Shoulder Complex Biomechanics Flashcards
The scapula lies on a plane _____ to the back and _____ to the clavicle
30º to the back
60º to the clavicle
List the possible morphologies of the acromion process
- Type 1: flat
- Type 2: curved
- Type 3: hooked
which morphology of the acromion is a good prognostic indicator for conservative management?
Type 1: Flat
Type 3: Hooked → negative prognositic indicator and also greatest correlation w/subacromial impingement syndrome
List the ligaments found at the scapalua
- coracoacromial ligament
- superior transverse scapular ligament
- inferior transverse scapular ligament
where is the superior/inferior transverse scapular ligament?
superior → completes scapular notch to make foramen
inferior → arches over suprascapular nerve (entering infraspinatus fossa)
what is the glenoid labrum?
ring of fibrocartilage attached to the margin of the glenoid cavity
deepens the glenoid cavity for congruency of articular surfaces
outer surface attaches to capsular ligaments
describe the relative position of the head of the humerus
faces superiorly, medially, and posterioly
angle of inclination = 135º
angle of retroversion = 30º
what structures stablize the glenohumeral joint?
- Joint capsule
- coraco-humeral ligament
- 3 bands of GH ligament (S/M/I)a
- rotator cuff muscles
where is the weakest portion of the glenohumerual capsule?
Z spread over the anterior aspect of the capsule between the bands of the glenohumeral ligament
when are the 3 GH ligaments taut?
during ER
slackened during IR
what is the quadrilateral space?
formed by teres major, teres minor, long head of triceps, and surgical neck of humerus
axillary nerve and posterior circumflex humeral artery pass through from anterior to posterior
what movements close the quadrilateral space?
Ext, ABD, and ER
what is the rotator cuff interval?
a triangular portion of the GH capsule that lies between the supraspinatus and subscapularis tendons
reinforced by S GH and coracohumeral ligaments
how would an adhesion at the rotator cuff interval impact the humerus?
it will cause anterior seating of humeral head
pulls the humeral head forward relative to the glenoid
we see this in adhesive capsulitis
what is the biceps pulley?
a tendo-ligamentous sling formed by the:
- S GH ligament
- Coracohumeral ligament
- distal attachement of the subscapularis tendon
it stabilizes the long head of the biceps in the biciptal groove and is located at the rotator cuff interval
what is the primary stabilizer of the GH joint?
rotator cuff muscles:
infraspinatus
supraspinatus,
teres minor
subscapularis
list the kinematic motions of the scapula involved in elevation of the shoulder complex and the muscles that preform them
- upward rotation = upper trap, lower trap, serratus anterior
- posterior tipping = serratus anterior
- internal rotation
shoulder abduction can be broken down into how many phases?
3
what occurs during phase 1 of shoulder abduction?
0-60º
deltoid and supraspinatus working
“locking” at 90º from greater tuberosity impacting superior margin of glenoid
lateral rotation and flexion of the humerus to delay lock
what occurs during phase 2 of shoulder abduction?
60-120º
60º rotation of scapula to orient glenoid superior and anterior, axial rotation of SC and AC joints
traps (upper and lower) and SA acting here
checked by Lats and pec major
what occurs during phase 3 of shoulder abduction?
120-180º
lateral flexion of T-spine
deltoid, supraspinatus, inferior traps, SA elevate UE
what occurs during phase 1 of shoulder flexion?
0-50/60º
anterior clavicular fibers of deltoid, coracobrachialis, and superior clavicular fibers of the pec major initaite shoulder flexion
what checks/opposes the initial shoulder flexion occuring in phase 1?
tension from the teres major/minor, infraspinatus, and coracohumeral ligament
what occurs during phase 2 of shoulder flexion?
60-120º
60º rotation of scapula to orient glenoid superior and anterior, axial rotation of SC and AC joints
traps and SA acting
checked/opposed by lats and inferior pec major
