D. J. (Daniel John) Cunningham.

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volar ulnar-carpal ligament also is found. When present, it
extends from the anterior aspect of the base of the styloid
process and the adjacent anterior part of the head of the ulna
to the triquetral, pisiform, and capitate bones.

The dorsal radio-carpal band springs from the posterior
border of the distal end of the radius, and is attached
distally to all the bones of the proximal row of the carpus,
except the pisiform. Its fibres are often separable into a
number of distinct bands.

The radial collateral carpal ligament passes from the tip
of the styloid process of the radius to the lateral part of the
navicular ; and the ulnar collateral carpal ligament connects
the styloid process of the ulna with the triquetral bone.

Articular Surfaces. Divide the anterior and collateral parts of the
capsule by a transverse incision carried across the front of the articulation.
The hand can now be bent backwards, so as to expose fully the articular
surfaces opposed to each other in this joint.

The carpal surface is composed of the proximal articular
facets of the navicular and lunate bones, and a very small



200 THE SUPERIOR EXTREMITY

articular facet on the extreme lateral part of the proximal
surface of the triquetral bone. Two interosseous ligaments
stretch across the narrow intervals between the three bones
one on each side of the lunate bone and complete the
carpal surface. The carpal surface thus formed is convex
in all directions. Further, it should be observed that the
articular surface extends distally to a greater extent on the
dorsal than on the volar aspect.

The proximal surface or socket (Fig. 97) is elongated from
side to side, and concave in all directions. The greater
part of it is formed by the distal end of the radius, but,
on the medial side, the articular disc of the distal radio-
Head of ulna



Styloid process
of ulna



Surface for,
navicular bone ^-_ -,,<

Apex of articular

Groove for tendon of ext. ^^ I ' .

pollicislongus Surfacefor ?*

lunate bone

FIG. 95. Carpal Articular Surfaces of the Radius and of the Articular
Disc of the Wrist.

ulnar joint also enters into its construction. The distal
articular surface of the radius extends further distally on its
dorsal and lateral sides than on its volar and medial sides,
and it is divided by a low ridge into a lateral triangular and
a medial quadrilateral facet. The lateral facet, in the
. ordinary position of the hand, is in contact with the greater
extent of the proximal articular surface of the navicular bone.
The medial facet of the radius, together with the articular
disc, forms a much larger surface, triangular in outline,
which is opposed to the proximal articular surface of the
lunate bone. When the hand is placed in line with the
forearm no part of the proximal articular surface is allotted
to the triquetral bone : its small articular facet rests against
the medial part of the capsule of the joint. When the hand
is moved medially (i.e. adducted), however, the triquetral
bone travels laterally, and its articular surface comes into




WRIST JOINT 201

contact with the distal surface of the articular disc. The
lunate bone at the same time crosses the bounding ridge on
the distal surface of the radius, and encroaches on the
territory of the navicular bone, whilst a considerable part of
the surface of the navicular bone leaves the radius and comes
into contact with the lateral part of the capsule.

Stratum Synoviale. The synovial stratum of the radio-
carpal joint lines the fibrous capsule and it covers the proximal
surfaces of the two interosseous ligaments which complete the
carpal surface. Sometimes the articular disc is imperfect,
and in those cases the synovial stratum of the radio- carpal
joint becomes continuous with the synovial stratum of the
distal radio-ulnar joint.

The nerve supply is derived from the volar and dorsal
interosseous nerves.

Movements at the Radio-carpal Joint. The hand can be moved in
four directions at the radio -carpal joint. Thus we have (a) volar
movement, or flexion ; (b) dorsal movement, or extension ; (c) ulnar
movement, or adduction ; (d) radial movement, or abduction. In
estimating the extent of these movements in the living person the student
is apt to be misled by the increase of range which is contributed by the
carpal joints. Thus, flexion is in reality more limited than extension,
although by the combined action of both carpal and radio-carpal joints
the hand can be carried much more freely volarwards than dorsalwards.
Adduction, or ulnar flexion, can be produced to a greater extent than
abduction, or radial flexion. In both cases the extent of movement at
the radio-carpal joint proper is very slight, but the range is extended by
movements of the carpal bones. The styloid process of the radius
interferes with abduction.

