The Bones of the Hand
The bones of the hand are of three types: the carpals of the wrist, the metacarpal bones of the palm, and the phalanges of the fingers.
The Carpal bones
The carpal bones are eight bones arranged in proximal and distal rows. From lateral to medial, the bones of the proximal row are the scaphoid, lunate, triquetal and pisiform. The distal row (from lateral to medial) consists of the trapezium, trapezoid, capitate and hamate.
The scaphoid and lunate articulate with the lower end of the radius, while the triquetal articulates with the inter-articular disc of the lower end of the ulna.
The bones of the distal row articulate with the proximal row proximally and with the bases of metacarpals distally. The trapezium articulates with first metacarpal, the trapezoid with the second, the capitate with third, and the hamate with the fourth and fifth metacarpals.
The palmar suface of the carpal bones is concave from side to side, forming an arch called the carpal arch. The medial margin of the arch is formed by the pisiform and hook of the hamate. The lateral margin of the arch is formed by the scaphoid tubercle and the crest of the trapezium. The carpal arch forms part of the carpal tunnel which consists of the flexor retinaculum, attached laterally to the tubercle of the scaphoid and the crest of the trapezium and medially to the pisiform and hook of hamate.
The scaphoid and lunate articulate with the lower end of the radius, while the triquetal articulates with the inter-articular disc of the lower end of the ulna.
The bones of the distal row articulate with the proximal row proximally and with the bases of metacarpals distally. The trapezium articulates with first metacarpal, the trapezoid with the second, the capitate with third, and the hamate with the fourth and fifth metacarpals.
The palmar suface of the carpal bones is concave from side to side, forming an arch called the carpal arch. The medial margin of the arch is formed by the pisiform and hook of the hamate. The lateral margin of the arch is formed by the scaphoid tubercle and the crest of the trapezium. The carpal arch forms part of the carpal tunnel which consists of the flexor retinaculum, attached laterally to the tubercle of the scaphoid and the crest of the trapezium and medially to the pisiform and hook of hamate.
Attachment of the carpal bones
1) Flexor carpi ulnaris is inserted into the pisiform.
2) The hypothenar muscles originate from the pisiform and the hamate.
3) The thenar muscles originate from the scaphoid and the trapezium.
4) The flexor retinaculum is attached medially to the pisiform and hook of the hamate and is laterally attached to the trapezium and tubercle of the scaphoid.
5) The extensor retinaculum is attached to the pisiform and hook of the hamate medially.
2) The hypothenar muscles originate from the pisiform and the hamate.
3) The thenar muscles originate from the scaphoid and the trapezium.
4) The flexor retinaculum is attached medially to the pisiform and hook of the hamate and is laterally attached to the trapezium and tubercle of the scaphoid.
5) The extensor retinaculum is attached to the pisiform and hook of the hamate medially.
Figure1: The bones of the hand
The metacarpal bones
There are five metacarpals, each of which has a base, a shaft and a head. The base is the proximal expanded end that articulates with the distal row of carpal bones. The shaft has palmar and dorsal surfaces. The head is the distal expanded end that articulates with the proximal phalanx.
Attachment of the metacarpal bones:
1) Flexor carpi radialis is inserted into the base of the second metacarpal on the palmar surface.
2) The palmar interossei originates from the metacarpals. The first originates from the medial side of the base of first metacarpal, the second from the medial side of the palamar surface of the second metacarpal, the third from the lateral side of the palmar surface of the fourth metacarpal, and the fourth from the lateral side of the palmar surface of the fifth metacarpal.
3) The oblique head of adductor pollicis originates from the bases of the second and third metacarpals, while the transverse head originates from the palmar surface of the third metacarpal.
4) Abductor pollicis longus is inserted into the palmar surface of the base of first metacarpal.
5) Extensor carpi radialis longus is inserted into the dorsal surface of the base of the second metacarpal bone.
6) Extensor carpi radialis brevis is inserted into the dorsal surface of the base of the third metacarpal.
7) Extensor carpi ulnaris is inserted into the dorsal surface of the base of the fifth metacarpal bone.
8) The dorsal interossei originates from the adjacent sides of the dorsal surface of the metacarpals.
1) Flexor carpi radialis is inserted into the base of the second metacarpal on the palmar surface.
2) The palmar interossei originates from the metacarpals. The first originates from the medial side of the base of first metacarpal, the second from the medial side of the palamar surface of the second metacarpal, the third from the lateral side of the palmar surface of the fourth metacarpal, and the fourth from the lateral side of the palmar surface of the fifth metacarpal.
3) The oblique head of adductor pollicis originates from the bases of the second and third metacarpals, while the transverse head originates from the palmar surface of the third metacarpal.
4) Abductor pollicis longus is inserted into the palmar surface of the base of first metacarpal.
5) Extensor carpi radialis longus is inserted into the dorsal surface of the base of the second metacarpal bone.
6) Extensor carpi radialis brevis is inserted into the dorsal surface of the base of the third metacarpal.
7) Extensor carpi ulnaris is inserted into the dorsal surface of the base of the fifth metacarpal bone.
8) The dorsal interossei originates from the adjacent sides of the dorsal surface of the metacarpals.
Figure2: Attachment of the palmar surface of the hand
The phalanges
There are fourteen phalanges in each hand, the medial four digits contains three phalanges, proximal, middle and distal, while the thumb has only two, the proximal and distal phalanges. Each phalanx has a base, shaft and a head.
Attachment of the phalanges
1) Flexor pollicis longus is inserted into the palmar surface of the base of the terminal phalanx of the thumb.
2) Flexor digitorum superficialis is inserted into the palmar surface of the middle phalanges of the medial four fingers.
3) Flexor digitorum profundus is inserted into the palmar surface of the bases of the terminal phalanges of the medial four fingers.
4) Extensor pollicis brevis is inserted into the dorsal surface of the base of the proximal phalanx of the thumb.
5) Extensor pollicis longus is inserted into the dorsal surface of the base of the terminal phalanx of the thumb.
6) Extensor expansion is inserted into the dorsal surface of the bases of the middle and distal phalanges of the medial four fingers.
