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arch. As it crosses the back of the distal end of the radius
it lies between the bone and the mucous sheath, which
encloses the tendons of the extensor digitorum communis
and the extensor indicis.

DORSAL ASPECT OF THE WRIST AND HAND.

Upon the dorsal aspect of the wrist and hand the following
structures have still to be examined :

1. The dorsal carpal ligament.

2. The radial artery and its branches.

3. The extensor tendons of the fingers.

Ligamentum Carpi Dorsale. The dorsal carpal ligament
is a fascial band which stretches obliquely across the wrist.
It is merely a thickened portion of the deep fascia, and its
attachments are so arranged that it does not interfere with the
free movement of the radius and hand during pronation and
supination. On the lateral side it is fixed to the lateral margin
of the distal end of the radius, whilst on the medial side it is
attached to the os triquetrum and os pisiforme, and also to the
palmar aponeurosis. In the case of the transverse carpal liga-
ment one large compartment, or tunnel, is formed for the flexor
tendons ; not so in the case of the dorsal carpal ligament.
Partitions or processes proceed from its deep surface, and
are attached to the ridges on the dorsal aspect of the distal
end of the radius, so as to form a series of six bridges or
compartments for the tendons. Each compartment is lined
by a mucous sheath which envelops the tendon or tendons
which pass through it, and facilitates their play between the
ligament and the bone. The different compartments should
now be successively opened up so that the arrangement of
the tendons with reference to the dorsal carpal ligament may
be studied.

The first compartment is placed on the lateral side of the
base of the styloid process of the radius, and corresponds with
the broad oblique groove which is present in that part of the
bone. It contains two tendons, viz., the tendons of the abductor
pollicis longus and the extensor pollicis brevis, with their
mucous sheaths. The second compartment corresponds with
the most lateral groove on the dorsal aspect of the radius.



THE SUPERIOR EXTREMITY



It is broad and shallow, and it holds the tendons of the
extensor carpi radialis longus and extensor carpi radialis brevis



Flexor digitorum sublimis

Median nerve M Flexor digitorum profundus
Palmaris longus
Flexor carpi radiali



Cavity of synovial sheath
Flexor carpi ulnaris



Flexor pollicis longus
Radial artery

Pronator quadratus

Abductor pollicis
longus

Ligamentum carpi
dorsale

Extensor pollicis
brevis




Ulnar artery

/Ulnar nerve

Dorsal branch 'of
ulnar artery
Basilic vein

Ant. ligament of

distal radio-ulnar

joint

Ulna

Styloid process
of ulna



Extensor carpi ulnaris
' Extensor digiti quinti proprius
Extensor digitorum communis



Cephalic veir
Extensor carpi radialis longus

Extensor carpi radialis brevis !

Extensor pollicis longus Extensor indicis proprius

FIG. 8 1. Transverse section through Forearm proximal to the Ligamentum
Carpi Transversum. Showing the relation of the mucous sheaths to the
tendons.

and their mucous sheaths. The third compartment is formed
over the narrow, deep, oblique intermediate groove on the
dorsum of the distal end of the radius. It contains the tendon




FIG. 82. (From Luschka.)



1. Middle metacarpal bone.

2. Tendon of flexor digitorum subliinis.

3. Tendon of flexor digitorum profundus.



4. Second lumbrical muscle.

5. Second dorsal interosseous muscle.

6. Common extensor tendon.



I., II., and III. The three phalanges.



of the extensor -pollicis longus and its mucous sheath. The
fourth compartment is placed over the wide shallow groove
which marks the medial part of the dorsal aspect of the distal



FOREARM AND HAND 191

end of the radius. It is traversed by tendons of the extensor
digitorum communis and the tendon of the extensor indicis
proprius and their mucous sheath, and by the terminal
parts of the dorsal interosseous nerve and the perforating
branch of the volar interosseous artery. The fifth compart-
ment is situated over the interval between the distal ends of
the radius and ulna. It contains the slender tendon of the
extensor digiti quinti proprius and its mucous sheath. The
sixth and most medial compartment^ which corresponds with the
groove on the dorsum of the distal end of the ulna, encloses
the tendon of the extensor carpi ulnaris and its mucous
sheath (see Fig. 76).

