Hand

Question 1

Median nerve

Answer 1

• The median nerve contains anterior division fibers C6 - T1, and thereby innervates mostly flexors within the forearm and hand.
• Innervates five muscles in the hand: the 3 muscles of the thenar eminence at the base of the thumb, and 2 lumbricals for the second and third digits. On the cutaneous side, the median nerve innervates the palmar surface of the lateral 3½ digits, as well as their nail beds.
• Also innervates all muscles of the anterior forearm except one and a half (the flexor carpi ulnaris and the medial half of the flexor digitorum profundum).

Question 2

Ulnar nerve

Answer 2

• Ulnar nerve innervates all of the intrinsic hand muscles not innervated by the median nerve
  
  • Innervates the hypothenar eminence, and most intrinsic hand muscles (contains T1)
  • Just not the thenar eminence
• (It also innervates the flexor carpi ulnaris and the medial half of the flexor digitorum profundus in the anterior forearm.)

Question 3

What is the anastamosis of radial and ulnar arteries?

Answer 3

• The radial artery and the ulnar artery anastomose in the hand, by forming two arches, the superficial palmar arch, and the deep palmar arch

Question 4

thenar eminence

• What does it allow us to do
• Muscles?
• Innervation?

Answer 4

• Intrinisc, At base of thumb
• The bigger of the two eminences
• 3 muscles that give us the ability to oppose our thumb
  
  • “OAF”
    
    • Opponence muscle - opponens pollicis
      
      • ​Allows us to roll thumb
    • ABductor muscle - abductor pollicis brevis (move in sagittal plane)
    • Flexor muscle - flexor pollicis brevis
      
      • Allows us to sweep thumb across flexed digits
• Innervated by recurrent branch of the median nerve
  
  • Very important, clinically significant
  • (whereas hypothenar innervated by ulnar nerve)

Question 5

hypothenar eminence

• Muscles?
• Innervation?

Answer 5

• At base of pinkie
• The less important eminence
• 3 muscles, OAF
  
  • Opponens digiti minimi
  • ABductor digiti minimi
  • Flexor digiti minimi
• Innervated by ulnar nerve
  
  • ​(whereas thenar innervated by recurrent branch of median nerve)

Question 6

palmar aponeurosis

• Where is it?
• Why do we have it?
• What muscle sometimes inserts into it?

Answer 6

• A broad aponeurois (connective tissue) which tightly attaches to the fascia under the skin
• Protects all the important stuff in the palm (blood vessels, nerves)
• The palmaris longus is a mysterious muscle that inserts into the palmar aponeurosis
  
  • absent in 15% of the population
• Thenar eminence and hypothenar eminences are positioned on the sides of the palmar aponeurosis.

Question 7

intrinsic hand muscles

Answer 7

• “intrinsic” means they start and end in the hand
• Protected by palmar aponeurosis
• Thenar and hypothenar eminences (3 each, OAF - opponens, abductor, flexor)
  
  • The opponens pollicis and abductor pollicis brevis = innervated by the median nerve. The flexor pollicis brevis has two heads a superficial and a deep. The superficial is innervated by the median nerve and the deep is innervated by the ulnar nerve
• 4 Lumbricals“wormlike”
  
  • Deep in palm of hand
  • Unusual in that don’t attach to bone - Attached to flexor digitorum profundus tendons
  • 1st and 2nd - innervated by median
  • 3rd and 4th - innervated by ulnar nerve
• interosseous muscles“DAB”
  
  • Allows us to finger spread and bring together
  • 2 sets - 4 dorsal (2 on the middle finger)
    
    • not needed by thumb or pinkie
  • found between metacarpals
  • innervated by ulnar nerve

Question 8

extrinsic hand muscles

Answer 8

• “extrinsic” means they start in the forearm, and send tendons into hand

Question 9

What’s the million dollar nerve?