The muscles which are chiefly concerned in producing the different
movements of the hand at this joint are the following : (a] flexors the
flexor carpi radialis, the palmaris longus, and the flexor carpi ulnaris ;
(b} extensors extensor carpi radialis longus, the extensor carpi radialis
brevis, and the extensor carpi ulnaris ; (c) abductors, or radial flexors
flexor carpi radialis, extensor carpi radialis longus, abductor pollicis
longus, and the extensor pollicis brevis ; (d} adductors, or ulnar flexors
extensor carpi ulnaris and flexor carpi ulnaris.

In addition, all the muscles whose tendons cross the volar aspect of the
joint can, under certain conditions, assist in the production of flexion,
and the muscles whose tendons cross the dorsal surface can assist in the
production of extension,

ARTICULATIONES RADIO-ULNARES (RADIO-ULNAR JOINTS).

At the two radio-ulnar joints, proximal and distal, the
movements of pronation and supination take place. At
the proximal joint the medial part of the head of the radius
fits into the radial notch of the ulna; at the distal joint the



202 THE SUPERIOR EXTREMITY

small capitulum of the ulna is received into the ulnar notch
on the medial side of the distal end of the radius. In
connection with these joints there are special ligaments
which retain the bones in apposition. They are (i) for
the proximal radio-ulnar joint, the annular ligament', and
(2) for the distal radio-ulnar joint, (a) a capsule, and (ti) the
discus articularis.

In addition there are other ligaments which pass between
the bodies of the two bones of the forearm, and are, therefore,
common to the two articulations, viz., the oblique cord and
the interosseous membrane.

Dissection. To expose the oblique cord and the inter-
osseous membrane, remove, completely, the volar and dorsal
muscles of the forearm.

Ligamentum Annulare Eadii (O.T. Orbicular Ligament).
The annular ligament is a strong fibrous collar which

Olecranon

V



Radial notch of ulna m _ u ______^__

Transverse portion
of ulnar collateral
ligament



Semilunar notch




Annular ligament Coronoid process

FIG. 96. Annular Ligament of the Radius.

encircles the head of the radius and retains it in the radial
notch of the ulna. It forms four -fifths of a circle, and is
attached by its extremities to the volar and dorsal margins of
the radial notch of the ulna. It is somewhat narrower distally
than proximally, so that, under ordinary circumstances, the
head of the radius cannot be withdrawn from it in a distal
direction, and it is braced tightly towards the elbow, and
greatly strengthened by the anterior and posterior portions



RADIO-ULNAR JOINTS 203

of the capsule of the elbow joint and by the radial collateral
ligament, which are attached to its proximal border. Its distal
border is attached, loosely, to the neck of the radius by a pro-
longation of the synovial stratum, which is covered externally
by a thin layer of fibrous tissue.

The Capsule of the Distal Radio -ulnar Joint. This
capsule consists of lax fibres which can have little influence
in retaining the distal extremities of the bones in apposi-
tion. It is attached to the volar and dorsal surfaces of
both bones of the forearm, to the most distal parts of the
interosseous crests and to the volar and dorsal borders of the
articular disc. A diverticulum of the capsule, which is
prolonged from the joint area for some distance proximally,
between the bones of the forearm, is called the recessus
sacciformis.

Discus Articularis (O.T. Triangular Fibro-Cartilage).
The articular disc is the true bond of union at the distal
radio-ulnar joint. It has already been noticed in connection
with the radio-carpal joint, where it extends the radial
articular surface in a medial direction, and is interposed
between the distal end of the ulna and the lunate and
triquetral bones. It is a thick, firm plate, attached by its
base to the distal margin of the ulnar notch of the radius.
The apex of the disc is placed medially, and is fixed to the
depression on the distal end of the ulna at the root of the
styloid process. It intervenes between the distal radio-ulnar
joint and the radio-carpal joint (Fig. 97).

Stratum Synoviale (Synovial Membrane). The synovial
stratum of the proximal radio-ulnar joint is continuous with
that of the elbow joint. It is prolonged distally to line the
annular ligament, and it protrudes beyond that ligament for
a short distance upon the neck of the radius.

The cavity of the distal radio-ulnar joint and the synovial
stratum are prolonged between the head of the ulna and
the articular disc.

Sometimes the articular disc is perforated ; when that is the case,
the distal radio-ulnar joint-cavity communicates with the cavity of the
radio-carpal joint.

