Fascia and compartments of the shoulder PECTORALIS FASCIA · -Brachialis-Coracobrachialis-Median...

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Muscles, Innervation and the Compartments of the Upper Limb Organized in an Unintentionally Difficult Manner

Fascia and compartments of the shoulder

PECTORALIS FASCIA - The only contents is Pectoralis Major; - Pectoralis fascia continue inferiorly as fascia of the anterior abdominal wall - It continues laterally-once it leaves the lateral edge of Pectoralis Major, it becomes AXILLARY FASCIA

AXILLARY FASCIA

- Continuous with the CLAVIPECTORAL FASCIA - Forms the floor of the axilla

CLAVIPECTORAL FASCIA

- Deep to the Pectoralis major muscle, the CLAVIPECTORAL FASCIA invests the subclavius muscle and pectoralis minor. - It forms the costocoracoid membrane above pectoralis minor, and the suspensory ligament of axilla below pectoralis

minor. The suspensory ligament drags the axillary fascia upwards when the arm is raised, forming the actual “pit” of the armpit -

Supraspinous, Infraspinous and Subscapular fascia - The supraspinatus, infraspinatus and subscapularis muscles are contained in their own little fascial compartments

Deltoid Fascia

- The deltoid has its own fascia, continous with the pectoral fascia and infraspinatus fascia - It has numerous fascial septa which separate the fascicles of the deltoid

Clavicle

Subclavius

Axillary fascia

Costocoracoid membrane

Axillary fascia

Pectoralis minor

Suspensory ligament of axilla

Lateral pectoral nerve

Pectoralis major, wrapped

up in pectoralis fascia

Supraspinatus

fascia

Subscapularis

fascia

Infraspinatus fascia

Spine of scapula

Clavicle

Pectoralis fascia

Deltoid fascia

Infraspinatus fascia

Fascial septa

Pectoralis fascia, infraspinatus fascia and deltoid fascia all continue down the arm to form the brachial fascia

and Thoracoacromial artery


Anterior Axioappendicular Muscles of the Shoulder There are 3 distinct groups of shoulder muscles: ANTERIOR AXIOAPPENDICULAR MUSCLES – 4 muscles which move the pectoral girdle POSTERIOR AXIOAPPENDICULAR MUSCLES – 4 muscles which attach the upper lumb to the skeleton of the trunk

SCAPULOHUMERAL MUSCLES – 6 muscles which act on the glenohumeral joint

Anterior Axioappendicular muscles All supplied by stupidly different nerves. No pattern whatsoever.

Pectoralis Major Two heads:

- CLAVICULAR HEAD: lateral pectoral nerve

o Originates from the medial half of the anterior clavicle

- STERNOCOSTAL HEAD: medial pectoral nerve

o Originates from the anterior surface of the sternum, and the first 6 costoclavicular cartilages

o Also originates from the aponeurosis of the external oblique muscle of the abdomen

- INSERTS INTO THE LATERAL LIP OF THE INTERTUBERCULAR GROOVE OF THE HUMERUS

- Its inferior border forms the anterior axillary fold

o Abducts and medially rotates the humerus

o Draws scapula anteriorly and inferiorly by pulling on the humerus

- The heads can act independently:

o Clavicular head alone acts to flex the humerus

o When flexed, the sternocostal head extends it from its flexed position.

Pectoralis Minor medial pectoral nerve

- Originates at the 3rd, 4th and 5th ribs near the costal cartilages

- Inserts into the medial border and superior surface of the coracoid process of scapula

- Its job is to stabilize the scapula by pulling it anteriorly and inferiorly against the chest wall

- It also assists in elevating the ribs when breathing

- All the vessels and nerves to the arm travel under the pectoralis minor.

Subclavius nerve to subclavius

- Originates at the junction of the 1st rib and its costal cartilage - Inserts into the “groove for subclavius” on the inferior surface

of the middle third of the clavicle - Depresses and anchors the clavicle - Protects the subclavian vessels when the clavicle is fractured

Serratus anterior long thoracic nerve - Originates from the lateral surfaces of the first 8 ribs - Inserts into the medial border of scapula - Protracts the scapula, holds it against the chest wall, and

rotates it superiorly (eg when reaching for something up high). THE MAIN PROTRACTOR OF THE SCAPULA

- One of the most powerful muscles in the pectoral girdle. - Its paralysis causes a winged scapula. Also, the arm cannot be

abducted past the horizontal position (the scapula doesn’t rotate upwards anymore)

- If you insert your chest drain BELOW the mid-axillary line, you will cause this sort of paralysis, which is embarrassing.

.

Innervation

Pectoralis Major :

clavicular head

Pectoralis major:

sternocostal head

Intertubercular groove

of the humerus

Pectoralis Minor Subclavius

Serratus Anterior

Long Thoracic Nerve:

Off the roots of C5, 6 and 7

Serratus Anterior

Nerve to Subclavius:

Off the superior trunk

Subclavius

Medial Pectoral nerve:

Branch of the medial cord

Pectoralis Minor; sternocostal head of Pectoralis Major

Lateral Pectoral nerve:

Branch of the lateral cord

clavicular head of Pectoralis Major


Posterior Axioappendicular Muscles of the Shoulder: the Extrinsic Group There are 2 layers, the superficial and the deep. The superficial group is trapezius and latissimus dorsi The deep group is the levator scapulae and the rhomboids

Posterior Axioappendicular Extrinsic Muscles Also supplied by confusingly different nerves.

Trapezius spinal accessory nerve - Originates from

o The external occipital protuberance

o Nuchal ligament o Medial third of superior nuchal line

o Spinous processes of C spine and T-spine

o he medial half of the anterior clavicle

- Inserts into : o Lateral third of the clavicle

o Acromion of scapula

o Spine of scapula

- Has 3 distinct parts: SUPERIOR (descending)part which elevates

the scapula

MIDDLE part which retracts the scapula

INFERIOR (ascending) part which depresses the scapula

All the parts together act to rotate the scapula superiorly, so the glenoid fossa faces up.

