Proximal upper limb

3 bones that compose the shoulder girdle

1. clavicle

2. scapula

3. proximal humerus

2 ends of the clavicle

1. acromial end (attaches at the shoulder)

2. sternal end (attaches at the sternum)

Jugular notch

• jugular (suprasternal) notch is located at the superior end of the sternum

• at lateral aspects of jugular notch will feel the medial end of the clavicle, which is bulbous and forms a prominence

Shape of clavicle

• S shaped

• medial 2/3 convex anteriorly

• lateral 1/3 concave anteriorly

Acromion

• will find it when you move laterally from the jugular notch, till the summit of the shoulder

• contributes to the contour of the shoulder

• is rectangular shape

Acromial angle

• felt at the point of junction of the lateral border of the acromion, with the inferior border of the crest of the spine of the scapula

• angle is used as the proximal point when measuring distances in the upper extremity

What part of the sternum articulates with the clavicle?

Manubrium of sternum

Important features of the proximal humerus

• head

• shaft

• anatomical and surgical necks

• greater tubercle (important feature related to shoulder abduction)

• lesser tubercle

• intertubercular groove

• deltoid tuberosity

• radial groove

Important features of the sternum

• manubrium

• jugular (suprasternal) notch

• body

• xyphoid process

Important features of the scapula include

• spine

• coracoid process

• acromion

• acromial angle

• medial border

• lateral border

• superior angle

• inferior angle

• supraspinous fossa

• infraspinous fossa

• glenoid cavity

4 joints of the shoulder girdle

1. sternoclavicular

2. acromioclavicular

3. glenohumeral

4. scapulothoracic

Sternoclavicular joint

• between the manubrium of the sternum and the medial end of the clavicle

• this joint is the only connection between the axial skeleton and the upper limb

• saddle-shaped synovial joint

Acromioclavicular (AC) joint

• plane synovial joint

• between acromion of scapula and lateral end of clavicle

• ligaments include:

  1. acromioclavicular ligament

  2. coracoclavicular ligament

Ligaments of acromioclavicular (AC) joint 

1. acromioclavicular ligament

2. coracoclavicular ligament

Acromioclavicular ligaments

• pair of intrinsic ligaments within the capsule of the joint

Coracoclavicular ligament

• extrinsic ligament

• is the major stabilizer of the AC joint

• 2 parts:

  1. conoid ligament

  2. trapezoid ligament

2 parts of coracoclavicular ligament

1. conoid ligament

2. trapezoid ligament

Glenohumeral joint

• very mobile ball and socket joint

• when a limb is raised above the head, ~2/3 of the apparent movement takes place at the glenohumeral joint and ~1/3 of movement is strenoclavicular and acromioclavicular joints

At what degree does the glenohumeral capsule become lax (and why does this happen?)

Capsule becomes lax when the humerus is abducted ~45° from the scapula —> this allows for considerable separation between the scapula and the humerus

What ligament prevents displacement superiorly at the head of the humerus?

Coracoacromial ligament

Scapulohumeral rhythm

• refers to the ratio of scapulothoracic and glenohumeral joint movement during shoulder movement

• when a limb is raised above the head:

  • ~2/3 of apparent movement is glenohumeral joint

  • ~1/3 of apparent movement is sternoclavicular and acromioclavicular joint

• scapula and humerus move in 1:2 ratio

  • i.e. when arm is abducted 180°, 120° is rotation of humerus at glenohumeral joint, 60° is rotation of scapula

    • can see the medial border and inferior angle of the scapula move during shoulder abduction

Features of the glenohumeral joint

1. glenoid fossa

2. glenoid labrum

3. tendon of long head biceps

4. coracoid process

5. acromion

6. coracoacromial ligament/coracoclavicular ligament

7. joint capsule

What is the glenoid labrum?

