Shoulder, Axilla and Posterior Triangle (Week 2--Miller)

Question 1

Axial skeleton

Answer 1

Bones of head (skull), neck (hyoid bone and cervical vertebrae), and trunk (ribs, sternum, vertebrae, sacrum)

Question 2

Appendicular skeleton

Answer 2

Bones of the limbs (extremities, appendages), including those forming the pectoral (shoulder) and pelvic girdles

Question 3

Pectoral (shoulder) girdle

Answer 3

Clavicle and scapula

Question 4

Joints of the shoulder

Answer 4

Glenohumoral joint

Acromioclavicular joint

Sternoclavicular joint

Question 5

Articulations that are not true joints

Answer 5

Suprahumeral“joint”

Scapulothoracic“joint”

Question 6

Glenohumoral joint

Answer 6

Synovial joint (ball and socket)

Allows flexion, extension, abduction, adduction, medial and lateral rotation, circumduction of humerus

Reinforced by rotator cuff tendons and anteriorly by glenohumeral ligaments (thickenings of joint capsule)

Often dislocated

Innervated by suprascapular, lateral pectoral and axillary nerves

Foramen of Weitbrecht is weakness between superior and middle glenohumeral ligaments

Glenoid labrum is fibrocartilagenous ring that surrounds glenoid fossa

Question 7

Foramen of Weitbrecht

Answer 7

Part of glenohumeral joint

Weakness in joint capsule between superior and middle glenohumeral ligaments

In anterior dislocation, head of the humerus penetrates through this weak area

Question 8

Tendon of the long head of the biceps

Answer 8

Invaginates the joint capsule (is intracapsular) but does not enter synovial cavity (is extrasynovial)

Tendon held in bicipital groove by transverse humeral ligament

Question 9

Glenoid labrum

Answer 9

Fibrocartilagenous ring that surrounds glenoid fossa and helps deepen socket of the shoulder joint

Fibrous joint capsule attaches to labrum, so any injury of the joint capsule can potentially involve the labrum

Question 10

Normal abduction and adduction

Answer 10

Normal range of abduction: 180 degrees overhead

Normal range of adduction: 45 degrees across the front of the body

Question 11

Normal range of external (lateral) and internal (medial) rotation

Answer 11

Normal range of external rotation: 40 - 45 degrees

Normal range of internal rotation: 55 degrees before motion interrupted by body

Question 12

Normal range of flexion and extension

Answer 12

Normal range of flexion: 90 degrees

Normal range of extension: 45 degrees posterior to vertical axis of body

Question 13

Circumduction

Answer 13

Motion where distal aspect of appendage goes in circle and proximal aspect remains relatively stationary

Question 14

Sternoclavicular joint

Answer 14

Synovial joint (saddle-type, but functions like ball and socket)

Articular disk divides joint into 2 separate joint cavities

Very strong, dislocation is rare

Mobile, to allow movements of pectoral girdle

Only joint between pectoral girdle and axial skeleton

Innervated by supraclavicular nerves and nerve to subclavius muscle

Question 15

Acromioclavicular joint

Answer 15

Synovial joint (plane-type)

Allows gliding movements

Weak and has incomplete articular disk

Protected by strong superior and inferior acromioclavicular ligaments

This joint involved in shoulder separation injuries

Innervated by supraclavicular, lateral pectoral, axillary nerves

Question 16

Coracoclavicular ligament

Answer 16

Provides means by which scapula and free limb are suspended from clavicular strut

Question 17

Suprahumeral “joint” space

Answer 17

Not a true joint

Space between head of humerus and the acromion and coracoacromial ligament

Contains biceps long head tendon, rotator cuff tendons, subacromial/subdeltoid bursa, gleno-humeral joint capsule

Question 18

Frozen shoulder syndrome

Answer 18

The result (sequelae) of shoulder tendinitis, bursitis, or partial tear

Shoulder injury initially painful but gradually becomes more restricted in motion in all directions (“frozen”)

