Download The Cubital Fossa Bones of the Forearm

378 CHAPTER 9 The Upper Limb
ligament of the elbow joint. It continues downward to enter
the forearm between the two heads of origin of the flexor
carpi ulnaris (see page 390).
Branches
The ulnar nerve has an articular branch to the elbow joint
(Fig. 9.23).
Profunda Brachii Artery The profunda brachii artery
arises from the brachial artery near its origin (Fig. 9.45).
It accompanies the radial nerve through the spiral groove,
supplies the triceps muscle, and takes part in the anastomosis around the elbow joint.
Superior and Inferior Ulnar Collateral Arteries The
superior and inferior ulnar collateral arteries arise from the
brachial artery and take part in the anastomosis around the
elbow joint.
laterally and the brachialis muscle medially. The roof is
formed by skin and fascia and is reinforced by the bicipital
aponeurosis.
Contents
The Cubital Fossa
The cubital fossa (Fig. 9.47) contains the following structures, enumerated from the medial to the lateral side: the
median nerve, the bifurcation of the brachial artery into the
ulnar and radial arteries, the tendon of the biceps muscle,
and the radial nerve and its deep branch.
The supratrochlear lymph node lies in the superficial
fascia over the upper part of the fossa, above the trochlea
(Fig. 9.40). It receives afferent lymph vessels from the third,
fourth, and fifth fingers; the medial part of the hand; and
the medial side of the forearm. The efferent lymph vessels
pass up to the axilla and enter the lateral axillary group of
nodes (Fig. 9.40).
The cubital fossa is a triangular depression that lies in front
of the elbow (Figs. 9.47 and 9.48).
Bones of the Forearm
The forearm contains two bones: the radius and the ulna.
Boundaries
■■
■■
Radius
Laterally: The brachioradialis muscle
Medially: The pronator teres muscle
The base of the triangle is formed by an imaginary line
drawn between the two epicondyles of the humerus.
The floor of the fossa is formed by the supinator muscle
biceps brachii tendon
biceps
cubital fossa
brachii
bicipital
brachioradialis
aponeurosis
cephalic vein
basilic vein
palmaris
longus
flexor
digitorum
superficialis
flexor carpi
radialis
site fo
palpati
of radi
artery
flexor carpi
ulnaris
pisiform
bone
FIGURE 9.48 The cubital fossa and anterior surface of the
forearm in a 27-year-old man.
The radius is the lateral bone of the forearm (Fig. 9.49).
Its proximal end articulates with the humerus at the elbow
joint and with the ulna at the proximal radioulnar joint. Its
distal end articulates with the scaphoid and lunate bones
of the hand at the wrist joint and with the ulna at the distal
radioulnar joint.
At the proximal end of the radius is the small circular
head (Fig. 9.49). The upper surface of the head is concave
and articulates with the convex capitulum of the humerus.
The circumference of the head articulates with the radial
notch of the ulna. Below the head, the bone is constricted
to form the neck. Below the neck is the bicipital tuberosity
for the insertion of the biceps muscle.
The shaft of the radius, in contradistinction to that
of the ulna, is wider below than above (Fig. 9.49). It
has a sharp interosseous border medially for the attachment of the interosseous membrane that binds the radius
and ulna together. The pronator tubercle, for the insertion of the pronator teres muscle, lies halfway down on
its lateral side.
At the distal end of the radius is the styloid process; this
projects distally from its lateral margin (Fig. 9.49). On the
medial surface is the ulnar notch, which articulates with
the round head of the ulna. The inferior articular surface
articulates with the scaphoid and lunate bones. On the posterior aspect of the distal end is a small tubercle, the dorsal
tubercle, which is grooved on its medial side by the tendon
of the extensor pollicis longus (Fig. 9.49).
The important muscles and ligaments attached to the
radius are shown in Figure 9.49.
Ulna
The ulna is the medial bone of the forearm (Fig. 9.49). Its
proximal end articulates with the humerus at the elbow
joint and with the head of the radius at the proximal
Basic Anatomy 379
capsule of elbow joint
olecranon process
radial notch of ulna
a
coronoid process
triceps
anc
anconeus
brachialis
pronator teres
head
neck
bicipital tuberosity
biceps brachii
biceps
flexor pollicis longus
supinator
aponeurosis for extensor
and flexor carpi ulnaris
oblique cord
supinator
flexor
digitorum
flexor digitorum
superficialis
abductor pollicis
longus
profundus
extensor pollicis longus
pronator teres
interosseous membrane
flexor pollicis
longus
extensor pollicis
brevis
extensor indicis
pronator quadratus
aperture for anterior
interosseous artery
dorsal tubercle of
radius
brachioradialis
styloid process
styloid process
capsule of wrist joint
anterior surface
posterior surface
FIGURE 9.49 Important muscular and ligamentous attachments to the radius and the ulna.
radioulnar joint. Its distal end articulates with the radius at
the distal radioulnar joint, but it is excluded from the wrist
joint by the articular disc.
The proximal end of the ulna is large and is known as
the olecranon process (Fig. 9.49); this forms the prominence of the elbow. It has a notch on its anterior surface,
the trochlear notch, which articulates with the trochlea
of the humerus. Below the trochlear notch is the triangular coronoid process, which has on its lateral surface
the radial notch for articulation with the head of the
radius.
The shaft of the ulna tapers from above down (Fig.
9.49). It has a sharp interosseous border laterally for the
attachment of the interosseous membrane. The posterior
border is rounded and subcutaneous and can be easily
palpated throughout its length. Below the radial notch
is the supinator crest that gives origin to the supinator
muscle.