Fibrocartilaginous ring that attaches to the rim of the glenoid fossa, to help deepen and stabilize the shoulder joint

3 movements of scapolothoracic articulation

1. elevation/depression

2. protraction/retraction

3. upward rotation/downward rotation

Scapulothoracic joint/articulation: description, movements

• not a true anatomical joint (really an articulation)

• used to describe basic movements of the scapula

  • acromioclavicular and strenoclavicular joints are involved

• basic movements of the scapula include: protraction/retraction, elevation/depression, rotation

3 anterior axioappendicular muscles

1. pectoralis major

2. pectoralis minor

3. serratus anterior

2 heads of pectoralis major

1. clavicular head

2. sternocostal head

Clavicular head of pectoralis major (proximal attachment, distal attachment, main action)

proximal attachment: clavicle

distal attachment: intertubercular groove of humerus

main action: flexes the glenohumeral joint

Sternocostal head of pectoralis major (proximal attachment, distal attachment, main action)

proximal attachment: sternum

distal attachment: intertubercular groove of humerus

main action: extends the glenohumeral joint from the flexed position

Distal attachment and main action of pectoralis major (as a whole)

distal attachment: anterior edge of intertubercular groove

main action: adduction and medial rotation of glenohumeral joint

Anterior axillary fold

Formed by the inferior border of the pectoralis major

(is the anterior aspect of the armpit,, “chicken wing”)

Pectoralis minor (proximal attachment, distal attachment, main action)

proximal attachment: ribs

distal attachment: coracoid process

main action: stabilization of the scapula against the thoracic wall

Serratus anterior (proximal attachment, distal attachment, main action)

proximal attachment: ribs

distal attachment: medial border of scapula

main action: scapular protraction

*important muscle that stabilizes scapula against body

Posterior axioappendicular muscles (4)

Muscles located from the trunk to the scapula on the back:

1. trapezius

2. latissimus dorsi

3. levator scapulae

4. rhomboids

How are latissimus dorsi and pectoralis major alike?

Both pass directly from the trunk to the humerus

Latissimus dorsi (proximal attachment, distal attachment, main action)

proximal attachment: thoracic vertebrae, ribs and iliac crest

distal attachment: intertubercular (bicipital) groove of humerus

Main action: glenohumeral extension, adduction and internal (medial) rotation

Relationship between lat dorsi and teres major

Lat dorsi wraps around teres major from posterior to anterior and together these muscles form the posterior axillary fold

What muscles is the posterior axillary fold made up of? (2)

Latissimus dorsi and teres major

3 parts of the trapezius

1. upper (descending/superior)

2. middle

3. lower (ascending/inferior)

Trapezius (medial attachment, lateral attachment, main action)

medial attachment: cranium, cervical and thoracic (T1-T3) vertebrae

lateral attachment: clavicle, acromion and spine of scapula

main action:

upper (descending/superior) fibers: shoulder elevation

middle fibres: scapular retraction

lower (ascending/inferior) fibres: shoulder depression

Where are the rhomboids located in relation to the trapezius?

Rhomboids are deep to the trapezius

2 rhomboids

1. rhomboid major

2. rhomboid minor

Rhomboid minor

Medial attachment: vertebrae in neck (C7, T1)

Lateral attachment: medial end of the spine of the scapula

Main action: scapular retraction + downward (medial) rotation

Rhomboid major

Medial attachment: thoracic vertebrae (T2-T5)

Lateral attachment: medial border of the scapula

Main action: scapular retraction and downward (medial) rotation

Rotator cuff muscles (4)

1. supraspinatus

2. infraspinatus

3. teres minor

4. subscapularis

SITS

What are rotator cuff muscles?

• these muscles attach to the scapula 

• is separated from the coracoacromial arch by the subacromial bursa

  • inflammation of this bursa is clinically termed subacromial bursitis

Subscapularis (origin, insertion, main action and where it is found)

Origin: subscapular fossa on the anterior surface of the scapula

Insertion: lesser tubercle of humerus

Main action: strong internal rotator of the shoulder + adducts the glenohumeral joint

Is on the anterior surface of the scapula

Supraspinatus (proximal attachment, distal attachment, main action)

Proximal attachment: supraspinatus fossa of the scapula

Distal attachment: greater tubercle of the humerus

Main action:

• initiation of the first 15° of glenohumeral abduction and assisting the deltoid

• from a fully adducted position, glenohumeral abduction MUST be initiated by the supraspinatus

Infraspinatus (proximal attachment, distal attachment, main action)

Proximal attachment: infraspinatus fossa of the scapula 

Distal attachment: greater tubercle of humerus

Main action: external (lateral) rotation of glenohumeral joint

Teres minor (proximal attachment, distal attachment, main action)

Proximal attachment: lateral border of scapula

Distal attachment: greater tubercle of humerus

Main action: external (lateral) rotation of glenohumeral joint

Parts of deltoid muscle (3)

