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George A. (George Arthur) Piersol.

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course till it reaches the end of the middle cuneiform, when it turns forward. It
has a short concave posterior border for the scaphoid and a long, nearly straight
one for the first metatarsal bone. It passes without a sharp boundary into the
lower surface. It is crossed by a faint groove, which exceptionally is deep, running
obliquely downward and forward to a smooth swelling for a bursa under the tendon



Fig. 441.



Fig. 442.



Mid. cuneiform



Scaphoid.




Right internal (



liform, outer aspect



of the tibialis anticus just before its insertion. The inferior surface, rough and
round, has a tubercle near the pro.ximal end for a part of the tibialis posticus. The
external surface is mostly rough, with a smooth articular strip for the middle
cuneiform following its upper and posterior border. The internal cuneiform articu-
lates with the scaphoid, middle cuneiform, and first and second metatarsal bones.

Development. — A centre appears in the third year. Very e.xceptionally it is
double, and the bone is divided by a suture into two, — a dorsal and a plantar.

THE MIDDLE CUNEIFORM.

The middle cuneiform ' has a sharp ridge below and an oblong surface above.
The latter, or superior surface, is very little longer than broad. The lateral
borders of this surface have an outward inclination. The inner of them corresponds
to the proximal part of the outer border of the first cuneiform. The outer border,
for its proximal two-thirds, rests against the external cuneiform, beyond which there
is a small space between the bones. The proximal side of this surface is a little
convex and the distal about straight. The posterior surface, wholly articular,



Fig. 443.





r aspect ; B, outer aspect.



is slightly concave. It is triangular, with the dorsal border rounded, the outer
concave, and the inner straight or slighdy convex. The anterior surface, ar-
ticular for the second metatarsal, is narrower. It has a slight convexity in the upper
part in a vertical plane. The internal surface has an articular facet corresponding
to that on the internal cuneiform and a rough depression for an interosseous liga-
ment. The external surface has a facet along the hind border, broader above
than below, and rarely a small one at the front lower angle, both for the external

^ Os cuneiforme secundum.



428 HUMAN ANATOMY.

cuneiform. The middle cuneiform articulates with the scaphoid, the internal and
external cuneiforms, and the second metatarsal.

Development. — One centre appears in the fourth year.

THE EXTERNAL CUNEIFORM.

The e.xternal cuneiform,' seen from above, is much longer than broad, with a
very oblique pro.ximal border slanting outward and backward, an anterior border
running less obliquely in the same direction, an inner one close against the middle
bone in its proximal third or one-half, then receding from it and extending onto the
outer side of the second metatarsal, and an outer border first running forward and
outward against the cuboid, and then forward not quite against it, but o\erlapping
the fourth metatarsal. The ridge constituting the inferior surface does not quite
reach the proximal end. The posterior surface, wholly articular, is oblong, with
the long axis vertical, and often a little convex. The anterior surface, articular for
the third metatarsal, is triangular and about plane. Its inner border rises higher
than the outer. The internal surface articulates with the second cuneiform bone by

Fig. 444.




one or two corresponding facets, as the case may be, and has, in addition, a facet for
the outer side of the base of the second metatarsal at the front upper angle, and
often extending down the border ; or the middle portion may be wanting. In the
middle of the surface is a roughness for the interosseous ligament. The external
surface is chiefly rough, giving origin to an interosseous ligament for the cuboid ;
at the upper proximal angle is a large facet for the same bone, and at the distal
upper angle there may or may not be a small one for the side of the fourth meta-
tarsal. The external cuneiform articulates with the scaphoid, the middle cuneiform,
the cuboid, and the second, third, and fourth metatarsals.

Development. — Ossification begins in the first year.

The Intercuneiform Bone. — On the dorsum there is a little pit which we
have called the intercuneiform fossa, situated between the proximal portions of the
internal and middle cuneiform bones, usually more at the expense of the latter than
of the former. We have at least twice seen a separate ossicle, the intercuneiform
bone' in this fossa. The better specimen was wedge-shaped, its length exceeding
one centimetre. It clearly was more intimately related to the middle than to the
internal cuneiform. Pfitzner has since seen it fused with the former.

THE METATARSAL BONES.

Of these five bones' the first is very much the largest, although the shortest.
The second is the longest, and the others of about equal length.

The first metatarsal bone has a concave base corresponding to the facet on
the internal cuneiform, which is prolonged down into a point (tuberosity) rather
to the outer side, on the external aspect of which the peroneus longus is inserted
into a round impression. On the inner side of the base is a small prominettce for
the tibialis anticus. A smooth facet for the second metatarsal is often found on the
outer side. A groove for the capsular ligament more or less perfectly encircles the
'Anat. Anzeiger, Bd. x.\., 1902.
^ Os cuneiforme tercium. ^Ossa metatarsalia 1-V.



