ent parts of the distal humerus are in contact with the corresponding
articular surface of the proximal ulna throughout the range of move-
ment; in full extension of the elbow, a medial segment of the distal
humerus is not in contact with the ulna, whereas in full flexion, a lateral
segment is not in contact.
The surface of the trochlear notch has an asymmetrical sellar surface
that allows some rotation during swing in the flexion–extension plane.
It is predominantly concave in the transverse plane, but convex in the
anteroposterior plane. There is a ‘bare area’ devoid of hyaline cartilage
between the olecranon and coronoid areas of the trochlear notch that
is covered by fibrofatty tissue and synovium. The humeral capitulum is
reciprocally convex with the concavity of the articulating surface of the
radial head. The more prominent medial rim of the radial head sits in
the groove between the capitulum and trochlea. Contact between the
capitulum and radial head is maximal with the elbow in mid-flexion
and the forearm in mid-pronation.
1 2 Fibrous capsule The fibrous capsule is broad and thin anteriorly. It
8
1 is attached proximally to the front of the medial epicondyle and
humerus above the coronoid and radial fossa, and distally to the edge
4 4
of the ulnar coronoid process and anular ligament. It may be aug-
A B
mented by fibres from brachialis and blends into the ulnar collateral
ligament medially and the radial collateral ligament laterally. Posteri-
Fig. 49.12 Radiographs of the forearm of a girl aged 11 years.
orly, the capsule is even thinner and is related to the tendon of triceps
A, Anteroposterior view. Key: 1, cartilaginous growth plates; 2, conjoined
and anconeus. It is attached proximally to the superoposterior aspect
epiphyses of capitulum and lateral epicondyle; 3, proximal radial
epiphysis; 4, distal radial epiphysis; 5, epiphysis of medial epicondyle; of the humeral capitulum, the posterior aspect of the medial epi-


6, diaphysial bone; 7, trochlear epiphysis; 8, distal ulnar epiphysis. condyle and the olecranon fossa. Only the lowest part of the olec ranon
B, Lateral view, semi-flexed at the elbow. Note the epiphyses and fossa is devoid of a capsular attachment. Inferomedially, it reaches the
adjacent radiotranslucent growth cartilages. Key: 1, olecranon; 2, superior and lateral margins of the olecranon and is laterally continu-
distal ulnar epiphysis; 3, proximal radial epiphysis; 4, distal radial ous with the superior radio-ulnar capsule deep to the anular ligament.
epiphysis. The olecranon bursa lies between the capsule of the elbow and the


Elbow and forEarm
844
6
noITCES
A C
Medial epicondyle
Anular ligament
Synovial membrane
B
Inferior band
Anterior band of ulnar collateral ligament
Posterior band
D
Olecranon
Synovial membrane
Anular ligament
Anular ligament
Tuberosity of radius
Radial collateral ligament
Joint capsule
Fig. 49.13 A–D, The left elbow joint. A, The synovial cavity partially distended: anterior aspect. The fibrous capsule of the elbow joint has been removed
but the thick part of the anular ligament has been left in situ. Note that the synovial membrane (blue) descends below the lower border of the anular
ligament. B, The synovial cavity partially distended: posterior aspect of the specimen represented in A. C, Medial aspect. D, Lateral aspect.
triceps insertion. Inflammation caused by pressure, friction or infection Radial collateral ligament The radial collateral ligament is attached
of the bursa can result in marked swelling and limitation in elbow low on the lateral epicondyle and to the anular ligament. Some of the
function. posterior fibres cross the ligament to the proximal end of the supinator
crest of the ulna. The ligament blends with the bony attachments of
Ligaments The humero-ulnar and humero-radial articulations have supinator and extensor carpi radialis brevis. It is taut throughout most
ulnar and radial collateral ligaments (see Fig. 49.13). of the range of flexion of the elbow and contributes to the stability of
the joint.
Ulnar collateral ligament This triangular ligament consists of thick
anterior, posterior and inferior bands connected by thinner tissue. The Synovial membrane The synovial membrane extends from the
strongest and stiffest anterior band is attached by its apex to the an- articular margins of the humerus and lines the corono id, radial and
terior aspect of the medial epicondyle and by its broader base to a olecranon fossae, the flat medial surface of the trochlea, the deep surface
proximal tubercle on the medial margin of the coronoid. The anterior of the elbow capsule and the distal part of the anular ligament. A cres-


band is taut throughout most of the range of flexion and contributes centic synovial fold projecting between the proximal radius and ulna
to the stability of the joint. The posterior band of the ulnar collateral contains extrasynovial fat and forms the division between the humero-
ligament is also triangular in shape; its apex attaches to the back of ulnar and humero-radial joints.
the medial epicondyle and its distal attachment is the medial margin There are three other fat pads between the capsule and synovium;
of the olecranon. The posterior band becomes taut between 90° and the largest is in the olecranon fossa, where it is pushed into the fossa
full flexion of the elbow. Connecting these two thick bands is a less by triceps during flexion of the elbow. The two other fat pads are in the
sturdy inferior oblique band that runs between the olecranon and coronoid and radial fossae, and are pushed into these fossae by bra-
coronoid processes, converting a depression on the medial margin of chialis on extension of the elbow. Smaller fat pads covered by synovium
the trochlear notch into a foramen, through which the intracapsular fat project into the joint at the trochlear notch and also cover non-articular
pad is continuous with the extracapsular fat medial to the joint. The areas of bone.
ulnar collateral ligament of the elbow lies beneath triceps, flexor carpi
ulnaris, the ulnar nerve and the attachment of flexor digitorum super- Vascular supply The articular arteries of the elbow are derived
ficialis as it extends from the medial epicondyle to the medial coronoid from numerous small periarticular anastomoses around the joint (see
border. Fig. 49.29).


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Innervation The elbow joint is innervated by filaments arising from radial head and holds it against the radial notch of the ulna. It is
all of the main nerves of the upper limb, except for the axillary nerve. attached to the anterior margin of the notch. The ligament is wider
The ulnar posterior part is supplied by the ulnar nerve and the medial posteriorly, where it may be composed of several bands. It is attached
cutaneous nerve of forearm; the ulnar anterior part is supplied by to a rough ridge at or behind the posterior margin of the notch. Some
the median and musculocutaneous nerves. The radial nerve is the sole bands may diverge and attach superiorly to the lateral margin of the
supplier of the radial posterior part, and the radial anterior part is trochlear notch, or inferiorly to the supinator crest. Proximally, the
innervated by both radial and musculocutaneous nerves (de Kesel et al anular ligament blends into the joint capsule, except posteriorly where
2012). the capsule is deep to the ligament. Distally, the anular ligament gives
off a few fibres, which pass over the synovial membrane to attach to
the radial neck. The superficial surface of the anular ligament blends
PROXIMAL RADIO-ULNAR JOINT
into the radial collateral ligament and provides an attachment for a part
of supinator. The deep surface of the anular ligament is lined with a
The proximal radio-ulnar joint is a uniaxial pivot joint (Fig. 49.14). thin layer of cartilage where it is in contact with the radial head. Distally,
there is a synovial membrane that is reflected up on to the radial neck.
Articulating surfaces Articulating surfaces include the articulation
The anconeus and the interosseous recurrent artery lie behind the
between the circumference of the radial head and the fibro-osseous ring
ligament.
of the ulnar radial notch and anular ligament.
Fibrous capsule The fibrous capsule of the proximal radio-ulnar Quadrate ligament The quadrate ligament is a much thinner and more
fibrous structure than the anular ligament. It runs between the radial
joint is continuous with that of the elbow and is attached to the anular


neck and the upper part of the supinator fossa of the ulna, and is taut
ligament.
throughout pronation and supination. It lies over the synovial mem-
Ligaments The proximal radio-ulnar joint has anular and quadrate brane on the distal surface of the joint.
ligaments.
Synovial membrane The synovial membrane of the proximal radio-
Anular ligament The anular ligament is the principal stabilizer of the ulnar joint is continuous with that of the elbow joint, forming one
joint. It is a strong composite band that winds around four-fifths of the continuous synovial cavity. It attaches to the joint margins, lining
A Median nerve Ulnar artery Median cubital vein Fig. 49.14 The proximal
Medial cutaneous
left radio-ulnar joint. A, A
nerve of forearm, anterior branch
transverse section. B, An axial
magnetic resonance imaging
Superficial group Radial artery
of flexor muscles (MRI) scan.
Lateral cutaneous
nerve of forearm
Medial cutaneous
Brachioradialis
nerve of forearm,
posterior branch Tendon of biceps brachii
Brachialis
Superficial radial and posterior
interosseous nerves
Extensor carpi
Ulnar nerve radialis longus
Palmaris longus Extensor carpi
radialis brevis
Flexor carpi ulnaris Supinator
Head of radius
Ulna
Anular ligament
Proximal radio-ulnar joint Common extensor tendon
Anconeus
B


Elbow and forEarm
846
6
noITCES
the capsule and anular ligament. The quadrate ligament prevents herni- fibrocartilage that extends across the dome of the ulnar head, ranging
ation of the synovial membrane between the free edges of the anular in thickness between 2 and 5 mm. The meniscal homologue is a broad
ligament. expansion of loose connective tissue that runs from the articular disc
to the ulnar styloid and the surrounding joint capsule; it is not a major
Vascular supply The vascular supply of the proximal radio-ulnar contributor to the structural integrity of the triangular fibrocartilage
joint is derived from a rich periarticular anastomotic plexus (Fig. 49.18; complex.
see Fig. 49.19). The triangular fibrocartilage complex is attached to the ulnar aspect
of the lunate fossa of the radius. Medially, it is inserted into the head
Innervation The proximal radio-ulnar joint is innervated by small of the ulna and the base of the ulnar styloid. Here, it is joined by fibres
branches arising from the musculocutaneous, median, radial and ulnar from the ulnar part of the ulnar styloid (the ulnar collateral ligament);
nerves. thus thickened, it attaches to the lunotriquetral interosseous ligament,
triquetrum, hamate and base of the fifth metacarpal. A constant perfor-
ation just distal to the level of the ulnar styloid leads to the prestyloid
RADIO-ULNAR SYNDESMOSES recess. The dorsal and palmar (volar) aspects of the triangular fibrocar-
tilage complex are thickened to form the dorsal and palmar radio-
ulnar ligaments, which are attached to the dorsal and volar ulnar
The radial and ulnar shafts are connected by two syndesmoses, an
corners of the distal radius and to the fovea of the ulnar head at the
oblique cord and an interosseous membrane.
base of the ulnar styloid (Palmer and Werner 1981, Pacek and Buter-
baugh 2015).
Oblique cord
The triangular fibrocartilage complex receives its blood supply


from the ulnar artery via its palmar and dorsal radiocarpal branches,
The oblique cord is a small, inconstant, flat fascial band on the deep the dorsal branch of the anterior interosseous artery and the palmar
head of supinator (see Fig. 49.10). It extends from the lateral side of branch of the anterior interosseous artery. Only the outer 15–20% of
the ulnar tuberosity to the radius a little distal to its tuberosity. Its fibres the disc is vascularized; the rest is avascular (Thiru-Pathi et al 1986,
are at right angles to those in the interosseous membrane. Its functional Bednar et al 1991) (Fig. 49.19).
significance is unclear. The triangular fibrocartilage complex acts as a cushion for the ulnar
carpus, preventing ulnocarpal abutment and overloading of the ulna in
Interosseous membrane ulnar deviation. It is a major stabilizer of the distal radio-ulnar joint.
Degenerative perforation of the triangular fibrocartilage complex
The interosseous membrane is a broad, thin, collagenous structure (see becomes more common with age and is a constant finding after the age
Fig. 49.10). Its fibres slant distomedially between the interosseous of 50 years (Mikić 1978).
borders of the radius and ulna, and its distal part is attached to the
posterior division of the radial shaft. Two or three posterior bands Synovial membrane The synovial membrane lines the capsule and
occasionally descend distolaterally across the other fibres. The mem- forms a sacciform recess in front of the distal part of the interosseous
brane is deficient proximally, starting 2 or 3 cm distal to the radial membrane (see Fig. 50.41).
tuberosity, and broadest at midlevel. An oval aperture near its distal
margin conducts the anterior interosseous vessels to the back of the Vascular supply The arterial supply of the distal radio-ulnar joint is
forearm. The posterior interosseous vessels pass through a gap between derived from the palmar and dorsal branches of the anterior interos-
its proximal border and the oblique cord. seous artery, reinforced by the posterior interosseous and ulnar


