D. J. (Daniel John) Cunningham.

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ligaments of the intercarpal, carpo-metacarpal, and proximal
intermetacarpal joints, though they are spoken of individually
as separate ligaments, constitute collectively a single capsule,
which surrounds a continuous joint cavity. The synovial
stratum of the capsule is prolonged over all parts of the
bones, enclosed within the capsule, which are not covered by
articular cartilage, and it is continued proximally between
the three bones of the proximal row of the carpus as far as
the interosseous ligaments which connect the bones together.
It covers the distal surfaces of those ligaments and is

VOL. i 14



210 THE SUPERIOR EXTREMITY

excluded by them from the radio-carpal joint. It passes
also between the four bones of the distal row of the carpus
and covers the inner surfaces of the ligaments of the
carpo-metacarpal joints and the ligaments of the medial four
intermetacarpal articulations.

In some cases the interosseous ligament which connects
the base of the third metacarpal to the capitate and hamate
bones shuts off the articulation of the hamate bone with the
medial two metacarpal bones, and converts the articulation
of the hamate bone with the medial two metacarpal bones
into a separate segment of the carpo-metacarpal joint.

Dissection. To display the articular surfaces of the carpo-
metacarpal articulations, the metacarpus should be detached
from the carpus. The interosseous ligaments between the carpal
bones of the second row, and also between the bases of the
medial four metacarpal bones, can likewise be demonstrated
by carrying the knife between the bones, and dividing the
ligaments.

Articular Surfaces. The base of the metacarpal bone of
the index will be seen to be hollowed out for the reception
of the lesser multangular bone. On the lateral side it also
articulates with the greater multangular bone, and on the
medial side with the capitate bone. The base of the third
metacarpal rests against the capitate bone alone. The base
of the metacarpal bone of the ring finger rests upon the hamate
bone, but articulates slightly with the capitate bone also. The
fifth metacarpal bone articulates with the hamate bone (Figs.
73, 77, 9 8 > 99, I00 )-

Movements of the Metacarpal Bones. The opposed saddle -shaped
surfaces of the greater multangular bone and the metacarpal bone of the
thumb allow free movement at that joint. Thus the metacarpal bone of the
thumb can be moved (i) dorso-laterally (extension); (2) volarwards and
medially (flexion) ; (3) medially towards the index (adduction) ; (4) laterally
(abduction); (5) medially across the palm towards the little finger (opposition);
(6) a combination of the above-mentioned movements, occurring one after
the other, constitutes circumduction. The muscles which operate on the
thumb are (i) the two special extensors, brevis and longus, and the
abductor pollicis longus, producing extension ; (2) the flexor pollicis brevis,
the opponens pollicis, and the adductor pollicis, producing flexion and
opposition, two movements which are similar in character ; (3) the
abductor pollicis longus and the abductor pollicis brevis, producing
abduction ; (4) the adductor pollicis and the first dorsal interosseous
muscle, which give rise to adduction.

The metacarpal bones of the index and middle fingers possess very
little power of independent movement. The metacarpal bone of the ring
finger, and more especially the metacarpal bone of the little finger, are
not so tightly bound to the carpus. When the hand is clenched they both



METACARPO-PHALANGEAL JOINTS 211

move volarwards. The metacarpal bone of the little finger is provided
with an opponens muscle, and has a feeble power of moving volarwards
and laterally towards the thumb.

The carpo-metacarpal and intermetacarpal joints are supplied by the
radial, ulnar and median nerves.



ARTICULATIONES METACARPOPHALANGE^E ET DIGITORUM
(METACARPO-PHALANGEAL AND INTERPHALANGEAL JOINTS).

The ligaments which connect the metacarpal bones with
the phalanges and those which connect together the
phalanges of adjacent rows are practically similar in character
although the joints belong to different groups. The ligaments
of each joint are :

1. Capsula articularis.

2. Lig. accessorium volare.

3. Ligg. collateralia.

Capsula Articularis. The fibrous stratum of the articular
capsule is blended, on the volar aspect, with the accessory
volar ligament and at the sides with the collateral ligaments.
Dorsally it is absent, and there the synovial stratum of the
capsule lies in direct relation with the extensor tendon or
tendons which cross the joint.

