Bones - Hand

Question 1

What are the different type of bones in the hand?

Answer 1

From proximal to distal:

1) Carpals - 8 irregular-shaped bones in the wrist area.
2) Metacarpals - 5 metacarpals, each one related to a digit.
3) Phalanges- the bones of the fingers. Each finger has three, except for the thumb, which has two.

Question 2

What are the bones of the proximal row of carpal bones?

Answer 2

From lateral to medial:

Scaphoid
Lunate
Triquetrium
Pisiform (sesamoid bone, formed within the tendon of the flexor carpi ulnaris).

Question 3

What are the bones of the distal row of carpal bones?

Answer 3

From lateral to medial:

Trapezium
Trapezoid
Capitate
Hamate

Question 4

What is the carpal tunnel?

Answer 4

This is the membranous band, the flexor retinaculum, spans between the medial and lateral edges of the carpal bones curve (in a coronal section).

Question 5

Which carpal bones articulate with the radius?

Answer 5

1) Scaphoid
2) Lunate

This forms the wrist joint (or radio-carpal joint). In the distal row, all the carpal bones articulate with the metacarpals.

Question 6

Clinical relevance: scaphoid fracture

Answer 6

This is most commonly fractured carpal bone - typically by falling of an outstretched hand (FOOH).

In a fracture of the scaphoid, the charateristic clinical feature is pain and tenderness in the anatomical snuffbox.

The scaphoid is at particular risk of avascular necrosis after fracture because of its so-called ‘retrograde blood supply’ which enters at its distal end. This means that a fracture to the middle (or ‘wrist’) of the scaphoid may interrupt the blood supply to the proximal part of the scaphoid bone rendering it avascular.

Patients with a missed scaphoid fracture are likely to develop osteoarthritis of the wrist later in life.

Question 7

Which carpals are associated with each digit?

Answer 7

M I - Thumb
M II - Index finger
M III - Middle finger
M IV - Ring finger
M V - Little finger

Question 8

What are the features of each metacarpal?

Answer 8

Each metacarpal consists of a base, shaft and a head. The medial and lateral surfaces of the metacarpals are concave, allowing attachment of the interossei muscles.

Question 9

Clinical relevance: fractures of the metacarpals

Answer 9

There are two common fractures of the metacarpals:

1) Boxer’s fracture - this is a fracture of the 5th metacarpal neck. It is usually caused by a clenched fist striking a hard object. The distal part of the fracture is displaced anteriorly, producing shortening of the affected finger.
2) Bennett’s fracture - a fracture of the 1st metacarpal base, caused by forces hyperabduction of the thumb. This fracture extends into the first carpometacarpal joint leading to instability and subluxation of the joint. As a result, it often needs surgical repair.

Question 10

How many phalanges are there in each finger?

Answer 10

There is a proximal and distal phalanx, while the rest of the digits have a proximal, middle and distal phalanges.