Rotator Cuff (Anatomy)

Intrinsic Muscles

muscles that move the shoulder joint (glenohumeral)

Deltoid Origin

lateral 1/3 of clavicle, acromion, spine of scapula

Middle Fibers of Deltoid

attaches to acromion

Anterior Fibers of Deltoid

attaches to clavicle

Posterior Fibers of Deltoid

attaches to spine of scapula

Deltoid Insertion

middle of humerus, deltoid tuberosity

Deltoid Innervation

axillary nerve (supplies all 3 fibers)

Axillary Nerve Location to Deltoid

runs in middle of muscle horizontally

Deltoid Action: Anterior Fibers

flexion in sagittal plane (front raises) and horizontal adduction

Horizontal Adduction of Shoulder

moving the arm across the body toward the midline of the body

Deltoid Action: Posterior Fibers

extension in sagittal plane; "I" motion

Deltoid Action: Middle Fibers

horizontal abduction; rear delt fly motion

Horizontal Abduction of Shoulder

moving shoulder away from midline of body

Deltoid Action: All Fibers

lateral raises; abduction of shoulder

What muscle is the prime mover of the genohumeral joint?

deltoids

What muscles are deep to the deltoid?

rotator cuff muscles

Rotator Cuff Muscles (SITS)

S = supraspinatus

I = infraspinatus

t = teres minor

S = subscapularis

General Characteristics of RC Muscles

- stabilizes GH joint

- deep to deltoid

- external rotators (except subscap)

- keeps head of humerus in socket

What happens if RC muscles are not functionally correct in reference to humerus head?

the ball rolls up towards the acromion where a subacromial impingement can occur

Subacromial Impingement

- very common

- bursa get's squished under acromion which have nerves / blood supply

Acromion Structure

3 different types (1, 2 and 3)

Type 1 Acromion Shape

Type 2 Acromion Shape

Type 3 Acromion Shape

most implicated in RTC tears

Supraspinatus Origin

supraspinous fossa of scapula

Supraspinatus Insertion

greater tubercle of humerus

Supraspinatus Innervation

suprascapular nerve

Suprascapular Nerve (C5-C6)

comes off upper trunk of brachial plexus

Supraspinatus Action

abduction of shoulder

Subdeltoid / Subacromial Bursa

a fluid-filled sac of synovial fluid to act as a cushion

Location of Subacromial Bursa

b/w deltoid, supraspinatus and /or acomion

Importance of Subacromial Bursa

can get beat up a lot especially in overhead position because humerus head continues to slide superiorly, which crunches the bursa causing swelling and pain

Infraspinatus Origin

below spine of scapula

Infraspinatus Insertion

more posteriorly / inferiorly of greater tubercle of humerus

Infraspinatus Innervation

suprascapular nerve

Infraspinatus Actions

external rotation of GH joint

Subscapularis Origin

costal (thoracic) side of scapula, anterior aspect of scapula, and lesser tuberosity

Subscapularis Innervation

upper and lower subscapular nerves

Subscapularis Action

internal rotation of shoulder

Teres Minor Origin

lateral border of scapula

Teres Minor Innervation

Axillary nerve (C5, C6)

Teres Minor Action

laterally (externally) rotates arm

Quadrangular Space Borders

Superior: teres minor

Inferior: teres major

Medial: long head of triceps

Lateral: humerus

What is located inside the quadrangular space?

- posterior humeral circumflex artery

- axillary artery

Triangular Space Borders

Superior: Teres minor

Inferior: Teres major

Lateral: Long head of triceps

Where is triangular space located?

medial to long head of triceps

Scapular Circumflex Artery

comes off subscapular which comes off axillary artery

Superior Transverse Scapular Ligament

bridges the scapular notch, suprascapular artery over & suprascapular nerve under

Supra-Scapular Foramen

suprascapular nerve through here

Omohyoid Muscle

attaches near supra-scapular foramen

Suprascapular Nerve

- comes off roots C5-C6 of brachial plexus

- innervates supraspinatus and infraspinatus

Suprascapular Nerve Pathway

goes under superior transverse scapular ligament into the scapular notch

Suprascapular Artery

comes off thyrocervical trunk

Suprascapular Artery Pathway

goes over top the superior transverse scapular ligament

Transverse Cervical Artery

necktie fashion resting on top of brachial plexus

Scapular Anastomosis

suprascapular artery (from subclavian artery), dorsal scapular artery, circumflex scapular artery (from subscapular artery, which is from axillary artery) and sometimes the intercostal arteries (from aorta)

- allows blood to flow regardless of position in shoulder

Anastomosis

connecting two tubular structures