Scapular region & arm Flashcards
Bony features of scapula
acromion process spine of scapula supra scapular notch supraspinous fossa infraspinous fossa
Bony features of anterior humerus
head of humerus anatomical neck (distal to head) greater tubercle (lat) lesser tubercle (med) intertubercular sulcus/bicipital groove surgical neck (*fracture site) deltoid tuberosity
Bony features of posterior humerus
anatomical neck greater tubercle surgical neck deltoid tuberosity radial (spiral) groove
scapular movements
elevation/depression
protraction/retraction
upward/downward rotation
scapulohumeral rythm
during 180 abduction, motion at scapulothoracic and glenohumeral joints
(1:2 ratio scapulothoracic/glenohumeral, 60 degrees at scapulothoracic, 120 at glenohumeral)
glenohumeral joint
most mobile joint in body (lgr surface area of humeral head than glenoid fossa), but less stability (non-weight bearing)
ball and socket joint
motions: flexion, extension, internal rotation, external rotation, adduction, abduction, circumduction
glenoid labrum
fibrocartilaginous ring surrounding glenoid fossa
biceps tendon attached to superior edge
glenohumeral joint capsule
- fibrous capsule (medial attach: to glenoid cavity, lateral attach: to anatomical neck of humerus)
- synovial membrane
reinforced on anterior/superior/posterior surfaces
What prevents anterior displacement of humeral head from glenoid cavity?
STATIC structures
- superior glenohumeral ligament (SGL)
- middle glenohumeral ligament (MGL)
- inferior glenohumeral ligament (IGL)
What prevents superior displacement of humeral head from glenoid cavity?
STATIC structures
- coracoacromial ligament (CAL)*
- coracohumeral ligament (CHL)
*pt of coraco-acromial arch
What can lead to glenohumeral dislocation?
GH is not reinforced inferiorly, so if arm is in ABduction + lateral rotation (joint capsule stretched) and ANTERIOR force is added –> xs extension –> head of humerus comes out inferiorly
What stabilizes the glenohumeral joint?
Rotator cuff muscles (dynamic structures)
- supraspinatus
- infraspinatus
- teres minor
- subscapularis
SItS
Provide compressive forces medially and inferiorly across GH joint
Of the rotator cuff muscles, which is the only one that inserts onto the lesser tubercle of humerus rather than greater tubercle?
Subscapularis
subacromial (subdeltoid) bursa
between the acromion process, coracoacoromial ligament, deltoid muscle, and supraspinatus tendon
bursae of shoulder
subacromial bursa
subdeltoid bursa
subscapular bursa
synovial sheath
3 causes of rotator cuff - subacromial impingement
- weak rotator cuff
- type of acromion
- AC joint OA
–> repeated abduction and flexion of arm –> humeral head and rotator cuff tendons (*supraspinatus) impinge on coracoacromial arch
Weak rotator cuff muscles can lead to
superior displacement of humeral head
Which muscle overrides rotator cuff muscle actions?
Deltoid (elevates humerus)
Which “type” of acromion process can lead to subacromial impingement?
a “hooked” acromion –> dips into where supraspinatus will be traveling and will start to fray the supraspinatous tendon as it runs underneath
What is the body’s reaction to stabilize the joint after loss of cartilage?
ostephyte formation
posterior axioappendicular (extrinsic shoulder muscles)
trapezius
latissimus dorsi
^superficial
levator scapulae
rhomboid major
rhomboid minor
^deep
scapulohumeral (intrinsic shoulder muscles)
deltoid teres major teres minor supraspinatous infraspinatus subscapularis
Which muscle initiates ABduction of the humerus?
supraspinatus
Scapular anastomosis key players
dorsal scapular a.
suprascapular a.
circumflex scapular branch of subscapular a.