Membrana Interossea Antibrachii. The interosseous
membrane is a fibrous membrane which stretches across
the interval between the two bones of the forearm, and is
attached to the crista interossea of each. Its proximal border



204 THE SUPERIOR EXTREMITY

is situated about 25 mm. (one inch) distal to the tuberosity of
the radius. Distally, it blends with the capsule of the distal
radio-ulnar joint. The fibres which compose it run for the most
part obliquely distally and medially from the radius to the ulna,
although several strands may be noticed taking an opposite
direction. The dorsal interosseous vessels pass backwards,
above its proximal margin, between the two bones of the
forearm ; whilst the terminal branch of the volar interosseous
artery pierces it about two inches from its distal end. The
membrane braces the two bones together in such a manner
that forces, passing proximally through the radius, are trans-
mitted from the radius to the ulna ; and it extends the surface
of origin for the muscles of the forearm. By its volar
surface it gives origin to the flexor digitorum profundus and
the flexor pollicis longus muscles, whilst from its dorsal
surface spring fibres of the two extensor muscles of the
thumb, the abductor pollicis longus, and the extensor indicis
proprius.

Chorda Obliqua (O.T. Oblique Ligament). The oblique
cord is a weak band of fibres which springs from the tuberosity
of the ulna. It extends obliquely, distally and laterally, to
find its attachment to the radius, immediately distal to the
tuberosity of that bone. It crosses the open space between
the bones of the forearm proximal to the proximal border
of the interosseous membrane. The oblique cord is often
absent ; and unless the utmost care is taken in removing the
adjacent muscles it is apt to be injured.

Movements at the Radio-ulnar Joints. The movements of prona-
tion and supination take place at the radio-ulnar joints. When the limb
is in a condition of complete supination the thumb is directed laterally, the
two bones of the forearm are parallel, the radius lying along the lateral side
of the ulna. In the movement of pronation the radius is thrown across the
ulna, so that its distal end comes to lie across the volar surface and on the
medial side of the ulna. Further, the hand moves with the radius, and
when the movement is completed the dorsal aspects of the hand and the
forearm are directed forwards, and the thumb is turned medially.

The dissector should analyse, as far as possible in the part upon which
he is engaged, the movements at the two radio-ulnar joints which produce
these effects. At the same time it is to be remembered that results
obtained from a limb in which the dissection has proceeded so far are apt
to be deceptive. Therefore the dissector should use himself and his friends
as subjects on which to study the movements.

In the case of the proximal radio-ulnar joint the movement is simple
enough. The head of the radius merely rotates within the annular
ligament, and accuracy of motion is obtained by the fovea capituli radii
resting and moving upon the distal end of the humerus. It should



RADIO-ULNAR JOINTS 205

be noticed that the head of the radius does not fit accurately upon
the capitulum in all positions of the elbow joint. In extreme extension
and extreme flexion of the elbow it is only partially in contact with it.
Therefore the semi-flexed condition of the elbow joint places the radius
in the most favourable position for free and precise movement at the
proximal radio-ulnar joint (Figs. 86, 87, 88, 91, 92, 93).

At the distal radio-ulnar joint the distal end of the radius revolves
around the distal end of the ulna. It carries the hand with it, and describes
the arc of a circle, the centre of which corresponds to the attachment of the
articular disc to the distal end of the ulna. As the movement occurs the
articular disc moves with the radius, and travels dorsally on the distal
end of the ulna in supination, and towards the volar surface in pronation.

But the question may be asked, Does the ulna move during pronation
and supination ? When the elbow joint is extended to its fullest extent the
ulna remains almost immovable. When, however, pronation and supination
are conducted in the semi-flexed limb, the ulna does move. A small
degree of lateral movement at the elbow joint is allowed, and the distal
end of the ulna during pronation is carried slightly dorsally and laterally,
and in the reverse direction during supination.

The muscles which are chiefly concerned in producing supination of the
forearm are the biceps brachii, the brachio-radialis and the supinator.
They are aided by the long abductor and the long extensor of the thumb.
The biceps brachii, from its insertion into the dorsal part of the tuberosity
of the radius, is placed in a very favourable position, in so far as its supinat-
ing action is concerned. The muscles which act as pronators of the limb are
the pronator teres, the pronator quadratus, and, to a certain extent, the
flexor carpi radialis. The pronator teres, from its insertion into the
point of maximum lateral curvature of radius, can exercise its pronating
action to great advantage. The balance of power is in favour of the
supinators, on account of the preponderating influence of the biceps.