Answer 9

• Recurrent branch of the median nerve
• Innervates the three thenar muscles
• “Recurrent” because it bends back on itself
• It’s prone to injury because it’s superficial
• Without it, no power grip
• Hand surgeons have to be careful when correcting carpal tunnel syndrome

Question 10

Metacarpal Phalangeal (MP) joints

• Muscle to abduct, adduct?
• Muscle to extend, flex?

Answer 10

• These are the knuckle joints (there are 4)
• They are condyloid (biaxial) because allow movements in two planes
• Abduction and adduction = intrinsic hand muscles
  
  • Abduction = spreading fingers
  • ADduction = making fingers come back together
  • Around midline in middle finger
• Flexion and extension = forearm muscles

Question 11

Proximal Interphalangeal (PIP) joint

• What actions are possible?

Answer 11

• There are two InterPhalangeal joints, this is the more proximal one
• Pure hinge joints
  
  • Only permit flexion and extension
  • Like the elbow
    *

Question 12

Distal Interphalangeal (DIP) joint

• What actions are possible?

Answer 12

• There are two InterPhalangeal joints, this is the more distal one
• Pure hinge joints
  
  • Only permit flexion and extension (sagittal plane)
  • Like the elbow

Question 13

Compare and contrast the actions of lumbricals and interosseous muscles, their innervation and joints where they act

Question 14

How do we make a fist?

Question 15

Most important digit of upper limb?

What’s special about it?

Answer 15

• The thumb!
• Has highly mobile metacarpal
  
  • carpometacarpal (CMC)
  • We can move the thumb in all the planes
• Only has a single phalanx bone. So the thumb only has two phalanges, whereas each finger has three.
• Moves differently, has its own planes
  
  • Flexion/extension occurs in coronal plane (whereas fingers in sagittal plane)
    
    • When flex thumb, sweeping it across the palm
  • Abduction/Adduction in sagittal plane
    
    • When abduct thumb, move it forward)
• Thumb opposition involves abduction, flexion, medial rotation. Allows us to:
  
  • Touch pads of other digits
  • Makes a power grip - oppose thumb across flexed digits

Question 16

metacarpal bones

Answer 16

• 5 of them

Question 17

number the digits in the hand

Answer 17

• Thumb = #1, so it’s the first metacarpal
• pinkie = #5

Question 18

bones of the wrist

Answer 18

• All 5 metacarpals articulate with distal row of carpal bones
• There are two rows of carpal bones:
  
  • Trapezium, trapezoid, capitate (largest bones in the wrist), hamate
  • Scaphoid, lunate, triquetrum, pisiform
• “Some Lovers Try Positions That They Can’t Handle”

Question 19

What happens when thumb opposition is weak?

What isn’t working?

Answer 19

• Then grip is weak
• Opposition of the thumb involves abduction, flexion, and medial rotation of the thumb

Question 20

pollicis

Answer 20

• pollicis = thumb
• 3 thenar muscles of thumb have pollicis in their name:
  
  • Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis

Question 21

What’s the innervation of intrinsic hand muscles?

Answer 21

• Ulnar nerve
  
  • C8, T1 fibers
  • T1 goes to hand
• This is the default answer because of the proximal to distal gradient!
• The only other possibility is the median nerve, it’s the only other one with T1 fibers
• All interosseous muscles of the hand, with the exception of the first and second lumbricals (the most radial two are innervated by the median nerve), are innervated by the deep branch of the ulnar nerve

Question 22

lumbricals

• Numbering?
• Where do they arise from?
• What do they attach to?
• Innervation?
• Actions?

Answer 22

• Arise from flexor tendons and attach to extensor tendons
  
  • Arise from Flexor digitorum profundus tendons
  • Pass anterior to joint, form “dorsal hoods” and attach to tendons of the Extensor Digitorum muscle
• Innervation
  
  • ​Median nerve innervates the index and middle fingers (1st and 2nd)
  • Ulnar nerve innervates the ring and pinkie (3rd and 4th)

The only muscles that give ability to extend fingers!