The membrane provides attachments for the deep forearm muscles. arteries.
Anteriorly, in its proximal three-quarters, it is related laterally to flexor
pollicis longus and medially to flexor digitorum profundus; between Innervation The distal radio-ulnar joint is innervated by branches of
them, it is related to the anterior interosseous vessels and nerve. In its the anterior and posterior interosseous nerves.
distal quarter, it is related to pronator quadratus. Its posterior relations
are supinator, abductor pollicis longus, extensors pollicis brevis, longus
and indicis, and, near the carpus, the anterior interosseous artery and MOVEMENTS AT THE HUMERO-ULNAR,
posterior interosseous nerve. HUMERO-RADIAL AND PROXIMAL
The interosseous membrane consists of several parts, the most
AND DISTAL RADIO-ULNAR JOINTS
important of which is the central band originally described by Hotch-
kiss et al (1989). This probably acts in conjunction with the radial head
to restrain the radius from proximal migration and stabilize the forearm. The main movements that occur at the humero-ulnar, humero-radial
Previously described as being at its most taut in almost every position and proximal and distal radio-ulnar joints are flexion, extension, supi-
of rotation of the forearm, it now appears to maintain the same tension nation and pronation.
throughout pronation and supination. Noda et al (2009) have described
Flexion and extension
four other subsidiary portions.
The elbow joint has relatively stable semi-congruent articular surfaces
DISTAL RADIO-ULNAR JOINT
that are assisted by strong static and dynamic stabilizers, and which
allow a flexion–extension arc of approximately 150°. When the elbow
The distal radio-ulnar joint is a uniaxial pivot joint. is extended and supinated, the forearm forms a ‘carrying angle’ with the
humerus of approximately 17°; the absolute angle varies from indi-
Articulating surfaces The articulating surfaces are between the vidual to individual. It exists because the medial edge of the trochlear
convex distal head of the ulna and the concave ulnar notch of the projects distally by 6 mm and because the superior articular surface of


radius; they are connected by an articular disc. the coronoid is oblique. The carrying angle is not present in flexion
when the humerus and ulna are in the same plane. With the arm
Fibrous capsule The fibrous capsule is thicker anteriorly and pos- adducted and the elbow flexed, the little finger meets the clavicle. If the
teriorly, and more lax proximally. humerus is rotated laterally, the little finger reaches the anterior shoul-
der. Pronation of the extended forearm masks the carrying angle by
Triangular fibrocartilage complex and distal radio-ulnar
lining up the arm, forearm and hand.
ligaments The triangular fibrocartilage complex (TFCC) is a ligamen-
tous and cartilaginous structure that suspends the distal radius and Accessory movements
ulnar carpus from the distal ulna. It stabilizes the ulnocarpal and radio-
ulnar joints, transmits and distributes load from the carpus to the ulna,
Available with the Gray’s Anatomy e-book
and facilitates complex movements at the wrist. By definition, it is made
up of the triangular fibrocartilage proper (the articular disc), meniscus
Pronation and supination
homologue (the ulnocarpal meniscus), ulnar collateral ligament, dorsal
and palmar radio-ulnar ligaments, floor of extensor carpi ulnaris sub-
sheath, and the ulnolunate and ulnotriquetral ligaments. The triangular Movements at the humero-radial, proximal and distal radio-ulnar joints
fibrocartilage proper is a biconcave body composed of chondroid pronate and supinate the hand. In pronation, the radius turns


Elbow and forearm
846.e1
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rETPaHC
The surface topography of the humero-ulnar joint permits some
rotation of the ulna against the humerus. The radius acts as a mobile
strut within the forearm, such that rotation of the distal radius around
the ulna carries the radiocarpal joint, wrist and hand into pronation or
supination. The medial side of the head of radius is longer than the
lateral side; this eccentric morphology causes a cam effect during rota-
tion of the proximal radio-ulnar joint. The radius gives longitudinal
stability to the forearm by protecting the ulna from side-to-side forces.
The interosseous membrane contributes to longitudinal stability by
virtue of its oblique course from the radius proximally to the ulna
distally. It appears to maintain the same tension throughout pronation
and supination (Ekenstam et al 1984). If the membrane is disrupted,
as in an Essex–Lopresti injury (fracture of the head of the radius, disrup-
tion of the interosseous membrane and dislocation of the distal radio-
ulnar joint), the radius will migrate proximally; persistent radio-ulnar
dissociation causes a complex instability of the forearm (Hotchkiss et al
1989). Correction of the fixed deformity of the forearm commonly seen
in untreated cases of spastic cerebral palsy or birth lesions of the bra-
chial plexus usually requires release of the membrane because it has
become relatively shortened. Pronator quadratus and supinator protect
the interosseous membrane, to some extent, during forced, rapid rota-
tion of the forearm by ‘paying out’ eccentrically, thereby reducing the
load applied across the membrane.
The elbow is stabilized by the intrinsic shape of the joint and by its
ligaments and muscles. The trochlear pulley is deeply seated within the
trochlear notch, while the olecranon provides anteroposterior stability.
Anterior stability in the sagittal plane is enhanced by the joint capsule,
biceps, brachialis and the bicipital aponeurosis; posterior stability is
enhanced by the triceps tendon and aponeurosis.
The radial and ulnar collateral ligaments are key to stability in the
coronal plane. Resistance to varus strain comes from the radial ligament


complex, of which the posterior band is the most important. Resistance
to valgus strain is provided by the ulnar collateral ligament complex,
of which the anterior band is the most important. If the head of the
radius is lost, an intact ulnar collateral ligament maintains stability of
the elbow. If the ligament is disrupted, the ulna drifts into valgus, there
is rotational instability and the trochlea is damaged. Stability of the
radius is enhanced by anconeus and by the muscles arising from the
lateral aspect of the distal humerus. Muscles that arise from the medial
epicondyle contribute to stability of the ulna. Muscles that act across
the elbow have a shunting effect, creating articular joint reaction com-
pression forces that contribute to close-packing (the position of a joint
in which the greatest stability is achieved for the least expended effort).
The humero-ulnar joint is most closely packed and, therefore, most
resistant to fatigue in flexion and supination.
The flexion–extension arc of the elbow is accompanied by some
rotation; the ulna is slightly pronated in extension and supinated in
flexion. In full extension, the radial head can be palpated posteriorly
because the radial facet is larger than the capitulum. The excursion of
the radial head in extension is limited by tension in the posterior
capsule, by the muscles anterior to the joint and by the tip of the olec-
ranon entering the olecranon fossa. In flexion, the rim of the radial
head enters the radial fossa and the tip of the coronoid process enters
the coronoid fossa. Flexion is principally limited by the apposition of
soft tissues.
Accessory movements include anterior and posterior translation of the
radial head on the ulnar radial notch, and of the ulnar head on the
radial ulnar notch.
Accessory movements of the human elbow are minimal and facilitate
the movements described above. The ulna rotates slightly at the elbow
and allows a few degrees of abduction and adduction. The radial head
exhibits a little anteroposterior translation on the capitulum when it
moves on the ulnar radial notch and the anular ligament moves back
and forth; this occurs maximally with the elbow in 90° of flexion.


Joints
847
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rETPaHC
Triceps brachii
Brachialis
Olecranon fossa
Biceps brachii
Tendon of
triceps
brachii Coronoid
1 fossa
2
Median cubital
Subcutanous vein
olecranon
bursa
6
3 Brachial artery
Pronator teres
7
4
8
Articular
5 9 cavity Median nerve
Ulna
Radial artery
(cut)
Trochlea Ulnar artery (cut)
Fig. 49.16 A sagittal section through the left elbow joint: medial aspect.
10 The synovial membrane is shown in blue. (With permission from Waschke
A J, Paulsen F (eds), Sobotta Atlas of Human Anatomy, 15th ed, Elsevier,
Urban & Fischer. Copyright 2013.)
Triceps brachii
1
Trochlea
Articular cavity
3
2
4
Ulna
B
Fig. 49.15 Radiographs of the left elbow joint of an adult.
A, Anteroposterior view. Key: 1, olecranon fossa; 2, medial humeral
epicondyle; 3, shadow of olecranon superimposed on trochlea; 4,
humero-ulnar joint; 5, radial head articulating with radial notch of ulna; 6,
lateral humeral epicondyle; 7, capitulum; 8, humero-radial joint; 9, head of
radius; 10, radial tuberosity. B, Lateral view. Key: 1, head of radius; 2, Fig. 49.17 A sagittal T1 weighted MRI section through the left elbow
profile of capitulum; 3, profile of trochlea; 4, olecranon. joint.
anteromedially and obliquely across the ulna. Its proximal end remains Extrinsic stabilizers Extrinsic stabilizers include the tendon of extensor
lateral to the ulna while its distal end lies medially and the interosseous carpi ulnaris, pronator quadratus, the interosseous membrane and the
membrane becomes spiralled. In supination, the radius returns to its sheath of the sixth dorsal compartment, which overlies extensor carpi


former position lateral and parallel to the ulna and the interosseous ulnaris (Spinner and Kaplan 1970).
membrane becomes unspiralled. The hand can be turned through 140–
150° with the elbow extended; this can be increased to nearly 360° by Intrinsic stabilizers Intrinsic stabilizers are stronger than extrinsic sta-
humeral rotation and movements of the scapula. Power is greater in bilizers. They include the radio-ulnar capsule and the dorsal and palmar
supination, a fact that has affected the design of nuts, bolts and screws, radio-ulnar ligaments. The dorsal and palmar radio-ulnar ligaments
which are tightened by supination in the right-handed. contain superficial and deep components. The superficial layers insert
on to the ulnar styloid. The stronger deep layers insert more laterally
Stability of the distal radio-ulnar joint into the fovea adjacent to the articular surface of the pole of the distal
ulna (Kleinmann 2010).
With the wrist in neutral extension and deviation, the main axis for
Muscles producing movement
transmission of force from the hand to the forearm passes through the
head of the capitate, then through the scapholunate ligament and
finally into the distal radius. Loading is transferred to the triangular Flexion Movement is produced by brachialis, biceps brachii and
fibrocartilage complex and distal ulna in ulnar deviation. The joint is brachioradialis. In slow flexion or its maintenance against gravity,
stabilized by extrinsic and intrinsic structures. brachialis and biceps are principally involved, even for light loads. With