Latissimus dorsi Thoracodorsal nerve

- Originates from

o Inferior 6 thoracic vertebrae o Thoracolumbar fascia o Iliac crest o Inferior 3 or 4 ribs

- Inserts into the ANTERIOR surface of the humerus, at the floor of the intertubrercular groove

- Extends, adducts, medially rotates the humerus

- Lifts the body up too the arms when climbing

Levator scapulae dorsal scapular and cervical nerves

- Originates at the posterior tubercles of the spinous processes of the C1, 2, 3 and 4 vertebrae

- Inserts into the medial border of scapula, superior to the spine - Elevates that corner of the scapula, rotating it so the glenoid

cavity faces down - Extends the neck (when acting bilaterally) or flexes it laterally

(when acting unilaterally)

Rhomboid Minor dorsal scapular nerve - Originates from the nuchal ligament and the spinous processes

of C7 and T1 - Inserts into the medial border of the scapula, at the root of the

scapular spine - Retracts the scapula - Rotates the scapula so the glenoid cavity faces down - Fixes the scapula to the thoracic wall

Rhomboid Major dorsal scapular nerve

- Originates from the spinous processes of T2,3 4and 5 - Inserts into the medial border of the scapula, from the root of

spine down. - Retracts the scapula - Rotates the scapula so the glenoid cavity faces down - Fixes the scapula to the thoracic wall

.

Viewed from above

Floor of the intertubercular

groove, anteriorly on the

humerus

Superior part of

Trapesius

Middle part of

Trapesius

Middle part of

Trapesius

T7

Latissimus dorsi

Innervation

Levator scapulae

Rhomboid Minor

Rhomboid Major

Dorsal scapular nerve:

Off the roots of C5

Rhomboid major and minor Levator scapulae

Thoracodorsal Nerve:

Off the posterior cord

Latissimus dorsi


Posterior Axioappendicular Muscles of the Shoulder: the Intrinsic Group with Rotator Cuff muscles These are the deltoid and teres major; and the 4 rotator cuff muscles (teres minor, supraspinatus, infraspinatus and subscapularis)

Posterior Axioappendicular Intrinsic muscles Again, supplied by totally different nerves.

Deltoid axillary nerve

- Originates from the lateral third of the clavicle, the acromion, and the lateral spine of scapula.

- Inserts into the deltoid tuberosity of humerus - THREE PARTS:

o Anterior part flexes and medially rotates the humerus

o Middle part abducts the humerus o Posterior part extends and laterally rotates the

arm o The middle part is multipennate; the others are

unipennate - It cannot initiate abduction on its own when the arm is fully

adducted- thus it needs supraspinatus to initiate the movement. It becomes effective after about 15 degrees of abduction.

- The deltoid’s anterior and posterior parts swing your arms while walking.it also helps to keep the humeral head in the glenoid fossa.

Teres major lower subscapular nerve

- Originates from the posterior surface of the inferior angle of scapula

- Inserts into the medial lip of the intertubercular groove of humerus

- Adducts and medially rotates the arm - Also keeps the head of humerus in the socket

Rotator Cuff Muscles Whatever other actions they may have, they all help hold the humeral head in the glenoid fossa

Supraspinatus suprascapular nerve - Originates in the supraspinous fossa of the scapula - Inserts into the superior facet of the greater tubercle of

humerus - Initiates abduction, and assists the deltoid with abduction of

the arm; its the only one that doesn't rotate the arm.

Infraspinatus suprascapular nerve - Originates in the infraspinous fossa of the scapula - Inserts into the middle facet of the greater tubercle of

humerus - Laterally rotates the arm

Teres Minor axillary nerve

- Originates from the middle of the lateral border of scapula - Inserts into the inferior facet of the greater tubercle of

humerus - Laterally rotates the arm

Subscapularis upper and lower subscapular nerves - Originates in the subscapular fossa - Inserts into the lesser tubercle of humerus - Medially rotates and abducts the arm

.

Innervation

Deltoid

Supraspinatus

Subscapularis

Teres Major

Iinsertion of deltoid, at the

Deltoid Tuberosity

Infraspinatus

Teres Minor

Deltoid

Supraspinatus

Subscapularis

Deltoid

Infraspinatus

Teres Major Teres Minor

Teres Major

Axillary nerve:

Off the posterior cord

Teres Minor Deltoid

Upper Subscapular nerve

Subscapularis Lower Subscapular nerve

Subscapularis Teres major

Suprascapular nerve

Supraspinatus Infraspinatus


Muscles and Nerves involved in the movements of the shoulder joint

flexion: pectoralis major (clavicular head) – medial and lateral pectoral nerve deltoid (anterior part) – axillary nerve coracobrachialis – musculocutaneous nerve biceps femoris– musculocutaneous nerve

extension: deltoid (posterior part) – axillary nerve teres major– lower subscapular nerve

abduction: deltoid (central part) – axillary nerve supraspinatus– suprascapular nerve

adduction: pectoralis major – medial and lateral pectoral nerve

latissimus dorsi – thoracodorsal nerve

subscapularis - upper and lower subscapular nerve

infraspinatus – suprascapular nerve

teres minor– axillary nerve

medial rotation: subscapularis

pectoralis major –medial and lateral pectoral nerve

deltoid (anterior part) – axillary nerve

latissimus dorsi – thoracodorsal nerve

lateral rotation: infraspinatus – suprascapular nerve long head of triceps – radial nerve coracobrachialis – musculocutaneous nerve short head of biceps – musculocutaneous nerve


Fascia and compartments of the proximal arm

Posterior Compartment: EXTENSORS

- Triceps Brachii - Anconeus

- Radial nerve - Deep artery of the arm (profunda brachii)

(A branch of the brachial artery)

- Superior ulnar collateral artery

- Ulnar nerve as depicted here is in the posterior

compartment; it travels anteriorly to the medial intermuscular septum, until it pierces it about half-way down the humerus, together with the superior ulnar collateral artery

Anterior Compartment: FLEXORS

- Biceps Brachii - Brachialis - Coracobrachialis - Median nerve - Musculocutaneous nerve

The medial cutaneous nerve of forearm is not inside

the fascial sheath, but is still important enough to warrant a brief mention.

- The Basilic vein and the Cephalic vein are usually superficial to the fascial planes

.

Brachial Fascia - Encloses the upper arm like a sleeve - Superiorly, it is continuous with the deltoid fascia,

infraspinatus fascia and pectoralis fascia - Inferiorly, it is attached to the epicondyles of the

humerus and the olecranon of ulna - It is continuous with the antebrachial fascia – the

fascia of the forearm o It contains two SEPTA: the MEDIAL and

LATERAL INTERMUSCULAR SEPTA. o The septa are attached to the supracondylar

ridges and to the shaft of humerus o They separate the arm into the

ANTERIOR COMPARTMENT and the POSTERIOR COMPARTMENT

Section at a level just short of half-way along the humeris

Anterior compartment

Posterior compartment

Medial intermuscular septum

Lateral intermuscular septum

Deltoid:

Not actually a part of the anterior

compartment, as it has its own

fascial compartment.