• Flex at MP joints
  
  • Pass anterior to the MP joints (anterior to knuckles at base of hand) –> flex there
  • (The extensor digitorum extends at MP)
• Extend at PIP and DIP joints
  
  • It’s the lumbricals that extend all of the interphalangeal joints (proximal and distal), all 4 fingers. ​

Question 23

divisions of the hand

Answer 23

Question 24

action of lumbricals

Answer 24

• Simultanesously flex at MP joints and extend at IP joints
• Lumbrical action is to hold a pea, that is to flex the metacarpophalangeal joint and extend the interphalangeal joints. When look at hand in this position, can see this makes an “L” shape, since L is for Lumbrical.

Question 25

Why is the name "extensor digitorum" an overstatement? What is its innervation?

Answer 25

* The name overestimates its true power: * **Extensor digitorum can only extend your fingers at the MP (knuckle) joints** * When you extend your fingers, the extensor digitorum canNOT extend all 4 fingers at the interphalangeal joint. No farther than knuckles. * Lumbricals give ability to extend all the way. (2 by 2 innervation) * Innervated by **radial nerve**

Question 26

how do lumbricals and extensor digitorum tendon work together?

Answer 26

* Extensor digitorum tendon extends the fingers at the MP (knuckle) joints * Lumbricals insert into extensor digitorum tendon and extend the fingers at the IP joints

Question 27

anatomic snuff box

Answer 27

* The tendons of the extensor pollicis longus and extensor pollicis brevis form what is known as the anatomical snuff box - an indentation on the lateral aspect of the thumb at its base * If localised pain is reported in the anatomical snuffbox, a fracture of the scaphoid is the most likely cause --\> risk of avascular necrosis and arthritis

Question 28

describe the 5 movements of thumb

Answer 28

Question 29

what are the nerves responsible for thumb movements: * Abduction * Adduction * Extension * Flexion * Opposition

Answer 29

* Abduction - median nerve * Adduction - ulnar nerve * Extension - radial nerve * Flexion - median nerve * Opposition - median nerve * The thenar muscles = **o**pponens pollicis, **ab**ductor pollicis brevis, **f**lexor pollicis brevis, and adductor pollicis muscles. All are **innervated by the median nerve**, except for the adductor pollicis and deep head of the flexor pollicis brevis, which are innervated by the ulnar nerve

Question 30

flex thumb using what nerves?

Answer 30

* median nerve, innervates flexor pollicus longus tendon

Question 31

Which 3 nerves control finger extension? What kinds of fibers?

Answer 31

* **Median and ulnar nerves** * Anterior division fibers * (so these 2 are a special exception) * **Radial nerve** * Pollicus longus tendon **extends the thumb** * **Median nerve** * Lumbricals extend the IP joints of all fingers (and flex MP joints) * **Median nerve** innervates the index and middle fingers (1st and 2nd) * **Ulnar nerve** innervates the ring and pinkie (3rd and 4th) * Extensor digitorum extends fingers at MP (knuckle joint) * **Radial nerve** (this make sense bc radial nerve innervates extensors everywhere for posterior upper limb)

Question 32

extend thumb

Answer 32

* Thumb is extended by two muscles that are innervated by the **radial nerve** (good!) * Extensor Pollicis Brevis and Extensor Pollicis Longus

Question 33

interosseous muscles what are they for? Which digits don't have them? Innervation?

Answer 33

* intrinsic to the hand, between metacarpals * dorsal interosseous muscles = DAB muscles - abduct, allow us to **finger spread** at the knuckle joints * On both sides of the middle finger, do both AB and ADduction of middle * Not needed by thumb or pinkie * Pinkie has its personal ABductor digitiminimi in the thenar eminence * Thumb has its personal ABductor in the thenar eminence (abductor pollicis brevis) * 2 sets - 4 dorsal (2 on the middle finger) * Innervation = **ulnar nerve**

Question 34

which nerve gives ability to finger spread?