Dissection. After the compartments of the dorsal carpal
ligament and their contents have been examined displace the
various tendons as far as may be necessary, and clean the dorsal
part of the radial artery and its branches. The artery enters
the dorsal part of the wrist region by curling round the lateral
border of the wrist deep to the tendons of the abductor pollicis
longus and the short and long extensors of the thumb, and it
disappears into the palm, at the proximal end of the first inter-
osseous space, between the two heads of the first dorsal inter-
osseous muscle. As it lies at the side of the wrist two dorsal
arteries of the thumb and the dorsal radial carpal branch spring
from it, and just before it disappears it gives off the dorsal artery
to the index finger, and the first dorsal metacarpal artery, unless
that branch rises in common with the dorsal radial carpal artery.

Radial Artery. Only a small portion of the radial
artery is seen in this dissection. At the distal end of
the radius the vessel turns dorsally, distal to the styloid
process and upon the radial collateral ligament of the
radio-carpal joint. Having gained the dorsal aspect of the
carpus, it runs distally upon the navicular and os mult-
angulum majus, and finally disappears from view by turning
volarwards, through the proximal part of the first interosseous
space and between the heads of origin of the first dorsal
interosseous muscle (Figs. 75, 76). In the palm it takes the
chief share in the formation of the deep volar arch.

While the radial artery rests on the radial collateral
carpal ligament, it is deeply placed, and is crossed by the
tendons of the abductor pollicis longus and the extensor
pollicis brevis. On the carpus it lies nearer the surface,
and is crossed obliquely by the extensor pollicis longus. It is
accompanied by two vena comites and some fine filaments from
the lateral cutaneous nerve of the forearm which twine around it.



192 THE SUPERIOR EXTREMITY

The branches which spring from the radial artery in this
part of its course are of small size. They are :

1. Ramus carpeus dorsalis.

2. Aa. metacarpeae dorsales.

3. Aa. digitales/Two dorsal arteries of the thumb.

dorsales. (One dorsal artery of the index digit.

The dorsal radial carpal artery takes origin on the lateral
aspect of the wrist, and runs medially, upon the carpus, to join
the corresponding carpal branch of the ulnar artery. The arch
thus formed is placed under cover of the extensor tendons, and
gives off two branches which run distally in the third and
fourth inter-metacarpal intervals. They are termed the second
and third dorsal metacarpal arteries.

The first dorsal metacarpal artery arises, as a rule, from the
radial trunk, although not infrequently it may be seen to
spring from the dorsal carpal arch. It extends distally in
the second interosseous space.

The three dorsal metacarpal arteries are brought into
connection with the arteries in the palm by communicating
branches. They are joined by the three perforating twigs of
the deep volar arch, which make their appearance on the
dorsum of the hand between the heads of the medial three
dorsal interosseous muscles. Further, at the distal ends of the
interosseous spaces the dorsal metacarpal arteries usually send
distal perforating branches to join the corresponding common
volar digital arteries in the palm.

The two dorsal arteries of the thumb run distally one
upon each side of that digit.

The dorsal artery of the index is distributed on the lateral
side of the index finger.

Dissection. The limb should now be turned round, so that
the transverse metacarpal ligament which stretches across the
volar aspects of the heads of the metacarpal bones may be
examined previous to the dissection of the interosseous muscles.

Ligamentum Capitulomm Transversum. The transverse
ligament of the heads of the metacarpal bones is a strong
band, composed of transverse fibres, which crosses the volar
aspects of the heads of the four metacarpal bones of the fingers.
Commencing on the lateral side, upon the distal extremity of
the index metacarpal, it ends at the medial margin of the
hand, upon the head of the metacarpal bone of the little finger.



FOREARM AND HAND 193

It is not directly attached to the bones, but is fixed to the
powerful volar accessory ligaments of the medial four metacarpo-
phalangeal joints, and it effectually prevents excessive separation
of the metacarpal bones from each other.

Dissection. To obtain a satisfactory view of the interosseous
muscles, the transverse part of the adductor pollicis, if not
previously reflected, should be detached from its origin, and
thrown laterally towards its insertion into the thumb. The
transverse metacarpal ligament also must be divided in the
intervals between the fingers. Then the palmar and dorsal
interossei must be cleaned and their limits must be defined. As
the fascia is cleaned from their surfaces the margins of the
muscles become evident. There is one dorsal interosseous
muscle in each intermetacarpal space, and in the medial three
spaces there is also a volar interosseous muscle.

Mm. Interossei. The interosseous muscles occupy the
intervals between the metacarpal bones. They are seven
in number, and are arranged in two groups, viz. a dorsal
and a volar.