Dissection. The annular ligament should be cut through,
and the oblique cord and the interosseous membrane should be
divided proximo-distally. By drawing the radius laterally and
opening the capsule of the distal radio-ulnar joint, the proximal
surface of the discus articularis of the wrist will be displayed
and its attachments more fully appreciated.



ARTICULATIONES CARPE^E (CARPAL JOINTS).

In the carpus two joints are recognised

1. Articulatio ossis pisiformis.

2. Articulatio intercarpea.

Pisiform Joint. The pisiform bone articulates with the
volar surface of the triquetral bone, to. which it is attached by
an articular capsule. The cavity of the pisiform joint is
quite distinct from those of the adjacent joints.

The dissector has previously noted that the tendon of the
flexor carpi ulnaris is inserted into the pisiform bone, and
as the capsule would be quite incapable by itself of with-



206



THE SUPERIOR EXTREMITY



standing the strain to which this muscle subjects the
articulation, certain accessory bands are provided which
anchor the pisiform firmly in place they are the piso-hamate
and the piso-metacarpal bands. The former passes from the
distal end of the pisiform to the hook of the hamate bone ;
and the latter attaches the pisiform to the proximal ends of
the fourth and fifth metacarpal bones.



ARTICULATIO INTERCARPEA (INTERCARPAL JOINT).

The intercarpal joint has one joint cavity, but it includes
not only the articulations between the proximal and distal



Os naviculare
manus

Os capitatum



Os mult-
angulum minus
Os multangu-
lum majus



Recessus
sacciformis




FIG. 97. Frontal section through Radio-carpal, Carpal, and Carpo-
metacarpal and Inter-metacarpal Joints to show Joint Cavities and
Interosseous Ligaments (diagrammatic).



rows of carpal bones, which form the transverse part of the
joint, but also the articulations between the bones of the
proximal row and those between the bones of the distal
row. The main part of the cavity of the joint lies between
the proximal and distal rows; but two prolongations pass
proximally, one between the lunate and navicular bones,
and the other between the lunate and triquetral bones, and
three diverticula are prolonged between the bones of the



INTERCARPAL JOINT 207

distal row, beyond which they become continuous with the
cavity of the carpo-metacarpal joint (Fig. 97).

The bones of the proximal row are connected together by
two dorsal, two volar, and two interosseous ligaments, which
pass from the lunate bone to the navicular and triquetral bones,
which lie to either side of it. The two interosseous
ligaments are composed of short, stout fibres which pass
between the non-articular portions of the opposed surfaces of
the bones. They are readily seen from the proximal aspect,
where they complete the distal surface of the radio-carpal
joint.

The members of the distal row of carpal bones are
bound together by three dorsal, three volar, and three inter-
osseous ligaments which pass transversely between the adjacent
bones. The interosseous ligament between the capitate
and the hamate bones is very strong ; that between the
capitate bone and the lesser multangular bone is weak and
not uncommonly absent.

At present the interosseous ligaments between the bones of the distal row
are hidden from view, but they can be studied when the transverse part of
the intercarpal joint is opened.

The transverse part of the intercarpal joint lies between
the proximal and distal rows of carpal bones. The two rows
of bones are bound together by an articular capsule which is
attached to the volar and dorsal surfaces and the medial and
lateral borders of each row. The lateral and medial parts
of the capsule are sometimes spoken of as the radial and
ulnar ligaments of the transverse carpal joint. The volar
and dorsal parts of the capsule are strengthened by numerous
bands of fibres. The bands on the dorsal surface are irregular
in number and strength, but those on the volar surface are
better marked and, for the most part, they radiate from the
capitate to the surrounding bones, forming the ligamentum
carpi radiatum. One of the bands of this ligament passes
from the capitate bone to the styloid process of the radius and
blends with the radial collateral ligament of the radio-carpal
joint.

Articular Surfaces. The individual bones of the proximal
row and the individual bones of the distal row articulate with
one another by flat surfaces. In the transverse part of the
intercarpal articulation the proximal parts of the capitate bone
and the hamate bone form a high convexity which fits into a



208 THE SUPERIOR EXTREMITY

concavity formed by the distal surfaces of the triquetral and
lunate bones and the distal part of the medial surface
of the navicular bone ; and the convex distal surface of the
navicular bone is received into a concavity formed by the
proximal surfaces of the greater and lesser multangular
bones. The two opposed surfaces of the transverse part of
the joint are, therefore, concavo-convex from side to side,
and adapted one to the other (Figs. 97, 98).

