Forearm Flexors and Superficial Hand

interosseous membrane

-a fibrous membrane that connects the interosseous borders located on the shafts of the radius and the ulna -a syndesmosis; its fibers are oriented obliquely downward from the radius toward the ulna; the interosseous membrane is the classic example of a syndesmosis; proximally directed forces from the hand pass through the radius and are transferred to the ulna through the interosseous membrane; marked proximally by the oblique cord

radiocarpal (wrist) joint

-palmar radiocarpal ligament -dorsal radiocarpal ligament -ulnar and radial collateral ligament

Ulnar artery

-source: brachial a. -branches: anterior ulnar recurrent a., posterior ulnar recurrent a., common interosseous a., palmar carpal br., dorsal carpal br., deep palmar br., superficial palmar arterial arch -supply: medial side of the anterior forearm, posterior forearm, superficial palm, fingers -notes: this supplies the majority of blood to the superficial palmar arterial arch; it normally arises at the level of the elbow, but high branching of the brachial a. may cause the ulnar a. to arise as far proximally as the axilla (Latin, ulna = elbow or arm) *the nerve runs with it in the forearm*

Tubercle of Scaphoid

B

Tubercle of trapezium

D

Triquetrum

G; -the most medial bone in the proximal row of carpal bones -it articulates with the pisiform which sits anterior to it -Latin, = having three corners

Hamate

I the most medial carpal bone in the distal row -its hook is its distinguishing characteristic; it is an attachment point of the flexor retinaculum -Latin, = a hook

synovia bursa (sheath)

These are bursae that stretch along tendons and reduce the friction produced by their movements

Flexor retinaculum

This lies below the palmar carpal ligament, which is cut in the diagram above.

elbow joint

-Humeroulnar joint -Humeroradial joint -Radioulnar joint (proximal) -- ulnar and radial collateral ligaments; annular ligament -Interosseous membrane -Distal radioulnar joint -- articular disc

Flexor carpi radialis muscle

-origin: common flexor tendon from the medial epicondyle of the humerus -insertion: base of the second and third metacarpals -action: *flexes the wrist, abducts the hand* -innervation: *median nerve* -blood supply: *ulnar a.* -notes: works with the extensor carpi radialis longus and brevis mm. to abduct hand (Latin, carpus = the wrist) *Superficial flexor*

lumbrical muscles

-origin: flexor digitorum profundus tendons of digits 2-5 -insertion: extensor expansion on the radial side of the proximal phalanx of digits 2-5 -action: flex the metacarpophalangeal joints, extend the proximal and distal interphalangeal joints of digits 2-5 -innervation: median nerve (radial 2) via palmar digital nerves & ulnar nerve (ulnar 2) via deep branch -blood supply: superficial palmar arterial arch -notes: these muscles arise from the profundus tendons and have the same pattern of innervation as does the profundus muscle (ulnar and median nn. split the task equally) (Latin, = earthworm)

Posterior interosseous artery

-source: common interosseous a. -branches: interosseous recurrent -supply: muscles of the posterior (extensor) forearm compartment: supinator m., abductor pollicis longus m., extensor pollicis longus m., extensor pollicis brevis m., extensor indicis m. -notes: this artery passes proximal to the interosseous membrane to reach the extensor compartment of the forearm (Latin, inter = between + os = bone)

Hook of Hamate

J

Carpal tunnel

This is formed by the flexor retinaculum and the carpal bones. Within it, the median nerve lies radial to the tendons of flexor digitorum superficialis and superficial to the tendon of flexor pollicis longus. There are 9 tendons within this compartment: 4 of flexor digitorum superficialis, 4 of flexor digitorum profundus, and 1 flexor pollicis longus.

Carpals

E

Radial nerve

This nerve runs along the thumb-side edge of the forearm. It wraps around the end of the radius bone toward the back of the hand. It gives sensation to the back of the hand from the thumb to the third finger. It also supplies the back of the thumb and just beyond the main knuckle of the back surface of the ring and middle fingers.

Extensor retinaculum

-a thickening of the antebrachial fascia at the wrist -it holds the extensor tendons against the distal radius and ulna to prevent their bow-stringing *Number 4*

Palmar carpal ligament

-a thickening of the antebrachial fascia over the palmar surface of the wrist -the palmaris longus and ulnar neurovascular bundle pass deep to it, and the flexor retinaculum lies deeper and more distal

anatomical snuffbox

-at the base of the thumb; bordered laterally by the tendons of abductor pollicis longus and extensor pollicis brevis, medially by tendon of extensor pollicis longus -branches of superficial radial n. cross the snuffbox; radial artery lies deeply in snuffbox; scaphoid can be palpated there in cases of suspected fracture *shaded in space in picture*

