extremity week 5

picture of nerves anterior forearm

1.Lateral cutaneous nerve of forearm (musculocutaneous) 2. Cephailic vein 7. Anterior & posterior branches of medial cutaneous nerve of forearm

Nerves of the Forearm

1.Musculocutaneous 2.Radial n. • deep •superficial 3.Median 4.Recurrent motor to thenar 5.Palmar digital 6.Superficial branch of ulnar 7.Median 8.Ulnar Radial

Median Nerve (C6, C7, C8, T1) branches

Anterior interosseous nerve Palmar cutaneous

Central Compartment - Lumbricals 3 & 4 insertion

Attach to the lateral sides of the extensor expansion of digits 4&5

ulnar branches

dorsal cutaneous palmar cutaneous

medial antebrachial cutaneous nerve

from the medial cord, pierces the brachial fascia with the basilic vein to run subcutaneously on the medial forearm to the wrist.

Hypothenar Muscles - Flexor Digiti Minimi brevis* origin

hook of hamate

Hypothenar Muscles - Opponens Digiti Minimi origin

hook of hamate

Interosseous Compartment - Dorsal Interosseous origin

•Adjacent two metacarpals •All four are bipennate

the hook grip

•This consumes less energy, involving the use of just the long finger flexors.

Deep branch/posterior interosseous nerve

(PIN) (motor), exits the cubital fossa winding around the radial neck to pierce and supply to supinator, it winds around the lateral neck of the radius while in the supinator and emerges in the posterior compartment as the PIN. It descends with the posterior interosseous artery and runs between the deep and superficial extensors.

Central compartment of the hand

Abductor pollicis brevis 2.Flexor pollicis brevis 3.Oblique head of adductor pollicis 4.Transverse head of adductor pollicis 5.Flexor digiti minimi 6.Abductor digiti minimi 7.Superficial palmar arch 8.Common palmar digital branches

deep veins of the forearm

Accompany the arteries and freely anastomose with the superficial veins.

The median nerve enters the carpal tunnel radial to the

FDS tendons abutting the transverse carpal ligament.

hypothenar eminence

abductor digiti minimi, flexor digiti minimi, opponens digiti minimi

thenar eminence

abductor pollicis brevis, flexor pollicis brevis, opponens pollicis

The fascia of the palm is continuous with the

antebrachial fascia and the dorsal fascia of the hand.

While the radial nerve is a posterior compartment structure, the radial artery is an

anterior compartment structure.

Long Descenders

branches off the cords of the brachial plexus that provide sensory innervation to the forearm.

Dorsal cutaneous

cutaneous branch forms in the distal 1/2 of the forearm between the ulna and the FCU, enters the subcutaneous tissue on the dorsum of the hand medial to the axis of the 4th digit.

Posterior cutaneous nerve of the forearm branches off the

radial nerve as it descends in the radial canal, perforates the lateral head of the triceps to run subcutaneously on the lateral aspect of the arm to the forearm & wrist.

Motor supply to the BR & ECRL derive from the

radial nerve prior to its bifurcation.

Lateral cutaneous nerve of the forearm

the distal extension of the musculocutaneous branch (lateral cord). Emerges lateral to the biceps on the brachioradialis, initially runs with the cephalic vein, and descends on the lateral forearm to the wrist.

The common interosseous trunk is a branch of the

ulnar artery.

Superficial branch

•(sensory) in the cubital fossa runs between the pronator teres and the brachioradialis. It arborizes over the anatomical snuff box to supply the skin on the dorsum of the hand lateral to the axis of the 4th finger.

