Lecture 13: The Upper Extremity Flashcards
Joints of the arm
5 joints
- shoulder : humerus + scapula
- shoulder “girdle” : scapula + ribcage
- elbow
- radio-ulnar jt.
- wrist
Shoulder
Glenohumeral jt.
Articulation btwn humeral head and glenoid fossa of scapula
Responsible for 50% of total range of motion of arm with respect to torso
Glenoid
Glenois fossa is a shalow depression in lateral scapula
Ringed by rotator cuff made up if tendons that mobilize + stabilize the jt
- Go from lateral –> medial side
Humeral head
hemisphere that fits into glenoid fossa like a golf ball on a tee
NOT much bony stability, so rotator cuff stops dislocation
Rotator cuff
Jt. capsule of GH jt + tendons of suprapsinatus, subscapularis, infraspinatus and teres minor
All pull MEDIALLY (stab. component)
All muscles except supraspinatus are adductors (down rotational vector) and supraspinatus is an abductor (up)
Lots of soft tissue = susceptible to tears + injury
Stabilization of the schoulder
4 muscles of the rotator cuff have significant stabilizing components that stabilize the humeral head into the glenoid fossa
Mobilization of the shoulder
Multiple muscles move the humerus with respect to the scapula
Anterior and posterior muscles cooperate to create internal-external rotation
Deltoid and supraspinatus play a big role
Deltoid and supraspinatus
Mobilization of shoulder
Deltoid is big b/c it is at a mechanical disadvantage w/ a small rotary component, so it has to produce a LOT of force
Supraspinatus has a larger rotary component
- does most of work in shoulder to pull towards abduction
Superficial vs deep muscles
Superficial muscles are big, good looking and dumb = don’t do much
Deep muscles do most of the work
Shoulder impingement syndrome
Not a lot of space btwn humeral head and acromion for supraspinatus tendon to pass through
Impingement can occur = tissues try to expand due to inflammation = pressure
Shoulder girdle
Clavicle + scapula
Accounts for 50% of total ROM of arm
2 jts:
- sternoclavicular jt
- scapulothoracic “joint”
Elevation of shoulder gridle
Translation/linear
Axis of translation is longitudinal axis/internal-external rotation axis
Depression of shoulder girdle
Translation/linear
Axis of translation is longitudinal axis/internal-external rotation axis
Serratus anterior has a DISLOCATING component going LATERALLY
Upward rotation of shoulder girdle
Motion in the FRONTAL plane
Lower trapezius go down to fix centre of rotation for the scapuls
Downward rotation of shoulder girdle
Motion in FRONTAL plane
Levator scapulae goes up to set centre of rotation