Flexor pollicis longus muscle

-origin: anterior surface of radius and interosseous membrane -insertion: base of the distal phalanx of the thumb -action: flexes the metacarpophalangeal and interphalangeal joints of the thumb -innervation: median nerve via anterior interosseous branch -blood supply: anterior interosseous a. -notes: the tendon of flexor pollicis longus passes through the carpal tunnel with the other long digital flexor tendons and the median nerve (Latin, pollicis = the thumb, from pollere, to be strong, because the thumb is stronger than the other fingers) *Deep flexor*

Flexor carpi ulnaris muscle

-origin: common flexor tendon & (ulnar head) from medial border of olecranon & upper 2/3 of the posterior border of the ulna -insertion: pisiform, hook of hamate, and base of 5th metacarpal -action: *flexes wrist, adducts hand* -innervation: *ulnar nerve* -blood supply: *ulnar a.* -notes: the ulnar nerve passes between the two heads of origin of this muscle (Latin, carpus = the wrist *Superficial flexor*

pronator teres muscle (superficial and deep heads)

-origin: common flexor tendon and (deep or ulnar head) from medial side of coronoid process of the ulna -insertion: midpoint of the lateral side of the shaft of the radius -action: pronates the forearm -innervation: median nerve -blood supply: ulnar a., anterior ulnar recurrent a. -notes: median nerve passes between the two heads of origin of this muscle.

palmar interossei muscles

-origin: four muscles, arising from the palmar surface of the shafts of metacarpals 1, 2, 4, & 5 (the 1st palmar interosseous is often fused with the adductor pollicis m.) -insertion: base of the proximal phalanx and extensor expansion of the medial side of digits 1 & 2, and lateral side of digits 4 & 5 -action: flexes the metacarpophalangeal, extends proximal and distal interphalangeal joints and adducts digits 1, 2, 4, & 5 (adduction of the digits of the hand is in reference to the midline of the 3rd digit) -innervation: ulnar nerve, deep branch -blood supply: palmar metacarpal aa. -notes: bipennate muscles; remember DAB & PAD - then you can figure out where they must insert to cause these actions (Latin, inter = between + os = bone)

dorsal interossei muscles

-origin: four muscles, each arising from two adjacent metacarpal shafts -insertion: base of the proximal phalanx and the extensor expansion on lateral side of the 2nd digit, lateral & medial sides of the 3rd digit, and medial side of the 4th digit -action: flex the metacarpophalangeal joint, extend the proximal and distal interphalangeal joints of digits 2-4, abduct digits 2-4 (abduction of digits in the hand is defined as movement away from the midline of the 3rd digit) -innervation: ulnar nerve, deep branch -blood supply: dorsal and palmar metacarpal aa. -notes: bipennate muscles; remember DAB & PAD - then you can figure out where they must insert to cause these actions (Latin, inter = between + os = bone)

flexor digitorum superficialis muscle

-origin: humeroulnar head: common flexor tendon; radial head: middle 1/3 of radius -insertion: shafts of the middle phalanges of digits 2-5 -action: flexes the metacarpophalangeal and proximal interphalangeal joints -innervation: median nerve -blood supply: ulnar a. -notes: median nerve travels distally in the forearm on the deep surface of this muscle. *intermediate flexor*

Palmaris longus muscle

-origin: medial epicondyle of humerus -insertion: distal half of flexor retinaculum and palmaris aponeurosis -action: *flexes hand (at wrist) and tightens palmar aponeurosis* -innervation: *median n.* (C7 and C8) -blood supply: *ulnar a.* -notes: this muscle is a useful guide to the median nerve at the wrist. *Superficial flexor*

Pronator quadratus muscle

-origin: medial side of the anterior surface of the distal one-fourth of the ulna -insertion: anterior surface of the distal one-fourth of the radius -action: pronates the forearm -innervation: median nerve via anterior interosseous branch -blood supply: anterior interosseous a. -notes: this muscle is the deepest muscle in the distal forearm; it works with pronator teres and has the same nerve supply *Deep flexor*