Lateral

intermuscular

septum

Cephalic vein Biceps brachii

Triceps brachii

Musculocutaneous nerve

Median nerve

Basilic vein

Brachial artery

Coracobrachialis

Brachialis

Medial

intermuscular

septum

Supplied by the MUSCULOCUTANEOUS NERVE

Ulnar nerve

Radial nerve

Superior ulnar collateral artery

Deep artery of the arm Lateral intermuscular septum

Supplied by the RADIAL NERVE

Medial intermuscular septum

Medial cutaneous

nerve of forearm


The innervation and mechanics of the flexor and extensor muscle compartments of the arm

Anterior Compartment: FLEXORS All supplied by the MUSCULOCUTANEOUS NERVE

Biceps Brachii Two heads:

- SHORT HEAD: o The medial head. o Originates from the tip of the coracoid process

- LONG HEAD: o The lateral head. o Originates from the supraglenoid tubercle of the

glenoid fossa

- The biceps inserts into the tuberosity of radius; and it also inserts into the antebrachial fascia by virtue of the bicipital aponeurosis.

- It does very different things depending on what position the arm is in:

o It supinates the forearm by pulling on the aponeurosis, when the arm is pronated; it is the MOST POWERFUL SUPINATOR of the forearm

o when the forearm is supine if FLEXES the elbow joint by pulling on the attachment to the radial tuberosity.

o It is useless as a flexor when the forearm is pronated. - The short head resists dislocation of the shoulder

Coracobrachialis

- Originates at the tip of the coracoid process of scapula

- Inserts into the middle third of the medial humerus

- Helps flex and adduct the arm

- Resists dislocation of the shoulder: it’s a SHUNT muscle, it resists the downward dislocation of the humeral head

- Stabilizes the glenohumeral goint - A landmark – it is pierced by the musculocutaneous nerve

Brachialis - Originates from the distal half of the anterior humerus

- Inserts into the tuberosity of the ulna, and the coronoid process

- Flexes the forearm in all positions – it’s the PRIMARY FLEXOR

-

- .

Posterior Compartment: EXTENSORS

All supplied by the RADIAL NERVE Triceps Brachii

- LONG HEAD: o Originates from the infraglenoid tubercle

- LATERAL HEAD: o Originates from the proximal humerus, more

proximal than the radial groove

- MEDIAL HEAD: o Originates from the posterior surface of the humerus,

distal to the radial groove

The united triceps inserts into the olecranon of ulna It is the chief extensor of the arm. The long head resists dislocation of the head of humerus, especially during abduction

Anconeus - Originates from the posterior lateral epicondyle of humerus

- Inserts into the lateral surface of olecranon

- Assists the triceps in flexing the forearm, and stabilizes the elbow joint. It also pulls the joint capsule out of the way of the olecranon upon extension; otherwise it would get pinched in the olecranon fossa . Many anatomists believe it to be a vestigial and forgotten 4th head of the triceps.

Coracobrachialis

Tip of the coracoid

process

Transverse

humeral

ligament

Supraglenoid tubercle

ligament

Biceps Brachii

Brachialis

Short head

Long head

Bicipital aponeurosis

Coronoid process and

the tuberosity of ulna

Tuberosity of radius

Long head of triceps

Medial head of triceps

Lateral head

of triceps

Anconeus

Infraglenoid tubercle

Some of the brachialis is

innervated by the radial nerve-

the half that is posterior to the

insertion of deltoid


Fascia and compartments of the distal arm

Section at the junction of distal third and proximal two thirds of the humerus

Section at the level of the humeral epicondyles

Superior ulnar collateral artery

Ulnar nerve

Deep artery of the arm

Radial nerve

Triceps brachii

Long

head

Medial

head Lateral

head

Cephalic vein

Biceps brachii

Musculocutaneous nerve

Median nerve

Basilic vein

Brachial artery

Coracobrachialis

Medial cutaneous nerve

of forearm which arises

from the MEDIAL CORD of the

brachial plexus

Posterior cutaneous nerve of

forearm which has just branched off

from the RADIAL nerve

Lateral cutaneous nerve of

forearm which has just branched off

from the MUSCULOCUTANEOUS nerve

Brachialis

Brachialis

Biceps brachii

Basilic vein

Cephalic vein

Radial nerve which has pierced the

lateral intermuscular septum a little while

ago, and now travels between brachialis

and brachioradialis

Brachial artery

Median nerve

Ulnar nerve

Triceps Brachii tendon Anconeus Which is unimportant, and arguably useless. In fact some anatomists believe it to a rudimentary 4th

triceps head. If it were missing, you would likely not notice.

Brachioradialis which is important for

a number of reasons: - Forms the lateral border

of the cubital fossa

- Innervated by the RADIAL NERVE

- Flexes the forearm, unlike

the rest of the forearm extensor

compartment

- Together with the Supinator, they

are the only extensor compartment

muscles which do not cross the wrist

and cause no movement there

PRONATOR TERES


Fascia and compartments around the cubital fossa and distal forearm

Antebrachial Fascia - Extension of the brachial fascia - Also envelops the forearm like a sleeve - There are no “intermuscular” septa per se; the

muscles are all invested in their own fascia; however there are still two recogniseable compartments: the FLEXOR compartment and the EXTENSOR compartment.

Section at the level of the neck of radius Basilic vein

Cephalic vein

In 20% of people, the basilic vein branches off into a

“median basilic” vein, and when it joins the median

cephalic vein they form a clear “M”.

Median cubital vein

Cephalic vein Median antebrachial vein

Basilic vein

Highly variable tributaries

Neck of

Radius

ULNA

COMPARTMENTS IN THIS SECTION are not clear-cut or sensible.

- This is an intersection of several compartments. The EXTENSOR compartment of the forearm is anterolateral, represented by brachioradialis, extensor carpi radialis longus and brevis, and extensor digitorum. The FLEXOR compartment is posteromedial and represented by pronator teres, palmaris longus, flexor carpi ulnaris, and flexor digitorum profundus and superficialis. The ANTERIOR compartment of the arm is represented by the biceps tendon, and by brachialis.

