Flashcards in Shoulder Deck (51)
What is normal retroversion angle of the humerus?
retroversion = angle of torsion, or degrees head is rotated back
- normal angle = 30 degrees
What athletes tend to have larger angles of torsion?
baseball players and volleyball players, giving them greater external rotation
Describe how the scapula and clavicle lie on the frontal plane.
- scapula lies 35 degrees anterior to frontal plane (angles forward)
- clavicle lies 20 degrees posterior to frontal plane (angles backward)
Your patient is having difficulty elevating their arm, and you believe it to be an SC joint issue. What exactly could be happening at the SC to prevent humeral elevation?
clavicle may not be sliding down while it's rolling up, preventing the motion of arm elevation
T/F: With arm elevation, the clavicle protracts.
What arthrokinematic motions occur at the SC joint?
roll/slide (in opposite directions for elevation/depression)
roll/slide (in same directions for protraction/retraction)
spin (when post. rotation of clavicle occurs)
T/F: SC joint isn't too important in ensuring full elevation.
false, need full motion of SC to get full elevation
Why are SC injuries so rare? When do they happen?
- due to strong ligaments protecting and good articulation
- could happen in traumatic injury: football, car accident, etc
What three ligaments keep the SC secure? What do they prevent?
- posterior portion: resists protraction
- anterior portion: resists elevation
2) interclavicular ligament: resists downward rotation
3) costoclavicular ligament: resists elevation and protraction
At what point does the clavicle posteriorly rotate?
after the costoclavicular ligament becomes taut, the clavicle rotates downward to keep elevating the arm
What's the most important ligament in arm elevation?
What arthrokinematics occur during retraction for the SC?
transverse diameter, so concave on convex, so:
- posterior roll and slide
T/F: AC is convex acromion on concave clavicle.
- false, convex clavicle moves on concave acromion
T/F: Rolls and slides are in opposite directions for the AC.
Why might we be running into the acromion during elevation? (because of what specific accessory movement not happening)
- the scapula isn't posteriorly tilting enough to bring the acromion back and out of the way
- this could be due to excessive anterior tilt; tight pec minor
How does the scapula sit at rest?
1) 35 degrees anterior to frontal plane (angled forward)
2) anteriorly tilted 10 degrees
3) slightly internally rotated
Anterior and posterior tilt of the scapula occur in what plane?
sagittal plane, about the frontal axis
Describe the scapulohumeral rhythm.
- scapula and humerus work together to allow extension at a 1:2 ratio, respectively
- first 30 degrees is from humerus, then scapula upwardly rotates 1 degree for every 2 from the humerus
• this ends with 60 degrees of rotation from scapula, and 120 degrees from the humerus
What motions occur at the AC during elevation? (think about what the clavicle is doing)
posterior roll, anterior slide (b/c clavicle retracts)
Upward and downward rotation of the scapula occur in what plane?
frontal plane along sagittal axis
What are 2 ligaments that become taught during elevation?
costoclavicular and coracoclavicular
What muscles elevate and depress the scapula?
1) elevate: levator scapulae, upper trap
2) depress: subclavius, lats, pec minor, lower trap
What muscles upwardly rotate and downwardly rotate the scapula?
- upward rotation: serratus anterior, upper and lower trap
- downward rotation: rhomboids, levator scapulae
What muscles protract and retract the scapula?
1) protract = serratus anterior, pec minor
2) retract = rhomboids, middle trap
With a weaker lower trap, what muscle is now utilized in elevation? How is this motion achieved, then?
upper trap used for elevation now
- since you've lost some upward rotation by losing some lower trap, you must rely on upper trap more, which means relying on elevation of scapula to get to full elevation vs upward rotation
What needs to happen at T-spine for full humoral elevation?
What muscle opposes the serratus anterior during upward rotation of the scapula?
middle trap: serratus anterior pulls and abducts scapula for upward rotation, and middle trap pulls in and adducts, making sure not too much abduction occurs
Why is it more common to have anterior dislocation of the humerus?
b/c the labrumis thinner anteriorly and posteriorly, and the humerus already sits in a slightly anterior position
What 4 static stabilizers are there for the GH joint?
1) bony geometry