Anterior Forearm

Why is the unlar claw not evident if the nerve injury was at the elbow?

because of FDP paralysis (cannot flex IP joints)

Where does the pronator quadratus attach?

(it is deepest; like a bracelet) proximal: distal anterior ulna distal: distal anterior radius

What would be the motor deficits with injury of the ulnar nerve at the wrist?

1. FCU and FDP would be unaffected 2. paralysis of interossei and medial 2 lumbricals (as in injury at the elbow)

Which muscles are involved in pronation and what is their innervation?

1. pronator teres (median n.) 2. pronator quadratus (median n.)

The ulnar nerve passes between _________

2 head of the flexor carpi ulnaris (in the cubital tunnel)

What is the clinical sign of ulnar nerve injury?

cannot grip paper between fingers (due to paralysis of interossei) If the injury is at the wrist -- there would also be ulnar claw

What is the function of the anular ligament

constrains the radius to the radial notch of the ulna

What is epicondylitis

an injury and inflammation of the musculotendinous unit attaching to the epicondyles of the humerus as a result of overuse strain.

Anterior compartment aka ______ Posterior compartment aka ______

anterior - flexor/pronator compartment posterior - extensor/supinator compartment

Why is flexion of the DIP joints of the 4th and 5th fingers not lost in pronator syndrome?

because the medial 1/2 of FDP is innervated by the ulnar nerve

Where is Guyon's canal?

fibro-osseous tunnel b/w hook of hamate and flexor tendons

Action of the FPL?

flex the thumb (remember that flexion of the thumb is like the boyscout symbol)

The median nerve passes between _______

the two heads of the pronator teres

Fibers of the interosseous membrane are oriented to prevent _____________

to prevent superior displacement of the radius and to transfer forces to the ulna (notice they are mostly oriented superior to inferior)

What is the main innervation of the anterior and posterior compartments?

Anterior - mostly innervated by the Median n. Posterior - innervated by radial n. (no exceptions)

Describe the sensory innervation of the hand

Anterior surface -medial side of thumb = radial -digit 1-3 = median -pinky and 1/2 of 4th finger = ulnar Posterior surface -Radial nerve digit 1- half of 4 -ulnar nerve is the rest

What are the two muscles involved in pronation?

Pronator teres (superficial) Pronator quadratus (deepest)

What are the distal attachments of the superficial muscles of the forearm?

Pronator teres - lateral radius Flexor carpi radialis - base of metacarpal 2&3 Palmaris longus - palmar aponeurosis Flexor carpi ulnaris - pisiform bone

Innervation of the superficial anterior forearm muscles?

Pronator teres, FCR, PL = median FCU = ulnar

What is the hand trick to remember which forearm flexors lie where are the arm?

"Pass-Fail-Pass-Fail"

Innfervation of FDS

Median n (C8,T1)

Where does the ulnar notch of the radius slide anteriorly over the ulna?

distal radioulnar joint

How would a physician test for pronator syndrome?

Provocative maneuver - should cause pain with pronation against resistance

Action of Pronator quadratus?

Pulls distal radius anteriorly over ulna during PRONATION

If ulnar nerve injury occurs at the elbow, what is the motor deficit?

1. Paralysis of FCU and FDP --> wrist can flex but accompanied by lateral deviation 2. paralysis of interossei --> no abd/add of digits 3. paralysis of medial 2 lumbricals --> decreased movement in digit 4 and 5

Which muscles are involved in supination? What are their innervations?

1. bicep brachii (musculocutaneous n.) 2. supinator (radial n.)

What is the ulnar claw?

1. hyperextension of MCP 4 and 5 (due to lumbrical paralysis and unopposed MCP extensor action) 2. Flexion at IP joints (b/c FDP is still intact)

What is the path of the ulnar artery?

Branches off the brachial artery in the cubital fossa Gives rise to common interosseous artery which in turn gives rise to anterior and posterior interosseous arteries traverses medial forearm in the fascial plane between FDP and FCU main supply to superficial palmar arch of hand

Ulnar nerve injury is called " ______"

Claw hand

What are the sensory sympatoms of pronator syndrome?

Compression of median n --> hypesthesia and activity-induced paresthesias where there is sensory innervation from the median n. (digit 1-3 on anterior surface, and tips of those fingers on the back)

Pronator syndrome is caused by compresion of the ___________ between ___________

Compression of median nerve between the 2 heads of pronator teres muscle near the elbow where it enters the forearm

Where is the ulnar nerve most often entrapped or compressed?

Elbow: Posterior to the medial epicondyle or the cubital tunnel between 2 heads of flexor carpi ulnaris ("F*CK U U trapped my ulnar nerve!) Wrist/Hand: Guyon's canal

Actions of the superficial anterior muscles of the forearm

Pronator teres - pronate forearm FCR - flex & abduct wrist Palmaris longus - flex wrist FCU - flex and adduct wrist

What are the only two anterior forearm muscles that are not innervated by the MEDIAN n?