Movements at the Carpal Joints. The movements at the carpal joints
supplement those at the radio-carpal joint, and tend greatly to increase the
range of movement at the wrist. Between the individual bones of each row
the movement is of a gliding character, and very limited. At the trans-
verse intercarpal joint volar and dorsal movements (flexion and extension)
alone are allowed.

By the multiplicity of joints in this part of the limb, strength and
elasticity are contributed to the wrist.

The nerve supply of the radio-carpal and intercarpal joints is derived
from the median, ulnar, radial and musculo-cutaneous nerves.

Dissection. The interosseous muscles should now be re-
moved from the metacarpal bones. At the same time the flexor
tendons and lumbrical muscles may be detached from the fingers.
The extensor tendons, however, should be left in position on the
dorsal surfaces of the metacarpo-phalangeal and interphalangeal
joints. The ligaments which connect the carpus and meta-
carpus, and those which pass between the bases of the medial
four metacarpal bones, should be cleaned and denned.



ARTICULATIONES INTERMETACARPE^E (INTERMETACARPAL
JOINTS).

The four metacarpal bones of the fingers articulate with
one another by their basal or proximal extremities, and are
united together by strong ligaments. The metacarpal bone
of the thumb stands aloof from its neighbours, and enjoys
a much greater freedom of movement.

The ligaments which bind the medial four metacarpal bones
to each other are

1. A series of volar and dorsal bands, which pass trans-
versely and connect their basal extremities.

2. Three stout interosseous ligaments, which occupy the
intervals between the basal ends of the bones.

3. The transverse ligaments of the heads, which connect the
heads or distal extremities of the bones (p. 192). This liga-
ment has been removed in the dissection of the interosseous
muscles.



Ulna



PLATE XVII



. Distal

epiphysis of

ulna

Styloid pro-
cess of ulna



Lum



Distal epiphy-
sis of radius



Pisiform

Triquetrum
Hamatum



5th meta-
carpal







Sesamoid
bone






Styloid pro-
cess of radius

Navicular

Multangulum
inajus



Multangulum
minus



Capitatum



ist meta-
carpal bone



Sesamoid
bones



FIG. 98. Antero- posterior Radiograph of the Wrist of a Person
of 19 years.

Note (i) The epiphyseal lines of the radius and ulna.

(2) The difference in level of the styloid process of the ulna as con-

trasted with the styloid process of the radius.

(3) The overlap of the shadows of adjacent bones.







fi

55 -S



II

S'B



I 1



C/3 PL, 2.



2

O ei

S

OJ D

X O

u-, a



U <u

rt

|1

rt w










3

T3

< ^
D X!

X be

*- s

<*H O

_Q

2 OJ



CARPO-METACARPAL JOINTS 209

The interosseous ligaments cannot be seen at present, but can be studied
later when the bases of the metacarpal bones are separated from each
other.



ARTICULATIONES CARPOMETACARPE^: (CARPO-METACARPAL
JOINTS).

The metacarpal bone of the thumb articulates with the greater
multangular bone by a joint which is quite distinct from the
other carpo-metacarpal articulations. An articular capsule
surrounds the joint, and is sufficiently lax to allow a very con-
siderable range of movement. On the dorsal and lateral
aspects of the articulation it is specially thickened. Its cavity
is distinct from that of the adjacent articulations.

The medial four metacarpal bones are connected to the carpus
by volar and dorsal ligaments, and by one interosseous ligament.

Each of these metacarpal bones, with the exception of the
fifth, possesses, as a rule, two dorsal ligaments and one volar
ligament. The articulation of the fifth metacarpal bone is
also closed on the medial side by ligamentous fibres.

The interosseous ligament springs from the contiguous distal
margins of the capitate and hamate bones, and passes to the
medial side of the base of the third metacarpal bone.

Dissection. To display the interosseous ligament, divide the
bands which connect the bases of the third and fourth metacarpal
bones, and sever the dorsal ligaments which bind the medial two
metacarpal bones to the carpus. The metacarpal bones thus set
free can then be forcibly bent volarwards, when the ligament in
question will come into view.

Synovial Membranes of the Carpal, Carpo-metacarpal, and
Intermetacarpal Joints. The articulation between the pisi-
form and the triquetral bones and the carpo-metacarpal joint
of the thumb both possess separate capsules ; but the various



Online LibraryD. J. (Daniel John) CunninghamCunningham's manual of practical anatomy (Volume 1) → online text (page 21 of 44)