Anatomy of the Forearm and Wrist

Question 1

Give the 4 types of grip in hand function

Answer 1

Power grip
-fist clenched holding something

Pinch grip
-pads of fingers together to hold something

Key grip
-making an “ok” sign with fingers (tips together rather than pads)

Tripod grip
-thumb, index and middle finger touching to give a tripod

Question 2

What is Colles’ fracture?

What is fractured? How can you spot it -> what does the wrist look like? What is it also called?

Answer 2

A Colles’ fracture is a fracture of the distal radius in the forearm with dorsal (posterior) and radial displacement of the wrist and hand. The fracture is sometimes referred to as a “dinner fork” or “bayonet” deformity due to the shape of the resultant forearm. Colles’ fractures are often seen in people with osteoporosis.

Hand will almost look like a fork shape with wrist displaced posteriorly

Question 3

How does the scaphoid bone lie in relation to the lunate bone?

(location and orientation)

Answer 3

Lateral at 45 degrees

Question 4

What is the most common type of carpal bone fracture?

How can you spot it? -> signs and symptoms

Answer 4

Scaphoid fracture

Scaphoid fractures usually cause pain and sensitivity to palpation in the anatomic snuffbox at the base of the thumb accompanied by swelling in the same area.

Question 5

What is Kienbocks Disease?

What is effected? How does this occur?

Answer 5

It is breakdown of the lunate bone, a carpal bone in the wrist that articulates with the radius in the forearm.

Specifically, Kienböck’s disease is another name for avascular necrosis (death and fracture of bone tissue due to interruption of blood supply) with fragmentation and collapse of the lunate.

This has classically been attributed to arterial disruption, but may also occur after events that produce venous congestion with elevated interosseous pressure.

Question 6

What bone is at the base of the thumb?

How do you remember this?

Answer 6

Trapezium

TrapeziUM -> Base of ThUMb
rhyhms

Question 7

What is the action of the anterior compartment of the forearm on the wrist?

Answer 7

Flex the wrist when acting together

Abduct or adduct the wrist in isolation

Question 8

Name the 5 anterior compartment muscles of the forearm

Answer 8

• Flexor carpi radialis
• Flexor carpi ulnaris
• Palmaris longus
• Pronator teres
• Brachioredialis

Question 9

What are the actions of flexor carpi radialis and flexor carpi ulnaris on the wrist when they act in isolation?

Answer 9

Flexor carpi radialis abducts

Flexor carpi ulnaris adducts

Question 10

The median nerve supplies most of the muscles of the anterior compatment of the forearm appart from which muscle?

Answer 10

Flexor carpi ulnaris

Question 11

What action do the muscles of the anterior compartment of the forearm have on the elbow?

Answer 11

Flexion

arise from the medial epicondyle of the humerus so act across the elbow as well as the wrist

Question 12

What are the actions of the pronator teres?

Answer 12

Pronation of the forearm by pulling on the radial bone

Question 13

What is the action of the brachioradialis?

Answer 13

Flexion of the elbow in the hammer curl position

Question 14

What role do the extensors of the wrist (on the posterior surface of the forearm) play in terms of grip strength?

Answer 14

Look at your hand side on and make a fist.

When you grip your wrist will extend slightly giving a stronger grip.

To break someones grip in a grappling hold you can flex the wrist disabling these extensors and weakening grip

Question 15

The posterior forarm compartment muscles arrise from what bony structure?

How does this compare to the anterior forarm compartment?

Answer 15

Medial epicondyle of the humerus -> anterior compartment

lateral epicondyle of the humerus -> posterior compartment

Question 16

What are the 3 muscles of the posterior compartment of the forearm?

Which muscles when acting in isolation adduct and abduct?

Answer 16

Abduction:

• Extensor carpi radialis longus
• Extensor carpi radialis brevis

Adduction
-Extensor carpi ulnaris

(remember the bone they follow)

Question 17

What are the actions of extensor digitorum muscle?

Answer 17

Extend the fingers, elbow and wrist

Question 18

What is the action of the extensor digiti minimi muscle?

Answer 18

It extends the wrist, which means it moves the back of the hand toward the back of the forearm. It also extends the little finger, which means it straightens the little finger from a fist.

Question 19

What are the attachments of the flexor digitorum superficialis?

Answer 19

Medial epicondyle of humerus
(anterior compartment so flexor)

Middle phalanges of digits 2-5 (not thumb)

Question 20

What are the 2 muscles which control fexion of the digits and lie under the flexor digitorum superficialis?

What fingers do they act on?

Answer 20

Flexor digitorum profundus
- Acts on fingers but not thumb

Flexor pollicis longus
-acts on the thumb

Question 21

What are the actions of the intermediate muscle layer of the forearm?

(3 muscles)

Answer 21

Flexor digitorum superficialis
- Primarily Flex proximal interphalangeal joints

Flexor digitorum profundus and Flexor pollicis longus
- Primarily Flex distal interphalangeal joint

all 3 muscles also act synergistically at all the other joints they cross (such as the wrist)

Question 22

What is the flexor sheath?

What does it do?

What is each sheath called?

Answer 22

The flexor sheath is a sheath of tissue which surrounds the flexors of the fingers.

Each sheath is called a pulley

This holds the tendons which flex the fingers against the finger like eyelets on a rod when fishing wire contracts

Question 23

What is the action of the deep extensors of the forearm?

What surface anatomy structure do they create when they contract?

Answer 23

Extend and abduct the thumb and index finger

Tendons of these muscles form the anatomical snuff box

Question 24

Name the 4 deep extensors of the forearm which act on the thumb and index finger

Answer 24

Abductor pollicis longus
Extensor pollicis brevis
Extensor pollicis longus
Extensor indicis

Question 25

Which two tendons form the anatomical snuff box?

Answer 25

Extensor pollicis longus

Extensor pollicis brevis

Question 26

The intrinsic muscles of the hand can be subdivided depending on the structure they act on.

What are these divisions called and on what structures fo they act on?

Answer 26

Intrinsic muscles subdivided into those moving the thumb (THENAR) and those moving the little finger (HYPOTHENAR) or all of the fingers

Question 27

Name the three thenar muscles.

What do these do individually and generally?
i.e. what do they move and individualy in what way

Answer 27

Flexor pollicis brevis
-flexion of the thumb

Abductor pollicis brevis

• abduction of the thumb
• i.e. separate thumb from hand in anatomical plane

Opponens pollicis
-moves the thumb across the palm in addition to flexion so that it can touch other finger tips

ALL ACT TO MOVE THE THUMB

Question 28

Name the three hypothenar muscles.

What do these do individually and generally?
i.e. what do they move and individually in what way

Answer 28

Flexor digiti minimi
-Flexes little finger

Abductor digiti minimi
-Abducts little finger

Opponens digiti minimi
-oves little finger across palm

ALL ACT ON THE LITTLE FINGER

Question 29

What is the action of the interossei?

Answer 29

Lie between the digits and contribute to the bulk of the hand.

Responsible for abduction and adduction

Question 30

What are the two kinds of interossei and what is their action?

Answer 30

Dorsal interossei
-abductors
(DAB)

Palmar interossei
-adductors
(PAD)

Question 31

What are the attachments and actions of the Lumbrical muscles?

(these are really odd)

Answer 31

Proximal attachments are to the tendons of flexor digitorum profundus.

Lumbricals simultaneously flex the MCP joint and extend the PIP joint.

Distal attachments of these muscles on to the dorsal expansions of the phalanges

Question 32

Claw hand is also described as what?

think of the muscle action

Answer 32

Intrinsic minus hand