- Anconeus is a lonely representative of the POSTERIOR compartment.

The BICEPS TENDON: one part blends with the antebrachial fascia;

The other part dives deep to attach to the radial tuberosity Brachial artery which bifurcates at the level

of the radial head in the cubital fossa

Pronator teres which originates proximally to

the medial epicondyle, and forms the medial border

of the cubital fossa

The Flexors of the forearm which originate

at the Common Flexor origin, at the medial

epicondyle of the humerus

Brachioradialis Which forms the lateral

border of the cubital fossa

Brachialis

Brachialis

Biceps tendon

Extensor Carpi Radialis

Longus and Brevis

Extensor Digitorum

Anconeus

Brachioradialis

Radial artery

Ulnar artery Daughters of the recently

bifurcated Brachial Artery

BrR

ECRL, B

ED

Superficial branch of the

radial nerve which travels

under brachioradialis down the

arm, where it supplies sensation

to the dorsum of the hand

Deep branch of the Radial Nerve which

will pierce the Supinator, penetrate the

interosseous membrane and become the

Posterior Interosseous Nerve

The branches of the Radial Nerve

Median nerve which travels between the heads of P. teres

Pronator Teres

Palmaris Longus

Annular Ligament

Flexor Carpi Ulnaris which is fully

innervated by the ulnar nerve, unlike the

rest of the flexors

Flexor Digitorum Superficialis

(humeral head)

Flexor Carpi Radialis

Flexor Digitorum Profundis Half of which is innervated by the ulnar nerve, unlike the rest

of the flexors (which are all supplied by the Median nerve)

Ulnar nerve, which runs between the two

heads of flexor carpii ulnaris

THERE ARE 17 MUSCLES CROSSING THE ELBOW JOINT.


Fascia and compartments of the middle forearm

Boundaries of the compartments:

Section at the level of the mid-forearm

FLEXOR COMPARTMENT This is the beefier compartment; twice as fat as the extensor compartment

4 layers of muscles:

EXTENSOR COMPARTMENT

Medial border: subcutaneous ulna

Interosseous membrane

Lateral border: radial artery

Flexor carpi radialis

Flexor

digitorum

superficialis

Median nerve

Palmaris Longus

Flexor carpi ulnaris

(ulnar nerve)

Flexor Pollicis

Longus

Flexor

digitorum

profundus

Anterior

Interosseous

Artery

Anterior Interosseous Nerve

Ulnar Nerve

Ulnar Artery

Medial cutaneous nerve of forearm

LAYER 1: pronator teres(not

shown, too proximal)


Palmaris longus

Flexor carpi ulnaris

LAYER 2: Flexor digitorum

superficialis

LAYER 3:Flexor pollicis longus

Flexor digitorum

profundis

LAYER 4:Pronator Quadratus

(not shown, too distal)

Brachioradialis

Radial artery

Superficial branch of the radial nerve

Extensor pollicis Brevis

Extensor carpi

radialis brevis

Lateral cutaneous

nerve of the forearm

Extensor carpi

radialis longus Supinator

Extensor digitorum

Abductor pollicis longus

Extensor pollicis Longus

Extensor carpi ulnaris

Extensor indices

Posterior interosseous nerve

Posterior interosseous artery

Half of the Flexor Digitorum Profundus which is

innervated by the ulnar nerve, unlike the rest of the

flexors (which are all supplied by the Median nerve

Muscles of a similar purpose are grouped together in compartments. The EXTENSORS are posteromedial, and the FLEXORS are anterolateral. They spiral round the arm and eventually the flexors become truly anterior and the extensors become truly posterior.

- Functionally, the forearm includes the distal humerus because the muscles that attach at the supracondylar ridges and the epicondyles stretch along the forearm to move the wrist and fingers.

BOUNDARIES OF THE COMPARTMENTS POSTERIORLY (proximal forearm) and MEDIALLY (distal forearm), the

subcutaneous border of the ulna ANTERIORLY (proximal forearm) and then LATERALLY (distal forearm),

the radial artery

Because neither of these boundaries

is crossed by motor nerves they are

used for surgical incisions

The border between layers 1-2 and layers 3-4 is the primary

neurovascular plane of the anterior compartment: the

neurovascular bundles exclusive to this compartment travel within it


The Flexor Compartment of the Forearm

The flexor compartment has 4 discrete layers:

LAYER 1: All of these, except the ulnar head of pronator quadratus, attach to the medial humeral epicondyle at the COMMON FLEXOR ORIGIN

- PRONATOR TERES o Forms the medial border of the cubital fossa; it’s the most lateral of the first layer of muscles o Has an ulnar head and a humeral head o The humeral head originates from the COMMON FLEXOR ORIGIN o The ulnar head originates from the coronoid process o Pronates and flexes the elbow

- FLEXOR CARPI RADIALIS o Originates from the COMMON FLEXOR ORIGIN o Inserts into the base of the 2nd metacarpal o Flexes and abducts the wrist o About half-way down the forearm, its belly is replaced

by a flat tendon which becomes cord-like at the wrist o It travels in the lateral carpal tunnel inside its own

synovial sheath (it doesn’t share) o The radial artery is just lateral to this tendon

- PALMARIS LONGUS o Originates from the COMMON FLEXOR ORIGIN o Inserts into the distal flexor retinaculum, and palmar aponeurosis. o Flexes and abducts the wrist, tenses the palmar aponeurosis o Its actually absent in 14% of people (usually on the left side). Those people don’t miss it being gone. o The tendon of palmaris longus is a marker for where the median nerve is – the tendon passes medially

to it, and then deep to it in the flexor retinaculum

- FLEXOR CARPI ULNARIS o Has an ulnar and a humeral head o Humeral head originates from the COMMON FLEXOR ORIGIN; Ulnar head originates from the

olecranon, and posterior border of ulna o Inserts into the pisiform, hook of hamate and the 5th metacarpal. o Flexes and abducts the wrist; has its own synovial sheath o The tendon of flexor carpi ulnaris is a marker for the ulnar artery, which passes laterally to it at the wrist