FCU - ulnar n FDP - medial 1/2 is ulnar, lateral 1/2 is anterior IO branch of the median

What is the action of the FDS?

Flex PIP and MCP joint digits 2-5 flex wrist (think of where it is crossing; it can't act on the DIP because it doesn't go down that far)

Flexion of which joints is affected in pronator syndrome?

Flexion of PIP : -lost in 2nd and 3rd digits -weakened in 4th & 5th (b/c FDP is still acting) Flexion of thumb lost Flexion in MCP weakened because the median n. supplies the lumbricles of the 2nd and 3rd digits (lumbicals aid in MCP joint flexion)

Which superficial layer anterior forearm muscles is the exception?

Flexor carpi ulnaris - it attaches to the medial epicondyle (like the other 3) as well as the ulna It is innervated by the ulnar nerve

What are the exceptions to the rule that the anterior compartment is mostly innervated by the median n?

Flexor carpi ulnaris gets the ulnar n. Flexor digitorum profundus: Medial 1/2 gets ulnar, lateral 1/2 gets Median (ant IO branch)

Which muscles are the deepest anterior forearm muscle?

Flexor digitorum profundus (FDP) Flexor pollicis longus (FPL) Pronator quadratus ""F*ck da police, FPL and mind ya P&Qs")

______________ forms 4 tendons which pass through the carpal tunnel.

Flexor digitorum superficialis (FDS)

Flexor-pronator compartment muscles arise by a common tendinouse attachment on the __________ Extensor/supinator muscles arise by a common tendon from the ____________

Flexor/pronator (anterior) -- medial edpicondyle Extensor/supinator (posterior - lateral epicondyle

What are the attachments of the supinator?

From the lateral epicondyle the muscle wraps around the posterior lateral radius to attach to the upper 1/3 of the shaft

What holds the radius and ulna together?

Interosseous membrane and articular disc at the distal radioulnar joint

What is the difference between medial and lateral epicondylitis?

Lateral epicondylitis is often referred to as "tennis elbow"- common extensor tendon Medial epicondylitis is often referred to as "golfers elbow" - common flexor tendon

Innervation of the FDP?

Medial 1/2 - ulnar Lateral 1/2 - Median (anterior IO branch) (its counterintuitive)

The superficial layer of the anterior forearm has 3 muscles with common proximla attachment and innervation. What are those?

Medial epicondyl and median nerve Muscles are: pronator teres, FCR, palmaris longus

Be able to identify the tendon surface anatomy

Notice the 3 tendons that you can see when you flex the wrist Note that palmaris longus is often sacrificed for surgical grafts since we don't really need this muscle

What are the 3 layers of anterior forearm muscles? (flexor/pronators)

SUPERFICIAL: "PFPF" -pronator teres -flexor carpi radialis -palmaris longus -flexor carpi ulnaris INTERMEDIATE: -flexor digitorum superficialis DEEP: "that girl must do DEEP lunges -because she has profound, long quads" -flexor digitorum profundus -Flexor pollicis longus -pronator quadratus

What attaches to the common flexor tendon? (medial epicondyle)

Superficial anterior forearm flexors (PFPF - pronator teres, FCR, palmaris longus, FCU)

Distal attachment of FDS?

Tendons SPLIT -- insert base of middle phalanges 2-5

What is the hand of benediction?

When a person attempts to make a fist, the 2nd & 3rd fingers remain partially extended while the 4th & 5th digits flex normally because of ulnar innervation. This is known as the "hand of benediction."

Attachments of the FDP?

a little below where the otheres attached -- ulna and IO membrane Distal: each tendon passes through carpal tunnel - deep to FDS -Each tendon passes through the split in FDS tendons to insert at base of distal phalanx of digits 2-4

Where does the palmaris longus tendon insert?

into palmar aponeurosis (however this is absent in 15% of the population)

Action of FDP

it crosses wrist, MCP, PIP, and DIP of 2-5 so it can flex all of those (Superficialis makes the girly fist... profundus makes the whole fist)

What is the sensory deficit with ulnar nerve injury at the elbow?

loss of sensation where ulnar nerve innervates

What would be the sensory deficit the ulnar nerve injury at the wrist?

palmar and superficial branches would be severed, but dorsal branch would be intact so sensory loss over palmar side of medial 1 and 1/2 fingers only

Attachment of flexor pollicis longus?

proximal: RADIUS and IO membrane distal: passes thru carpal tunnel lateral (most lateral) to FDS and FDP tendons; inserts at base of distal phalanx of the thumb

In pronation and supination, the radial head spins on ________ and slides in __________

spins on capitulum slides in radial notch of ulna

What is the function of the interosseous membrane?

unites radius and ulna separates posterior and anterior compartments attachment for some deep forearm muscles