L40. Joints of the Wrist and Hands

Question 1

How are the carpals arranged?

Answer 1

In two rows the proximal row (towards forearm) and the distal row (towards the fingers)

Question 2

What are the carpals of the proximal row?

Answer 2

From lateral to medial:

Scaphoid, Lunate, Triquetrium, Pisiform

Question 3

What are the carpals of the distal row?

Answer 3

From lateral to medial:

Trapezium, Trapezoid, Capitate, Hammate

Question 4

The hand is subdivided into three regions, what are these?

Answer 4

Short bones (carpals of the wrist)
Metacarpals (long bones of the hand - palm)
Phalanges

Question 5

How are the phalanges subdivided?

Answer 5

All (except the first metacarpal phalange) is divided into three: proximal, middle and distal (the thumb only has 2 subdivisions)

Question 6

What bone forms the floor of the anatomical snuff box?

Answer 6

The scaphoid

Question 7

The pisiform bone is an example of a sesamoid bone. What does this mean?

Answer 7

It lies completely within a tendon

Question 8

The metacarpal of the thumb is at a right angle to the other metacarpals. What does this signify?

Answer 8

This has an impact on the movement of the thumb in relation to the rest of the hand (the thumb has relative increased range of movement)

Question 9

Metacarpals are examples of long bones however they differ in their development to typical long bones. How is this so?

Answer 9

They only ossify at one end

Question 10

Why is there are large (boney) gap between the head of the ulnar and the triquetrium?

Answer 10

Because the ulna is not in any way involved in the wrist joint. There is a cartilaginous disc there

Question 11

The two wrist creases form important landmarks in terms of underlying boney anatomy. What do they form?

Answer 11

Distal wrist crease: the proximal attachement of the flexor retinaculum (ligament) that extends to the palm of the hand

Proximal wrist crease: where the wrist joint itself is

Question 12

Do the carpal bones ossify before or after birth?

Answer 12

Only after birth and progressively so. The captitate is the first one to ossify and then progressively in a counterclockwise direction ossify (hammate, triquetrium, lunate etc)
The pisiform is the last to ossify

Question 13

The pisiform sits up and projects anteriorly than the rest of the carpal. What is a major significance of this?

Answer 13

A muscle lies on top of it and this raised bone allows higher efficiency of the muscle in flexor action

Question 14

The flexor retinaculum ligament overlies and attaches to certain parts of the carpal bones forming a tunnel. Where does it attach to?

Answer 14

Pisiform
Hook of the hammate
Scaphoid tubercle
Trapezium tubercle

Question 15

What runs through the tunnel made by the carpal bones and the flexor retinaculum ligament?

Answer 15

a key structure of vessels tendons and nerves enter the hand through it.

Question 16

What are the two major joints of the wrist complex?

What type of joint is each one?

Answer 16

Radiocarpal joint (wrist joint proper) between the radius and the scaphoid+lunate
= synovial ellipsoid joint (also called condylar) = circumduction movement

Intercarpal (midcarpal) joint between the proximal and distal carpal rows
= plane synovial joints

Question 17

Is there a joint cavity in the wrist?

Answer 17

There is no single joint cavity. The bones simply articulate with each other

Question 18

What kind of movements occur at the wrist complex joints?

Answer 18

Biaxial movement:
Flexion and extension
AND
Radial and ulnar deviation (adduction and abduction)

Question 19

The radiocarpal (wrist joint) has articular surfaces that are concave in 2 different directions. What does this mean for its movement?

Answer 19

There is no pure rotation of the joint

there is CIRCUMDUCTION which means a combination of all movements

Question 20

With the movements of the wrist, flexion is greater than extension. Why is this so?

Answer 20

Because posteriorly, the radius descends further than in the anterior plane. Thus there is more potential of movement in the anterior part of the wrist which is the flexor movement.

Question 21

Which movement in the wrist is larger, ulnar deviation (adduction) or radial deviation (abduction)?

Answer 21

Ulnar deviation is much greater than radial deviation because the radial styloid process blocks complete movement of the wrist in the radial direction.

Question 22

Are the intercarpal joints functional or anatomic?

Answer 22

The are functional

Question 23

The amalgum of spaces of the intercapal joints are linked by what?

Answer 23

Interosseus ligaments

Question 24

How are the movements related (ie. which is greater) in the intercarpal joints to that of the wrist?

Answer 24

movement is generally much, much smaller overall

Movement trends are opposite to the wrist.
Thus intercarpal:
extension>flexion
radial > ulnar

Question 25

Both the radiocarpal and the intercarpal joints contain synovial membrane and hyaline cartilage. What does this mean?

Answer 25

They are synovial joints

Question 26

The joints are reinforced by ligaments. What are the 2 major functions of these ligaments?