LAYER 2

- FLEXOR DIGITORUM SUPERFICIALIS o The fast flexor of the fingers. Has two heads: humeroulnar head and radial head o The humeroulnar head originates from BOTH the COMMON FLEXOR ORIGIN and the coronoid process

of ulna; the radial head originates the proximal half of the radius o It inserts into shafts of the middle phalanges o It flexes the metacarpophalangeal joints and the proximal interphalangeal joints; it can flex each joint

independently of the others. o Its tendons are enclosed in the COMMON FLEXOR SHEATH together with the tendons of flexor

digitorum profundus

LAYER 3 - FLEXOR DIGITORUM PROFUNDUS

o The slow flexor of the fingers o Originates from the interosseous membrane, and from the proximal three quarters of the anterior surface

of the ulna. It has two parts: medial and lateral parts; o The medial part is innervated by the ulnar nerve o The medial part flexes the distal interphalangeal joints of the 4th and 5th digits o The lateral part flexes the distal interphalangeal joints of the 2nd and 3rd digits o All parts can flex the wrist joint as well as the fingers o The lateral part is innervated by the ANTERIOR INTEROSSEOUS NERVE (a branch of the median

nerve). o The tendon to the index finger tends to separate early; it’s the only one which can operate independently.

Unlike the flexor digitorum superficialis, the profundus flexes all the DIPs together.

- FLEXOR POLLICIS LONGUS o Originates from the anterior surface of the radius and the nearby interosseous membrane o Inserts into the base of the distal phalanx of thumb. It has its own synovial sheal in the carpal tunnel o Also innervated by the ANTERIOR INTEROSSEOUS NERVE o It flexes the phalanges of the thumb; mainly the distal interphalangeal joint (it’s the only muscle that

flexes the DIP of the thumb)

LAYER 4 - PRONATOR QUADRATUS

o It originates from the distal quarter of the ulna, and inserts into the distal quarter of the radius o It is innervated by the ANTERIOR INTEROSSEOUS NERVE o It pronates the forearm (it’s the PRIMARY PRONATOR of the forearm) and its fibers hold the radius and

ulna together. When speed is needed, it is assisted by the Pronator Teres.

All supplied by the MEDIAN NERVE, …except:

Flexor Digitorum Profundis, ulnar half

Flexor Carpi Ulnaris, whole

Ulnar nerve

Ulnar nerve

Median nerve: mainly Layers 1 and 2 - Pronator teres - Flexor carpi radialis - Palmaris longus - Flexor digitorum superficialis

Anterior Interosseous nerve: mainly layer 3 - Flexor digitorum profundus, lateral half - Flexor pollicis longus - Pronator quadratus

Ulnar nerve: - flexor digitorum profundus, medial half - flexor carpi ulnaris

Pronator teres

Humeral head

Ulnar head is

hidden, but it

originates from

the coronoid

process

COMMON FLEXOR ORIGIN:

Pronator teres, humeral head


Palmaris longus

Flexor carpi ulnaris, humeral head

Flexor digitorum superficialis, humeral head

Flexor carpi

radialis

The belly is

replaced by

a flat tendon

which

becomes

cord- like at

the wrist

Palmaris Longus

Flexor carpi Ulnaris

Two heads, one originating

from the humerus, the

other from the olecranon

Inserts into the Pisiform

Hook of hamate

Base of the 5th metacarpal

Median nerve

Lateral to the

palmaris

longus tendon

Radial

Artery

Lateral to the

flexor carpi

radialis

tendon

Flexor digitorum superficialis

Humeroulnar head

(common flexor origin and the

coronoid process)

Radial head

Flexor pollicis longus

Flexor digitorum

profundus:

Supplied by

MEDIAN NERVE

ULNAR NERVE

Pronator Quadratus

The flexors digitorum profundus and

superficialis are WEAKER when the

wrist is flexed, the tendons aren’t tense


Extensor Compartment of the Forearm: Superficial layer

SUPERFICIAL LAYER OF EXTENSORS two originate from the supracondylar ridge as well as the adjacent

intermuscular septum:

Brachioradialis o radial nerve o Inserts at the lateral surface of the distal end of the radius o Flexes the forearm, in a feeble way, and mostly when the forearm

is pronated; it also acts as a shunt muscle to prevent subluxation of the head of radius. its most active in quick movements, and in movement against resistance.

o Forms the lateral border of the cubital fossa o under it run the radial nerve and the radial artery o Distally, its tendon is covered by the tendons of Abductor Pollicis

Longus and Extensor Pollicis Brevis.

Extensor Carpi Radialis Longus o radial nerve o Inserts at the dorsum of the 2nd metacarpal, at the base o extends and abducts the hand at the wrist o probably more involved in abduction than the ECRB o it is crucial in the clenching of the closed fist.

Four originate from the common extensor origin, at the lateral epicondyle of the humerus

Extensor Carpi Radialis Brevis o deep branch of radial nerve o Inserts into the dorsum of the 3rd metacarpal at the base o extends and abducts the hand at the wrist o it is covered by the Extensor Carpi Radialis Longus o They also share the same extensor tendon sheath at the wrist o the brevis is more involved in extension than the longus

Extensor Digitorum o posterior interosseous nerve which is really the continuation of

the deep branch of the radial nerve o inserts at the extensor expansions of the fingers o THE EXTENSOR EXPANSIONS are triangular aponeuroses

which wrap around the metacarpal head, and the proximal phalanx. They are united with the insertions of the lumbricals and the interosseous muscles.

o The tendons thus divide into a median band which passes to the base of the middle phalanx, and two lateral bands which insert at the base of the distal phalanx.

o Extends the fingers, primarily at the metacarpophalangeal joint; secondarily at the distal interphalangeal joint.

o Occupies a lot of space in the extensor compartment o Shares an extensor tendon sheath with the Extensor Indicis o Just proximally to the metacarpophalangeal joints, the

tendons are linked by intertendinous connections which prevent the fingers from being independently extended; thus you can never fully extend a finger while the others remain flexed. This is most true of the ring finger.

Extensor Digiti Minimi o posterior interosseous nerve o Divides into two tendons- the lateral one joins the pinky tendon of

the extensor digitorum, and then together with the medial one all three insert into the extensor expansion of the pinky finger.

o extends the pinky, primarily at the metacarpophalangeal joint; secondarily at the distal interphalangeal joint.

o this is really just a detached part of the extensor digitorum o However, it has its own tendon sheath

Extensor Carpi Ulnaris o posterior interosseous nerve o yes it does originate at the common extensor origin; thats the

humeral head. There is also an ulnar head, which originates at the ulnar border posteriorly, via an aponeurosis. This origin is also shared with the Flexor Digitorum profundis and the Flexor Carpi Ulnaris.

o inserts at the dorsum of the base of 5th metacarpal o extends the hand at the wrist joint, and abducts it o It has its own tendinous sheath at the wrist o It is also crucial to the formation of the closed fist

All extend the forearm, wrist or fingers – EXCEPT BRACHIORADIALIS Brachioradialis is the solitary exception: it is in the extensor compartment, but it flexes the forearm.