Answer 34

* **ulnar nerve** * the ulnar nerve is the default innervator of intrinsic hand muscles * innervates all interosseous muscles, both palmar and dorsal * also innervates the adductor pollicis, for the thumb

Question 35

adduct fingers * Muscles? * Innervation

Answer 35

* 3 **palmar interosseous muscles**"PAD muscles" * for index, ring, and little fingers * _Don't need for middle finger, because dorsal interosseous muscles that attach to middle finger do both_ * _Don't need for thumb, because it has its own personal ADuctor, the aductor pollicis deep in palm of hand_ * ADduct, so fingers touch each other again * All interosseous muscles (both palmar and dorsal) are innervated by deep branch of **ulnar nerve**

Question 36

What gives us the exclusive power to flex our distal phalanx at each of the four fingers?

Answer 36

* tendons of the **flexor digitorum profundus** muscle * arises in the flexor forearm * also helps with flexing at other joints, but its major action is at last joint, the distal phalanx * Innervated by **median nerve**

Question 37

default nerve for flexor foream muscles?

Answer 37

* median nerve and its branches

Question 38

default nerve for innervation of flexor ARM muscles?

Answer 38

* musculocutaneous * The musculocutaneous nerve innervates the muscles in the anterior compartment of the arm – the biceps brachii, brachialis and coracobrachialis. These muscles flex the upper arm at the shoulder and the elbow. In addition, the biceps brachii also performs supination of the forearm.

Question 39

default nerve for intrinsic hand muscles

Answer 39

* ulnar nerve * All interosseous muscles of the hand, with the exception of the first and second lumbricals (the most radial two are innervated by the median nerve), are innervated by the deep branch of the ulnar nerve. * anterior division fibers

Question 40

innervation of flexor digitorum profundus and lumbricals?

Answer 40

* flexor digitorum profundus innervation matches the innervation of the lumbricals: * **those that go to index and middle finger are innervated by median nerve** * ​Median nerve innervates 1st and 2nd * **those going to ring and pinkie are innervated by ulnar nerve** * Ulnar nerve innervates 3rd and 4th

Question 41

flexor digitorum superficialis - what's significant about it?

Answer 41

* innervated by median nerve, which runs deep to it * **gives exclusive ability to flex middle phalanges at PIP** * **​**since most distal joint is most important place where muscle acts * Innervated by **median nerve** * (default answer for flexor forearm) * in the intermediate layer of flexor muscles in anterior forearm

Question 42

wrist flexors and extensors

Answer 42

* 2 flexor carpi muscles: * flexor carpi radialis, flexor carpi ulnaris * **Flexor carpi radialis innervated by median nerve** * **Flexor carpi _ulnaris_ innervated by _ulnar_ nerve** * 3 extensor carpi muscles: wrist extensors * All innervated by **radial nerve** * (extensor carpi ulnaris, extensor carpi radialis longus/brevis)

Question 43

**where is the major action of:** the flexor digitorum profundus? flexor digitorum superficialis? lumbricals? interosseous muscles

Answer 43

* Flexor digitorum profundus - DIP * Flexor digitorum superficialis - PIP * Lumbricals - IPS (and also MP) * The major muscles that **extend** all four fingers at both the interphalangeal joints * share their innervation between median and ulnar nerve * Extensor digitorum - MP * Just the knuckles * Dorsal interosseous vs. palmar interosseous * Dorsal abduct "DAB" at MP joints * Palmar adduct "PAD" at MP joints * All innervated by branches of ulnar nerve

Question 44

blood supply to forearm and hand

Answer 44

* have primary blood supply and back-up blood supply * **Brachial artery splits into the ulnar artery and radial artery** at the cubital fossa (anterior to the elbow) * They run close to their respective bones. * Radial artery supplies posterior forearm, ulnar supplies anterior. * Ulnar artery gives rise to **superficial palmar arch --\>** palmar ulnar digital arteries --\> supply medial and lateral sides of every thumb/finger * Radial artery --\> **deep palmar arch** --\> supplies thumb and lateral index finger * The two arches can **anastamose** with each other. * Readily available collateral blood supply

Question 45

what lies under the aponeurosis of the palm?