Ligamentum Accessorium Volare. The volar accessory
ligament is a strong fibrous plate which is firmly attached to
the volar aspect of the base of the distal bone of the joint.
It extends proximally over the volar aspect of the head of
the proximal bone of the joint and is loosely attached to its
neck. Its margins are connected with the collateral ligaments
and with the fibrous flexor sheath of the finger. The volar
surfaces of the volar accessory ligaments of the metacarpo-
phalangeal joints are grooved by the flexor tendons and they
are connected with one another by the transverse ligament
of the heads of the metacarpal bones. Two sesamoid bones
are usually developed in the volar accessory ligaments of the
metacarpo-phalangeal joint of the thumb and not uncommonly
sesamoid bones are found in the corresponding ligaments of
other metacarpo-phalangeal joints (Figs. 98, 99).

Dissection. The extensor tendons should now be raised
from the dorsal surfaces of the metacarpo-phalangeal joints.
If this is done carefully the dorsal part of the capsule of each
joint will be left intact. It is very thin, and consists, practically,
i Ha



2i2 THE SUPERIOR EXTREMITY

of the synovial stratum only, the protection afforded by the
extensor tendon rendering the presence of the fibrous stratum
unnecessary.

Movements of the Metacarpo-phalangeal Joints. In each metacarpo-
phalangeal joint the single concavity at the proximal end of the first
phalanx articulates with the rounded distal extremity or head of the
metacarpal bone. The joints are condyloid joints, therefore the move-
ments which occur at them are: (i) flexion, (2) extension, (3) abduc-
tion, (4) adduction, (5) circumduction.

During flexion of the fingers the first phalanx travels volarwards with
the thick accessory volar ligament upon the head of the metacarpal
bone. The interosseous and lumbrical muscles are chiefly instrumental
in producing this movement, but they are aided by the long and short
flexors of the digits.

The first phalanges of the fingers, in the movement of extension, can
be carried dorsally only to a very slight degree beyond the line of the
metacarpal bones. The extensor communis and the special extensors of the
index and little finger are the muscles which operate in this case.

Abduction and adduction are movements of the first phalanx away from
and towards a line prolonged distally through the middle finger, and
are seen when the fingers are spread out and again drawn together.
The abductor digit i quint i and the dorsal interosseous muscles act as
abductors of the fingers, whilst the volar interosseous muscles operate
as adductors of the little, ring, and index fingers. In the case of
the middle digit, the second and third dorsal interosseous muscles act
alternately as abductors and as adductors. In connection with the
movements of abduction and adduction, it should be noticed that in the
extended position of the fingers they are very free ; but if flexion is
induced, the power of separating the fingers becomes more and more
restricted, until it becomes lost when the hand is closed. An examina-
tion of the collateral ligaments will afford the explanation of this fact.
They " are attached so far dorsally on the metacarpal bones, as to be much
nearer to their distal ends than to their volar aspects " (Cleland). Con-
sequently, while they are comparatively lax in the extended position of
the fingers, the further flexion advances the tighter they become, and in
this way they interfere with the lateral movements of the first phalanges.

The first phalanx of the thumb has only a limited range of movement
at the metacarpo-phalangeal joint.

Movements of the Interphalangeal Joints. The inter phalangeal
joints are hinge joints, therefore the only movements possible are flexion
and extension. Flexion of the second phalanges of the fingers is brought
about by the flexor sublimis, and of the ungual phalanges by the flexor
profundus. Extension of the phalanges at the interphalangeal joints is
produced not only by the extensors of the digits but also by the interosseous
and lumbrical muscles acting through the extensor expansions, into which
they are inserted. The interossei and lumbricals, therefore, flex the first
phalanges at the metacarpo-phalangeal joints and extend the second and
ungual phalanges at the interphalangeal joints.

In the case of the thumb, the flexor pollicis longus and the extensor
pollicis longus operate at the interphalangeal joint.

Some of the metacarpo-phalangeal joints and interphalangeal joints are
supplied by the median and some by the ulnar nerve.



PLATE XIX



5th lumbar Posterior superior spine
vertebra

ILIUM

/X

'Anterior
Superior spine

SACRUM *- -

.Head Head \



N Symphysis pubis
Lesser trochanter



Adductor tubercle,
Medial epicondyle




Adductor tubercle
Medial epicondyle
Medial condyle



Medial malleolus



Talus

Navicular



ist metatarsal

ist phalanx .
Terminal phalanx

FIG. 101. Bones of Inferior
Extremity.

