scapula

What is the origin of the deltoid muscle?

Lateral third of clavicle, acromion, and spine of scapula.
Mnemonic: CAS = Clavicle, Acromion, Spine.

A patient with axillary nerve injury has a flat shoulder. Which muscle is affected, and what is its origin?

Deltoid muscle — originates from lateral 1/3 of clavicle, acromion, and spine of scapula.

What is the insertion of the deltoid muscle?

Deltoid tuberosity of humerus.

In a case of shoulder trauma, the injured muscle inserts on the deltoid tuberosity. Which muscle is that?

Deltoid muscle.

What are the actions of the deltoid muscle?

Anterior fibers: flexion & medial rotation
Middle fibers: abduction (15–90°)
Posterior fibers: extension & lateral rotation.
Mnemonic: FML = Flex, Medial, Lateral.

A patient cannot abduct their arm from 15° to 90°. Which muscle is likely injured?

Deltoid muscle — responsible for abduction 15–90°.

What is the nerve supply of the deltoid muscle?

Axillary nerve (C5, C6).

Loss of shoulder contour and inability to abduct arm 15–90° suggests damage to which nerve and muscle?

Axillary nerve supplying deltoid muscle.

What is the origin and insertion of supraspinatus?

Origin: Supraspinous fossa of scapula
Insertion: Superior facet of greater tubercle of humerus.

A patient cannot initiate abduction (0–15°). Which muscle is affected?

Supraspinatus — initiates abduction 0–15°.

What is the nerve supply of supraspinatus?

Suprascapular nerve (C5, C6).

Which nerve innervates the muscle that initiates arm abduction?

Suprascapular nerve — supplies supraspinatus.

What is the main action of supraspinatus?

Initiates abduction (0–15°) of arm.

In shoulder impingement, which muscle is most commonly affected and what is its action?

Supraspinatus — initiates abduction (0–15°).

What are the origin and insertion of infraspinatus?

Origin: Infraspinous fossa of scapula
Insertion: Middle facet of greater tubercle of humerus.

A patient has weak lateral rotation of the arm. Which muscle might be affected?

Infraspinatus — laterally rotates the arm.

What is the nerve supply of infraspinatus?

Suprascapular nerve (C5, C6).

Which nerve supplies both supraspinatus and infraspinatus muscles?

Suprascapular nerve (C5, C6).

What is the action of infraspinatus?

Lateral rotation of the arm.

A patient cannot laterally rotate their arm. Which rotator cuff muscle might be injured?

Infraspinatus.

What are the origin and insertion of teres minor?

Origin: Upper 2/3 of lateral border of scapula
Insertion: Inferior facet of greater tubercle of humerus.

A patient with axillary nerve injury loses lateral rotation and adduction of the arm. Which muscle is involved?

Teres minor.

What is the nerve supply of teres minor?

Axillary nerve (C5, C6).

Which muscle supplied by the axillary nerve assists in lateral rotation of the arm?

Teres minor.

What is the action of teres minor?

Adduction and lateral rotation of the arm.

Loss of adduction and lateral rotation of shoulder suggests injury to which muscle?

Teres minor.

What are the origin and insertion of teres major?

Origin: Lower 1/3 of lateral border of scapula
Insertion: Medial lip of bicipital groove of humerus.

A patient with weak adduction and medial rotation of the arm likely has injury to which muscle?

Teres major.

What is the nerve supply of teres major?

Lower subscapular nerve (C5, C6).

Which muscle supplied by the lower subscapular nerve causes medial rotation of the arm?

Teres major.

What is the action of teres major?

Adduction, extension, and medial rotation of the arm.

A climber with weak adduction and medial rotation of shoulder likely injured which muscle?

Teres major.

What are the origin and insertion of subscapularis?

Origin: Subscapular fossa of scapula
Insertion: Lesser tubercle of humerus.

Which muscle lies on the costal surface of the scapula and inserts into the lesser tubercle?

Subscapularis.

What is the nerve supply of subscapularis?

Upper and lower subscapular nerves (C5, C6).

Which muscle is supplied by both upper and lower subscapular nerves?

Subscapularis.

What are the actions of subscapularis?

Medial rotation and adduction of arm.

A patient with weakness in medial rotation of the arm likely has injury to which muscle?

Subscapularis.

What are the rotator cuff muscles?

Supraspinatus, Infraspinatus, Teres minor, Subscapularis.
Mnemonic: SITS.

A patient has difficulty stabilizing the shoulder joint. Which muscle group provides stability?

Rotator cuff muscles — SITS.

What is the function of the rotator cuff muscles?

Stabilize head of humerus in glenoid cavity.

In shoulder dislocation, which group of muscles helps stabilize the joint normally?

Rotator cuff muscles.

List the key facts about scapular region muscles.

1. All arise from scapula
   2. Insert into humerus
   3. Act on shoulder joint
   4. Supplied by C5–C6
   5. All are adductors except deltoid & supraspinatus.

D.e Ito pectoral Groove

^ Groove between deltoid and pectoral region

1. cephalic vein

2. delto pectoral lymph

3. Deltoid branch of accromium artery

Cool doctors live

Cool cephalon

Doctor artery

Live lymph node