Elbow and forearm
847.e1
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rETPaHC
Rotation of the forearm occurs between the head of the radius and
the radial notch of the ulna proximally and the articulation of the head
of the ulna and sigmoid notch. These proximal and distal radio-ulnar
joints are pivot-type synovial joints; they act as a unit, permitting stable
rotary motion (pronation 61–66°, supination 70–77°). During rota-
tion, the distal radius moves around the head of the ulnar. The axis for
pronation and supination is often represented as a line through the
centre of the radial head proximally and the ulnar attachment of the
articular disc distally. This represents the axis of movement of the radius
relative to the ulna but this does not remain stationary. The radial head
rotates in the fibro-osseous ring; its distal lower end and articular disc
swing round the head of the ulna. Rotation of the radial head occurs
on the humeral capitulum. As the forearm moves from full pronation
into supination, the ulna translocates medially by 9–10 mm, so that
the axis of rotation shifts but still passes through the head of the ulna.
In addition, the sigmoid notch changes its position of contact with the
ulnar head, lying dorsal proximally in pronation and volar distally in
supination. The distal end of the ulna is not stationary during these
movements; it moves along a curved course, posterolaterally in prona-
tion and anteromedially in supination. The axis of movement, as
defined above, is therefore displaced laterally in pronation and medially
in supination. Hence, the axis for pronation and supination of the
forearm and hand passes between the bones at both the proximal and
distal radio-ulnar joints when ulnar movement is marked, but through
the centres of the radial head and ulnar styloid when it is minimal. The
axis may be extended along any digit, depending on whether the distal
end of the ulna is medially or laterally displaced. The hand will rotate
further than the forearm because of the sliding–rotatory movement that
occurs between the carpal bones and the bases of the metacarpals, and,


to a very minor degree, at the radiocarpal joint.


Elbow and forEarm
848
6
noITCES
Radioscapholunate ligament Long radiolunate ligament Supination Movement is produced by supinator, in slow unresisted
movement and extension, assisted by biceps in fast movements in
Radioscaphocapitate ligament Articular disc (fibrocartilage)
flexion, especially when resisted.
Radial collateral Disk-carpal ligaments
ligament (D-L) (D-T)
Ulnar collateral MUSCLES OF THE FOREARM
ligament
There is some anatomical segregation by function of muscles that cross
the elbow. Most of those that arise medially pass to the flexor aspect of
the wrist, or stabilize or move the ulnar column of the carpus and the
ulnar side of the hand. Those that arise laterally pass to the lateral
column of the forearm and carpus, and to the extensor aspect of the
wrist. The muscles that act on the thumb have a wide origin; the exten-
sor and abductor muscles arise from the entire width of the interosseous
membrane. Rotator muscles, such as supinator, pronator teres and pro-
nator quadratus, pass between the radius and ulna, crossing the longi-
tudinal axis of the forearm.
Extensor
carpi ulnaris
ANTERIOR COMPARTMENT
Deep and superficial
radioulnar ligaments The anterior compartment contains the flexor muscles of the forearm.
These are arranged in superficial and deep groups.
Dorsal branch of anterior Superficial flexor (volar) compartment
interosseous artery Dorsal radioulnar capsule
Fig. 49.18 The prime intrinsic stabilizer of the distal radio-ulnar joint is the Muscles of the superficial flexor compartment are pronator teres, flexor
triangular fibrocartilage. The triangular fibrocartilage complex consists of carpi radialis, palmaris longus, flexor digitorum superficialis and flexor
superficial and deep radio-ulnar fibres, the two disc carpal ligaments carpi ulnaris.
(disc–lunate (D-L) and disc–triquetraI (D-T)), and the central articular disc.
Pronator teres
The articular disc is responsible for transferring load from the medial


carpus to the pole of the distal ulna. The vascularized, peripheral Attachments Pronator teres arises from two heads. The humeral
radio-ulnar ligaments are nourished by dorsal and palmar branches of the origin of pronator teres is the larger and more superficial. It arises at
posterior interosseous artery and are responsible for guiding the the medial supracondylar ridge just proximal to the medial epicondyle
radiocarpal unit around the seat of the ulna. (Redrawn with permission from the common tendon of origin of the flexor muscles, from the
from Kleinmann WB 2010 Stability of the distal radioulnar joint: intermuscular septum between it and flexor carpi radialis, and from the
biomechanics, pathophysiology, physical diagnosis and restoration of antebrachial fascia (see Fig. 49.6, Figs 49.20–49.22). The smaller ulnar
function. In: Slutsky DJ (ed) Principle and Practice of Wrist Surgery. head arises from the medial side of the coronoid process of the ulna,
Chapter 5, pp. 41–45.)
distal to the attachment of flexor digitorum superficialis, and joins the
humeral head at an acute angle. This ulnar coronoid attachment may
be absent in some individuals. The muscle passes obliquely across the
forearm to end in a flat tendon that is attached to a rough area midway
Dorsal radiocarpal along the lateral surface of the radial shaft at the apex of its lateral curve
Dorsal branch, anterior
branch, ulnar artery (see Fig. 49.25). Accessory slips may arise from a supracondylar process
interosseous artery
Ulna Radius of the humerus, if present, or from biceps, brachialis or the medial
intermuscular septum.
Relations The median nerve usually enters the forearm between the
two heads of pronator teres, separated from the ulnar artery by the ulnar
head. The lateral border of pronator teres is the medial margin of the
cubital fossa (see Fig. 46.29). Proximally, the medial border of pronator
teres is related to the lateral aspect of flexor carpi radialis. Pronator teres


is anterior to flexor digitorum superficialis.
Vascular supply The humeral head of pronator teres is supplied by
the inferior ulnar collateral and anterior ulnar recurrent arteries. The
ulnar head is supplied by the common interosseous artery, the mid
portion of the muscle belly by direct branches from the ulnar artery,
and the radial insertion by the radial artery.
Palmar branch, anterior interosseous artery
Palmar radiocarpal branch Innervation Pronator teres is innervated by the median nerve, C6
Ulnar artery and 7.
Fig. 49.19 The arterial anatomy of the triangular fibrocartilage complex.
(Redrawn with permission from Thiru-Pathi RG, Ferlic DC, Clayton Ml, Actions Pronator teres pronates the forearm by rotating the radius
McClure DC 1986 Arterial anatomy of the triangular fibrocartilage of the medially on the ulna. It is a weak flexor of the elbow joint.
wrist and its surgical significance. Journal of Hand Surgery 11A,
258–263.) Testing Pronator teres is tested by palpating its contracting fibres
during pronation against resistance.
Flexor carpi radialis
increasing speed and activity, brachioradialis is increasingly prominent; Attachments Flexor carpi radialis arises from the medial epicondyle
its attachments determine that it acts most effectively in mid-pronation. via the common composite flexor tendon, from the antebrachial fascia
Against resistance, pronator teres, longus and brevis, flexors carpi radia- and from adjacent intermuscular septa (see Fig. 48.11A). Its fusiform
lis and ulnaris, and extensor carpi radialis may contribute. muscular belly converges in the mid-forearm into a long tendon that
passes within a synovial sheath through a lateral canal, formed by the
Extension Movement is produced by triceps, anconeus and gravity. flexor retinaculum above and a groove on the trapezium beneath. It
inserts on the palmar surface of the base of the second metacarpal and
Pronation Pronator quadratus is aided in rapid movement and sends a slip to the third metacarpal. These distal attachments lie beneath


against resistance by pronator teres. Gravity also assists. the oblique head of adductor pollicis. Rarely, the muscle may be absent.


muscles of the forearm
849
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rETPaHC
Brachial fascia Biceps brachii
Basilic vein Cephalic vein
Brachial artery
Triceps brachii, medial Radial nerve
head Ulnar nerve
Ulnar nerve, superior Biceps brachii
ulnar collateral artery Posterior
interosseous
Brachialis Medial epicondyle nerve
Medial intermuscular
septum of arm Ulnar artery
Median nerve Brachialis
Brachial artery Radial artery
Humerus, medial epicondyle Median nerve
Bicipital aponeurosis
Radial recurrent
Antebrachial fascia Biceps brachii, tendon Pronator teres, artery
ulnar head
Supinator raS du iap le nrf eic rvia el
Ulnar artery Radial artery
Pronator teres Supinator
Pronator teres
Brachioradialis
Brachioradialis U arl tn ea rr y recurrent Pronator teres
(cut)
Flexor Common
carpi interosseous artery
Extensor carpi radialis
radialis brevis
Flexor digitorum
Flexor carpi ulnaris Flexor carpi radialis superficialis, radial Flexor pollicis longus
head
Radial artery
Palmaris longus
Flexor digitorum superficialis
Ulnar artery Superficial
radial nerve
Ulnar nerve
Ulnar nerve
Brachioradialis
Flexor pollicis longus
Ulnar nerve, dorsal branch Radial artery
Abductor pollicis longus
Radial artery Ulnar nerve, pM ae lmdi aa rn bn re ar nv ce h,
Pronator quadratus dorsal branch
Ulnar artery Flexor carpi radialis
Ulnar artery,
dorsal carpal
Antebrachial fascia Extensor pollicis brevis branch Radial artery,
superficial palmar
Flexor carpi branch
Palmar aponeurosis ulnaris
Palmaris longus
Palmaris brevis
Fig. 49.21 The deep flexor muscles of the left forearm. (With permission
from Waschke J, Paulsen F (eds), Sobotta Atlas of Human Anatomy, 15th


ed, Elsevier, Urban & Fischer. Copyright 2013.)
Fig. 49.20 The superficial flexor muscles of the left forearm. (With
permission from Waschke J, Paulsen F (eds), Sobotta Atlas of Human
Actions Flexor carpi radialis is a wrist flexor. It acts with flexor carpi
Anatomy, 15th ed, Elsevier, Urban & Fischer. Copyright 2013.)
ulnaris to effect balanced wrist flexion, and in concert with the radial
extensors of the wrist to achieve balanced abduction of the hand.
There may be accessory slips from the biceps tendon, bicipital aponeu-
rosis, coronoid process or radius. Distally, it may also be attached to Testing Flexor carpi radialis is tested by palpating its contracting fibres
the flexor retinaculum, trapezium or fourth metacarpal. during flexion of the wrist against resistance.
Relations At its origin, flexor carpi radialis lies medial to pronator Flexor digitorum superficialis
teres. In the lower part of the forearm, the radial artery lies between the Attachments Flexor digitorum superficialis is the largest of the super-
tendon of flexor carpi radialis and the tendon of brachioradialis; the ficial flexors, and arises by two heads (see Figs 48.11A, 49.20–49.21).
radial pulse may be palpated proximal to the wrist between these two The humero-ulnar head arises from the medial epicondyle of the
tendons. humerus via the common flexor origin, the anterior band of the ulnar
collateral ligament, adjacent intermuscular septa, and from the medial
Vascular supply Flexor carpi radialis is supplied by a single domi- side of the coronoid process proximal to the ulnar origin of pronator
nant proximal pedicle and several distal minor pedicles. The dominant teres. The radial head, a thin sheet of muscle, arises from the anterior
pedicle is formed by a branch that arises from either the anterior or the radial border between the radial tuberosity and the insertion of prona-
posterior ulnar recurrent artery. The posterior ulnar recurrent artery tor teres. The median nerve and ulnar artery descend between the heads.


