2.0)Myology of the Rotator Cuff Muscles Flashcards
The rotator cuff muscles
Form a musculotendinous cuff around the glenohumeral joint hold the head of humerus in fossa
Pass between pectoral girdle and humerus protect joint suspended upper limb from pectoral girdle =stability
Key dynamic stabilisers for the joint
4 Rotator cuff muscles
Supraspinatus
Subscapularis
Infraspinatus
Teres minor
Suprapsoinatis
S:
O: medial 2/3 supraspinous fossa
I:Upper facet on greater tubercle of humerus
D: laterally, below trapezius Acromion and coracoacromion ligament crosses over top of shoulder joint
A: abducts arm at shoulder joint - *early range
Holds head of humerus against glenoid fossa prevents upward shearing of humeral head
F: keep head of humerus in glenoid fossa during shoulder movement
Ns: Suprascapular nerve C5, C6
Subscapularis
S: multipennate
Forms greater part of post wall of axilla
O: medial 2/3 Subscapular fossa
I: Lesser tubercle of humerus
Bursa that communicate with shoulder joint separates tendon from neck of scapula
D: Laterally
A: Strong medial rotator assists adduction of arm
F: keeps head of humerus within the glenoid fossa resists a poor displacement of humeral head when e.g. deltoids are active
NS: Upper and lower subscapular nerves C5,6,7
Infraspinatus
S: Thick triangular muscle
O: medial 2/3 of Infraspinous fossa
I: Middle facet on greater tubercle of humerus posterior part of joint capsule
Bursa which occasionally communicates with shoulder separates muscle from the neck of scapula
D: laterally
A: Lateral rotator
F: important one arm is fully abducted during latter part of movement humorous is laterally rotated greater tubercle is clear of the coracoacromial arch allows remaining part of numeral head come into contact with glenoid fossa and full abduction to occur
NS: Suprascapular nerve C5, 6
Teres minor
S: Thin
Forms up are Boundry of triangular and quadrangular spaces
O: Two heads separated by a groove for the circumflex scapula artery
- upper 2/3 lat boarder of scapula fascia between it and teres major and infraspinatus
I: inferior facet on the greater tubercle of humerus and the bone immediately below
D: upwards and laterally
A: Lateral Rotates but when arm is abducted it also adducts
F: important one arm is fully abducted during latter part of movement humorous is laterally rotated greater tubercle is clear of the coracoacromial arch allows remaining part of numeral head come into contact with glenoid fossa and full abduction to occur
NS: Axillary nerve C5,6
Which muscles are anterior and which are posterior
Supraspinatus- posterior
Subscapularis- anterior
Infraspinatus- posterior
Teres minor- posterior
Dynamic stability
Concurrent force system
Off set the superior translatory force of deltoid as rotator cuff produces inferior translators force
Unopposed movement of deltoid would cause impaction of humeral head under coracoacromial arch
Prevent inferior movement of head of humerus causes depression of humerus
Compresses humeral head into glenoid fossa
What could cause weak rotator cuffs
Difficulty initiating abduction (supraspinatus)
Superior migration of head of humerus during abduction
Reduced lateral rotation during abduction
Head of humerus not being in glenoid fossa