groove gives insertn to the subclavius muscle. Margins of the groove give attachment to the clavipectoral fascia.
e) posterior surface close to the medial end gives origin to sternohyoid muscle
f) subclavian vessels and division of trunks of brachial plexus pass towards axilla lying bw inferior surface of clavicle and upper surface of first rib. Subclavius muscle acts as a cushion.
Nutrient foramen transmits a branch of the suprascapular artery.
When and how does clavicle ossify?
Clavicle is the first bone to start ossification. It undergoes membranous ossification except its medial end. It ossifies at 2 primary centres and 1 secondary centre.
The 2 primary centres appear in the shaft bw 5th and 6th weeks of IUL, and fuse about the 45th day.
The secondary centre for the medial (sternal) end appears during 15-17y, and fuses with the shaft during 21-22y. Occasionally, there may be a secondary centre for the lateral (acromial) end.
CLINICAL ANATOMY Q1.
Which is the most common site of fracture of clavicle? How does this fracture happen?
The most common site of fracture is the jn. bw medial 2/3rd and lateral 1/3rd of the bone (jn bw the 2 curvatures of the bone) which is the weakest point. The lateral (acromial) fragment is displaced downwards by the wt of the limb as trapezius muscle (insertn from the posterior border in the lateral 1/3rd) alone is unable to support the wt. of the upper limb.
Fracture is commonly caused by falling on the outstretched hand (indirect violence).
CLINICAL ANATOMY Q2.
What is cleidocranial dysostosis/dysplasia?
The clavicles may be congenitally -nt/imperfectly developed in a disease called cleidocranial dysostosis. In this conditn, the shoulders droop and can be approximated anteriorly in front of the chest.
CCD affects mostly bones derived from intramembranous ossificatn, such as cranium and clavicles. It is characterized by delayed closure of cranial sutures.
How to hold clavicle anatomical position?
Hold the clavicle horizontally in such a way that the medial end is directed slightly forward and inferiorily as compared to the lateral end.
- Sternoclavicular joint is which type of joint?
- Acromioclavicular joint is which type of joint?
- Saddle variety of synovial joint
- Plane “ “ “ “
Describe the general features of medial 2/3 and lateral 1/3 of the clavicle, in terms of borders and surfaces.
The medial two thirds of the clavicle is cylindrical, therefore borders are ill defined, and it has four surfaces, namely superior, anterior, posterior, and inferior.
Lateral one third of the clavicle, is flat from above downwards, it has two borders, anterior and posterior and two surfaces, superior and inferior.