passes deep to pronator teres to enter the deep surface of flexor carpi The muscle usually separates into two strata, directed to digits two to
radialis; from here, it divides into a small ascending branch and a larger five. The superficial stratum, joined laterally by the radial head, divides
descending branch. The distal minor pedicles supplying flexor carpi into two tendons for the middle and ring fingers. The deep stratum gives
radialis are six to eight branches from the radial artery that enter the off a muscular slip to join the superficial fibres directed to the ring
muscle on the anterolateral side. finger, and ends in two tendons for the index and little fingers. As the
tendons pass behind the flexor retinaculum, they are arranged in pairs;
Innervation Flexor carpi radialis is innervated by the median nerve, the superficial pair passes to the middle and ring fingers, the deep pair
C6 and 7. to the index and little fingers (see Fig. 50.41). The four tendons diverge


Elbow and forEarm
850
6
noITCES
Superior ulnar both the ulnar and the radial arteries. The posterior surface is supplied
collateral artery by the ulnar artery and median artery, and the lateral surface by addi-
Brachial artery
tional branches from the radial artery.
Ulnar nerve Biceps brachii
Inferior ulnar Radial nerve Innervation Flexor digitorum superficialis is innervated by the median
collateral artery nerve, C8 and T1.
Medial Radial collateral Actions Flexor digitorum superficialis is a flexor of all the joints over
epicondyle artery, anterior branch which it passes, i.e. the wrist, metacarpophalangeal and proximal inter-
phalangeal joints; its precise action depends on which other muscles
Brachialis Supinator
are acting. It has independent muscle slips to all four fingers, and is
Posterior therefore able to flex the proximal interphalangeal joints individually,
interosseous nerve unlike flexor digitorum profundus, which has a muscle group common
to the middle, ring and little fingers.
Ulnar recurrent
artery Radial recurrent artery
Testing The independent action of flexor digitorum superficialis for
Biceps brachii, tendon a particular finger is tested by flexing that digit while holding the three
Median nerve other fingers in full extension. This eliminates any simultaneous con-
Common traction of the flexor digitorum profundus that might flex the digit.
interosseous artery
Superficial flexor
Palmaris longus
muscles of
Pronator teres
forearm Attachments Palmaris longus arises from the medial epicondyle of
the humerus via the common flexor origin and from adjacent intermus-
Posterior
Median artery interosseous artery cular septa and deep fascia. It is a slender, fusiform muscle that runs
medial to flexor carpi radialis (see Figs 48.11A, 49.20, 49.32). It becomes
Anterior interosseous
Anterior interosseous nerve tendinous in the mid-forearm, and the long tendon passes anterior
artery
(superficial) to the flexor retinaculum. A few fibres leave the tendon and


Brachioradialis interweave with the transverse fibres of the retinaculum but most of the
tendon passes distally. As the tendon crosses the retinaculum, it broad-
Ulnar artery Superficial ens out to become a flat sheet that becomes incorporated into the
radial nerve palmar aponeurosis. Palmaris longus is occasionally absent on one or
Ulnar nerve both sides.
Radial artery
Flexor carpi Median nerve Relations Palmaris longus runs distally, flanked by flexor carpi radia-
ulnaris lis and flexor carpi ulnaris, and superficial to flexor digitorum super-
ficialis. The median nerve at the wrist lies partly under the cover of the
Brachioradialis
Flexor digitorum tendon of palmaris longus and partly between the tendons of palmaris
profundus longus and flexor carpi radialis.
Pronator quadratus
Vascular supply The muscle belly of palmaris longus is supplied by
Ulnar nerve, Flexor pollicis longus a small branch from the anterior ulnar recurrent artery. A contribution
dorsal branch
is sometimes made by the median artery, if this is well developed.
Flexor digitorum Flexor carpi radialis
Innervation Palmaris longus is innervated by the median nerve, C7 superficialis
and 8.
Radial artery,
Flexor carpi superficial palmar branch Actions Palmaris longus is a weak wrist flexor. Through its insertion
ulnaris
in the palmar aponeurosis, it also acts as an anchor for the skin and
Palmaris longus
fascia of the hand against horizontal shearing forces.
Fig. 49.22 The deep flexor aspect of the left forearm. (With permission
from Waschke J, Paulsen F (eds), Sobotta Atlas of Human Anatomy, 15th Testing If the wrist is flexed against resistance, the taut tendon of
ed, Elsevier, Urban & Fischer. Copyright 2013.) palmaris longus will be seen in the midline of the flexor wrist crease as
the tendon passes superficial to the flexor retinaculum. When testing
palmaris longus, it helps to oppose the thumb to the middle fingertip


distal to the carpal tunnel. Each passes towards a finger superficial to at the same time as the wrist is flexed, in order to make palmaris stand
the corresponding tendon of flexor digitorum profundus. The two out.
tendons for each finger enter the digital flexor sheath at the metacar-
Flexor carpi ulnaris
pophalangeal joint. The superficialis tendon splits into two bundles
that pass around the profundus to lie posteriorly, and then reunite to Attachments Flexor carpi ulnaris is the most medial of the superficial
insert into the anterior surface of the middle phalanx. Some fibres forearm flexors (see Figs 49.20, 49.31, 49.32). It arises by two heads,
interchange from one bundle to another. humeral and ulnar, connected by a tendinous arch. The smaller humeral
An intermediate tendon is always found in the central branching head arises from the medial epicondyle via the common composite
area of the muscle belly and is an important landmark in deep dissec- tendon (see Fig. 48.11A). The ulnar head has an extensive origin from
tion; it may be confused with the median nerve. The radial head of the medial margin of the olecranon and proximal two-thirds of the
flexor digitorum superficialis may be absent and the muscular slip from posterior border of the ulna (from an aponeurosis shared with extensor
the deep stratum may provide most or all of the fibres acting on the carpi ulnaris and flexor digitorum profundus) and from the intermus-
index finger. The fibres associated with the little finger may be absent, cular septum between it and flexor digitorum superficialis (see Fig.
in which case they are replaced by a separate slip from the ulna, flexor 49.6). Occasionally, there is a slip from the coronoid process. A thick
retinaculum or palmar fascia. Variations occur in the arrangement of tendon forms along its anterolateral border in its distal half. The tendon
the tendons. is attached to the pisiform, and from here it is prolonged to the hamate
and fifth metacarpal by pisohamate and pisometacarpal ligaments. The


Relations Flexor digitorum superficialis runs deep to pronator teres attachment to the flexor retinaculum and the fourth or fifth metacarpal
and flexor carpi radialis. The median nerve and ulnar artery descend bones is sometimes substantial.
between the heads of flexor digitorum superficialis, and the nerve con-
tinues distally deep to the muscle. Relations Flexor carpi ulnaris is the most medial of the forearm
flexors and forms the bulk of the soft tissue cover of the medial aspect
Vascular supply The humeral head of flexor digitorum superficialis of the ulna. The ulnar nerve and posterior ulnar recurrent artery pass
is supplied by the anterior ulnar recurrent artery. The main body of the under the tendinous arch between its humeral and ulnar heads. Ulnar
muscle is supplied on its anterior surface by three or four branches from vessels and nerve lie lateral to its tendon in the distal forearm.


muscles of the forearm
851
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rETPaHC
Vascular supply The main arterial supply of flexor carpi ulnaris is Flexor pollicis longus
derived from three pedicles. The proximal pedicle arises from a branch Attachments Flexor pollicis longus arises from the grooved anterior
of the posterior ulnar recurrent artery as it passes between the humeral surface of the radius, and extends from below its tuberosity to the upper
and ulnar heads. The middle pedicle arises from the ulnar artery and attachment of pronator quadratus (see Figs 49.5, 49.21–49.22). It also
enters the muscle at the junction of the upper and middle thirds. The arises from the adjacent interosseous membrane and, frequently, by a
distal pedicles arise from the ulnar artery and enter the muscle at the variable slip from the lateral, or more rarely medial, border of the
musculotendinous junction. Flexor carpi ulnaris also receives a small coronoid process, or from the medial epicondyle of the humerus. The
supply near its origin from the inferior ulnar collateral artery. muscle ends in a flattened tendon that passes behind the flexor reti-
naculum, between opponens pollicis and the oblique head of adductor
Innervation Flexor carpi ulnaris is innervated by the ulnar nerve, C7, pollicis, to enter a synovial sheath. It inserts on the palmar surface of
8 and T1. the base of the distal phalanx of the thumb.
Flexor pollicis longus can sometimes be connected to flexor digit-
Actions Flexor carpi ulnaris is a powerful flexor and also adductor orum superficialis or profundus, or pronator teres. The interosseous
(ulnar deviation) of the wrist. When it acts with flexor carpi radialis, attachment, and, indeed, the whole muscle, may be absent. Anomalous
balanced wrist flexion is achieved. When it acts with extensor carpi tendon slips from the flexor pollicis longus to flexor digitorum profun-
ulnaris, balanced adduction occurs. dus are common.