Exact mechanism unknown but many tissues of suprahumeral “joint” space may be involved (subdeltoid bursa synovium, glenohumeral capsule synovium, conjoined tendon tenosynovium, biceps long head tendon synovial lining)

Question 19

Subdeltoid/subacromial bursa

Answer 19

Synovial-lined sac that has 2 parts that may be fused or separated: subacromial bursa and subdeltoid bursa

Bursa lies between supraspinatus tendon and deltoid muscle in suprahumeral “joint” space

Reduces friction during abduction so if inflamed, will have pain during abduction

Question 20

Extrinsic muscles of the shoulder

Answer 20

In general, act on scapula (except pec major and lat dorsi), which is important because scapula must move in order to place the hand in functional position

Anterior group: pectoralis major, pectoralis minor, subclavius, seratus anterior

Posterior group = superficial “back” muscles: trapezius, levator scapulae, rhomboids, latissimus dorsi

Question 21

In addition to latissimus dorsi, what other shoulder muscles attach to the bicipital groove of the humerus?

Answer 21

Pectoralis major, teres major, latissimus dorsi all attach to bicipital groove of the humerus

Thus, have similar actions on humerus as latissimus dorsi (lat dorsi adducts, medially rotates and extends at shoulder; pec major adducts and medially rotates; teres major adducts and medially rotates at shoulder)

Question 22

Movements of scapula

Answer 22

Retract: trapezius middle fibers, rhomboids

Protract: serratus anterior

Elevate: trapezius superior fibers, levator scapulae

Depress: trapezius inferior fibers

Superiorly (upwardly) rotate: trapezius superior and inferior fibers, serratus anterior (glenoid cavity pointed superiorly)

Inferiorly rotate: levator scapulae, rhomboids (glenoid cavity pointed inferiorly)

Note: in order to position the hand, the scapula and humerus must move in a smoothly coordinated and integrated fashion (this is called scapulohumeral rhythm)

Question 23

Scapulohumeral rhythm

Answer 23

Integrated movement of scapula and humerus together; involved in any movement of upper limb which places hand in functional position

Simultaneous movement of humerus at glenohumeral joint and rotation of scapula

For every secondary abduction at glenoheral joint, there is primary rotation of scapula

When arm abducted 90 degrees, 60 degrees occurs at glenohumeral joint and 30 degrees is from scapular rotation

Question 24

Intrinsic muscles of the shoulder

Answer 24

Deltoid muscle

Teres major muscle

Supraspinatus (rotator cuff)

Infraspinatus (rotator cuff)

teres minor (rotator cuff)

Subscapularis (rotator cuff)

Question 25

Conjoined tendon of rotator cuff

Answer 25

This IS the rotator cuff itself Rotator cuff muscles' tendons (at the ends) form common tendon ("cuff")/conjoined tendon which is contained within **suprahumeral "joint" space** **Tendons** cover **fibrous capsule** of shoulder joint and reinforce it, however note that shoulder joint NOT reinforced by cuff inferiorly, so is weak inferiorly Within the rotator cuff is a "critical zone" which is potential site of tears and Ca2+ deposit buildup

Question 26

Abduction of the humerus

Answer 26

Initiated by **supraspinatus** muscle and then **deltoid** muscle takes over (and is major abduction of humerus)

Question 27

Rotator cuff muscles

Answer 27

SItS **Supraspinatus**: posterior, greater tubercle of humerus **Infraspinatus**: posterior, greater tubercle of humerus **Teres** **minor**: posterior, greater tubercle of humerus **Subscapularis**: anterior, lesser tubercle of humerus

Question 28

Critical Zone

Answer 28

Area of **vascular anastomoses** within the **rotator cuff** Is alternately **ischemic** of **hyperemic** depending on whether there is tension on the cuff This is often the site of **degeneration, Ca2+ deposits, tears**