1. anterior (clavicular)

2. middle (acromial)

3. posterior (spinal)

Deltoid (proximal attachment, distal attachment, main action)

Proximal attachment: clavicle, acromion and spine of scapula

Distal attachment: deltoid tuberosity

Main actions:

Anterior (clavicular): glenohumeral flexion and internal (medial) rotation

Middle (acromial): glenohumeral (shoulder abduction) —> BUT does not become a fully effective abductor until 15 degrees of abduction

Posterior (spinal): part of glenohumeral extension and external (lateral) rotation

What muscles contribute to glenohumeral flexion? (4)

1. anterior deltoid

2. coracobrachialis

3. pectoralis major (clavicular head)

4. biceps brachii (long head)

What muscles contribute to glenohumeral extension? (6)

1. posterior deltoid

2. latissimus dorsi

3. teres major

4. teres minor

5. triceps (long head)

6. pectoralis major (sternocostal head)

What muscles contribute to glenohumeral abduction? (2)

1. middle deltoid

2. supraspinatus

What muscles contribute to glenohumeral adduction? (6)

1. latissimus dorsi

2. pectoralis major

3. teres major

4. coracobrachialis

5. anterior deltoid (if GH is flexed)

6. posterior deltoid (if GH is extended)

What muscles contribute to glenohumeral external rotation? (3)

1. infraspinatus

2. teres minor

3. posterior deltoid

What muscles contribute to glenohumeral internal rotation? (5)

1. subscapularis

2. pectoralis major

3. latissimus dorsi

4. teres major

5. anterior deltoid

6. serratus anterior

What muscles contribute to scapulothoracic retraction? (3)

1. rhomboids

2. trapezius (middle fibers)

3. latissimus dorsi

What muscles contribute to scapulothoracic elevation? (3)

1. trapezius (upper fibers)

2. levator scapulae

3. rhomboids

What muscles contribute to scapulothoracic depression? (5)

1. trapezius (lower fibers)

2. serratus anterior

3. lat dorsi

4. pectoralis major (sternocostal head)

5. pectoralis minor

What muscles contribute to scapulothoracic upward rotation? (2)

1. trapezius (upper and middle fibers)

2. serratus anterior

What muscles contribute to scapulothoracic downward rotation? (5)

1. rhomboids

2. lat dorsi

3. levator scapulae

4. pectoralis major (sternocostal head)

5. pectoralis minor

Key features of the distal humerus (6)

1. medial epicondyle (important structure related to tendonitis and fractures)

2. lateral epicondyle (important structure related to tendonitis and fractures)

3. trochlea

4. capitulum

5. coronoid fossa

6. olecranon fossa

Olecranon process

Olecranon process forms a prominence on the dorsum of the elbow between the 2 epicondyles

Plane of olecranon process and medial/lateral epicondyles

When elbow extended: olecranon process and medial/lateral epicondyles lie upon the same horizontal plane

When elbow flexed: 3 bony points mark the positions of the angles of an equilateral triangle 

Carrying angle

When elbow is extended, the humerus and ulna do not lie with each other but meet at an angle (carrying angle) of ~10-15°

This is the natural resting posture of these structures

Note that the angle is greater in women

Important features on proximal ulna (4)

1. olecranon process

2. coronoid process

3. trochlear notch

4. radial notch

Important features on the proximal radius (2)

1. radial head

2. neck

3 articulations of the elbow joint

1. humeroulnar

2. proximal radioulnar

3. humeroradial

What type of joint is the elbow joint?

Hinge (flexion/extension)

Ligaments in the elbow joint (3)

1. ulnar collateral ligament

2. radial collateral ligament

3. annular ligament

Movement of humeroradial articulation?

Radius pivots in the annular ligament at the humeroradial articulation and the proximal radioulnar joint

Muscles of the arm (4)

1. triceps brachii

2. biceps brachii

3. corachobrachialis

4. brachialis

What is the primary component of arm extensor group of muscles?