It is the only flexor innervated by the radial nerve.

All supplied by the RADIAL NERVE, or some branch thereof

two layers: the SUPERFICIAL and DEEP

Brachioradialis

Extensor Carpi

Radialis Longus

Extensor Carpi

Radialis Brevis which

lies under the Extensor

Carpi Radialis Longus

Brachioradialis tendon

which lies under

the tendons of

Abductor Pollicis Longus

and

Extensor Pollicis Brevis

Common extensor origin

The Insertions of the Extensors

Carpi Radialis tendons:

Bases of the metacarpals

Longus inserts into the 2nd

Brevis inserts into the 3rd

The common tendon

sheath of th extensors

carpi radialis: both travel

within the same sheath

Extensor Carpi Ulnaris

Extensor Digiti Minimi

The Tendon of Extensor

Digit Minimi divides into

two tendons; the lateral

one joins the extensor

digitorum tendon to the

little finger

Extensor Digitorum

The fattest muscle here

Tendon sheaths:

Extensor carpi ulnaris

has its own; and so

does extensor digiti

minimi. The extensor

digitorum shares a

sheath with the tendon

of Extensor Indicis

Intertendinous connections which

unite the extensor digitorum

tendons and prevent the digits from

extending independently


Extensor Compartment of the Forearm: Deep layer

DEEP LAYER OF EXTENSORS "true" deep layer

Supinator o deep branch of radial nerve which pierces it on its way

to transforming into the posterior interosseous nerve o originates from everywhere... the lateral humeral

epicondyle, the radial collateral ligament, the annular ligament, the supinator fossa and the crest of ulna

o inserts into the lateral posterior and anterior surfaces of the proximal third of radius

o it supinates the forearm, turning the arm to face anteriorly and superiorly when the forearm is flexed. It is the PRIME MOVER for slow unopposed suination

o The supinator forms the floor of the cubital fossa together with brachialis. It is a sheet-like muscle, and it envelops the radius.

Extensor Indicis o Posterior interosseous nerve o originates from the posterior surface of the distal third of

the ulna, and the interosseous membrane o inserts into the extensor expansion of the index finger o extends the index finger, enabling independent extension o helps extend the hand at the wrist

"outcropping" deep layer these originate from the proximal, middle and distal thirds of the ulna (as a generalization). They emerge in the surface in the furrow that forms in the extensor compartment

Abductor Pollicis Longus o Posterior interosseous nerve o originates from the posterior surface of the proximal

radius and ulna, as well as the interosseous membrane o inserts into the base of the 1st metacarpal, and

occasionally also the trapezium. o abducts and extends the thumb at the carpometacarpal

joint o shares a common tendon sheath with the extensor

pollicis brevis at the wrist

Extensor Pollicis Brevis o Posterior interosseous nerve o originates from the posterior surface of the distal third of

the ulna, and the interosseous membrane o inserts into the dorsum of the base of the proximal

phalanx of the thumb o extends the proximal phalanx of the thumb at the

metacarpophalangeal joint; also extends the carpometacarpal joints of the thumb.

o partly covered by the abductor pollicis longus o its tendon is immediately medial to the APL o these two tendons form the anterior boundary of the

anatomical snuffbox.

Extensor Pollicis Longus o Posterior interosseous nerve o originates from the posterior surface of the middle third

of the ulna, and the interosseous membrane o inserts into the dorsum of the base of the distal phalanx

of the thumb o extends the distal phalanx of the thumb; also extends

the metacarpophalangeal and the carpometacarpal joints of the thumb. It also rotates the thumb laterally.

o It enjoys its own tendon sheath at the wrist; it passes medially over the dorsal tubercle of radius, using it as a pulley.

o the EPL forms the posterior border of the anatomical snuffbox

Supinator

Attachments of the Supinator to the

Epicondyle of humerus

Radial collateral ligament

Annular ligament of radius

Ulnar Supinator crest and fossa

Ulnar posterior surface

Abductor pollicis longus

Extensor Pollicis Longus


Interosseous membrane

Extensor Indices

Which shares an extensor

tendon sheath with the

Extensor Digitorum tendon

Common sheath for the

tendons of the extensor

pollicis brevis and abductor

pollicis longus

APL inserts into the base of 1st metacarpal

EPB inserts into the base of proximal phalanx

EPL inserts into the base of distal phalanx

the Supinator wraps around the

radius to insert into the anterior

surface of it. Together with the

brachialis it forms the floor of

the cubital fossa

Extensor digitorum tendon

Extensor expansion

Medial band attaches to the base of

the middle phalanx

Lateral bands attach to the

base of the distal phalanx

The hood which attaches to the palmar tendon


Flexor and Extensor Tendons at the Wrist: level of the Distal Radioulnar Joint

- attaches

Palmaris Longus

Ready to merge with the

palmar aponeurosis

Median Nerve

Ulnar Artery

Ulnar nerve

Flexor Carpi Ulnaris can cover the ulnar

artery and obscure its pulsation


Flexor Pollicis Longus

Radial Artery



Extensor Carpi Radialis Longus

Extensor Carpi Radialis Brevis


Extensor Indices

Extensor Digitorum

Extensor Digiti Minimi


Flexor Digitorum Superficialis

Flexor Digitorum Profundus

RRAADDIIUUSS

UULLNNAA

The Extensor Retinaculum - Attaches to the lateral border of the radius - Does NOT attach to the border of the ulna, because the ulna moves too much. - Instead, attaches to the pisiform and the triquetrum - Also attaches to the ridges of the radius, thus forming osseofibrous tunnels for the above tendons to run

through - There are 6 tunnels in total:

1. One for abductor pollicis longus and extensor pollicis brevis 2. One for extensor carpi radialis longus and extensor carpi radialis brevis 3. One for extensor pollicis longus 4. One for extensor digitorum and extensor indices 5. One for extensor digiti minimi 6. One for extensor carpi ulnaris


