Lecture #9 (Shoulder, Elbow & Hand) Flashcards
What is the only attachment of the arm to the axial skeleton?
SC joint
What type of joint is the SC joint? How many degrees of freedom does it have?
Saddle joint with 3 degrees of freedom
- elevation/depression
- protratction/retraction
- rotational
How much elevation and depression does the SC joint have? Protraction and retraction? Rotation?
Elevation= 45 degrees Depression= 10-15 degrees Protraction= 15-30 degrees Retraction= 30-60 degrees Rotation= posterior-30-45 degrees anterior-10 degrees or less
Why does the clavicle swing backward during abduction of the arm?
It swings backward because that allows the scapula and acromion to move out of the way for the humeral head during the motion
What is GH abduction limited to if the clavicle does not elevate and rotate?
120 degrees
What ribs does the scapula span? How far is it from the vertebrae column?
2nd-7th ribs
6cm lateral from the vertebral column
True or false:
The AC joint is a stable joint.
True…this is because of the ligamentous support (i.e. superior/inferior acromioclavicular ligaments and coracoclavicular ligament)
What are the motions of the AC joint?
Primary= rotation
Also winging and tilting/tipping
How is the scapula orientated in the plane of the scapula?
It’s orientated 30-45 degrees anteriorly from the frontal plane and tilted anteriorly 10 degrees
Describe the scapula-clavicle motion.
With humeral abductionn, the scapula rotates superiorly combined with 30 degrees of elevation of the clavicle. Then the clavicle rotates 38-50 degrees posteriorly which adds an extra 30 degrees of superior rotation of the scapula
Describe scauplohumeral rhymthn:
During abduction of the GH joint, the scapula and humerus move in a relationship to keep the glenoid fossa and the humeral head in the correct positions. After 20-30 degrees of abduction, the scapula begins to rotate superiorly. After this, the humerus and scapula move in a 2:1 ratio.
Of 180 degrees of humeral abduction, how much is accomplished by scapular movement?
60 degrees
What are force couples?
Parallel and opposite forces that aren’t perfectly in line to create rotation (torque) at a joint
How much bigger is the humeral head compared to the glenoid fossa?
2 times larger
How is the glenoid fossa orientated?
Superiorly and 30-45 degrees anteriorly