Answer 45

* First thing you see under the palm's aponeurosis is the **superficial palmar arch**, on the medial side of the palm * Comes from the ulnar artery * (Whereas the radial artery gives rise to deep palmar arch)

Question 46

dorsal interossei vs palmar interossei * where do they (both) act? * What's the difference in their action

Answer 46

* Dorsal abduct "**DAB**" * Palmar adduct "**PAD**" * All at **MP** joints * All innervated by branches of **ulnar nerve**

Question 47

Nerves that control thumb movements? * ABduction (2) * ADduction * Extension * Flexion * Opposition

Answer 47

* 3 nerves control thumb: * Radial - ABduction, extension, * Median - ABduction, flexion, opposition * Ulnar - ADduction * Abduction: 2 muscles and 2 nerves * **Abductor pollicis longus - radial nerve** (in extensor compartment) * **Abductor pollicis brevis** - recurrent branch of **median nerve** (in thenar eminence) * So unusual for patient to totally lose ability to oppose thumb * Adduction: * **Adductor pollicis - ulnar nerve** (shares interosseus innervation) * Extension: * ​Extensor pollicis longus, brevis, extensor digitorum * **posterior interosseus branch of radial nerve** (controls extension of anything except fingers beyond MPs) * Flexion: * Flexor pollicis brevis * Flexor pollicis longus (one of the 9 tendons through the carpal tunnel) - **anterior interosseus branch of median nerve** * Opposition (for power grip) * muscles in thenar eminence innervated by **recurrent branch of median nerve** * ulnar nerve to a lesser extend (hypothenar eminence to pull pinkie over)

Question 48

what can't the thumb do if... * Radial nerve is lesioned * Median nerve is lesioned * Ulnar nerve is lesioned

Answer 48

* Radial - ABduction, extension, * Median - ABduction, flexion, opposition * Ulnar - ADduction

Question 49

what's important at this point

Answer 49

* Carpal-metacarpal joint * Formed by distal row of carpal bones, specifically the **trapezium**, and the first metacarpal - where most of thumb actions take place

Question 50

Answer 50

Question 51

name hand bones and joints

Answer 51

Question 52

which finger joints allow for more motion?

Answer 52

* The interphalangeal joints are relatively restricted in action; they are simple hinge joints that permit only flexion and extension. * The **metacarpophalangeal joints also permit flexion and extension, as well as abduction (finger spreading) and adduction**

Question 53

nerves and muscles involved for flexion and extension of fingers: Digits 2 + 3: - MCP joint: - PIP joint: - DIP joint: Digits 4 + 5: - MCP joint: - PIP joint: - DIP joint:

Answer 53

## Footnote Digits 2 + 3: - MCP joint: flexion by lumbricals (median nerve), extension by extensor digitorum (radial) - PIP joint: flexion by flexor digitorum superficialis (median nerve), extension by lumbricals (median nerve) - DIP joint: flexion by flexor digitorum profundus (median nerve), extension by lumbricals (median nerve) Digits 4 + 5: - MCP joint: flexion by lumbricals (ulnar nerve), extension by extensor digitorum (radial) - PIP joint: flexion by flexor digitorum superficialis (median nerve), extension by lumbricals (ulnar nerve) - DIP joint: flexion by flexor digitorum profundus (ulnar nerve), extension by lumbricals (ulnar nerve)

Question 54

List all joints where a muscle or muscles innervated by the radial nerve act as extensors.

Answer 54

A,B,E,H,I Muscles which produce MCP joint extension, all innervated by **PIN branch** of radial nerve: * Thumb: **Extensor Pollicis Brevis and Extensor Pollicis Longus** (PIN) * Index: **Extensor Indicis** (PIN) * Index, middle, ring and pinkie: **Extensor Digitorum** (PIN) * Pinkie: **Extensor Digiti Minimi** (PIN)