Common:

•1st large branch of the ulnar distal to the bifurcation of the brachial artery passes deep and lateral and bifurcates into: anterior posterior recurrent

recurrent

•: passes superiorly to the radioulnar joint to anastomose with the middle collateral branch of the Profunda brachii artery. comes off posterior interoceous

Hypothenar Muscles - Abductor Digiti Minimi action

•Abduct digit 5

Ulnar Innervated Muscles digiti minimi

•Abductor Digiti Minimi (C8-T1) •Opponens Digiti Minimi (C8-T1) •Flexor Digiti Minimi (C8-T1)

Interosseous Compartment - Dorsal Interosseous action

•Abducts digits away from digit 3 •These muscles fill the space between the metacarpal bones; these muscles are easily monitored indicators of muscle wasting. •The 1st and 5th digits lack these because they have their own abductors.

Thenar Muscles - Abductor Pollicis Brevis action

•Abducts thumb at CMC and MCP joints

Adductor Compartment - Adductor Pollicis action

•Adduct digit 1 • The only THENAR muscle innervated completely by the ulnar nerve.

Interosseous Compartment - Palmar Interosseous action

•Adducts digits towards digit 3 •The flexor pollicis brevis is the interosseous of the 1st metacarpal

Interosseous Compartment - Palmar Interosseous origin

•Arise from palmar surface of metacarpals 2, 4, & 5 •All three are unipennate

Radial recurrent branch:

•Arises from the lateral side of the radial artery just distal to the bifurcation of the brachial artery, ascends between the Brachialis and Brachioradialis muscles to meet the radial collateral branch of the Profunda brachii artery.

Central Compartment - Lumbricals 1 & 2 insertion

•Attach to the lateral sides of the extensor expansion of digits 2&3

Thenar Muscles - Abductor Pollicis Brevis insertion

•Base of proximal phalanx, digit 1 lateral side

Thenar Muscles - Flexor Pollicis Brevis insertion

•Base of proximal phalanx, digit 1 •lateral side

Hypothenar Muscles - Opponens Digiti Minimi insertion

•Body of 5th metacarpal •Palmar surface

Radial Innervated Muscles forearm

•Brachioradialis (radial) •Extensor Carpi Radialis Longus (radial) •Extensor Carpi Radialis Brevis (deep branch) •Supinator (deep branch) •Extensor carpi ulnaris (PIN) •Extensor digiti minimi (PIN) •Extensor digitorum (PIN) •Abductor pollicis longus (PIN) •Extensor pollicis brevis (PIN) •Extensor pollicis longus (PIN) •Extensor indicis (PIN)

superficial veins of forearm

•Cephalic •Basilic •Median Cubital

Interosseous compartment:

•Contains interosseous muscles.

Palmar aponeurosis; This is a strong well-defined deep fascial structure that:

•Covers the soft tissue of the palm and overlies the long flexor tendons •Is continuous with the flexor retinaculum and Palmaris longus tendon. •Forms 4 longitudinal bands as it radiates distally to the bases of the proximal phalanges and is continuous with the digital sheaths.

Hypothenar Muscles - Abductor Digiti Minimi innervation

•Deep branch of ulnar nerve

Hypothenar Muscles - Flexor Digiti Minimi brevis* inneration

•Deep branch of ulnar nerve

Hypothenar Muscles - Opponens Digiti Minimi innervation

•Deep branch of ulnar nerve

Brachial Artery Entering the Forearm

•Enters the cubital fossa lateral to median nerve. •Beneath the bicipital aponeurosis. •Anterior to the biceps tendon.

Median Nerve (C6, C7, C8, T1)

•Enters the cubital fossa medial to the brachial artery, exits between the heads of the pronator teres •Descends in the fascial plane between the FDS & FDP, deep to the palmaris longus tendon and the flexor retinaculum to the carpal tunnel. •Sends branches to the pronator teres as it passes by the elbow, it sends branches to the FCR & palmaris longus proximal to the FDS. •It supplies the superficial(except FCU), intermediate and deep flexors (except ulnar ½ FDP) •via the anterior interosseous nerve (AIN).