Flexor digitorum profundus muscle

-origin: posterior border of the ulna, proximal two-thirds of medial border of ulna, interosseous membrane -insertion: base of the distal phalanx of digits 2-5 -action: flexes the metacarpophalangeal, proximal interphalangeal and distal interphalangeal joints -innervation: median nerve via anterior interosseous branch (radial one-half); ulnar nerve (ulnar one-half) -blood supply: ulnar a., anterior interosseous a. -notes: ulnar nerve innervates the portion of profundus that acts on digits 4 & 5 (the ulnar 2 digits) *Deep flexor*

posterior compartment

-separated from the anterior compartment by the interosseous membrane -also called the extensor compartment *Superficial* (medial to lateral with palm down): 1) Brachioradialis 2) Extensor carpi radialis longus 3) Extensor carpi radialis brevis 4) Extensor digitorum 5) Extensor digiti minimi 6) Extensor carpi ulnaris 7) Aconeus *Deep* (medial to lateral with palm down): 1) Supinator 2) Abductor pollicis longus 3) Extensor pollicis brevis 4) Extensor pollicis longus 5) Extensor indicis

anterior compartment of forearm

-separated from the posteror compartment by the interosseous membrane -also called the flexor compartment *Superficial* (medial to lateral with palm up): 1) Flexor carpi ulnaris 2) Palmaris longus 3) Flexor carpi radialis 4) Pronator teres *Intermediate*: 1) Flexor digitorum superficialis *Deep* (medial to lateral with palm up): 1) Flexor digitorum profundus 2) Flexor pollicis longus 3) Pronator quadratus

Radial artery

-source: brachial a. -branches: radial recurrent a., palmar carpal br., superficial palmar br., dorsal carpal br., 1st dorsal metacarpal a., princeps pollicis a., radialis indicis a., deep palmar arterial arch -supply: posterior elbow, posterior forearm, posterior hand, deep portion of palmar side of the hand, thumb -notes: radial a. provides the majority of blood supply to the deep palmar arterial arch; normally it arises at the level of the elbow but high branching of the brachial a. may result in the radial a. arising as proximal as the axilla *the nerve runs with it in the forearm*

Anterior interosseous artery

-source: common interosseous a. -branches: muscular brs.; a. of the median nerve -supply: flexor pollicis longus m., flexor digitorum profundus m., pronator quadratus m., radius, ulna, carpal bones -notes: anterior interosseous a. pierces the interosseous membrane at its distal end to reach the dorsal carpal anastomosis (Latin, inter = between + os = bone)

Median nerve

-source: lateral and medial cords of the brachial plexus -branches: anterior interosseous n., palmar br., recurrent (motor) br., common palmar digital nn. (for digits 1-3) -motor: pronator teres m., flexor carpi radialis m., palmaris longus m., flexor digitorum superficialis m., flexor digitorum profundus m. (radial half), flexor pollicis longus m., pronator quadratus m., abductor pollicis brevis m., flexor pollicis brevis m., opponens pollicis m., lateral 2 lumbrical mm. -supply: skin of the radial half of the palm and palmar side of the lateral 3 1/2 digits (and nail bed for these digits) -notes: This nerve is motor to the flexor muscles of the forearm (except flexor carpi ulnaris and the medial 1/2 of the flexor digitorum profundus),the muscles of the thenar compartment and the lateral 2 lumbricals *travels through carpal tunnel*

Anterior interosseous nerve

-source: median n. -branches: no named branches -motor: flexor pollicis longus m., radial half of flexor digitorum profundus m., pronator quadratus m. -supply: none -notes: courses along the anterior surface of the interosseous membrane

superficial radial nerve

-source: radial n. -branches: dorsal digital brs. -motor: sympathetic motor for the skin -supply: skin of the posterolateral wrist and hand; dorsum of the lateral 2 1/2 digits (excluding the skin over the distal phalanx/nail bed) -notes: this is located deep to the brachioradialis muscle *Letter B*

deep radial nerve

-source: radial n. -branches: posterior interosseous n. -motor: extensor carpi radialis brevis m., supinator m., extensor digitorum m., extensor digiti minimi m., abductor pollicis longus m., extensor pollicis longus m. extensor pollicis brevis m., extensor indicis m. -supply: no cutaneous branches -notes: this nerve passes through the supinator m.; some authors believe that the posterior interosseous n. and this nerve are synonymous, others say that when this nerve emerges from the supinator in the posterior forearm it becomes the posterior interosseous n., and others say that this nerve does not become the posterior interosseous n. until after its last muscular br. has been given off *Letter A*

Common interosseous artery

-source: ulnar a. -branches: anterior interosseous a., posterior interosseous a. -supply: deep structures of the forearm -notes: this artery supplies the deep forearm flexor and deep forearm extensor muscles (Latin, inter = between + os = bone)

superficial palmar arterial arch

-source: ulnar a., superficial palmar br. of the radial a. -branches: common palmar digital aa. (3) -supply: superficial palm, palmar surface of the digits excluding thumb, dorsum of the distal phalangeal segments of digits 2-5 -notes: superficial palmar arterial arch receives the majority of its blood supply from the ulnar a.