Triceps brachii

3 heads of triceps brachii

1. long

2. lateral

3. medial

Positioning of long, lateral and medial heads of the triceps brachii

Long and lateral heads lie side by side superficially to the medial head that lies alone on a deeper plane

Triceps brachii long head (proximal attachment, distal attachment, main action)

Proximal attachment: infraglenoid tubercle of scapula

Distal attachment: olecranon 

Main action: elbow extension

*crosses over the shoulder and elbow joints —> extends the elbow as well as the shoulder joint

Triceps brachii lateral head (proximal attachment, distal attachment, main action)

Proximal attachment: posterior humerus

Distal attachment: olecranon

Main action: elbow extension

Triceps brachii medial head (proximal attachment, distal attachment, main action)

Proximal attachment: posterior humerus

Distal attachment: olecranon

Main action: elbow extension

When is triceps brachii activated?

Triceps brachii is activated with elbow extension against resistance

3 flexor muscles in the arm

1. coracobrachialis

2. biceps brachii

3. brachialis

Coracobrachialis (proximal attachment, distal attachment, main action)

Proximal attachment: coracoid process

Distal attachment: humerus

Main action: flexion and adduction of the arm at the glenohumeral joint

Biceps brachii long head (proximal attachment, distal attachment, main action + extra info)

Proximal attachment : supraglenoid tubercle of the scapula

Distal attachment: tuberosity of radius

Main action: forearm supination and elbow flexion

• originates inside the shoulder joint and inserts onto the radius and indirectly to the ulna via the bicipital aponeurosis

• crosses the shoulder and elbow —> flexes the elbow and shoulder

Biceps brachii short head (proximal attachment, distal attachment, main action)

Proximal attachment: coracoid process

Distal attachment: tuberosity of radius

Main action: forearm supination and elbow flexion

Brachialis (proximal attachment, distal attachment, main action)

Proximal attachment: humerus

Distal attachment: coronoid process

Main action: flexes the elbow joint in all positions

What connects the radius and ulna?

Radius and ulna are connected by the interosseus membrane

Anterior and posterior compartments of the forearm

Anterior compartment: contains flexors and pronators of the forearm

Posterior compartment: contains the extensors and supinators of the forearm

Muscles in the posterior compartment of the forearm (8)

1. supinator

2. brachioradialis

3. extensor carpi radialis longus

4. extensor carpi radialis brevis

5. extensor carpi ulnaris

6. extensor digitorum

7. extensor digiti indicis

8. extensor digiti minimi

Where are the supinator and brachioradialis found?

Along with the wrist and digital (finger and thumb) extensor muscles in the posterior compartment of forearm

Supinator muscle (proximal attachment, distal attachment, main action)

Proximal attachment: lateral epicondyle of the humerus and posterior ulna

Distal attachment: radius

Main action: rotates the radius to turn the palm anteriorly (up)

Brachioradialis (proximal attachment, distal attachment, main action)

Proximal attachment: supraepicondylar ridge of humerus

Distal attachment: radius

Main action: elbow flexion when forearm is in neutral position

Is apparent when the elbow is flexed 90° against resistance with the forearm in the middle position between supination and pronation

Is referred to as the drinking muscle

What 2 muscles contribute to supination of the forearm?

1. Biceps brachii

2. Supinator

What are the wrist extensors? (3)

1. Extensor carpi radialis longus

2. Extensor carpi radialis brevis

3. Extensor carpi ulnaris

Where do extensor carpi radialis brevis, extensor digitorum and extensor digiti minimi attach proximally?

They form a common extensor tendon and attach to the lateral epicondyle of the humerus

Where is extensor digiti indicis found?

In the posterior compartment of the forearm

Originates from the distal 2/3 of the ulna

Extensor carpi radialis longus (proximal attachment, distal attachment, main action)

Proximal attachment: supracondylar ridge of humerus

Distal attachment: base of 2nd metacarpal

Main action: wrist extension and abduction (radial deviation)

Extensor carpi radialis brevis (proximal attachment, distal attachment, main action)

Proximal attachment: forms common extensor tendon and attaches to lateral epicondyle of humerus

Distal attachment: base of 3rd metacarpal

Main action: wrist extension and abduction (radial deviation)

Extensor carpi ulnaris

Proximal attachment: forms common extensor tendon and attaches to lateral epicondyle of humerus

Distal attachment: base of 5th metacarpal

Main action: wrist extension and adduction (ulnar deviation)

Extensor digitorum (proximal attachment, distal attachment, main action)

Proximal attachment: forms common extensor tendon and attaches to lateral epicondyle of humerus

Distal attachment: extensor expansions of fingers

Main action: extends fingers primarily at metacarpophalangeal joint (secondarily at the interphalangeal joint)