Interosseous Compartment - Palmar Interosseous insertion

•Extensor expansion at bases of proximal phalanges of digits 2, 4, & 5

•Classically the AIN supplies:

•FPL •½ FDP* (digits 2 and 3) •Pronator quadratus

Central Compartment - Lumbricals 1 & 2 action

•Flexes MCP joints •Extends the IP joints

Central Compartment - Lumbricals 3 & 4 action

•Flexes MCP joints •Extends the IP joints

Thenar Muscles - Flexor Pollicis Brevis action

•Flexes digit 1 at MCP joint

Hypothenar Muscles - Flexor Digiti Minimi brevis* action

•Flexes digit 5 at MCP

Ulnar Innervated Muscles forearm

•Flexor Carpi Ulnaris (C7-T1) •Flexor digitorum profundus IV and V (C7-C8)

Bifurcation and Ulnar Artery

•Forms as a direct continuation of the brachial artery, descends distally deep to the pronator teres, palmaris longus and the flexor digitorum superficialis to reach the medial aspect of the forearm near the wrist . •It passes superficially to the flexor retinaculum with the ulnar nerve in the Guyon canal to enter the hand. Pulsations of the ulnar artery can be palpated on the lateral side of the FCU tendon

Ulnar Innervated Muscles palm

•Hypothenar muscles (C8-T1) •Adductor Pollicis (C8-T1) •Flexor Pollicic Brevis (C8-T1)

Interosseous Arteries

•It is a short stump that branches to form the: •Anterior interosseous artery •Posterior interosseous artery •Each follows its namesake nerve.

Extensor Expansion also know as dorsal expansion or dorsal hood

•It is an anatomical term that refers to the special connective attachments by which the extensor tendons insert into the phalanges. •These aponeuroses of extensor muscles span the proximal and middle phalanges. •At the distal end of the metacarpal, the extensor tendon will expand to form a hood, which covers the back and sides of the head of the metacarpal and the proximal phalanx. •The lumbricals, extensor indicis, dorsal interossei, and palmar interossei insert on these bands. •All of these muscles serve to extend the interphalangeal joints. The interossei and lumbricals flex the metacarpal phalangeal joints.

fascia of the hand

•It is thin over the thenar and hypothenar eminences but thick centrally (palmar aponeurosis) and in the fingers where it forms the digital sheath.

Thenar Muscles - Opponens Pollicis insertion

•Lateral side of 1st metacarpal

Central Compartment - Lumbricals 1 & 2 innervation

•Lateral two (digits 2&3) = median nerve

Central Compartment - Lumbricals 1 & 2 origin

•Lateral two tendons of flexor digitorum profundus

Fibrous digital sheaths:

•Ligamentous tube that encloses synovial sheaths of both the deep & superficial flexor tendons and the FPL tendon. •These sheaths are composed of five annular and four cruciform parts. •Insertions of forearm and intrinsic hand muscle tendons form mechanically complex structures.

Adductor Compartment

•Located deep to the thenar space superficial to the interossei muscles, it contains the adductor pollicis.

hand muscles •Characteristics of primates:

•Loss of claws, replaced by nails •Increased sensitivity of the palmar digit pads •Enlarged clavicle •Enhanced mobility of shoulder joint •Enhanced mobility of the individual digits •Opposable 1st digit •

Central Compartment - Lumbricals 3 & 4 origin

•Medial three tendons of flexor digitorum profundus

Central Compartment - Lumbricals 3 & 4 innervation

•Medial two (digits 4&5) = deep branch of ulnar nerve

Adductor Compartment - Adductor Pollicis origin

•Oblique head = metacarpal 2 and 3 and capitate Transverse head = metacarpal 3

Thenar Muscles - Opponens Pollicis action

•Opposes digit 1 •pulls and rotates 1st metacarpal across the palm

Hypothenar Muscles - Opponens Digiti Minimi action

•Opposes digit 5 •Abducts, flexes and laterally rotates the 5th metacarpal, cupping the hand

Ulnar Innervated Muscles fingers

•Palmar Interosseous (C8-T1) •Dorsal Interosseous (C8-T1) •III and IV Lumbricals (C8-T1)

Anterior

•Passes distally on the anterior surface of the interosseous membrane between the FDP & FPL, proximal to the pronator quadratus it pierces the membrane to enter the posterior compartment and join the dorsal carpal arch.