Antebrachial fascia

1 -anterior and posterior thickening forming the extensor retinaculum; immediatel distal but deeper to the palmar carpal ligament it forms the flexor retinaculum -formation of the carpal tunnel through which the median n. and flexor tendons pass

Palmar aponeurosis

3, strong thick fascia that covers and protects the flexor tendons in the palm

Distal phalanges

A -the distal bone in the digits of the hand -there are a total of 5 of these in the hand; the thumb has one and each finger has one. -Latin, phalanx = line of soldiers

Scaphoid

A; the most lateral carpal bone of the proximal row -is located in the floor of the anatomical snuff box; it is frequently fractured by hyperextension and abduction of the wrist -Greek, = boat-shaped

Intermediate phalanges

B -the second to most distal bone in the digits of the hand -there are a total of 4 of these in the hand; each finger has one, but the thumb does not have one. -Latin, phalanx = line of soldiers

Trapezium

C -the most lateral carpal bone of the distal row -it forms a saddle joint with the metacarpal bone of the thumb; "the thumb swings on this bone"

Proximal phalanges

C -the third most distal bone in the digits of the hand -there are a total of 5 of these in the hand; the thumb has one and each finger has one. -Latin, phalanx = line of soldier

Metacarpals

D -the bones located between the carpal bones and the phalanges of the hand -there are a total of five of these bones in the hand; these bones of the four fingers are bound together by ligaments to form a firm foundation for finger movements; this bone of the thumb is more independent in its range of motion.

Trapezoid

E -the carpal bone located between the trapezium and the capitate in the distal row -This bone is named for its shape

Lunate

F; -the carpal bone located between the scaphoid and triquetrum in the proximal row -named because it is "moon-shaped" (crescent shaped) in longitudinal section; the head of the capitate sits within the crescent of this bone. -Latin, = lunatus, crescent-shaped, from luna, the moon

Pisiform

H -a sesamoid bone in the tendon of the flexor carpi ulnaris m. -it articulates with the triquetrum; this bone provides a protective function for the flexor carpi ulnaris tendon by bearing the forces generated by the tendon riding across the triquetrum, especially during wrist extension -Latin, = pea-shaped

Capitate

K -the carpal bone located between the trapezoid and the hamate in the distal carpal row - this bone is the largest carpal bone; it is named for its rounded head; forces generated in the hand (as during a punching blow with the fist) are transmitted through the third metacarpal bone to this bone and proximally through the lunate to the radius -Latin, = head

scaphoid fracture

This bone is the most frequently fractured carpal bone, and injury to this bone is the most common wrist injury. Pain occurs primarly during extension and abduction of the hand, and is felt on the lateral side of the wrist. Because of poor blood supply to the proximal part of this bone, union of the fractured parts may take several months. *Avascular necrosis* of the proximal fragment of this bone may occur and produce degenerative joint disease of the wrist. In some cases, it is necessary to fuse the carpals surgically.

Ulnar nerve

This nerve travels through a separate tunnel, called *Guyon's canal*. This tunnel is formed by two carpal bones, the pisiform and hamate, and the ligament that connects them. After passing through the canal, the ulnar nerve branches out to supply feeling to the little finger and half the ring finger. Branches of this nerve also supply the small muscles in the palm and the muscle that pulls the thumb toward the palm.

tennis elbow

also called elbow tendinitis, it is due to repetitive use of the superficial extensor muscles of the forearm. The *pain is felt on the lateral epicondyle* and radiates down the posterior surface of the forearm. Patients with this condition will often feel pain when they open a door or lift a glass. The repeated forceful flexion and extension of the wrist strains the attachment of the common tendon, producing inflammation of the periosteum of the lateral epicondyle and the common extensor attachment of the muscles.

epicondylitis

inflammation of the epicondyle or of the tissues adjoining the epicondyle of the humerus. - The lateral version is also referred to as "tennis elbow". (Greek, kondylos = the knob formed by the knuckle of any joint) - The medial version is known as golfer's elbow (or thrower's elbow)

dorsal radial tubercle

lies dorsally between grooves for the passage of the forearm tendons *Number 7*

Colles fracture

most common fracture of the forearm. The *distal end of the radius is broken*, and distal fragment is displaced dorsally and is often comminuted (broken into pieces). The fracture results from forced extension of the hand, usually as the result of trying to ease a fall by outstretching the upper limb.

wrist drop

the radial nerve is usually injured when the humeral shaft fractures. An injury of this kind is going to be proximal to the wrist extensors, thus wrist drop is a common clinical manifestation. The deep branch of the radial nerve can be injured by deep puncture wounds to the forearm. The deep branch of the radial nerve is responsible for extending the thumb and MP joints. Neither deep nor superficial radial nerve injury causes much sensory loss, but cutting the superficial leaves a coin-shaped area distal to the bases of the 1st and 2nd metacarpals without sensation.