Shoulder Muscles😍

Rotator Cuff Muscles (SITS Muscles)

• Forgotten muscle
• Subscapularis → Deep muscle.
• Localization of pathology → Difficult.

Function

• Stability to the shoulder joint.

Muscles and Location

• Posterior
• Supraspinatus
• Infraspinatus
• Teres minor

• Anterior
• Subscapularis

Shoulder

Subscapularis

• Insertion: Lesser tubercle

• Adduction and IR

Lady between 2 majors

• Intertubercular groove

• Pec major → Adduction and IR + Flexion

• Latissimus Dorsi → Adduction and IR + Extension
• Climbing muscle

• Teres major → Adduction and IR

• Mneumonic:
• Lady between 2 majors → LML → Addupichitt Internally (Add + IR) rotate cheyyan nokkum

SIT Muscles

• Greater tubercle has three prominences
• provide Insertion to ‘SIT’ muscles

• Initial abduction (0-15 degrees)
1. Supraspinatus

• External rotation
2. Infraspinatus
3. Teres minor

• Function
• Adduction?? and External Rotation

• When sitting (SIT muscle except Supraspinatus) in Lap → Addupich (Add) Externally (ER) rotate cheyyanam

 

Adduction and IR

• MLM +

• Subscapularis

• ”Mneumonic: Sabu (Subscapularis) nte Wife 2 major (MLM) nte kude kidannu (Add+ IR)

Abduction of the Shoulder Joint

• 0–15°: Supraspinatus

• 15–90°: Middle fibers of deltoid

• 90–180°:
• Trapezius, serratus anterior
• Sar (Serratus anterior) trapped (Trapezius) us and said Hands up (overhead abduction)

Dorsal scapular nerve Injury

• Mneumonic: Door to School (Dorsal scapular) → makes u Levate (Levator Sc) and Rotate (R. major, minor) Up {imagine} → look down and see Globe going down (Glenoid fossa downwards)

• 3 muscles supplied
1. Rhomboid major
2. Rhomboid minor
• Retraction of scapula
3. Levator scapulae

Injury

1. Winging of scapula
• worsen with slow lowering of arm

2. Rotation of glenoid fossa downwards

Trapezius Muscle – Middle and Lower Fibers

• Location: Upper back and neck

• Shape:
• Alone: Triangular
• Together: Rhomboid

• Function:
• Scapular retraction
• Pulls the scapula backward toward the spine
• Overhead Abduction (90-180 degree)

• Primary role:
• Movement and stabilization of the scapula

Humeral Fractures and nerve injury

Winging of scapula

Feature	Spinal Accessory Nerve (CN XI)	Long Thoracic Nerve	Dorsal Scapular Nerve
Muscle Innervated	Trapezius, Sternocleidomastoid	Serratus anterior	Rhomboids, Levator scapulae
Mechanism of Injury	Surgery in posterior triangle of neck	Sports injury, mastectomy	Rare; trauma or stretch injury
Main Deficit	Dropped shoulder, weak abduction, weak shrugging of shoulder	Winging scapula, can't lift arm above head	Winging scapula, esp. on slow lowering
Winging Increases When	Arm abducted at shoulder level	Wall push-up, head tilt	Slow lowering of raised arm

Clavipectoral fascia

• Mnemonic:
• CLAvi Pectoral
• Cephalic vein
• Lateral pectoral N
• Acromial artery (Thoracoacromial artery)
• ClaVi (CV → Cephalic Vein), Pectoral (Lateral pectoral), fAscia (Acromial)
• All less
• Subclavius
• Pec minor

Muscles enclosed

• Pectoralis minor

• Subclavius

Structures piercing clavipectoral fascia :

1. Cephalic vein.

2. Thoracoacromial trunk.

3. Lateral pectoral nerve.

4. Lymphatics.

Extensions :

• Superior : Continues with investing layer (Posterior layer) of deep cervical fascia.

• Inferior : Suspensory ligament of axilla

NOTE

• Medial pectoral nerve
• Laterally located
• Pierces pectoralis minor

• Lateral pectoral nerve
• Medially located
• Runs anterior to pectoralis minor

 

Cubital Fossa → MBTR structures

Carrying Angle and Cubitus Valgus

Biceps Tendon Rupture

Proximal

• Usually long head rupture.

• Sudden pop with pain.

• Popeye deformity in arm.

• Loss of supination strength.

• Often due to degeneration or overuse.

• Treatment:
• Conservative
• Surgical repair for young or high-demand patients.

Distal

• Tear of biceps insertion on radial tuberosity.

• Sudden pain + Loss of supination and flexion strength

• Reverse Popeye appearance

• Caused by forceful extension of flexed elbow.

• Hook test: tendon not palpable.

• Treatment:
• Surgical repair preferred

• proximal pop eye (aduth ullavare onnu nokkikonda mathi) ( conservative in elderly)

• distant aayi ponavare hook vach pidich thunni vaykkam (repair must)

Arteries of Upper Limb

Subclavian Artery

• Divided into 3 parts by scalenus anterior muscle

1st Part	VIT C D
ㅤ	Vertebral artery
ㅤ	Internal thoracic artery
ㅤ	Thyrocervical trunk ↳ Suprascapular artery ↳ Inferior thyroid artery ↳ Transverse cervical artery
2nd Part	ㅤ
ㅤ	Costocervical trunk
3rd Part	ㅤ
ㅤ	Dorsal scapular artery

Inferior Thyroid Artery supplies

• Thyroid

• Parathyroid

• Cervical part of oesophagus

• Thymus

Axillary Artery

• Axillary vein lies medial to the artery throughout.

• Anterior shoulder dislocation may compress the 2nd part of axillary artery by the humeral head.

Scapular Anastomosis

• Between 1st part of subclavian artery and 3rd part of axillary artery.

Arteries of the Arm (Branches of Brachial Artery)

• Profunda brachii artery
• Runs in spiral groove with radial nerve
• Gives radial collateral arteries

• Superior ulnar collateral artery

• Inferior ulnar collateral artery

• Ulnar artery and Radial artery

• Muscular branches

Applied: Volkmann's ischemic contracture

Subscapular Artery

• Supplies:
• Subscapular muscle
• Latissimus dorsi

Arteries of Forearm and Palm

• Ulnar artery → Common interosseous artery

• Common interosseous artery divides into:
• Anterior interosseous artery
• Pierces interosseous membrane
• Enters 4th compartment of extensor retinaculum
• Posterior interosseous artery
• Gives Recurrent interosseous artery

Allen’s Test (Radial–Ulnar Patency)

• Allen’s Test:
• 2 hands → 1 artery
• Negative: Normal.

• Modified Allen’s:
• 2 hands → 2 artery
• Positive: Normal (radial & ulnar patent).