Testing Flexor carpi ulnaris is tested by palpating its tendon while the Relations Flexor pollicis longus runs lateral to flexor digitorum pro-
wrist is flexed against resistance, or by palpating the tendon while the fundus. The anterior interosseous nerve and vessels descend on the
patient abducts the little finger against resistance. The muscle synergisti- interosseous membrane between these muscles.
cally stabilizes the pisiform, giving abductor digiti minimi a stable
origin. Vascular supply The medial half of flexor pollicis longus is supplied
by the anterior interosseous artery. The lateral half is supplied by
Deep flexor (volar) compartment branches of the radial artery. The median artery may contribute if it is
well developed.
The muscles of the deep flexor compartment are flexor digitorum
profundus, flexor pollicis longus and pronator quadratus (see Fig. Innervation Flexor pollicis longus is innervated by the anterior inter-
49.22). osseous branch of the median nerve, C7 and 8.
Flexor digitorum profundus Actions Flexor pollicis longus principally flexes the phalanges of the
Attachments Flexor digitorum profundus arises deep to the superfi- thumb. It also flexes the carpometacarpal joint of the thumb, especially
cial flexors from the proximal three-quarters of the anterior and medial if the more distal joints are stiff or fused.
surfaces of the ulna (see Figs 49.5, 49.6, 49.22). It embraces the attach-
ment of brachialis above and extends distally almost to pronator quad- Testing Flexor pollicis longus is tested by flexing the interphalangeal
ratus. It also arises from a depression on the medial side of the joint of the thumb against resistance.
coronoid process, from the proximal three-quarters of the posterior
ulnar border by an aponeurosis that it shares with flexor and extensor Pronator quadratus
carpi ulnaris, and from the anterior surface of the ulnar half of the Attachments Pronator quadratus is a flat, quadrilateral muscle that
interosseous membrane. The muscle ends in four tendons that run extends across the front of the distal parts of the radius and ulna (see


deep to the tendons of flexor digitorum superficialis and the flexor reti- Figs 49.5, 49.27). It arises from the oblique ridge on the anterior surface
naculum (see Fig. 50.41). The part of the muscle that acts on the index of the shaft of the ulna, the medial part of this surface and a strong
finger is usually distinct throughout, while the tendons for the other aponeurosis that covers the medial third of the muscle. The fibres pass
fingers are interconnected by areolar tissue and tendinous slips as far laterally and distally to the distal quarter of the anterior border and
as the palm. Anterior to their proximal phalanges, the tendons pass surface of the shaft of the radius (see Fig. 50.30). Deeper fibres insert
through the tendons of flexor digitorum superficialis to insert on the into the triangular area above the ulnar notch of the radius.
palmar surfaces of the bases of the distal phalanges. The tendons of the
profundus undergo fascicular rearrangement as they pass through Vascular supply Pronator quadratus receives its main arterial supply
those of superficialis. Flexor digitorum profundus may be joined by from the anterior interosseous artery as it passes through the interos-
accessory slips from the radius (which act on the index finger), flexor seous membrane.
superficialis, flexor pollicis longus, the medial epicondyle or the coro-
noid process. Innervation Pronator quadratus is innervated by the median nerve,
C7 and 8.
Relations Flexor digitorum profundus forms most of the surface
elevation medial to the palpable posterior ulnar border. In the forearm, Actions Pronator quadratus is a pronator of the forearm. The deeper
the median nerve runs on the anterior surface of its lateral aspect. In fibres oppose separation of the distal ends of the radius and ulna when
the palm, the lumbricals are attached to its tendons. axial load is transmitted through the carpus.
Vascular supply The origin of flexor digitorum profundus is sup- Testing Pronator quadratus is tested by pronation of the forearm


plied by the inferior ulnar collateral and ulnar recurrent arteries. The against resistance while the wrist finger flexors are relaxed. The simul-
proximal part is supplied by one or two branches from either the ulnar taneous contraction of pronator teres makes it difficult to test the inde-
or the common interosseous artery. The distal part is supplied by a pendent action of pronator quadratus.
series of branches from the ulnar artery, the anterior interosseous artery
and the median artery.
POSTERIOR COMPARTMENT
Innervation The medial part of flexor digitorum profundus, i.e. the
muscle bellies to the little and ring fingers, is innervated by the ulnar The posterior compartment contains the extensor muscles of the
nerve. The lateral part, i.e. the muscle bellies to the middle and index forearm, brachioradialis and supinator. The superficial posterior
fingers, is innervated by the anterior interosseous branch of the median muscles include anconeus, brachioradialis, extensor carpi radialis
nerve, C8 and T1. longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti
minimi and extensor carpi ulnaris. The deep posterior group of muscles
Actions Flexor digitorum profundus flexes the distal interphalangeal
includes supinator, abductor pollicis longus, extensor pollicis brevis,
joints of the fingers. It is also capable of flexing any or all of the joints
extensor pollicis longus and extensor indicis.
over which it passes and therefore has a role in coordinated finger
flexion. The index finger tendon is usually capable of independent func-
Superficial extensor compartment
tion, whereas the other three work together.
Testing Flexor digitorum profundus is tested by flexing the distal Brachioradialis
interphalangeal joint while holding the proximal interphalangeal joint Attachments Brachioradialis is the most superficial muscle along the
in extension. radial side of the forearm and forms the lateral border of the cubital


Elbow and forEarm
852
6
noITCES
fossa (see Figs 49.22, 49.25). It arises from the proximal two-thirds of its surface, and adjacent intermuscular septa. The muscle belly ends at
the lateral supracondylar ridge of the humerus and the anterior surface mid-forearm in a flat tendon that closely accompanies that of extensor
of the lateral intermuscular septum (see Figs 48.11A, 49.5). The muscle carpi radialis longus to the wrist. The tendon passes under the extensor
fibres end above mid-forearm level in a flat tendon that is inserted on retinaculum, is crossed by the tendon of extensor pollicis longus, and
the lateral side of the distal end of the radius, just proximal to the is attached to the dorsal surface of the base of the third metacarpal on
styloid process. This attachment may be more proximal; the muscle may its radial side, distal to its styloid process, and on adjoining parts of the
fuse proximally with brachialis and the tendon may, occasionally, base of the second metacarpal. The tendons of both extensor carpi
divide into two or three separately attached slips. In rare instances, it is radialis longus and brevis share a common synovial sheath (see Fig.
double or absent. 50.41); they may split into slips that are variably attached to the second
and third metacarpal bones. The muscles themselves may be united or
Relations The radial nerve and the anastomosis between the pro- may exchange muscular slips.
funda brachii artery and the radial recurrent artery lie in the groove
between brachioradialis and brachialis, anterior to the lateral intermus- Relations Extensor carpi radialis brevis is shorter than extensor carpi
cular septum. The tendon is crossed near its distal end by the tendons radialis longus and is covered by it. The tendon passes deep to abductor
of abductor pollicis longus and extensor pollicis brevis. The radial artery pollicis longus and extensor pollicis brevis in the distal third of the


is on its ulnar (medial) side. The superficial radial nerve emerges from forearm, then under the extensor retinaculum, where it lies in a shallow
between brachioradialis and extensor carpi radialis brevis to run super- groove on the back of the radius, medial to the tendon of extensor carpi
ficially over the tendon of extensor carpi radialis brevis and extensor radialis longus, and separated from it by a low ridge.
pollicis brevis, and then superficial to the extensor retinaculum.
Vascular supply Extensor carpi radialis brevis receives its arterial
Vascular supply Brachioradialis is supplied by branches of the radial supply principally from two pedicles: a single branch from the radial
recurrent artery that pierce the posteromedial surface of the muscle. It recurrent artery, and a branch of the radial artery that arises about one-
also receives branches from the radial collateral branch of the profunda third of the way down the forearm. There is an additional blood supply
brachii and directly from the radial artery in the distal part of the proximally from branches from the radial collateral branch of the pro-
muscle. funda brachii.
Innervation Brachioradialis is innervated by the radial nerve, C5 Innervation Extensor carpi radialis brevis is innervated by a branch
and 6. from the radial nerve or from the posterior interosseous nerve, C7 and
8. The branch to extensor carpi radialis brevis arises before the nerve
Actions Brachioradialis is a powerful flexor of the elbow, acting most enters the arcade of Frohse.
strongly with the forearm in mid-pronation. It is minimally active in
slow flexion or with the forearm supine, but generates a powerful burst Actions Extensor carpi radialis brevis is the prime dorsiflexor of the
of activity in both flexion and extension when movement is rapid. wrist. It acts with extensor carpi radialis longus as an extensor and
Under these conditions, it develops a pronounced transarticular com- abductor of the wrist and mid-carpal joints. It acts in synergism with
ponent of its force that helps to stabilize the elbow joint by balancing the finger flexors when making a fist.
the centrifugal force of rapid swings in either direction.


Testing The muscle belly and tendon of extensor carpi radialis brevis
Testing Brachioradialis can be seen and felt when the semi-pronated can be palpated when the wrist is extended and abducted against resist-
forearm is flexed against resistance. ance with the forearm pronated.
Extensor carpi radialis longus ‘Mobile wad’ of Henry
Attachments Extensor carpi radialis longus arises from the distal
third of the lateral supracondylar ridge of the humerus and the front of Available with the Gray’s Anatomy e-book
the lateral intermuscular septum (see Fig. 48.11A). Some fibres join
from the common tendon of origin of the forearm extensors. The
Extensor digitorum
muscle belly ends at the junction of the proximal and middle thirds of
the forearm in a flat tendon that runs along the lateral surface of the Attachments Extensor digitorum arises from the lateral epicondyle
radius, deep to abductor pollicis longus and extensor pollicis brevis. of the humerus via the common extensor tendon, the adjacent inter-
The tendon passes deep to the dorsal carpal ligament in a radial groove muscular septa and the antebrachial fascia (see Fig. 48.11A). The muscle
behind the styloid process alongside extensor carpi radialis brevis. Just belly divides in the distal third of the forearm into four tendons, which
before it is inserted on the radial side of the dorsal surface of the base pass in a common synovial sheath with the tendon of extensor indicis
of the second metacarpal, the tendon is crossed obliquely by the tendon through a tunnel under the extensor retinaculum (see Fig. 50.41). The
of extensor pollicis longus. It may send slips to the first or third meta- tendons diverge on the dorsum of the hand, one to each finger. The
carpal bones and contributes to the intermetacarpal ligaments. tendon to the index finger is accompanied by extensor indicis, which
lies ulnar (medial) to it. On the dorsum of the hand, adjacent tendons
Relations Extensor carpi radialis longus runs alongside brachioradia- are linked by three variable intertendinous connections (juncturae


lis and is partly overlapped by it. tendinae), which are inclined distally and radially (see Figs 49.23,
50.6). The digital attachments enter a fibrous expansion on the dorsum
Vascular supply Extensor carpi radialis longus receives its principal of the proximal phalanges, to which lumbrical, interosseous and digital
arterial supply from a single branch of the radial recurrent artery. Addi- extensor tendons all contribute.
tional blood supply comes from branches of the radial collateral branch The tendons of extensor digitorum may be variably deficient. More
of the profunda brachii and directly from the radial artery in the distal commonly, they are doubled, or even tripled, in one or more digits:
part of the muscle. most often, the index finger or the middle finger. Occasionally, a slip
of tendon passes to the thumb. The arrangement of the intertendinous
Innervation Extensor carpi radialis longus is innervated by the radial connections on the dorsum of the hand is highly variable. The medial
nerve, C6 and 7. connection is strong and pulls the tendon of the little finger towards
that of the ring finger, whereas the connection between the middle two
Actions Extensor carpi radialis longus acts as an extensor and abduc- tendons is weak and may be absent.
tor of the wrist and midcarpal joints.
Relations The extensor tendon to the index finger lies radial (lateral)
Testing The muscle belly and tendon of extensor carpi radialis longus to the tendon of extensor indicis. The extensor tendon to the little finger
can be palpated when the wrist is extended and abducted against resist- lies radial (lateral) to the tendon of extensor digiti minimi.
ance with the forearm pronated.
Vascular supply The proximal third of extensor digitorum is sup-
Extensor carpi radialis brevis
plied by branches from the radial recurrent artery, and the distal two-
Attachments Extensor carpi radialis brevis arises from the lateral thirds are supplied by branches from the posterior interosseous artery.
epicondyle of the humerus by a common tendon shared with extensor The very distal portion is supplied by a perforating branch from the


digitorum, extensor digiti minimi and extensor carpi ulnaris, the radial anterior interosseous artery that passes through the interosseous
collateral ligament of the elbow joint, a strong aponeurosis that covers membrane.


