The hand

Question 1

What are the 3 types of grip?

Answer 1

Power grip
Precision grip
Hook grip

Question 2

What is a power grip?

Answer 2

The fingers are flexed around an object with counter pressure from the thumb, e.g. grasping a rod.

Question 3

What muscle groups must be activated to form a power grip?

Answer 3

Long flexors of the fingers and thumb
Intrinsic muscles of the palm
Extensors of the wrist joint (to give more power to the long flexors)

Question 4

What is a precision grip?

Answer 4

The object is gripped between the tips of the fingers and the thumb, with the intrinsic muscles of the hand carrying out the fine movements needed. Typically, the wrist and fingers are held rigidly by the long flexors and extensors.
e.g. unbuttoning a shirt.

Question 5

What is the palmar aponeurosis?

Answer 5

A well-defined region of palmar fascia in the hand that overlies the long flexor tendons of the hand.
Proximal end is continuous with flexor retinaculum and palmaris longus tendon.
Distal end forms 4 bands continuous with fibrous digital sheaths of each finger.

Question 6

What are the fibrous digital sheaths?

Answer 6

Tubes which contain flexor tendons and their sheaths.

Question 7

What are septa?

Answer 7

Extensions of fascia that separate the space between the palmar aponeurosis and the bones of the hand into compartments.

Question 8

What are the muscles in the extensor compartment of the forearm that move the digits?

Answer 8

Extensor digitorum (ED)
Extensor indicis (EI)
Extensor digiti minimi (EDM)

Question 9

What are the muscles in the extensor compartment of the forearm that move the thumb?

Answer 9

Abductor pollicis longus (APL)
Extensor pollicis brevis (EPB)
Extensor pollicis longus (EPL)

Question 10

What are the thenar muscles?

Answer 10

Abductor pollicis brevis
Flexor pollicis brevis
Opponens pollicis

Question 11

What are the adductor (intrinsic) muscles of the hand?

Answer 11

Adductor pollicis

Question 12

What are the hypothenar muscles?

Answer 12

Abductor digiti minimi
Flexor digiti minimi
Opponens digiti minimi

Question 13

What are the actions of the lumbricals?

Answer 13

Flex at the MCPs

Extend at the IPJs

Question 14

What are the actions of the palmar interossei?

Answer 14

Adduct the digits (PAD)

There are 3.

Question 15

What are the actions of the dorsal interossei?

Answer 15

Abduct the digits (DAB)

There are 4.

Question 16

What type of joint is the carpometacarpal joint of the thumb?

Answer 16

Synovial saddle joint. Articulation between the trapezium and the thumb metacarpal- clinically important as it often becomes osteoarthritic.

Question 17

What type of joints are the carpometacarpal joints of the digits (excluding thumb)?

Answer 17

Synovial elipsoid joints between the trapezoid, capitate and hamate with the metacarpals of the digits.
CMCs of the index and middle fingers are very rigid, that of the ring finger is less rigid and that of the little finger is very mobile.

Question 18

What type of joints are the intermetacarpal joints?

Answer 18

Plane synovial joints between the metacarpals and their bases.

Question 19

What movements occur at the carpometacarpal and intermetacarpal joints?

Answer 19

Flexion and extension
Radial deviation and ulnar deviation
Circumduction

Question 20

What type of joints are the metacarpophalangeal joints?

Answer 20

Condylar synovial joints between the metacarpal heads and the proximal phalanges. Allow flexion, extension, abduction and adduction.

Question 21

What type of joints are the interphalangeal joints?

Answer 21

Hinge synovial joints which allow for flexion and extension. There is a proximal IP joint and a distal IP joint in each digit. The thumb only has one IP joint.

Question 22

What is the volar plate?

Answer 22

Important structure on the anterior surface of the proximal interphalangeal joint.
Dense condensation of fibrous tissue formed by the collateral ligaments at the front of the proximal IP joint- frequently damaged.

Question 23

What are the movements of the thumb?

Answer 23

Abduction
Adduction
Extension
Flexion
Opposition

Question 24

What are the muscles responsible for abduction of the thumb?

Answer 24

Abductor pollicis longus

Abductor pollicis brevis

Question 25

What are the muscles responsible for adduction of the thumb?

Answer 25

Adductor pollicis | First dorsal interosseous

Question 26

What are the muscles responsible for extension of the thumb?

Answer 26

Extensor pollicis longus Extensor pollicis brevis Abductor pollicis longus

Question 27

What are the muscles responsible for flexion of the thumb?

Answer 27

Flexor pollicis longus | Flexor pollicis brevis

Question 28

What are the muscles responsible for opposition of the thumb?

