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 lessWhy 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
What can a spasm of the levator cause?
“Drop scap”…the tightness of the levator rotates the scaupla superiorly which in turn lowers the glenoid. This lowering of the glenoid not only causes instability of the GH joint, but can also limit a person’s ability for abduction
When the upper extremity is relaxed, the joint capsule is taunt where and slack where?
Taunt= superiorly Slack= anteriorly and inferiorly
What is the rotator interval?
A weakened spot of the joint capsule (located above the subscapularis and in front of the supraspinatus)
What helps to add dynamic stability to the GH joint?
Rotator cuff
What role does the biceps have in the stability of the GH joint?
The long head tendon helps to depress the humeral head and stabilize it in the joint capsule–this is important to counteract the pull of the deltoid during abduction
What is the MOI for dislocation of the GH joint?
Abduction and external rotation
What are the three ligaments of the GH joint?
Superior and coracohumeral=post-ant instability at 0 degrees
Middle= helps stabilize joint at 45 degrees abduction
Inferior= aids in proper abduction
What provides superior reinforcement to the GH joint? Inferior? Anterior? Posterior?
Superior= supraspinatus & long head of biceps Inferior= long head of triceps Anterior= subscapularis, pec major, & teres major Posterior= infraspinatus & teres minor
Describe what maintains the static stability of the GH joint.
The humeral head naturally rests on the inferior rim of the glenoid as it is pulled inferiorly by gravity and the superior structures (i.e. capsule, coracohumeral ligament, supraspinatus, deltoid, and biceps) of joint (creating a static locking). The labrum help stabilize inferiorly. Then the inter-articular pressure also creates a vacuum to help hold the joint in place.