Elbow and forearm
852.e1
94
rETPaHC
Henry (1957) described a ‘mobile wad’ of three muscles, brachioradi-
alis and the extensors carpi radialis longus and brevis, which are visible
and palpable below the lateral epicondyle of the humerus, lying on the
lateral aspect of the radius. The wad is tethered by a fan-shaped leash
of vessels derived from the radial artery (the radial recurrent artery) that
has to be released before the muscles can be fully mobilized. Its anterior
and posterior margins are used to define the surgical approaches to the
radius and to discover planes of cleavage. The anterior margin is used
to define the anterior approach (of Henry) to the radius and can be
extended down to the wrist at the level of the insertion of brachioradi-
alis. This requires detachment of supinator from the radius, taking care
not to damage the posterior interosseous nerve. More distally, pronator
teres is released. This approach is particularly useful for plating fractures
of the radius. The posterior margin is used to expose the back of the
forearm (posterior approach of Thompson) and, if need be, the pos-
terior interosseous nerve, which, in any event, should be protected;
unlike the anterior approach, this approach cannot be extended.


muscles of the forearm
853
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rETPaHC
Innervation Extensor digitorum is innervated by the posterior interos-
seous nerve, C7 and 8.
Triceps brachii
Actions Extensor digitorum can extend any or all of the joints over
which it passes: wrist, metacarpophalangeal, and proximal and distal
interphalangeal joints (the latter two via the extensor expansion of the Brachioradialis
digits). When acting on the metacarpophalangeal joints, extensor digi-
torum tends to spread the digits apart because of the different axes of
Extensor carpi radialis longus
the individual joints imposed by the transverse arch of the hand. The
intertendinous bands stabilize the individual tendons as they cross the Fascial origin of
dorsum of the hand and permit some extension when a tendon has extensor carpi ulnaris
been divided in the metacarpal segment. The extent to which this occurs Extensor carpi radialis brevis with anconeus deep
to this
depends on the presence and orientation of the juncturae tendinae.
Testing The tendons of extensor digitorum can be readily felt, and Extensor digitorum
usually seen, when the fingers are extended against resistance and the
forearm is pronated.
Extensor digiti minimi
Attachments Extensor digiti minimi is medial to, and usually covered
by, extensor digitorum; proximally, the bellies of these two muscles may
be connected and indistinct from each other, whereas, in the mid-
forearm, extensor digiti minimi is clearly discernible as a slender muscle
(Fig. 49.23). It arises from the common extensor tendon by a thin,
Abductor pollicis longus
tendinous slip and adjacent intermuscular septa, and frequently has an
Extensor digiti minimi
additional origin from the antebrachial fascia. It forms a long tendon Radial nerve,
that constitutes the fifth dorsal compartment as it proceeds beneath the superficial branch
extensor retinaculum. Distal to the retinaculum (see Fig. 50.41), the Extensor pollicis brevis Extensor carpi ulnaris
tendon typically splits into two, and the lateral slip is joined by a


tendon from extensor digitorum. All three tendons are attached to the Extensor carpi radialis brevis Extensor indicis
dorsal digital expansion of the fifth digit; there may be a slip to the Ulna
fourth digit. Extensor digiti minimi is rarely absent but, sometimes, it Extensor carpi radialis longus Ulnar artery,
is fused with extensor digitorum. dorsal branch
Extensor pollicis longus
Ulnar nerve,
Relations The tendon of extensor digiti minimi lies ulnar (medial) Radial artery in anatomical dorsal branch
Extensor retinaculum
to the common extensor tendon to the little finger. The dorsal branch snuff-box
of the ulnar artery and the dorsal branch of the ulnar nerve pass super-
ficial to the extensor retinaculum and cross the tendon of extensor digiti
minimi as it lies beneath the retinaculum. Extensor digiti minimi
Abductor digiti minimi
Vascular supply Extensor digiti minimi is supplied by branches First dorsal
from the radial recurrent and posterior interosseous arteries, and by interosseous Intertendinous
connections
terminal branches from the anterior interosseous artery after it has
pierced the interosseous membrane.
Innervation Extensor digiti minimi is innervated by the posterior
interosseous nerve, C7 and 8.
Actions Extensor digiti minimi can extend any of the joints of the
little finger, or contribute to wrist extension. It permits extension of the
little finger independently of the other digits, even in extremes of ulnar
or radial wrist deviation.
Testing Extensor digiti minimi is tested by extending the little finger Fig. 49.23 The superficial extensor muscles of the left forearm.
while holding the remaining fingers flexed at the metacarpophalangeal
joints; this eliminates any simultaneous contraction of extensor
Actions Extensor carpi ulnaris works synergistically with extensors
digitorum.
carpi radialis longus and brevis and the digital flexors to effect balanced
wrist extension, enabling a power grip with a clenched fist. It also acts
Extensor carpi ulnaris
with flexor carpi ulnaris to adduct the hand.


Attachments Extensor carpi ulnaris arises from the lateral epicondyle
(where it forms the most medial part of the common extensor origin), Testing The tendon can be felt lateral to the groove that overlies the
the posterior border of the ulna (by an aponeurosis shared with flexor posterior subcutaneous border of the ulna when the wrist is adducted
carpi ulnaris and flexor digitorum profundus) and overlying fascia (see against resistance.
Fig. 49.6). It runs between extensor digiti minimi and anconeus proxi-
mally, and extensor digiti minimi and flexor carpi ulnaris in the mid- Anconeus
forearm (see Figs 49.31, 49.32). It forms a tendon in the distal third of Attachments Anconeus is a short, triangular muscle posterior to the
the forearm that slides in a groove between the head and the styloid elbow joint, partially and variably blended with triceps or extensor carpi
process of the ulna. It forms the content of the sixth dorsal compart- ulnaris (Fig. 49.24). It arises by a separate tendon from the posterior
ment as it runs under the extensor retinaculum (see Fig. 50.41) and is surface of the lateral epicondyle of the humerus, proximal to the
attached to a tubercle on the medial side of the base of the fifth common extensor tendon. The tendon lies beneath the muscle belly of
metacarpal. extensor carpi radialis longus. The muscle fibres run obliquely and
medially towards the ulna, covering the posterior aspect of the anular
Vascular supply Proximally, extensor carpi ulnaris receives branches ligament, and are attached to the lateral aspect of the olecranon and
from the radial recurrent artery. Distally, it is supplied by several proximal quarter of the posterior surface of the shaft of the ulna.
branches from the posterior interosseous artery.
Vascular supply Anconeus is supplied by branches of the posterior
Innervation Extensor carpi ulnaris is innervated by the posterior inter- interosseous recurrent artery. A small number of musculocutaneous
osseous nerve, C7 and 8. perforators reach the skin overlying the muscle.


Elbow and forEarm
854
6
noITCES
Radial collateral Olecranon of extensor pollicis brevis. It runs under the extensor retinaculum in the
ligament first dorsal compartment (see Fig. 50.41). It usually splits into two slips;
Lateral epicondyle
Anular ligament one is attached to the radial side of the first metacarpal base, and the
other is attached to the trapezium. Slips from the tendon may continue
Extensor carpi
radialis brevis into opponens pollicis or abductor pollicis brevis. Occasionally, the
Anconeus muscle itself may be wholly or partially divided.
Relations Abductor pollicis longus runs on the radial aspect of exten-
sor pollicis longus. The posterior interosseous nerve runs over the belly
of abductor pollicis longus with the accompanying posterior interos-
Supinator
seous artery; the nerve runs to the border of abductor pollicis longus
Flexor carpi ulnaris
and then dives between the muscles bellies of abductor pollicis longus
and extensor pollicis longus at the apex of their divergence.
Vascular supply Abductor pollicis longus is supplied proximally by
Ulna
a lateral branch from the posterior interosseous artery. Distally, it is
Radius supplied on the medial side by a perforating branch from the anterior
interosseous artery.
Pronator teres, tendon
Innervation Abductor pollicis longus is innervated by the posterior
Extensor pollicis longus
interosseous nerve, C7 and 8.
Actions Abductor pollicis longus abducts the metacarpal of the
Abductor pollicis longus thumb. It is the prime radial abductor of the thumb. It also acts to
Extensor indicis
abduct the wrist. With abductor pollicis brevis, it effects palmar
abduction.
Extensor pollicis brevis Interosseous membrane Testing The tendon of abductor pollicis longus can be seen and felt
at the radial aspect of the anatomical snuff-box when the thumb and
Extensor carpi ulnaris, wrist are abducted against resistance at the carpometacarpal joint.
Abductor pollicis longus, tendon
tendon


Extensor pollicis longus
Ulna
Radius Attachments Extensor pollicis longus arises from the lateral part of
Extensor retinaculum the middle third of the posterior surface of the shaft of the ulna below
Extensor pollicis brevis,
tendon abductor pollicis longus and from the adjacent interosseous membrane.
It partly overlies the proximal attachment of the smaller extensor pol-
Extensor carpi radialis licis brevis (see Fig. 49.24). The tendon is formed just proximal to the
brevis, tendon
wrist and passes through the third compartment of the extensor reti-
naculum in a narrow, oblique groove on the back of the distal end of
the radius (see Fig. 50.41). It turns around a bony fulcrum, Lister’s
tubercle, which changes its line of pull from that of the forearm to that
of the thumb, and is attached to the base of the distal phalanx of the
thumb. The sides of the tendon are joined on the dorsum of the proxi-
mal phalanx by expansions from the tendon of abductor pollicis brevis
laterally and from the first palmar interosseous and adductor pollicis
medially.
Fig. 49.24 The deep layer of the dorsal muscles of the forearm. (With
permission from Waschke J, Paulsen F (eds), Sobotta Atlas of Human Relations Extensor pollicis longus runs between abductor pollicis
Anatomy, 15th ed, Elsevier, Urban & Fischer. Copyright 2013.) longus and extensor indicis in the forearm. The posterior interosseous
artery runs over its muscle belly. After passing around Lister’s tubercle,
the tendon of extensor pollicis longus crosses the tendons of extensor
Innervation Anconeus is innervated by the radial nerve, C6, 7 and 8. carpi radialis brevis and longus obliquely.
Actions Anconeus is an extensor of the elbow. Its principal function Vascular supply Extensor pollicis longus is supplied on its superfi-
is not fully understood but it may control ulnar abduction in pronation, cial surface by branches from the posterior interosseous artery, and on


which is necessary if the forearm is to turn over the hand without its deep surface by perforating branches from the anterior interosseous
translating it medially. In this way, a tool can be revolved ‘on the spot’ artery.
or it can be swept through an arc.
Innervation Extensor pollicis longus is innervated by the posterior
Deep extensor compartment interosseous nerve, C7 and 8.
The five deep forearm extensor muscles are abductor pollicis longus, Actions Extensor pollicis longus extends the distal phalanx of the
extensor pollicis longus and extensor pollicis brevis (all of which act thumb. Acting in association with extensor pollicis brevis and abductor
on the thumb), extensor indicis and supinator. Apart from supinator, pollicis longus, it extends the proximal phalanx and the metacarpal. In
the other four deep forearm extensors all arise from the bones of the continued action, as a consequence of the obliquity of its tendon, exten-
forearm and do not, therefore, act on the elbow. sor pollicis longus adducts the extended thumb and rotates it lat erally.
It is a weak extensor of the wrist.
Abductor pollicis longus
Attachments Abductor pollicis longus arises in part from the pos- Testing The tendon of extensor pollicis longus can be palpated at the
terior surface of the shaft of the ulna, just distal to the insertion of ulnar border of the anatomical snuff-box when the thumb is extended
anconeus, and from the adjoining interosseous membrane (see Fig. at the interphalangeal joint against resistance. When the thumb is
49.6). The muscle runs obliquely in a lateral and distal direction from opposed and adducted, abductor pollicis brevis can extend the inter-
an apex formed by anconeus and supinator, and is joined by fibres that phalangeal joint of the thumb, mimicking the action of extensor pol-
arise from the middle third of the posterior surface of the radius distal licis longus.
to the attachment of supinator (see Fig. 49.24). As it proceeds distally,