A. Anterior view.



Talus
Calcaneus



FIG. 102. Bones of Inferior
Extremity.

B. Posterior view.




JT3SJT2JTJJ3UJ }SI



INTRODUCTION 213



INFERIOR EXTREMITY.

Introduction. Before commencing the dissection the student
should be familiar with the bones of the region to be
dissected and with the surface markings which indicate the
positions of the structures which are to be displayed. He
should also possess a general knowledge of the constitution
and distribution of a spinal nerve.

The bones of the inferior extremity are : The os coxce or
hip bone ; the femur or thigh bone ; the patella or knee-cap ;
the tibia and fibula, which are the bones of the leg ; seven
tarsal and five metatarsal bones, which are the bones of the
foot ; and fourteen phalanges, which are the bones of the
toes, three for each except the great toe, which has only two
phalanges (Figs. 101, 102, 103).

The os coxce. or hip bone lies in the lower part of the trunk.
It is jointed posteriorly to the vertebral column, whilst in
front it meets its fellow of the opposite side in the median
plane, at the symphysis pubis. The upper part of the os coxae
is called the ilium. Its highest part forms a curved ridge,
the crest of the ilium, which is easily felt at the side of the
body and is a little below the level of the elbow when the
arm hangs by the side. The posterior end of the crest of the
ilium is the posterior superior spine of the ilium. The anterior
end of the crest is the anterior superior spine of the ilium.

The lower and posterior part of the os coxae, upon which
the body rests in the sitting posture, is the ischium ; it is a
landmark of importance when the posterior part of the
inferior extremity is being dissected.

The lower and front part of the os coxae is the pubis. It
meets its fellow of the opposite side, in the median plane, at the
symphysis pubis, where it is easily felt. From the upper end
of the symphysis pubis a ridge, called the crest of the pubis,
runs laterally and terminates in a projection termed the
pubic tubercle.

A faint groove, called the inguinal sulcus, extends from the
pubic tubercle to the anterior superior spine of the ilium. It
indicates the separation between the lower or inguinal region
of the trunk and the upper or subinguinal region of the
front of the thigh. If pressure is made along the line of the
inguinal sulcus, elastic resistance will be felt; it is due to

1146



2i 4 THE INFERIOR EXTREMITY

a fibrous band called the ligamentum inguinale (Poupartii),
which is attached medially to the pubic tubercle and laterally
to the anterior superior spine of the ilium.

The finger should now be carried, downwards, along the
symphysis pubis to its lower margin, which is at the apex of
the pubic arch. From its apex the pubic arch must be traced
laterally and backwards. It is formed by the rami of the
pubis and ischium, and it terminates posteriorly at the tuber
ischiadicum, which is the protuberant inferior end of the ischial
part of the os coxae. The pubic arch marks the superior
boundary of the medial side of the thigh, which is called
the medial femoral region.

Between the region of the hip and the knee lies the
region of the thigh, which is the proximal segment of the free
part of the inferior extremity. The bone of the thigh is the
femur. It articulates proximally with the lateral aspect of the
os coxae at the junction of the three segments of that bone,
and distatly it articulates with the tibia^ which is one of the
bones of the leg, and with \\\z patella or knee-cap (Fig. 101).

In the greater part of its extent the femur is deeply
embedded amidst the muscles of the hip and thigh and
cannot easily be felt, but two parts of its proximal end can
be distinguished, viz., the head of the femur and the greater
trochanter. If pressure is made below the middle of the
inguinal sulcus whilst the thigh is rotated, the rounded head
of the femur can be distinguished as it moves in the cavity
of the hip joint. A more readily felt portion of the proximal
end of the femur is the prominent projection called the greater
trochanter. It lies about ten centimetres (4 inches) below the
iliac crest, on a level with the pubic crest, and its highest point
is crossed by a line drawn from the anterior superior spine of
the ilium to the inferior end of the tuberosity of the ischium.
The position of the greater trochanter is indicated, on the
surface, by a prominence due to the projection of the bone,
and the region of the prominence is the trochanteric region.
The area between the trochanteric region and the crest of
the ilium is the region of the hip. The lateral part of the
thigh, distal to the trochanteric region, is the lateral femoral
region.