The three volar interossei can be seen only on the palmar
aspect of the hand. They act as adductors of the index,
ring, and little fingers towards the middle digit, and each
muscle is placed upon the metacarpal bone of the finger upon
which it acts. The first volar interosseous muscle therefore
arises from the metacarpal bone of the index finger, and
its delicate tendon is inserted upon the medial side of that
digit, partly into the base of the first phalanx, and partly
into the extensor expansion. The second volar interosseous
muscle springs from the metacarpal bone of the ring finger,
and has a similar insertion into the lateral side of that digit.
The third volar interosseous muscle takes origin from the
metacarpal bone of the little finger, and is inserted into the
lateral side of the first phalanx and the extensor expansion
of that finger.

The dorsal interossei are four in number, and are larger
than the volar muscles. They are seen best on the dorsal
aspect of the hand, but they are visible in the palm also.
They act as abductors of the fingers from the central line
of the middle digit, and their insertions are arranged in
accordance with that action. Each muscle arises by two
heads from the contiguous surfaces of the two metacarpal
bones between which it lies, and the fibres converge in a
pennate manner upon a delicate tendon. In the case of the

VOL. i 13



194 THE SUPERIOR EXTREMITY

first or most lateral dorsal interosseous muscle, the tendon is
inserted into the lateral side of the base of the first phalanx,
and also into the lateral margin of the dorsal expansion of the
extensor tendon of the index. The second and third dorsal
interosseous muscles are inserted in a similar manner, one on
each side of the base of the first phalanx of the middle finger;
whilst the fourth has a corresponding insertion upon the medial
aspect of the base of the first phalanx of the ring finger.

The first dorsal interosseous muscle is frequently termed
the abductor indicts ; and between its two heads of origin the
radial artery enters the palm. Between the heads of the other
three muscles the small perforating arteries pass.

In addition to acting as adductors or abductors of the
fingers the interossei flex the metacarpo-phalangeal joints and
help to extend the interphalangeal joints (see p. 178). The
interosseous muscles are supplied by the deep branch of the
ulnar nerve.

Tendon of the Flexor Carpi Radialis. The tendon of the
radial flexor of the carpus should now be traced through the
groove on the volar aspect of the os multangulum majus to its
insertion into the base of the metacarpal bone of the index
finger. It presents also a minor attachment to the base of the
middle metacarpal bone. On its way to its insertion it passes
behind the tendon of the flexor pollicis longus.

Dissection. All the muscles around the elbow joint should
be removed. As the brachialis and the triceps are raised from
the anterior and posterior aspects of the articulation, some care
is required to avoid injury to the anterior and posterior parts of
the capsule. It is advisable to remove the supinator last, because
it is only when that muscle is completely isolated that a proper
idea of its attachments and mode of action can be obtained.
Before it is removed its attachments and actions must be studied.

M. Supinator (O.T. Supinator Brevis). The supinator
muscle envelops the proximal part of the body and the neck
of the radius, covering it completely, except on its medial
side (Figs. 64, 78). It arises from the deep depression
distal to the radial notch of the ulna, and also from the
radial collateral ligament of the elbow and the annular
ligament of the radius. From their origin the fibres sweep
round the dorsal, lateral, and volar surfaces of the radius, and
clothe its body as far distally as the insertion of the pronator
teres. The dorsal interosseous nerve supplies the muscle,
traverses its substance, and separates it into two layers.



ELBOW JOINT 195

ARTICULATIONS.

ARTICULATIO CUBITI (ELBOW JOINT).

This joint includes (i) the articulatio humero-ulnaris, (2)
the articulatio humero-radialis, and (3) the articulatio radio-
ulnaris proximalis. In the humero-ulnar articulation the
trochlea of the humerus is grasped by the semilunar
notch of the ulna. In the radio-humeral articulation the
capitulum of the humerus rests in the shallow fovea capituli of
the radius, and in the proximal radio-ulnar articulation the
articular circumference of the head of the radius is held in
apposition with the radial notch of the ulna by the annular
ligament (Figs. 85, 96).

The joint is surrounded by a capsule which is reinforced at
the sides by collateral ligaments ; in addition, the interosseous
membrane, which passes between the interosseous crests of the
radius and ulna, and the oblique cord, which connects the
tuberosity of the ulna with the proximal part of the inter-
osseous crest of the radius, help to keep the radius and ulna in
apposition, and are therefore included in the ligaments of the
elbow joint. The ligaments of the elbow joint are therefore



1. Capsula articularis.

2. Lig. collaterale ulnare.

3. Lig. collaterale radiale.



4. Lig. annulare radii.

5. Membrana interossea antibrachii.

6. Chorda obliqua.



The articular capsule is attached proximally to the antero-
medial and antero-lateral surfaces of the humerus, proximal to
the coronoid and radial fossae, respectively. At the sides,
it is attached to the epicondyles ; and, posteriorly, to the
posterior surface, on which the line of attachment passes through
the proximal part of the olecranon fossa. Distally, the capsule
is attached to the anterior margin of the proximal, medial,
and lateral surfaces of the olecranon ; to the medial and volar
margins of the coronoid process of the ulna, and to the an-
nular ligament of the radius. The anterior part of the capsule
consists of fibres which take an irregular course over the
anterior aspect of the joint. The posterior part of the
capsule is weaker than the anterior and its attachment to
the posterior surface of the humerus is comparatively loose.