abductor pollicis longus becomes more superficial in the forearm, Extensor pollicis brevis
where it is visible as an oblique elevation. The muscle fibres form a Attachments Extensor pollicis brevis arises from the posterior surface
tendon just proximal to the wrist. The tendon runs in a groove on the of the radius distal to abductor pollicis longus and from the adjacent
lateral side of the distal end of the radius, accompanied by the tendon interosseous membrane (see Fig. 49.6). It runs between abductor


muscles of the forearm
855
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rETPaHC
pollicis longus and extensor pollicis longus. The tendon is attached to
the base of the proximal phalanx of the thumb and, commonly, has an
additional attachment to the base of the distal phalanx, usually through
Humerus
a fasciculus that joins the tendon of extensor pollicis longus. Extensor
pollicis brevis may be absent or fused completely with abductor pollicis
longus.
Brachioradialis
Relations Extensor pollicis brevis is ulnar (medial) to, and closely
connected with, abductor pollicis longus. In the distal forearm, the two
muscles emerge between extensor carpi radialis brevis and extensor
digitorum, and pass obliquely across the tendons of extensors carpi
Biceps brachii
radialis brevis and longus (see Fig. 49.24). They cover the distal part of
Median nerve
brachioradialis, and pass through the most lateral compartment of the
extensor retinaculum in a single synovial sheath, sharing a groove in
the distal radius. Ultimately, they cross, superficial to the radial styloid
process and radial artery, to reach the dorsolateral base of the proximal
phalanx of the thumb. Posterior
interosseous
nerve
Vascular supply Extensor pollicis brevis is supplied from branches
from the posterior interosseous artery, together with perforating
Biceps brachii,
branches from the anterior interosseous artery. tendon
Innervation Extensor pollicis brevis is innervated by the posterior
Supinator
interosseous nerve, C7 and 8.
Pronator teres
Actions Extensor pollicis brevis extends the proximal phalanx and
Palmaris longus
metacarpal of the thumb.
Flexor carpi radialis
Testing The tendon of extensor pollicis brevis can be felt at the radial
border of the anatomical snuff-box, lying medial to the tendon of Ulna Radius
abductor pollicis longus, when the metacarpophalangeal joint of the
thumb is extended against resistance.
Extensor indicis
Pronator quadratus


Attachments Extensor indicis is a narrow muscle that lies medial and
parallel to extensor pollicis longus (see Fig. 49.24). It arises from the
posterior surface of the ulna distal to extensor pollicis longus and the
adjacent interosseous membrane. The tendon is formed just proximal
to the wrist and passes under the extensor retinaculum in a common
compartment with the tendons of extensor digitorum (see Fig. 50.41).
Opposite the head of the second metacarpal, it joins the ulnar side of
the tendon of extensor digitorum that serves the index finger. Extensor
indicis occasionally sends accessory slips to the extensor tendons of
other digits. Its tendon may be interrupted on the dorsum of the hand
by an additional muscle belly (extensor indicis brevis manus).
Relations The posterior interosseous artery passes over the muscle Fig. 49.25 The forearm, antebrachium, in supination position. (With
belly of extensor indicis. On the dorsum of the hand, the tendon of permission from Waschke J, Paulsen F (eds), Sobotta Atlas of Human
extensor indicis lies on the ulnar aspect of the tendon of extensor digi- Anatomy, 15th ed, Elsevier, Urban & Fischer. Copyright 2013.)
torum to the index finger.
Vascular supply Extensor indicis is supplied on its superficial surface
by branches from the posterior interosseous artery, and on its deep variation; small parts have acquired individual names, e.g. lateral and
surface by perforating branches from the anterior interosseous artery. medial tensors of the anular ligament.
Innervation Extensor indicis is innervated by the posterior interos- Relations Supinator emerges under the lower border of anconeus and
seous nerve, C7 and 8. is related to abductor pollicis longus at its inferior medial border. Exten-
sor carpi radialis brevis and longus pass over its radial aspect. The
Actions Extensor indicis extends the index finger independently of the posterior interosseous nerve enters the forearm by passing between its
other digits. It is a weak extensor of the wrist. superficial and deep heads.


Testing Extensor indicis is tested by extending the index finger while Vascular supply The superficial part of supinator is supplied by
holding the remaining fingers flexed at the metacarpophalangeal joints branches from the radial recurrent artery. The deep part of supinator is
in order to eliminate the effects of any simultaneous contraction of supplied by branches from the posterior interosseous artery and the
extensor digitorum. posterior interosseous recurrent artery.
Supinator Innervation Supinator is innervated by the posterior interosseous
Attachments Supinator is a wide muscle that surrounds the proximal nerve, C6 and 7.
third of the radius. It has superficial and deep layers The two parts arise
together – the superficial by tendinous fibres, and the deep by muscular Actions Supinator rotates the radius to bring the palm to face anteri-
fibres – from the lateral epicondyle of the humerus, the radial collateral orly. It acts alone in slow, unopposed supination, and together with
ligament of the elbow joint, the anular ligament of the superior radio- biceps brachii in fast or forceful supination. An object, which poten-
ulnar joint, the supinator crest of the ulna and the posterior part of the tially may be heavy, is often picked up with the forearm initially pro-
triangular depression in front of it, and an aponeurosis that covers the nated. The more powerful supinator lifts the object against gravity;
muscle (see Figs 49.5, 49.6; Figs 49.25–49.26). Supinator is attached rotation is often combined with increasing elbow flexion in order to
distally to the lateral surface of the proximal third of the radius, down bring the object towards the eyes.
to the insertion of pronator teres. The radial attachment extends on to
the anterior and posterior surfaces between the anterior oblique line Testing Supinator lies too deep to be palpated. It may be assessed by
and the fainter posterior oblique ‘ridge’. Supinator is subject to frequent supinating the forearm against resistance with the elbow extended, on


Elbow and forEarm
856
6
noITCES
A
Axillary artery
Humerus
Brachioradialis Anterior circumflex humeral artery
Posterior circumflex humeral artery
Biceps brachii
Median nerve
Profunda brachii artery
(in radial groove)
Posterior
interosseous
nerve Nutrient artery to humerus
Pronator teres,
ulnar head
Supinator Brachial artery
Pronator teres,
Middle collateral artery
humeral head
Superior ulnar collateral artery Radial collateral artery
Palmaris longus
Flexor carpi radialis Inferior ulnar collateral artery
Interosseous
Radius Ulna recurrent artery
Radial recurrent
Pronator quadratus Anterior ulnar recurrent artery artery
Posterior ulnar recurrent artery
Radial artery
Common interosseous artery
Posterior interosseous artery
Ulnar artery
Anterior interosseous artery
Fig. 49.26 The forearm, antebrachium, in pronation position. (With
permission from Waschke J, Paulsen F (eds), Sobotta Atlas of Human
Anatomy, 15th ed, Elsevier, Urban & Fischer. Copyright 2013.)
the grounds that biceps brachii is inactive on supination when the
elbow is fully extended.
COMPARTMENT SYNDROME OF THE FOREARM
Available with the Gray’s Anatomy e-book
VASCULAR SUPPLY AND LYMPHATIC DRAINAGE
B
ARTERIES
Fig. 49.27 A, The arterial anastomoses around the left elbow joint, viewed
Brachial artery
from the anterior aspect. B, Arteriogram demonstrating anterior arterial
anastomoses around the elbow.
The brachial artery is medial in the arm but moves towards the midline,
medial to the tendon of biceps brachii and deep to the bicipital aponeu-
rosis. The latter separates the artery from the anterior structures, namely: passes deep to brachioradialis and gives off the radial recurrent artery
the skin, superficial fascia and the median cubital vein. Post eriorly, before continuing into the forearm. It descends along the lateral side
brachialis separates it from the elbow joint. The median nerve passes of the forearm, accompanied by paired venae comitantes, from the


close to the medial side of the artery. The artery divides into its terminal medial side of the neck of the radius to the wrist. The artery is medial
branches, the radial and ulnar arteries, at the level of the radial neck to the radial shaft proximally, and anterior to it distally. Proximally, it
(Fig. 49.27A). is overlapped anteriorly by the belly of brachioradialis, but elsewhere
in its course it is covered only by the skin and superficial and deep
Radial artery
fasciae. Its posterior relations in the forearm are, successively, the
tendon of biceps, supinator, the distal attachment of pronator teres, the
The radial artery is smaller than the ulnar artery, yet appears a more radial head of flexor digitorum superficialis, flexor pollicis longus, pro-
direct continuation of the brachial artery (see Figs 49.21–49.22). It nator quadratus and the lower end of the radius (where its pulsation is


Elbow and forearm
856.e1
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rETPaHC
A compartment syndrome exists where increased pressure in an osseo-
fascial compartment leads to decreased perfusion of the contents of the
compartment. In the forearm, this commonly occurs as a result of
trauma, external pressure, burns, arterial injury or post-ischaemic swell-
ing. The resultant increase in interstitial pressure causes vascular occlu-
sion and myoneural ischaemia. The patient presents with pain that is
disproportionate to the severity of the injury and which is provoked or
markedly increased by passive extension of the fingers. There may also
be reduced sensation or paraesthesiae in the affected hand. If a compart-
ment syndrome is suspected, compartment pressure measurements may
be indicated, but, in unequivocal cases, the definitive treatment is emer-
gency fasciotomies of the forearm. The absolute intracompartmental
pressure threshold for decompression is the subject of debate: an abso-
lute value of 30 mmHg is generally accepted, although some authorities
prefer a figure that comes within 30 mmHg of diastolic pressure. The
pressure in each compartment should be measured separately.
Incisions to decompress the flexor compartment (Ronel et al 2004)
run from the medial epicondyle and curve down the anterior aspect of
the forearm, ending on the radial side of flexor carpi ulnaris; from here,
they may be extended distally to decompress the carpal tunnel, if neces-
sary. The bicipital aponeurosis (lacertus fibrosus) is routinely released
to decompress the median nerve. After retraction of the superficial
flexors, the fascia over the deep muscles of the forearm may be incised
over its full length. Both median and ulnar nerves should be inspected
to ensure that their decompression is complete. The mobile wad and
dorsal compartment are decompressed through a straight longitudinal
incision that starts just distal to the lateral epicondyle; this is deepened
through the plane between extensor digitorum and extensor carpi radia-
lis brevis, and ends over the midline of the wrist. In both cases, the
wounds are left open and dressed, and only closed when circumstances
permit.
Failure to decompress a compartment syndrome promptly may lead


to Volkmann’s ischaemic contracture with severe loss of function in the
affected forearm and hand. Subsequent amputation is not unknown.