Question 29

Neurovascular structures and spaces of the shoulder

Answer 29

**Quadrangular space**: transmits **axillary nerve**, **posterior circumflex humeral artery** (these also wrap around surgical neck of humerus so if you fracture that, could affect that artery and nerve) **Triangular space**: transmits branches of **circumflex scapular artery** **Scapular anastomosis**: network of interconnecting arteries formed by **branches of the subclavian artery, 3rd part of axillary artery, and intercostal arteries**

Question 30

Quadrangular space boundaries

Answer 30

Lateral: lateral head of **triceps** Medial: long head of **triceps** Superior: **teres** **minor** Inferior: **teres** **major** Remember, transmits **axillary** **nerve** and **posterior** **circumflex** **humeral** **artery** which also wrap around **surgical neck of humerus**

Question 31

Suprascapular nerve and artery

Answer 31

**Suprascapular** **nerve** and **artery** are both found deep to **supraspinatus** and **infraspinatus** **muscles** From supraspinous fossa to scapular spine to infraspinous fossa Suprascapular nerve is a branch of the **upper trunk** of the **brachial plexus**

Question 32

Arteries of the Scapular Anastomosis

Answer 32

**Dorsal scapular** goes toward spine (if this isn't present, transverse cervical artery takes its place) **Suprascapular artery** in upper area **Subscapular artery** in lower area **Circumflex scapular artery** closes the loop

Question 33

Brachial plexus

Answer 33

**Somatic** nerve plexus formed by **ventral rami** of **C5-T1** spinal cord segments (innervates skeletal muscle, bone, joints, skin, and NOT blood vessels) Located across two different anatomical regions: **posterior** **triangle** (**supraclavicular** part) and **axilla** (**infraclavicular** part) 5 roots --\> 3 trunks (visible in posterior neck)--\> 6 divisions (under clavicle, not visible) --\> 3 cords (visible in axilla) --\> 5 terminal branches (also have non-terminal branches that originate from different regions of the brachial plexus)

Question 34

How are the 3 cords named?

Answer 34

All in relation to the **axillary artery** Posterior cord is posterior to axillary artery Lateral cord is lateral to axillary artery Medial cord is medial to axillary artery

Question 35

What does the classic M of the brachial plexus include?

Answer 35

**Musculocutaneous** nerve **Median** nerve **Ulnar** nerve

Question 36

Which spinal levels do fibers of the 5 terminal branches of the brachial plexus predominantly originate from?

Answer 36

Axillary: C5-6 Musculocutaneous: C5-7 Median: C5-T1 Radial: C5-T1 Ulnar: C8, T1 Memorize these!!

Question 37

What non-terminal branches arise from the **roots** of the brachial plexus?

Answer 37

**Dorsal scapular** nerve (levator scapulae and rhomboids) **Long thoracic** nerve (serratus anterior)

Question 38

What non-terminal branches arise from the **upper trunk** of the brachial plexus?

Answer 38

**Nerve to the subclavius** (subclavius) **Suprascapular** nerve (supraspinatus and infraspinatus)

Question 39

What non-terminal branches arise from the **medial cord** of the brachial plexus?

Answer 39

**Medial pectoral** nerve (pec major and pec minor) **Medial brachial cutaneous** nerve **Medial antebrachial cutaneous** nerve

Question 40

What non-terminal branches arise from the **lateral cord** of the brachial plexus?

Answer 40

**Lateral pectoral** nerve (pec major)

Question 41

What non-terminal branches arise from the **posterior cord** of the brachial plexus?

Answer 41

**Upper subscapular** nerve (subscapularis) **Thoracodorsal** nerve (latissimus dorsi) **Lower subscapular** nerve (subscapularis and teres major)

Question 42

The axilla

Answer 42

The pyramidal-shaped region or space inferior to shoulder joint; the armpit Has apex, base, **anterior** (**pec major, pec minor, clavicle, subclavius muscle**), **posterior** (**lat dorsi, teres major, subscapularis**), **medial** (**thorax** and **serratus** **anterior**) and **lateral** **walls** (conceptually by **bicipital** **groove** **of humerus**) Contains **axillary artery, axillary vein, distal part of brachial plexus, axillary lymph nodes**

Question 43

Axillary lymph nodes

Answer 43

Receive lymph from **upper limb** but also **75%** of lymph drainage from **breast** (so important in diagnosing breast cancer)

Question 44

What part of the brachial plexus does the axilla contain?