Answer 28

``` Opponens pollicis (works at carpo-metacarpal joint). Opposition also occurs at the metacarpo-phalangeal joint and involves abduction, flexion and then adduction at the metacarpo-phalangeal joint. ```

Question 29

What does the ulnar artery divide into, and where?

Answer 29

Runs into the hand over the flexor retinaculum, lateral to the pisiform and through the semi-rigid ulnar (Guyon's) can with the ulnar nerve. Divides just beyond this. Superficial palmar arch, which receives a contribution from the superficial palmar branch of the radial artery. Deep palmar branch of the ulnar artery. Superficial palmar arch gives off 3 common palmar digital arteries, which subsequently divide into palmar digital arteries.

Question 30

Where does the radial artery enter the hand?

Answer 30

Crosses the floor of the anatomical snuff box and enters the palm of the hand between the 2 heads of the first dorsal interosseous muscle. It then also passes between the 2 heads of the adductor pollicis muscle.

Question 31

What forms the deep palmar arch of the hand?

Answer 31

Radial artery anastomoses with deep palmar branch of ulnar artery. Gives origin to palmar metacarpal arteries.

Question 32

Discuss venous drainage of the hand.

Answer 32

Superficial and deep palmar arterial arches have corresponding palmar venous arches (deep drainage).  Dorsal digital veins drain into the dorsal venous arch (superficial system) on the dorsum of the hand. This arch gives rise to the cephalic vein laterally and the basilic vein medially. Most venous drainage of the hand is via the superficial system but some is via the deep system.

Question 33

What are the 3 main nerves to the hand?

Answer 33

``` Median nerve (C678,T1) Ulnar nerve (C8,T1) Radial nerve (C5678,T1) ```

Question 34

What nerve supplies the thenar muscles?

Answer 34

Median nerve.

Question 35

Describe the path and functions of the median nerve (C678,T1) to the hand.

Answer 35

At the wrist lies between FDS and FDP, deep to PL. Enters the carpal tunnel with FDP, FDS and FPL. Motor to: thenar muscles (APB, FPB, OP) and lumbricals I and II (lateral). Sensory to: palmar surface of thumb, IF, MF and half of RF; some of the dorsal surface of those digits.

Question 36

Describe the path and functions of the ulnar nerve (C8,T1) to the hand.

Answer 36

``` At the wrist lies by FCU. Runs over (not under) the flexor retinaculum, lateral to the pisiform. Divides into: superficial branch, sensory to palmar surfaces of LF and half of RF; deep branch, motor to hypothenar muscles, adductor pollicis, lumbricals III and IV, and all the interossei. ```

Question 37

Describe the path and functions of the radial nerve (C5678,T1) to the hand.

Answer 37

Divides just above the level of the elbow into: deep branch- the posterior interosseous nerve (motor); superficial branch- the superficial radial nerve (sensory). No motor supply in the hand. Sensory supply to the dorsum of the hand.

Question 38

What are the bony attachments of the carpal tunnel?

Answer 38

Scaphoid, trapezoid, pisiform, hamate | Form a gutter.

Question 39

What is the roof of the carpal tunnel?

Answer 39

Flexor retinaculum.

Question 40

What does the carpal tunnel contain?

Answer 40

Median nerve FPL tendon 4 tendons of FDP 4 tendons of FDS

Question 41

What is a hook grip?

Answer 41

Consumes little energy, mainly involves long flexors of digits, e.g. carrying shopping bag or briefcase.

Question 42

What part of the hand does the median nerve provide the sensory supply to?

Answer 42

Palmar surface of the thumb, index and middle finger, lateral half of ring finger. Some of the dorsal surface of these digits.

Question 43

What does carpal tunnel syndrome result from?

Answer 43

Compression of the median nerve in the carpal tunnel, resulting in tingling, loss of sensation and pain in the hand.

Question 44

What does the radial nerve (C5678,T1) supply in the hand?

Answer 44

The superficial branch of the radial nerve is cutaneous only. It is sensory to the lateral two-thirds of the dorsum of the hand, the dorsum of the thumb and the proximal portions of the dorsal index and middle fingers.

Question 45

What does the ulnar nerve (C8,T1) supply in the hand?

Answer 45

Palmar cutaneous branch– supplies medial palm of hand. Dorsal cutaneous branch– supplies medial half of dorsum of hand, including little and ring fingers. Superficial branch of the ulnar nerve– sensory to the palmar surface of the little finger and the medial side of the ring finger. Deep branch of the ulnar nerve– motor to -hypothenar muscles (abductor digiti minimi, flexor digiti minimi and opponens digiti minimi) medial (third and fourth) lumbricals -all the interossei Controls most of the muscles involved in fine movements of the hand.

Question 46

Describe the path of the ulnar nerve (C8,T1) from wrist to hand.

Answer 46

At the wrist it lies anteriorly, between the FCU (medially) and the ulnar artery (laterally) and then passes into the hand. Beyond the wrist the ulnar nerve passes over the flexor retinaculum in the ulnar canal with the ulnar artery, just lateral to the pisiform bone. It divides distal to the flexor retinaculum into superficial and deep branches.

Question 47

What is the clinical importance of the unusual blood supply to the scaphoid bone?

Answer 47

Its blood vessels tend to pass from distal to proximal. They can be interrupted by fracture of the waist of the bone, which can cut off the blood supply to its proximal portion causing avascular necrosis.

Question 48

What is Allen's test?

Answer 48

A visual test or relative contribution of radial and ulnar arteries to the hand. Subject is asked to raise the hand and make a clenched fist. Examiner compresses both radial and ulnar arteries. When the fist is released the palmar skin appears pale. The examiner releases either one of the arteries and notes the time for the return of the hand colour.