Sternoclavicular Joint Flashcards
What kind of joint is the sternoclavicular joint?
Saddle-type synovial joint
Where is the sternoclavicular joint?
Between the clavicle and manubrium of the sternum
How is the sternoclavicular joint unique?
It is the only attachment of the upper limb to the axial skeleton
Is the sternoclavicular joint a mobile joint?
Yes, very
How can the sternoclavicular joint function?
Like a ball-and-socket type joint
What does the sternoclavicular joint consist of?
The sternal end of the clavicle, the manubrium of the sternum, and part of the 1st costal cartilage
What are the articular surfaces of the SC joint covered with?
Fibrocartilage (as opposed to hyaline cartilage, present in the majority of synovial joints)
What is the SC joint separated into?
Two compartments
How is the SC joint separated into two compartments?
By a fibrocartilaginous articular disc
What does the joint capsule consist of?
A fibrous outer layer and an inner synovial membrane
Where does the fibrous layer of the joint capsule extend?
From the epiphysis of the sternal end of the clavicle, to the borders of the articular surfaces and the articular disc
What lines the inner surface of the joint capsule of the SC joint?
A synovial membrane
What does the synovial membrane of the joint capsule of the SC joint do?
Produces synovial fluid
What is the purpose of the synovial fluid in the joint capsule of the SC joint?
Reduces friction between articulating surfaces
What do the ligaments of the sternoclavicular joint provide?
Much of its stability
Where are the major ligaments of the sternoclavicular joint?
Sternoclavicular ligaments (anterior and posterior)
Interclavicular ligament
Costoclavicular ligament
What do the sternoclavicular ligaments do?
Strengthen the joint capsule anteriorly and posteriorly
What does the interclavicular ligament do?
Spans the gap between the sternal ends of each clavicle, and reinforces the joint capsule superiorly
What often separates the two parts of the costoclavicular ligament?
A bursa
Where do the two parts of the costoclavicular ligament bind?
At the 1st rib and cartilage inferiorly, and to the anterior and posterior borders of the clavicle superiorly
What does the costoclavicular ligament do?
Very strong ligament, main stabilising force for the joint, resting elevation of the pectoral girdle
What can the sternoclavicular and interclavicular ligaments be considered to be?
Thickenings of the joint capsule
What is the arterial supply to the SC joint from?
The internal thoracic artery and suprascapular artery
What is the SC joint supplied by?
The medial supraclavicular nerve (C3 and C4) and the nerve to the subclavius
What movements require SC joint involvement?
Elevation of shoulders- shrugging shoulders of abducting the arm over 90º
Depression of shoulders- dropping shoulders or extending the arm at the shoulder behind the boy
Protraction of the shoulders- Moving the shoulder girdle anteriorly
Retraction of the shoulders- Moving the shoulder girdle posteriorly
Rotation- when the arm is raised over the head by flexion, the clavicle rotates passively as the scapula rotates
How is the rotation of the scapula transmitted to the clavicle?
By the coracoclavicular ligaments
What do the costoclavicular ligaments act as?
A pivot for the movements of the clavicle
What is the sternoclavicular joint require for?
To accommodate the movements of the upper limb
What is the result of the SC joint being required to accommodate the movements of the upper limb?
It has a high degree of mobility
What does the SC joint require?
Much stability
Why does the SC joint require much stability?
Because it’s the only connection between the upper limb and the axial skeleton
What contributes to the SC joints mobility?
The type of joint
The articular disc
How does the type of joint contribute to the SC joints mobility?
Being a saddle joint, it can move in two axis
What does the articular disc of the SC joint allow?
The clavicle and the manubrium to slide over each other more freely, allowing for the rotation and movement in a third axis
What contributes to the stability of the SC joint?
Strong joint capsule
Strong ligament
Which ligament in particular contributes to the strength of the SC joint?
The costoclavicular ligament
How does the costoclavicular ligament contribute to the strength of the SC joint?
It transfers stress from the clavicle to the manubrium (via the costal cartilage)
How common is a dislocation of the sternoclavicular joint?
Quite rare
What does a dislocation of the SC joint require?
Considerable force
Why is a dislocation of the SC joint rare?
Because the costoclavicular ligament and the articular disc are highly effective at absorbing and transmitting forces away from the joint into the sternum
What are the major types of sternoclavicular joint dislocation?
Anterior dislocations
Posterior dislocations
Which is the more common type of sternoclavicular joint dislocation?
Anterior
How do anterior sternoclavicular joint dislocations occur?
Following a blow to the anterior shoulder which rotates the shoulder backwards
How do posterior dislocations of the SC joint occur?
Normally result from a force driving the shoulder forwards, of from direct impact to the joint
What is a sternoclavicular joint accompanied with in younger people?
A fracture through the epiphysial plate
Why is a SC joint dislocation accompanied with a epiphyseal plate fracture in younger people?
Because the epiphyseal growth plate of the sternal end of the clavicle has not fully closed