The Flexor retinaculum is stretched between four

bony posts:

1) Hook of hamate

2) Pisiform bone

3) Tuberosity of scaphoid

4) Tuberosity of trapezium

The Carpal Tunnel and its Contents

Radial Artery

Crossing over to the

dorsum of the hand



Extensor Carpi Radialis Longus

Extensor Carpi Radialis Brevis


Extensor Digiti minimi

Palmaris Longus

Thenar muscles

Hypothenar muscles

Extensor Digitorum Extensor Indices


TRAPEZIUM

TRAPEZOID

CAPITATE

HAMATE

Ulnar Artery

Ulnar Nerve

Flexor retinaculum Median Nerve

Flexor Digitorum Profundus

Flexor Digitorum

Superficialis


Flexor Pollicis Longus

Hook of Hamate Tuberosity of

Trapezium

Tuberosity

of Scaphoid

Pisiform

This is a narrow enclosed space. Needless to say, if anything in here swells, the median nerve will get compressed. It is the most sensitive structure in the carpal tunnel.

- The lateral three and a half digits will get diminished sensation - Sensation on the thenar eminence will be spared because the palmar cutaneous branch splits

from the median nerve long before the flexor retinaculum - The movement of the thenar muscles is controlled by a terminal motor branch of the median nerve,

and so the thenar muscles will atrophy in carpal tunnel syndrome


A Summary of the Innervation of the Extensors and Flexors of the Forearm

Extensors All innervated by branches of the RADIAL NERVE Radial nerve itself: innervates muscles with attachments proximal to

the cubital fossa - Brachioradialis - Extensor Carpi Radialis Longus - Both of these originate at the supracondylar ridge

Deep branch of the radial nerve: a branch which splits off from

the radial nerve at the level of the humeral condyle in the cubital fossa; it pierces the supinator muscle, and becomes the posterior interosseous nerve

- Extensor Carpi Radialis Brevis - Supinator

Posterior interosseous nerve: travels along the posterior aspect

of the interosseous membrane; innervates most of the extensor muscles

- Extensor digitorum - Extensor Indicis - Extensor Digiti minimi - Extensor Carpi Ulnaris - Extensor Pollicis Longus - Extensor Pollicis Brevis - Abductor Pollicis Longus

Flexors Innervated by either the ULNAR or the MEDIAN nerves

Median nerve itself: - Pronator Teres - Palmaris Longus - Flexor carpi Radialis - Flexor Digitorum Superficialis

Anterior interosseous nerve, a branch of the median nerve:

- Flexor Digitorum Profundus - lateral half - Flexor Pollicis Longus - Pronator Quadratus

Ulnar nerve: - Flexor Digitorum profundus, only the medial half - Flexor Carpi Ulnaris

Deep branch of

the radial nerve

is in pink

Radial nerve is in red

Posterior interosseous nerve is in green

Ulnar nerve :

Innervates the muscles

directly adjacent to it along

its course down the arm

Median nerve:

Innervates mainly the 1st

and 2nd layer of flexors

Anterior Inerosseous

nerve: innervates the 3

deepest muscles


Fascia, Septa, Tendon Sheaths and the Potential Spaces of the Hand

These fascial layers are continuous with the fascial sleeve of the forearm. Centrally the fascia of the palm thickens in the centre, where the palmaris longs tendon attaches to it, which is also where it merges with the flexor retinaculum. This whole thickened area is called the palmar aponeurosis. Distally, the palmar aponeurosis divides into four bands which attach to the bases of the proximal phalanges, and there it becomes a part of the digital sheaths

Palmaris Longus tendon

Antebrachial Fascia

Flexor retinaculum

All merge into the

Palmar Aponeurosis

Palmar Aponeurosis so thick and tough that any infections

in the palmar spaces will actually

cause the weaker DORSAL fascia to

bulge out.

In Dupuytren’s contracture, the

palmar aponeurosis becomes nodular,

fibrosed, and thickened

Thenar fascia

Hypothenar fascia

Palmar Aponeurosis

Lateral fibrous septum of the palm which stretches from the palmar

aponeurosis to the 3rd metacarpal

Medial fibrous septum of

the palm which stretches from the palmar

aponeurosis to the 5th metacarpal

The Thenar Space

Of the two septa, the LATERAL is the strongest

The Midpalmar Space Unlike the thenar

space, this one is

continuous with the

anterior compartment

of the forearm- it

communicates with it

via the carpal tunnel.

Common flexor sheath: FDS and FDP

The common flexor sheath continues to the

5th digit. The other digits have their own

Digital Synovial Sheaths

Digital Synovial Sheaths

Synovial sheath for Flexor

Pollicis Longus

Synovial sheath for Flexor

Carpi Radialis


Compartments of the palm and their contents

Thenar compartment Contains the thenar muscles

Central compartment Contains the flexor tendons and their sheaths, the lumbricals, the superficial arterial palmar arch, and the digital vessels and nerves Hypothenar compartment Contains the hypothenar muscles

Adductor compartment Contains only Adductor Pollicis

Interosseous compartments Contains the interossei muscles

Flexor Pollicis Brevis: Superficial head

which is innervated by the MEDIAN NERVE

Deep Head which is innervated by the

DEEP BRANCH OF THE ULNAR NERVE

Abductor Pollicis Brevis

Opponens Pollicis

1st Dorsal Interoissei

2nd Dorsal Interoissei

3rd Dorsal Interoissei

4th Dorsal Interoissei

1st Palmar Interoissei 2nd Palmar Interoissei

3rd Palmar Interoissei

Abductor Digiti Minimi

Flexor Digiti Minimi Brevis

Opponens Digiti Minimi

1st and 2nd Lumbricals which are unipennate and which are

innervated by the MEDIAN NERVE 3rd and 4th Lumbricals which are bipennate and which are

innervated by the DEEP BRANCH OF THE ULNAR NERVE

Adductor Pollicis

Thenar Compartment

Adductor compartment

Interosseous compartment

Hypothenar

Compartment

Central

Compartment


Thenar and Hypothenar muscles There are 3 Thenar muscles, 3 Hypothenar muscles, 1 Adductor muscle, 4 Lumbricals, 4 dorsal interossei and 3 palmar interossei