At the distal end of the anterior part of the thigh is the
regio genu anterior. In the middle of the region lies the
patella. The outline of the patella can be seen as well as



INTRODUCTION 215

felt. When the knee is straight (extended) the extensor
muscles of the anterior part of the thigh are relaxed and the
patella is freely movable ; it lies on the front of the distal end
of the femur. As the knee is bent the patella moves off
the front of the femur and passes into contact with its distal
surface ; then the patellar surface on the front of the distal end
of the femur can be felt beneath the skin (Figs. 183, 184, 185).
The patellar surface is formed by the fused anterior parts of the
two condyles which constitute the expanded distal extremity of
the femur. The lateral condyle lies at the distal end of the
lateral femoral area. It is easily palpated, and upon its lateral
surface, nearer the posterior than the anterior end, a small
rounded eminence can be distinguished ; it is the lateral
epicondyle. The medial condyle, which lies at the distal end of
the medial femoral region, is more prominent than the
lateral condyle. Near its posterior end the large rounded
medial epicondyle is very obvious to the touch. Above the
medial epicondyle, on the upper border of the condyle, is a
much smaller and less easily felt prominence, the adductor
tubercle, so called because the tendon of a muscle called the
adductor magnus is attached to it (Figs. 101, 102).

Immediately distal to the condyles of the femur are the
condyles of the tibia, and below them, in front, is the tuberosity
of the tibia. Extending from the patella to the tuberosity of
the tibia is a thick, broad band called the Hgamentum patella^
which is most easily felt when the knee joint is half bent. Im-
mediately distal to the posterior part of the lateral condyle
of the femur, on the same horizontal plane as the tuberosity
of the tibia, lies the head of the fibula. The rounded tendon
descending to it, from the thigh, is the tendon of the biceps
femoris.

Between the knee and the ankle lies the region of the leg.
In it there are two bones, the tibia and ti\e fibula. The tibia
is the more medial, the more anterior, and much the stronger
and more massive of the two bones. It lies immediately
beneath the skin and extends the whole way from the knee
to the ankle, where it terminates, on the medial side of the
ankle, in a visible projection, called the medial malleolus. Its
anterior border is the shin\\\. is easily traced from the tuberosity
of the tibia to the anterior border of the medial malleolus.
The proximal end of the tibia articulates by its condyles with
the condyles of the femur at the knee joint. Its distal end
i 14 c



216 THE INFERIOR EXTREMITY

articulates at the ankle with a bone of the foot called the
talus. Unlike the tibia, the fibula is deeply situated in the
greater part of its length, but its proximal end, the head of
the fibula, is easily felt immediately below the posterior part
of the lateral condyle of the tibia; its distal end, which is
called the lateral malleolus, is also superficial, and forms a
prominent visible projection on the lateral side of the ankle.
The fibula takes no part in the formation of the knee joint, for
its proximal end reaches only to the lateral condyle of the tibia
with which it articulates. Its distal end articulates with the
lateral surface of the distal end of the tibia and with the
lateral surface of the talus ; it enters therefore into the
formation of the ankle joint (Figs. 101, 102, 103).

The region below the ankle joint is the foot. In it are
seven tarsal bones, five metatarsal bones, and fourteen phalanges.
The tarsal bones form the skeleton of the posterior half of
the foot ; the metatarsal bones are situated in the anterior
half of the foot ; they are numbered one to five from the
medial to the lateral side. The phalanges are in the toes ;
two in the great toe, and three in each of the other toes.

Each of the tarsal bones is named. The highest of the
group, the talus, takes part in the formation of the ankle
joint, where it lies directly below the tibia, wedged between
the malleoli of the tibia and the fibula. It articulates
therefore with both the bones of the leg. Its anterior part,
the head, can be felt below the tibia and in front of the lateral
malleolus. The inferior surface of the talus rests upon the
calcaneus, which projects backwards, behind the malleoli, to
form the prominence of the heel. The strong tendon which
descends in the back of the leg to the prominence of the
heel is the tendo calcaneus. In front of the talus, in the
medial part of the foot, is the os naviculare. Its tuberosity,
which is an important landmark, can be felt about 25 mm.
(one incJi) in front of the tip of the medial malleolus (Fig. 103).