Hypothenar Muscles - Abductor Digiti Minimi origin

•Pisiform bone

Median Innervated Muscles forearm

•Pronator Teres (median) •Flexor Carpi Radialis (median) •Palmaris Longus (median) •Flexor Digitorum Superficialis (median) •Flexor Digitorum Profundus (AIN) •Digits II and III •Flexor Pollicisis longus (AIN) •Pronator Quadratus (AIN)

•Classically the Median supplies:

•Pronator teres •FDS •FCR Palmaris longus

Interosseous Compartment - Dorsal Interosseous insertion

•Proximal phalanx •Extensor expansion

Hypothenar Muscles - Abductor Digiti Minimi insertion

•Proximal phalanx of digit 5 •Medial side

Hypothenar Muscles - Flexor Digiti Minimi brevis* insertion

•Proximal phalanx of digit 5 •Medial side

Thenar Muscles - Abductor Pollicis Brevis innervation

•Recurrent Branch of Median nerve

Thenar Muscles - Opponens Pollicis innervation

•Recurrent branch of median nerve

Thenar Muscles - Flexor Pollicis Brevis innervation

•Recurrent branch of median nerve •Superficial head •Deep branch of ulnar •Deep head

Thenar Muscles - Abductor Pollicis Brevis origin

•Scaphoid bone •Trapezium

Adductor Compartment - Adductor Pollicis insertion

•Sesamoid bone on medial side of MCP •Proximal phalanx of digit 1

Thenar Muscles - Flexor Pollicis Brevis origin

•Superficial head from flexor retinaculum and trapezium •Deep head from the floor of the carpal tunnel (over trapezoid and capitate)

Collateral Circulation around the Elbow

•Superior ulnar collateral and posterior ulnar recurrent • •Inferior ulnar collateral and anterior ulnar recurrent • •Middle collateral and recurrent interosseous • •Radial collateral and recurrent radial

The position of rest:

•The position automatically assumed by the inactive hand when the forearm and hand are supported on a flat surface, this position is used in casting of proximal wrist and forearm fractures.

Supinator Syndrome (Posterior Interosseous Nerve Palsy)

•The posterior interosseous nerve may be compressed where it passes through the supinator muscle in the proximal forearm. This nerve controls finger extension, and to a small degree, wrist extension. Patients have pain and tenderness in the proximal forearm during activity and may have some degree of finger extension weakness compared to the normal arm. Numbness should not be present.

Radial Nerve (C5 -T1)

•The radial nerve enters the cubital fossa between the brachioradialis and the brachialis muscles, anterior to the lateral epicondyle it divides into the deep and superficial branches.

Medial fibrous septum

•The tough septum extends from the medial border of the palmar aponeurosis to the 5th metacarpal. Medial to this septum is the hypothenar compartment containing the hypothenar muscles.

Ulnar Nerve (C8, T1)

•The ulnar nerve enters the forearm between the humeral & ulnar heads of the FCU from posterior of the medial epicondyle. •It descends between the FCU & FDP and becomes superficial in the distal forearm with the ulnar artery. •It proceeds on the surface of the transverse carpal ligament lateral to the pisiform and medial to the hook of the hamate in Guyon's canal then splits into a deep and superficial branch. •The ulnar supplies motor in the forearm to the: FCU, Ulnar ½ FDP (digits 4 and 5) . It supplies the intrinsic muscles of the hand.

Median Innervated Muscles palm

•Thenar muscles (recurrent branch) • I and II Lumbricals

Thenar space and Midpalmar space:

•These spaces are bounded by the septa from the edges of the palmar aponeurosis to the metacarpals. The lateral fibrous septa separated the thenar and midpalmar spaces. The midpalmar space is continuous with the anterior compartment of the forearm via the carpal tunnel. They function as bursa.