Hypothenar Muscles In the HYPOTHENAR compartment

Opponens Digiti Minimi o deep branch of ULNAR NERVE o originates from hook of hamate and the flexor retinaculum o inserts into the medial border of the 5th metacarpal o pulls the 5th metacarpal anteriorly, and rotates the 5th digit so

it can participate in opposition with the thumb o acts exclusively at the MCP joint

Flexor Digiti Minimi Brevis o deep branch of ULNAR NERVE o originates from hook of hamate and the flexor retinaculum o inserts into the medial side of the base of the 5th proximal

phalanx o flexes the proximal phalanx of the 5th digit

Abductor digiti Minimi o deep branch of ULNAR NERVE o originates from the pisiform o inserts into the medial surface of the bae of the 5th proximal

phalanx o Abducts the 5th digit and assists in its flexion o It is the most superficial of the three hypothenar muscles

Thenar Muscles In the ADDUCTOR compartment

Adductor Pollicis o deep branch of the Ulnar nerve

- TRANSVERSE HEAD originates from the anterior surface of the 3rd metacarpal

- OBLIQUE HEAD originates from the bases of the 2nd and 3rd metacarpals, from the capitate bone, and from any carpals around the capitate.

- Inserts into the medial side of the base of proximal phalanx of thumb. There tends to be a sesamoid bone at the site of insertion.

- Adducts the thumb towards the lateral border of the palm (presses it against the palm)

In the THENAR compartment

Flexor Pollicis Brevis o DEEP HEAD: deep branch of ULNAR NERVE o SUPERFICIAL HEAD: Recurrent branch of MEDIAN NERVE o originates from the flexor retinaculum and the tubercles of the

scaphoid and trapezium. o Inserts into the lateral aspect of the base of the proximal phalanx

of the thumb o Flexes the thumb: brings its tip towards the base of pinky

Abductor Pollicis Brevis: Recurrent branch of MEDIAN NERVE o originates from the flexor retinaculum and the tubercles of the

scaphoid and trapezium. o Inserts into the lateral aspect of the base of the proximal phalanx

of the thumb o Abducts and helps oppose the thumb

Opponens Pollicis Brevis: Recurrent b. of MEDIAN NERVE o originates from the flexor retinaculum and the tubercles of the

scaphoid and trapezium; Inserts into the lateral side of the 1st metacarpal.

o Opposes the thumb: medially rotates and the pulls medially the 1st metacarpal. Acts exclusively at the MCP joint

ADDUCTOR POLLICIS, which has

2 heads, between the origins of which the

RADIAL ARTERY emerges to form the

deep palmar arch

Transverse head of Adductor Pollicics,

which originates from the 3rd metacarpal

Oblique head of Adductor Pollicics,

which originates from the 3rd metacarpal

as well as from the 2nd metacarpal, the

capitate bone, and all adjacent carpal

bones

Adductor pollicis inserts into the lateral

part of the 1st proximal phalanx

Flexor pollicis brevis with two heads: the

superficial and the deep. The deep head is

innervated by the deep branch of the ulnar

nerve

Opponens Pollicis

Abductor Pollicis Brevis

Both of these muscles originate from the

flexor retinaculum and the tubercles of

scaphoid and trapezium; they both insert

into the lateral aspect of the base of the

proximal phalanx of the thumb.

Also originates from the flexor

retinaculum and the tubercles of scaphoid and trapezium;

however it inserts into the lateral border of the 1st metacarpal.

Both of these muscles originate from the flexor retinaculum

and the tubercles of scaphoid and trapezium; they both insert

into the lateral aspect of the base of the proximal phalanx of the

thumb.

Flexor retinaculum

Abductor Digiti Minimi

Which originates at the

pisiform and inserts into the

medial side of the base of

base of 5th proximal phalanx

Flexor Digiti Minimi Brevis

Which originates from the flexor

retinaculum and the hook of

hamate, and inserts into the

medial side of the base of the 5th

proximal phalanx

Opponens Digiti Minimi

Which originates from the

flexor retinaculum and the

hook of hamate, and inserts

into the medial border of

the 5th metacarpal

There is also Palmaris Brevis; a useless little muscle which wrinkles

the skin of the palm; it originates at the flexor retinaculum and inserts

into the skin. The ulnar nerve innervates it.

IT IS NOT PART OF THE HYPOTHENAR COMPARTMENT


Short muscles of the Hand

o there are 4 lumbricals, 4 dorsal interossei, and 3 palmar interossei; you count them starting at the THUMB

The LUMBRICALS - Originate from the tendons of the FLEXOR DIGITORUM PROFUNDIS

- Sit in the central compartment of the palm - From the palm, cross over to the dorsum of the hand

- Insert into the extensor expansions on the dorsum of the proximal phalanges

- The FIRST and SECOND lumbricals are innervated by the median nerve. All other short muscles are innervated by the deep branch of the ulnar nerve

- The THIRD and FOURTH lumbricals are bipennate; the other two are unipennate

- FLEX the metacarpophalangeal joints

- EXTEND the proximal interphalangeal joints

The DORSAL INTEROSSEI - Originate from the sides of two metacarpals (ALL of them are bipennate) - Sit in their own INTEROSSEOUS compartment of the hand - Insert into the bases of the proximal phalanges and into the extensor

expansions

- ABDUCT the hand away from the axis of the middle finger (the axis as shown)- hence “DAB” (“ Dorsal Interosei ABduct”)

- Also help the lumbricals flex the MCPs and extend the PIPs

- When the thumb is flexed, the first dorsal interossei can be seen as the lump that appears on the dorsum of the hand.

The PALMAR INTEROSSEI - Originate from the palmar surfaces of the metacarpals

- Sit in the anterior part of the INTEROSSEOUS compartment of the hand - Inset into the bases of the proximal phalanxes and into the extensor

expansions - ADDUCT the fingers towards the middle finger,

hence “PAD”- Palmar Interossei Adduct - There are only 3 palmar interossei; the deep part of the Flexor Pollicis

Brevis can be described as the 4th, because it does much the same thing as the rest, and is innervated by the same nerve

The Interossei all live inside the INTEROSSEOUS compartment. The Palmar

interossei occupy the anterior (palmar )part of it, and the dorsal interossei are

more properly between the metacarpals.

Together the short muscles all produce the “Z” movement of the fingers; the MCPs are

flexed, and the PIPs extended. This is the opposite of what happens in ulnar nerve palsy

(“claw hand”) when the MCPs are extended and the PIPs are flexed.

References: Moore’s Clinically Oriented Anatomy 5th

edition

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