In front of the navicular lie the three cuneiform bones,
first, second, and third from the medial to the lateral side.
The first can be felt in front of the tuberosity of the navicular.
The other two can be recognised by pressure applied in the
dorsum of the foot, but they are not easily distinguished in
the undissected foot. In the lateral border of the foot, in
front of the calcaneus, is the last of the seven tarsal bones,
the cuboid. It is difficult to palpate, but immediately in front



INTRODUCTION 217

of it, about seven and a half centimetres anterior to the
lateral malleolus, is the prominent posterior end of the fifth
metatarsal bone, and the joint between the posterior surface
of the cuboid and the anterior end of the calcaneus is about
midway between the lateral malleolus and the posterior end
of the fifth metatarsal (Fig. 103).

All the metatarsal bones can be felt from the dorsum of
the foot, but the large first and the fifth are the most easily
distinguishable. The first lies in the medial border of the
foot between the first cuneiform and the first phalanx of the
great toe. The second and third lie respectively between the
second and third cuneiform and the first phalanges of the
second and third toes. The fourth and fifth extend from
the cuboid behind to the first phalanges of the fourth and
fifth toes respectively.

All the above-mentioned points can be verified by the
dissector upon his own person whilst he is waiting to
commence the dissection of his "part."

Since many students commence dissecting before they
have attended lectures or demonstrations on anatomy, they
are unacquainted with terms which must be used in the
instructions given regarding the dissections which are to be
made. Fortunately most of the terms used refer to things
which can be seen and felt. They, therefore, are easily
understood. There are, however, certain terms used when
branches of spinal nerves are under consideration which are
not self-explanatory, and it is necessary, therefore, that the
student should possess a knowledge of the terms used in
connection with spinal nerves before the actual work of
dissection is commenced. The following points should be
noted : (i) Every spinal nerve is attached to the spinal
medulla (spinal cord) by two roots, an anterior and a
posterior-, (2) as they are leaving the vertebral canal through
an intervertebral foramen the two roots unite to form
a nerve trunk (3) immediately after its exit from the
intervertebral foramen the trunk breaks up into a posterior
ramus and an anterior ramus, of which except in a few cases
the posterior is the smaller ; (4) each posterior ramus divides
into a medial branch and a lateral branch \ (5) each anterior
ramus divides into a lateral branch and an anterior branch (Fig.
4, p. 6).

Every anterior root consists of nerve fibres passing from



218 THE INFERIOR EXTREMITY

nerve cells in the spinal medulla to the fibres of the muscles ;
they carry motor impulses to the muscles. Each posterior
root consists of nerve fibres passing to and from the nerve
cells in the ganglion of the root. The fibres of the posterior
root convey sensory impulses pain, heat, cold, etc. The
sensory impulses pass through the nerve cells of the ganglion
and then onwards to the spinal medulla. The trunk of
every spinal nerve, therefore, contains both motor and sensory
nerve fibres, and the posterior and anterior rami into which
it divides also contain both motor and sensory fibres. The
branches of the rami may contain both motor and sensory rami
or one or the other only ; eventually, however, the peripheral
parts of the fibres conveying impulses from the spinal medulla
and those conveying impulses to the spinal medulla separate
from one another. Every nerve consists of one or more fibres.
The fibres which convey impulses from the spinal medulla
become the motor nerves which end in muscle fibres, whilst
the fibres which convey impulses to the spinal medulla are
the sensory nerves, and those sensory nerves which carry
impulses from the skin are called cutaneous nerves.



THE THIGH.

On the morning of the fourth day after the subject has
been brought into the dissecting room, it is placed upon the
table lying upon its back ; the pelvis is supported by two
blocks, and the inferior extremities are stretched out at full
length. In this position it is allowed to remain for five days,
and during that period the dissector of the inferior extremity
has a very extensive dissection to perform. He has to dissect
(i) the anterior region of the thigh, including the trigonum
femorale and its contents, (2) the medial region of the thigh, in-
cluding the adductor canal and its contents. With so much
work to be completed, within a limited time, he must appor-
tion the five days to the best advantage. During the first day
he should dissect the superficial structures of the whole of the
anterior and medial aspects of the thigh. During the second
and third days he should complete the dissection of the
femoral triangle and the anterior region of the thigh, and the
remainder of the period should be devoted to the dissec-
tion of the medial region.

Surface Anatomy. Before making the preliminary incisions



THE THIGH 219

in the skin the dissector must verify the positions of the most



Sternal end of clavicle



Acromial end of clavicle
Head of humerus

Nipple -I-
Lower end of body of sternum _L



Online LibraryD. J. (Daniel John) CunninghamCunningham's manual of practical anatomy (Volume 1) → online text (page 22 of 44)