Answer 44

**Infraclavicular** part (**cords** and **terminal** **branches**) Also contains **tendons of biceps** (long head tendon and short head tendon) and **coracobrachialis** This is where you see the **"M"**

Question 45

Relationship of axillary artery/vein with cords of brachial plexus

Answer 45

Cords of brachial plexus surround the axillary artery **Brachial plexus** and **axillary artery** are contained within fascial sheath called **axillary sheath**

Question 46

Branches of the axillary artery

Answer 46

**Subclavian** artery passes **1st rib** --\> **axillary** artery has 3 branches --\> passes **teres major** to become **brachial** artery 1st part (medial; medial to pec minor): **supreme thoracic artery** (supplies 1st intercostal space) 2nd part (deep; deep to pec minor): **thoraco-acromial artery** (related to **superior margin of pec minor**, has pectoral deltoid, acromial and clavicular branches) and **lateral thoracic artery** (runs along border of pec minor and supplies the breast) 3rd part (lateral; lateral to pec minor): **anterior circumflex humeral artery** (goes lateral and anterior to neck of humerus; anastomoses w/posterior), **posterior circumflex humeral artery** (goes lateral and posterior to neck of humerus; anastomoses w/anterior), **subscapular artery** (medial and divides into **circumflex** **scapular** and **thoracodorsal** **arteries**)

Question 47

Posterior triangle of the neck

Answer 47

**Supraclavicular** part of the **brachial plexus**, **phrenic nerve, accessory nerve, subclavian artery** all course through it Important for control of upper limb, diaphragm and trapezius Boundaries: anterior margin of **trapezius**, posterior margin of **SCM**, **clavicle**

Question 48

Cervical fascia

Answer 48

**Investing fascia**: **roof** of posterior triangle and **surrounds SCM and trapezius** **Prevertebral fascia**: covers **muscular** **floor** of triangle and surrounds prevertebral and true (deep) back muscles **Pretracheal fascia**: surrounds **thyroid gland, trachea, esophagus**

Question 49

Roof (investing fascia) of posterior triangle

Answer 49

Contains cutaneous branches of **cervical plexus**: **lesser occipital, great auricular, transverse cervical, supraclavicular nerves** (these are all **sensory** nerves)

Question 50

Cervical plexus

Answer 50

**Somatic** nerve plexus with cutaneous (**sensory**) and **motor** branches Formed by **C1-4 ventral rami** nerves Cutaneous branches **Phrenic nerve** **Ansa cervicalis** **Motor** branches to **prevertebral** **muscles** **Contributions** to accessory nerve Note: hypoglossal and accessory nerves are NOT part of cervical plexus

Question 51

External jugular vein

Answer 51

Descends inferiorly across external surface of **SCM** muscle Drains into **subclavian** vein or junction of internal jugular and subclavian veins

Question 52

Floor of posterior triangle

Answer 52

**Splenius capitis**, **levator scapulae**, **middle** and **anterior scalene muscles** **Brachial plexus** (**supraclavicular** part; **roots/trunks**) is **between** anterior and middle scalene muscles and deep to the clavicle **Subclavian artery** is inferior to brachial plexus roots/trunks **Phrenic nerve** (C3,4,5) goes over **anterior scalene muscle** **Accessory nerve** travels on **levator scapulae** as is dives deep to **trapezius** to innervate it **Transverse cervical artery** (to trapezius) is superior to suprascapular artery and **suprascapular artery** (to supraspinatus) is deep to clavicle; both are branches of **thyrocervical trunk** (which comes off 1st part of subclavian artery) **Prevertebral fascia** covers structures on floor of posterior triangle