The cavity of the joint is closed distally on the radial
side by lax fibres which pass from the distal border of the
annular ligament to the neck of the radius, and by a thin
sheet of fibres, called the ligamtntum quadratum, which extends

i 13 a



196



THE SUPERIOR EXTREMITY



from the medial side of the neck of the radius to the distal
border of the radial notch of the ulna.

Ligamentum Collaterale Radiale (O.T. External Lateral
Ligament). The radial collateral ligament is a strong but
short band which is attached proximally to the distal aspect
of the lateral epicondyle of the humerus. Distally, it is
fixed to the annular ligament of the radius, and also, more
posteriorly, to the lateral side of the olecranon of the ulna.
The annular ligament is a strong ligamentous collar which
surrounds the head of the radius, and retains it in the radial
notch of the ulna.



Humerus
Triceps muscle
Tendon of triceps



Pad of fat

Triceps bursa

Posterior.

ligament

Olecranon bursa

Trochlea of

humerus



Flexor digitorum
profundus




'-,'- Brachialis



Anterior ligament

[_ Tendon of biceps
muscle



13L Profunda vein



Coronoid process of
ulna

Deep fascia
f- Flexor carpi radialis

HH Radial artery
rr^S Ulnar artery
fr^r Pronator teres

PW Flexor digitorum
profundus



FIG. 83. Sagittal section of the Right Elbow Region.

Ligamentum Collaterale Ulnare (O.T. Internal Lateral
Ligament). The ulnar collateral ligament, taken as a whole,
is fan-shaped. By its proximal pointed part it is attached to
the medial epicondyle of the humerus. Distally it spreads
out and is inserted into the coronoid process and the
olecranon. It consists of three very distinct portions, viz., an
anterior, a posterior, and a transverse (Fig. 84).

The anterior part springs from the distal and anterior part of
the medial epicondyle, and is attached to the medial margin
of the coronoid process of the ulna. The posterior part is
attached, proximally, to the distal and dorsal part of the medial
epicondyle, whilst distally, it is fixed to the medial border of



ELBOW JOINT



197



the olecranon. The transverse part consists of a band of fibres
which bridges across the notch between the olecranon and
the coronoid process, to both of which it is attached.

The annular ligament and the oblique cord will be
described later (see pp. 202-204).

Stratum Synoviale (Synovial Membrane). The joint
should be opened by making a transverse incision through the
anterior part of the capsule. The synovial stratum will be
seen lining the deep surface of the capsule, from which it is



Interosseous Coronoid

membrane Radius process




Ulna



Medial epi-
condyle

Anterior part of
ulnar collateral
ligament
Posterior part of
ulnar collateral
ligament
Olecranon



\

Transverse part of ulnar
collateral ligament



FIG. 84. Medial aspect of Elbow Joint.

reflected upon the non-articular parts of the bones which
are enclosed within the capsule. Anterior to the humerus
it lines the radial and coronoid fossae, and posteriorly it is
prolonged proximally, in the form of a loose diverticulum,
into the olecranon fossa. In the fossae a quantity of
soft oily fat is developed between the bone and the synovial
stratum. In that way pliable pads are formed which occupy
the recesses when the bony processes are withdrawn from
them.

Distally, the synovial stratum of the elbow joint is prolonged
into the proximal radio-ulnar joint, so that both articulations
possess a single, continuous synovial cavity.
1136



198



THE SUPERIOR EXTREMITY



The nerve supply of the joint is derived from the median,
ulnar, and radial nerves.

Movements at the Elbow Joint. The movements at the elbow joint
must not be confounded with those that take place at the proximal radio-
ulnar joint. At the elbow joint two movements, viz. , fexion, or forward
movement of the forearm, and extension, or backward movement of the
forearm, are permitted.

