2.0)Myology of the Rotator Cuff Muscles Flashcards

1
Q

The rotator cuff muscles

A

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

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2
Q

4 Rotator cuff muscles

A

Supraspinatus
Subscapularis
Infraspinatus
Teres minor

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3
Q

Suprapsoinatis

A

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

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4
Q

Subscapularis

A

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

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5
Q

Infraspinatus

A

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

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6
Q

Teres minor

A

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

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7
Q

Which muscles are anterior and which are posterior

A

Supraspinatus- posterior
Subscapularis- anterior
Infraspinatus- posterior
Teres minor- posterior

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8
Q

Dynamic stability

A

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

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9
Q

What could cause weak rotator cuffs

A

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

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