At the distal end of the ulna is the small rounded head,
which has projecting from its medial aspect the styloid process (Fig. 9.49).
The important muscles and ligaments attached to the
ulna are shown in Figure 9.49.
Bones of the Hand
There are eight carpal bones, made up of two rows of
four (Figs. 9.51 and 9.52). The proximal row consists of
(from lateral to medial) the scaphoid, lunate, triquetral,
and pisiform bones. The distal row consists of (from lateral to medial) the trapezium, trapezoid, capitate, and
hamate bones. Together, the bones of the carpus present
on their anterior surface a concavity, to the lateral and
medial edges of which is attached a strong membranous
band called the flexor retinaculum. In this manner, an
osteofascial tunnel, the carpal tunnel, is formed for the
passage of the median nerve and the flexor tendons of the
fingers.
The bones of the hand are cartilaginous at birth. The
capitate begins to ossify during the first year, and the others begin to ossify at intervals thereafter until the 12th year,
when all the bones are ossified.
A detailed knowledge of the bones of the hand is
unnecessary. The position, shape, and size of the scaphoid
bone, however, should be studied, because it is commonly
fractured. The ridge of the trapezium and the hook of the
hamate should be examined.
380 CHAPTER 9 The Upper Limb
C L I N I C A L
N O T E S
Fractures of the Radius and Ulna
Fractures of the head of the radius can occur from falls on the
outstretched hand. As the force is transmitted along the radius,
the head of the radius is driven sharply against the capitulum,
splitting or splintering the head (Fig. 9.10).
Fractures of the neck of the radius occur in young children
from falls on the outstretched hand (Fig. 9.10).
Fractures of the shafts of the radius and ulna may or may
not occur together (Fig. 9.10). Displacement of the fragments is
usually considerable and depends on the pull of the attached
muscles. The proximal fragment of the radius is supinated by the
supinator and the biceps brachii muscles (Fig. 9.10). The distal
fragment of the radius is pronated and pulled medially by the
pronator quadratus muscle. The strength of the brachioradialis
and extensor carpi radialis longus and brevis shortens and angulates the forearm. In fractures of the ulna, the ulna angulates
posteriorly. To restore the normal movements of pronation and
supination, the normal anatomic relationship of the radius, ulna,
and interosseous membrane must be regained.
A fracture of one forearm bone may be associated with a dislocation of the other bone. In Monteggia’s fracture, for example,
the shaft of the ulna is fractured by a force applied from behind.
There is a bowing forward of the ulnar shaft and an anterior dislocation of the radial head with rupture of the anular ligament. In
Galeazzi’s fracture, the proximal third of the radius is fractured
and the distal end of the ulna is dislocated at the distal radioulnar
joint.
A
B
FIGURE 9.50 Fractures of the distal end of the radius.
A. Colles’ fracture. B. Smith’s fracture.
The Metacarpals and Phalanges
There are five metacarpal bones, each of which has a base,
a shaft, and a head (Figs. 9.51 and 9.52).
The first metacarpal bone of the thumb is the shortest and most mobile. It does not lie in the same plane as
the others but occupies a more anterior position. It is also
Fractures of the olecranon process can result from a fall on
the flexed elbow or from a direct blow. Depending on the location of the fracture line, the bony fragment may be displaced by
the pull of the triceps muscle, which is inserted on the olecranon
process (Fig. 9.10). Avulsion fractures of part of the olecranon
process can be produced by the pull of the triceps muscle. Good
functional return after any of these fractures depends on the
accurate anatomic reduction of the fragment.
Colles’ fracture is a fracture of the distal end of the radius
resulting from a fall on the outstretched hand. It commonly
occurs in patients older than 50 years. The force drives the distal fragment posteriorly and superiorly, and the distal articular
surface is inclined posteriorly (Fig. 9.50). This posterior displacement produces a posterior bump, sometimes referred to as the
“dinner-fork deformity” because the forearm and wrist resemble
the shape of that eating utensil. Failure to restore the distal articular surface to its normal position will severely limit the range of
flexion of the wrist joint.
Smith’s fracture is a fracture of the distal end of the radius
and occurs from a fall on the back of the hand. It is a reversed
Colles’ fracture because the distal fragment is displaced anteriorly (Fig. 9.50).
Olecranon Bursitis
A small subcutaneous bursa is present over the olecranon process of the ulna, and repeated trauma often produces chronic
bursitis.
rotated medially through a right angle so that its extensor
surface is directed laterally and not backward.
The bases of the metacarpal bones articulate with the
distal row of the carpal bones; the heads, which form the
knuckles, articulate with the proximal phalanges (Figs. 9.51
and 9.52). The shaft of each metacarpal bone is slightly
concave forward and is triangular in transverse section. Its
surfaces are posterior, lateral, and medial.
There are three phalanges for each of the fingers but
only two for the thumb.
The important muscles attached to the bones of the
hand and fingers are shown in Figures 9.51 and 9.52.
The Forearm
Skin
The sensory nerve supply to the skin of the forearm is from
the anterior and posterior branches of the lateral cutaneous
nerve of the forearm, a continuation of the musculocutaneous nerve, and from the anterior and posterior branches
of the medial cutaneous nerve of the forearm (Fig. 9.38).
A narrow strip of skin down the middle of the posterior
surface of the forearm is supplied by the posterior cutaneous
nerve of the forearm.
The superficial veins of the forearm lie in the superficial fascia (Fig. 9.39). The cephalic vein arises from the
lateral side of the dorsal venous arch on the back of the