Vascular supply and lymphatic drainage
857
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rETPaHC
most accessible). Brachioradialis is lateral to the artery throughout its
length. Pronator teres is medial to the proximal part of the artery, and
the tendon of flexor carpi radialis is medial to the distal portion. The Triceps
superficial radial nerve lies lateral to the middle third of the radial brachii
artery; multiple branches from the artery supply the nerve throughout Medial intermuscular
its length. septum
The radial artery may occasionally arise from a continuation of a Lateral intermuscular Superior ulnar
superficial brachial artery, or as a high proximal division of an otherwise septum collateral artery
normal brachial artery. It can give rise to the common interosseous
Middle collateral branch Inferior ulnar
artery. of profunda brachii artery collateral artery
Branches in the forearm Ulnar nerve
Radial recurrent artery The radial recurrent artery is given off by
the radial artery just distal to the elbow joint (see Figs 49.21–49.22, Synovial membrane
49.27). It passes between the superficial radial nerve and the posterior
interosseous nerve before ascending beneath brachioradialis, anterior
to supinator and brachialis. It supplies these muscles and then anasto- Ulnar collateral
moses with the radial collateral branch of the profunda brachii artery. ligament
The radial recurrent artery also gives branches to extensor carpi radialis
longus, extensor digitorum, extensor digiti minimi and extensor carpi Extensor carpi Flexor digitorum
ulnaris. Its cutaneous branches are described on page 837. ulnaris (cut tendon) superficialis
Anconeus (cut tendon)
Muscular branches Muscular branches are distributed to the Posterior ulnar
muscles on the radial side of the forearm. Direct branches from the Anular ligament recurrent artery
Interosseous
radial artery supply the radial insertion of pronator teres, the antero-
recurrent artery Flexor digitorum
lateral aspect of flexor carpi radialis, the lateral surface of flexor digito-
profundus
rum superficialis, the lateral half of flexor pollicis longus, and the distal


sections of extensor carpi radialis longus and extensor carpi radialis Supinator
brevis. Anconeus
Flexor carpi
Ulnar artery Posterior interosseous ulnaris
nerve
Extensor carpi
The ulnar artery arises from the brachial artery just distal to the flexion ulnaris
crease of the elbow at the level of the radial neck, and reaches the
medial side of the forearm in its upper third (see Figs 49.21–49.22). It
is larger than the radial artery and is accompanied throughout its length Fig. 49.29 The posterior aspect of the left elbow region: deep structures.
by venae comitantes. In the forearm, the ulnar artery initially lies on
brachialis before passing deep to pronator teres, flexor carpi radialis,
palmaris longus and flexor digitorum superficialis. It then lies on flexor
digitorum profundus, between flexor carpi ulnaris and flexor digitorum Anterior interosseous artery The anterior interosseous artery
superficialis, and is covered by the skin and superficial and deep fasciae. arises from the common interosseous artery and descends on the anter-
The artery crosses the flexor retinaculum, lateral to the ulnar nerve and ior aspect of the interosseous membrane with the anterior interosseous
pisiform bone, to enter the hand. The median nerve is a medial relation branch of the median nerve (see Figs 49.10, 49.22, 49.27, 49.32). It is
for approximately 2.5 cm distal to the elbow, and then crosses the overlapped by contiguous sides of flexor digitorum profundus and
artery, from which it is separated by the ulnar head of pronator teres. flexor pollicis longus. Shortly after its origin, it usually gives off a
The ulnar nerve lies medial to the distal two-thirds of the artery, which slender median artery. This accompanies and supplies the median nerve
supplies the nerve throughout its length; the palmar cutaneous branch as far as the palm, where it may join the superficial palmar arch or end


of the ulnar nerve descends along the ulnar artery to reach the hand. as one or two palmar digital arteries. The median artery can also arise
The ulnar artery may arise above the elbow, when it can lie superficial from the ulnar or the common interosseous artery. Muscular and nutri-
to the forearm flexors under the deep fascia; only rarely is it subcutane- ent branches from the anterior interosseous artery pierce the interos-
ous. When this occurs, the brachial artery supplies the common interos- seous membrane to supply deep extensor muscles and the radius and
seous and the ulnar recurrent arteries. ulna, respectively. A branch descends deep to pronator quadratus before
piercing the interosseous membrane to join the anterior ‘carpal’ arch.
Branches in the forearm The anterior interosseous artery leaves the anterior compartment by
Anterior ulnar recurrent artery The anterior ulnar recurrent artery piercing the interosseous membrane proximal to pronator quadratus.
arises from the ulnar artery distal to the elbow and close to the origin It anastomoses with the posterior interosseous artery in the posterior
of the ulnar artery itself. It ascends between brachialis and pronator compartment of the forearm, and travels through a tunnel under the
teres, which is supplies, then anastomoses with the inferior ulnar col- extensor retinaculum with the tendons of the digital extensors before
lateral artery anterior to the medial epicondyle (see Fig. 49.27A). joining the dorsal carpal arch. Three small cutaneous perforating
branches supply the skin over the lower lateral border of the forearm.
Posterior ulnar recurrent artery The posterior ulnar recurrent
artery arises from the ulnar artery distal to the anterior ulnar recurrent Posterior interosseous artery The posterior interosseous artery
artery, passes dorsomedially between flexor digitorum profundus and arises from the common interosseous artery and is usually smaller than
flexor digitorum superficialis, and ascends between the posterior the anterior interosseous artery (see Figs 49.10, 49.27A). It passes dor-


aspect of the medial epicondyle and the olecranon. It is deep to flexor sally between the oblique cord and proximal border of the interosseous
carpi ulnaris, ascending between its heads with the ulnar nerve. It membrane, and then between supinator and abductor pollicis longus.
supplies flexor digitorum profundus, flexor digitorum superficialis, It descends deep in the groove between extensor carpi ulnaris and the
flexor carpi ulnaris, the ulnar nerve, underlying bone and the elbow extensor digiti minimi component of extensor digitorum. While in the
joint, and anastomoses with the ulnar collateral artery and interosseous groove, it gives rise to multiple muscular branches that supply these
recurrent artery. The posterior ulnar recurrent artery and ulnar nerve muscles and fasciocutaneous perforators that travel in the intermuscular
are both vulnerable to injury behind the medial epicondyle (Figs septum between extensor carpi ulnaris and extensor digiti minimi. The
49.28–49.29). posterior interosseous artery accompanies the deep branch of the radial
nerve (posterior interosseous nerve) on abductor pollicis longus. Dis-
Common interosseous artery The common interosseous artery tally, it anastomoses with the terminal part of the anterior interosseous
is a short branch of the ulnar artery (see Figs 49.10, 49.22). It arises just artery and the dorsal carpal arch.
distal to the radial tuberosity and passes back to the proximal border Sometimes, the posterior interosseous artery disappears halfway
of the interosseous membrane, where it divides into the anterior and down the forearm, in which case the anterior interosseous artery pierces
posterior interosseous arteries. Occasionally, the common interosseous the interosseous membrane more proximally to anastomose with it.
artery is a branch of the radial artery. Occasionally, the two vessels do not anastomose.


Elbow and forearm
857.e1
94
rETPaHC
Brachioradialis Triceps
brachii
Extensor carpi
radialis longus
Lateral epicondyle
Common extensor Medial
tendon epicondyle
Ulnar nerve
Posterior ulnar
recurrent artery
Olecranon
Deep fascia covering
anconeus
Flexor carpi ulnaris
Fig. 49.28 The posterior aspect of the left elbow: superficial structures.


Elbow and forEarm
858
6
noITCES
Posterior interosseous recurrent artery The posterior interos- LYMPHATIC DRAINAGE
seous recurrent artery leaves the posterior interosseous artery near its
origin and ascends between the lateral epicondyle and olecranon, either One or two supratrochlear nodes are superficial to the deep fascia
on or through supinator, and deep to anconeus. It anastomoses with proximal to the medial epicondyle and medial to the basilic vein; their
the middle collateral branch of the profunda brachii artery, posterior efferents accompany the vein to join the deep lymph vessels. Small,
ulnar recurrent artery and ulnar collateral artery. Occasionally, the artery isolated nodes sometimes occur along the radial, ulnar and interos-
is absent. Its cutaneous branches are described on page 837. seous vessels, in the cubital fossa near the bifurcation of the brachial
artery, or in the arm medial to the brachial vessels.
Collateral circulation at the elbow
INNERVATION
Available with the Gray’s Anatomy e-book
Median nerve
VEINS In the cubital fossa, the median nerve lies medial to the brachial
artery, deep to the bicipital aponeurosis and anterior to brachialis. It
Deep veins usually enters the forearm between the heads of pronator teres,
although, occasionally, it may pass posterior to both heads of the
Venae comitantes run with the radial and ulnar arteries to drain the muscle, or it may pass through its humeral head (Fig. 49.31; see Figs
deep and superficial palmar venous arches, respectively. They unite near 49.21–49.22). The nerve crosses to the lateral side of the ulnar artery,
the elbow as paired brachial veins. The radial veins are smaller and from which it is separated by the deep head of pronator teres, passes
receive the deep dorsal veins of the hand. The ulnar veins are larger and behind a tendinous bridge between the humero-ulnar and radial
drain the deep palmar venous arch. They connect with superficial veins heads of flexor digitorum superficialis, and descends through the


near the wrist and receive the venae comitantes of the anterior and forearm posterior and adherent to flexor digitorum superficialis and
posterior interosseous arteries near the elbow. A large branch connects anterior to flexor digitorum profundus. It is accompanied by the
them to the median cubital vein. median branch of the anterior interosseous artery. The first branch of
the median nerve to pronator teres arises 2–3 cm above the medial
Superficial veins epicondyle. A second branch, or leash of branches, arises at the level
of the tip of the medial epicondyle and innervates palmaris longus,
flexor carpi radialis and flexor digitorum superficialis. About 5 cm
Cephalic vein
proximal to the flexor retinaculum, the median nerve emerges from
The cephalic vein usually forms over the anatomical snuff-box on the behind the lateral edge of flexor digitorum superficialis, and becomes
radial side of the wrist from the radial end of the dorsal venous plexus superficial just proximal to the wrist. Here, it lies between the tendons
(see Figs 46.4, 50.39). It curves proximally around the radial side of the of flexor digitorum superficialis and flexor carpi radialis, projecting
forearm, receiving tributaries from both radial and ulnar aspects of the laterally from beneath the tendon of palmaris longus. It then passes
forearm. Distal to the elbow, a branch, the median cubital vein, diverges deep to the flexor retinaculum into the palm (see Fig. 50.41).
proximomedially to reach the basilic vein. The median cubital vein is
joined by a branch from the deep veins (Fig. 49.30). The further course Branches in the forearm
of the cephalic vein is described on page 830.
anterior interosseous nerve
Accessory cephalic vein The accessory cephalic vein may arise The anterior interosseous nerve arises from the posterior aspect of
the median nerve between the two heads of pronator teres, just distal
either from a dorsal forearm plexus or from the ulnar side of the dorsal
to the branches to the superficial forearm flexors and proximal tendi-