Human Anatomy Vol 1

elbow is extended, and an equilateral triangle when

the elbow is flexed to a right angle (see Fig. 2.19).

The relative position of the three bony points is

disturbed when the elbow is dislocated.

T}ae head of the radius can be palpated in a depression

on the posterolateral aspect of an extended elbow

just below the lateral epicondyle of the humerus. Its

rotation can be felt during pronation and supination

of the forearm.

The posterior border of the ulna is subcutaneous in its

entire length. It can be felt in a longitudinal groove

on the back of the forearm when the elbow is flexed

and the hand is supinated. The border ends distally

in the styloid process of the ulna. It separates the

flexors from the extensors of the forearm. Being

superficial, it allows the entire length of the ulna to

be examined for fractures.

Tlte head of the ulna forms a surface elevation on the

posteromedial. aspect of the wrist in a pronated

forearm.

The styloid processes of the radius and ulna are

important landmarks of the wrist. The styloid

process of the radius can be felt in the upper part of

the anatomical snuff box.Itprojects down 1 cmlower

than the styloid process of the ulna. The latter

descends from the posteromedial aspect of the ulnar

head. The relative position of the two styloid

processes is disturbed in fractures at the wrist, and

is a clue to the proper realignment of fractured bones.

The dorsal tubercle of the radius (Lister's tubercle) can

be palpated on the dorsal surface of the lower end of

the radius in line with the cleft between the index

and middle fingers. It is grooved on its medial side

by the tendon of the extensor pollicis longus.

FOBEARM AND HAND

The anatomical snuff box (Fi9.9.33) is a triangular

depression on the lateral side of the wrist. It is seen

best when the thumb is extended. It is bounded

anteriorly by tendons of the abductor pollicis longus

and extensor pollicis brevis, and posteriorly by the

tendon of the extensor pollicis longus. It is limited

above by the styloid process of the radius. The floor

of the snuff box is formed by the scaphoid and the

trapezium, and is crossed by the radial artery, radial

nerve and cephalic vein.

The heads of the metacarpals form the knuckles.

DISSECIION

Make the incision in the centre of dorsum of hand.

Reflect the skin of dorsum of hand till the respective

borders. Reflect the skin of dorsum of middle finger on

each side. Look for nerves on the back of forearm and

hand. These are superficial branch of radial nerve and

dorsal branch of ulnar nerve.

The dorsal venous network is the most prominent

component of the superficialfascia of dorsum of hand.

(ldentify the beginning of cephalic and basilic veins by

tying a tourniquet on the forearm and exercising the

closed fist on oneself).

The deep fascia at the back of wrist is thickened to

form extensor retinaculum. Define its margins and

attachments. ldentify the structures traversing its six

compaftments.

Clear the deep fascia over the back of forearm.

Define the attachment of triceps brachii muscle on the

olecranon process of ulna. Define the attachments of

the seven supedicial muscles of the back of the forearm.

Separate the anterolateral muscles, i.e.

brachioradialis, extensor carpi radialis longus and brevis

from the extensor digitorum lying in the centre and

extensor digiti minimi and extensor carpi ulnaris situated

on the medial aspect of the wrist. Anconeus is situated

on the posterolateral aspect of the elbow joint. Dissect

all these muscles and trace their nerve supply.

DORSUM OF HAND

1. Skin: It is loose on the dorsum of hand. It can be
   pinched off from the underlying structures
   2 Superficial fascia: The fascia contains dorsal venous
   plexus and cutaneous nerves
   a. Dorsal aenous plexus: The digital veins from adja-
   cent sides of index, middle; ring and little fingers
   form 3 dorsal metacarpal veins (seeFig.7.7).These
   join with each other on dorsum of hand. The
   lateral end of this arch is joined by one digital vein

icl

tr

=

oq

CL

f

c

.a

oo

a

lncision for

ulnar bursa

lncision for
thenar space

lncision for

pulp space

incision for

midpalmar

space

Fig. 9.54: The surgical incisions of the hand