The muscles which are chiefly concerned in flexing the forearm upon the



Anterior
part of capsule



Lig. collaterale
radiale



Lig. annulare



Radius




Epicondylus
medialis



Lig. collaterale
u In are



Tendon of biceps hrachii

Chorda obliqua
Ulna



FIG. 85. Anterior aspect of the Elbow Joint.



arm at the elbow joint are the biceps, the brachialis, the muscles attached
to the medial epicondyle, and the brachio-radialis. The muscles which
extend the forearm are the triceps and anconseus and the muscles which
spring from the lateral epicondyle.

Dissection. It is advisable to study the radio-carpal or wrist
joint, before the articulations between the two bones of the
forearm are examined. The transverse, volar, and dorsal carpal
ligaments, together with the extensor and flexor tendons, should
be completely removed from the wrist. No attempt, however,
should be made to detach the extensor tendons from the dorsal
aspects of the fingers and thumb. The short muscles of the
thenar and hypothenar eminences must also be taken away.



PLATE XI



Humerus



Medial epicondyle



Olecranon

Interval between

trochlea and

coronoid process



Ulna




Lateral epicondyle



ead of radius



FIG. 86. Antero- posterior Radiograph of extended Elbow Joint.
(Mr. A. D. Reid.)



Shadow caused by

overlap of olecranon

and trochlea of

humerus



Shadow caused by

overlap of radius on

coronoid process




Shadow caused by
overlap of coronoid
process on trochlea
of humerus



FIG. 87. Lateral Radiograph of extended Elbow Joint.
(Dr. R. Knox.)



PLATE XII



Overlap of coronoid process
on trochlea of humerus



Overlap of head of

radius on coronoid

process of ulna





Humerus



Overlap of ole-
cranon on trochlea
of humerus



Olecranon



FIG. 88. Lateral Radiograph of partly bent Elbow.



Overlap of head of radius Overlap of coronoid process

on coronoid process on trochlea




Olecranoi



FIG. 89. Lateral Radiograph of half-bent Elbow.
(Mr. Martin.)



PLATE XIII




FIG. 90. Radiograph of the Elbow Joint.

Note (i) The medial epicondyle has not yet united with the shaft.

(2) The proximal epiphysis of the radius.

(3) That the nodular epiphysis of the olecranon is not distinctly visible.

(4) That all the distal epiphyses of the humerus have fused with the shaft

except the epiphysis of the medial epicondyle.

(Mr. A. D. Reid.)



PLATE XIV



Humerus



Medial epicondyle



Epiphysis of
olecranon

Overlap of head of

radius on coronoid

process



Ulna




FIG. 91. Lateral Radiograph of a partly bent Elbow Joint, showing
Epiphysis of Olecranon.

(Mr. A. D. Reid.)



PLATE XV




Epiphysis of

lateral epi-

condyle

Lateral distal

epiphysis of

humerus

Epiphysis of
head of rad




FIG. 92. Antero-posterior Radiograph of young Elbow Joint, showing
all Epiphyses.



t>LATE XVI




Epiphysis of
medial epicondyle

Overlap of

olecranon on

humerus



Olec



Epiphysis of head
of radius



FIG. 93. An tero-posterior Radiograph of young Elbow Joint. The epiphysis
of the lateral epicondyle of the humerus has not yet appeared.

Note that the lateral distal epiphysis forms not only the capitulum of the
humerus but also a part of the trochlea.



Medial distal
epiphysis of
Epiphysis'of head of radius humerus ^Lateral distal epiphysis of humerus




Epiphysis of olecranon
FIG. 94. Lateral Radiograph 01 a half-bent young Elbow Joint.



WRIST JOINT 199

ARTICULATIO RADIOCARPEA (WRIST JOINT).

The radio-carpal or wrist joint is the joint between the
forearm and the hand. The proximal face of the joint is
formed by the distal articular surface of the radius and the
discus articularis ; and the distal surface consists of the navi-
cular, lunate, and triquetral bones, and the two interosseous
ligaments which connect them together. The opposed surfaces
are retained in apposition by an articular capsule in which at
least four thickened bands can be recognised, they are :

1. Lig. radiocarpeum volare. 3. Lig. collaterale radiale.

2. Lig. radiocarpeum dorsale. 4. Lig. collaterale ulnare.

The capsule is attached proximally to the borders of the
distal ends of the radius and the ulna, and to the borders
of the articular disc. Distally it is connected with the bones
of the proximal row of the carpus, with the exception of the
pisiform, and some of its fibres can be traced to the capitate
bone.

The volar radio-carpal ligament springs from the anterior
border of the styloid process of the radius and the adjacent
part of the anterior border of the distal end of the radius.
Distally it breaks up into flat bands which are attached to
the navicular, lunate, and capitate bones. In many cases a



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