Answer 26

1. Stabilise the joints

2. All of them transmit vessels to the bones

Question 27

What are the major ligaments that support the joints?

Answer 27

1. Palmar ligaments: ANTERIOR
   - ventral radiocarpal palmar ligament attaching from the radius then travelling obliquely distally and medially towards the metacarpals
   - ventral ulnocarpal palmar ligmant similarily attaching to the ulna and travelling obliquely
2. Dorsal ligaments: POSTERIOR
   - dorsal radiocarpal
   - dorsal ulnocarpal (much smaller and less significant)

Question 28

Which of the ligmanets is stronger?
Palmar or dorsal?
Ulnar or radial?

Answer 28

Palmer are stronger than dorsal

AND

Radio are stronger than ulnar (because they prevent the carpal bones from sliding medially into the gap)

Question 29

Where do the main flexor and extensor tendons (off muscles in the forearm) extend to?

Answer 29

They attach to proximal aspects of the metacarpals

NOTHING ATTACHES TO THE CARPAL BONES (except the pisiform)

Question 30

Describe how contraction of the flexor and extensor tendons reinforces the joints?

Answer 30

Contraction pulls the metacarpals distally towards the carpals leading to compressive forces that stabilise the joints

Question 31

What percent of all fractures and dislocations of the body occur at the wrist?

Answer 31

About 6%

Question 32

What is the most commonly fractured bone in the upper limb? How does this occur?

Answer 32

The distal radius (and the clavicle), especially in the elderly
= called Colles Fracture

Forces on the hand transmit especially from the capitate carpal up to the scaphoid (and lunate) and to the distal radius.

Question 33

What is the most frequently fractured carpal bone? How does this occur?

Answer 33

The scaphoid

Forces on the hand act on the capitate (large and strong) which transmits forces that fracture the scaphoid bone

Question 34

Which is the most commonly subluxed bone of the hand? Why is this so?

Answer 34

The lunate bone is most commonly subluxed because it lies adjacent to the ‘gap’ between the ulnar and the wrist.

This is particularly common secondary to ligament, radio-scaphoid-lunate injury

Question 35

There is a specialised ligament in the wrist, what is it called and what is the function?

Answer 35

The radio-scapho-lunate ligament from the radius over the scaphoid and onto the lunate to stabilise the lunate and prevent it from subluxation

Question 36

What are the two common fractures of the metacarpals?

Answer 36

At the base of the first metacarpal = bennet’s fracture

At the neck of the 5th metacarpal = boxer’s fracture

Question 37

What are the different movements of the thumb?

Answer 37

Extension, Flexion, Abduction, Adduction, Circumduction and Opposition

Question 38

What bones make up the major carpometacarpal joint of the thumb and what kind of joint is this?

Answer 38

Trapezoid and first metacarpal

Saddle joint

Question 39

What is the pathology of a scaphoid fracture?

Answer 39

The scaphoid bone has numerous vascular foraminae between the two articular surfaces. These allow for vessels to pass through.

In about 30-35% of the population, the location of the foraminae are only distally (hence supply goes to distal and then back to proximal).

Fracture occurs through the waist where these vessels lie and if it occurs in these people, interruption of proximal blood supply occurs leading to avascular necrosis.

Question 40

What kind of joints are the carpometacarpal joints?

Answer 40

All are synovial

Question 41

The four carpometacarpal joints (exception is the thumb saddle joint) are linked, what by and what does this mean?

Answer 41

By a deep transverser metacarpal ligament

Means that joints II-III are immobile between the joints and that there is force transmission

Question 42

Carpometacarpal joints IV and V are slightly more mobile that the others. How so

Answer 42

IV and V are hinge joints allowing for flexion and extension and V is also able to abduct further.

Question 43

What kind of joint are the metacarpophalangeal joints?

Answer 43

Condyloid joints
Convex head of the metacarpal joins with the concave base of phalax.

Also hinge joints

Question 44

What is the volar plate?

Answer 44

A fibrocartilaginous plate that expands the surface of articulation between the metacarpals and the phalages (this is also present in the interphalangeal joints).

Question 45

How are the metacarpophalangeal joints stabilised?

Answer 45

They all have collateral ligaments attached to them

Question 46

What is easier, flexed abduction/adduction or extended abduction/adduction of the fingers. Why is this so?

Answer 46

It is easier to be extended and abduct and adduct because of the tension of the ligaments.

Thus it is better to immobilise in flexion (tensed/tightened ligament)

Question 47

What are the two different types of injury to the interphalangeal joints? What happens in compensation?

Answer 47

Palmar (hyper extension): swan’s neck with compensatory flexion of the tip

Dorsal (flexion): boutonniere with compensatory hyperextension of the tip