Central compartment

•This exists between the medial and lateral compartments and contains the flexor tendons and their sheaths, the lumbricals, the superficial palmar arterial arch and digital arteries and nerves.

Lateral fibrous septum

•This extends from the lateral border of the aponeurosis to the 3rd metacarpal. Lateral to this septum is the thenar compartment containing the thenar muscles.

The precision handling grip:

•This grip involves a change in the position of a handled object that requires fine control of the thumb and fingers. In this grip the wrist and fingers are held firmly by the long flexors and extensors while the intrinsic hand muscles perform the fine movements of the digits.

The power grip:

•This involves the long flexor muscles acting at the interphalangeal joints, the intrinsic muscles of the palm acting at the metacarpophalangeal joints and the extensors of the wrist acting at the radiocarpal and midcarpal joints. Engagement of the wrist extensors lengthens the distance over which the finger flexors work allowing more powerful grip.

Dupuytren's Fasciitis and Contracture

•This is a disease of the palmar fascia resulting in progressive thickening and contracture of fibrous bands on the palmar surface of the hand and fingers. •Fasciitis implies inflammation of the fascia and contracture implies thickening and tightening of the diseased fascia. The tissue on the palmar surface of the hand thickens (up to 0.5cm) and essentially "shrinks" and produces a tightness in the area of the hand which the diseased tissue overlies. •It occurs most often in the fourth and fifth digits. It is a common problem and often arises in the hands of middle aged persons; however, it can be seen as early as the twenties. •This entity does run in families in some cases. It is seven times more common in men than women. •It has been associated with diabetes and can be seen in alcoholics with cirrhosis of the liver. •It has also been associated with epilepsy but may be a result of the use of anticonvulsant drugs rather than the presence of epilepsy itself. •The underlying cause is unknown. A propensity of local fibroblasts to differentiate into active myofibroblasts when exposed to TNF has been identified in Duputrens patients.

Thenar Muscles - Opponens Pollicis origin

•Trapezium

The ulnar artery is a continuation of the

•brachial artery.

palmar cutaneous

•branch forms in the mid-forearm anterior to the ulnar artery and perforates the deep fascia in the distal forearm to enter the subcutaneous palmar tissue medial to the 4th digit. •Occasionally there are communicating branches between the ulnar and median nerves as they pass through the forearm.

Adductor Compartment - Adductor Pollicis innervatino

•deep branch of ulnar nerve

Interosseous Compartment - Dorsal Interosseous innervation

•deep branch of ulnar nerve

Interosseous Compartment - Palmar Interosseous innervation

•deep branch of ulnar nerve

Anterior interosseous nerve

•in the distal cubital fossa median gives off the AIN as it emerges from beneath the pronator teres, it runs on the anterior interosseous membrane with the artery between the FDP & FPL and innervates the pronator quadratus.

The smaller terminal branch of the brachial artery, runs

•inferolaterally beneath the Brachioradialis medial to the FCR tendon on top of the supinator, distal pronator teres and FDS, traverses around the lateral aspect of the radius to pass through the anatomic snuff box. deep palmer supply

The flexor digiti minimi longus is not normally found in humans

•it is a rare anatomical variation.

Palmar cutaneous branch emerges at the

•mid-distal forearm proximal to the flexor retinaculum; it crosses the retinaculum to the skin of the central palm.

posterior

•passes posterior to the interosseous membrane sometimes giving off the recurrent interosseous artery, then distally runs between the deep and superficial extensors.

The radial recurrent branch forms part of the

•peri-articular anastomotic system.

The posterior interosseous artery supplies the

•posterior compartment in the forearm.$

The radial branch projects laterally over the

•supinator to run beneath the brachioradialis.

The main arteries of the forearm are

•the radial and ulnar arteries, the terminal branches of the brachial artery. •They bifurcate at the neck of the radius in the inferior part of the cubital fossa. •The ulnar is a direct continuation of the brachial artery and larger than the radial branch.

Deep branch of the radial nerve pierces

•the supinator muscle and exits at the distal border where it changes names to the PIN.