THE METATARSAL BONES.



429



base. The strong shaft has three sides : an iyiteryial^ looking also upward, in the
main convex ; an external, concave and nearly vertical ; and an inferior, or p2a7ita?\




Phalangeal surface




Internal surface
Inferior surface



Impression of peroneus longus Tuberosity Internal cuneiform

Right first metatarsal. A, proximal aspect; B, plantar aspect; C, dorsal aspect.

also concave. The borders bounding the outer surface are the most distinct. One
or two nutrient foramina enter this surface, running distally. The enlarged and

Fig. 446.



Lateral ligament



Ext. cuneiform
Third metatarsal



Third metatarsal
Ext. cuneiform





External cuneiform
Right second metatarsal. A, proximal aspect ; By outer aspect ; C. i



rounded distal end, the head, is articular except at the sides, where it is flattened.
The facet extends farther onto the plantar aspect, where it expands laterally. It



430



HUMAN ANATOMY.



has there a median elevation, with a groove on either side for a sesamoid bone.
There is a rough surface for ligaments on each side of the head.

Fig. 447.



Middle cuneiform.




Fourth metatarsal



Right third metatarsal. .-I, pr




Second melata



External cunt
al aspect ; B, outer aspect ; C, inner aspect




The four outer metatarsal bones are distinguished by their bases. That
of the second is concave at the end, and fits the middle cuneiform ; on the inner
side a small facet at the top meets the outside of the first cuneiform ; on the older
side there are two, an upper and a lower, with a deep cut between each, resting

Fig. 448.






Third metatarsal

External cuneiform
Fifth metatarsal

Cuboid
Right fourth metatarsal. A. proximal aspect ; B, outer aspect ; C. inner aspect.

on both the outer cuneiform and the third metatarsal. The occasional facet for the
first metatarsal is on the shaft rather than on the end. It is often wanting on the



THE METATARSAL BONES.



431



second when present on the first, implying the presence of a bursa rather than of a
joint. The base of the third metatarsal fits the outer cuneiform, and is nearly
plane. The posterior upper border, seen from the dorsum, is oblique, running

Fig. 449.






Fourth metatarsal



Right fifth metatarsal. A, distal aspect ; B, dorsal aspect ; C, plantar aspect.

outward and backward. The inner surface has two facets for the second, and the

outer surface one at the top for the fourth metatarsal. The base of the fourth

metatarsal is also oblique. It has an oblong facet for the

cuboid, and a single internal one at the top for the third. Fig. 450.

which is separated from the proximal end by a rough space

for the insertion of an interosseous ligament from the tarsus.

There is externally a triangular facet at the upper angle

for the fifth. This last facet is bounded in front by a deep

groove which receives the edge of the facet on the fifth.

The fifth metatarsal has an even more oblique base, the

inner two-thirds of which bear a facet for the cuboid. The

outer part is prolonged as the hiberosity beyond the edge

of the foot, overhanging the joint. The inner side has a

facet for the fourth metatarsal bone.

The shafts of the metatarsal bones are flattened lat-
erally, but theoretically three-sided, like the first. The
second has an external surface looking directly outward ; a
superior one at the base, which twists so as to become in-
ternal. This is separated from the former in the distal two-
thirds of the shaft by a sharp ridge. The third side is internal
at the base, but soon becomes inferior. The shaft of the
third differs only slightly, the external surface looking some-
what upward and there being more of a ridge below. In
the fourth it seems as if the proximal part of the shaft had
been bent outward on its axis, so that the outer side looks
more upward and . the other two are less twisted. In the
fifth this process has gone farther ; the originally outer side
is now the upper, separated by one border from the inner and by another from the
inferior. This last border, now external, represents the one that was the inferior
of the third metatarsal. The nutrient foranii7ia of the four outer metatarsals are
in the external surfaces, running upward. They are not very constant.




Right fifth metatarsal,
aspect.



432



HUMAN ANATOMY.



Fig. 451.

Os intermetatarseum



The heads of the metatarsal bones are compressed, like the shafts, from side
to side, and have each a pair of lateral tubercles at the dorsal aspect of the end of
the shaft, separated by a groove from the articular surface. Lateral ligaments are
attached both to the tubercles and the grooves. The ar-
ticular surface is oblong, extending well onto the plantar
side, where it ends in two lateral prolongations, of which
the outer is the more prominent. A line connecting their
ends would be oblique to the shaft, especially in the outer
toes.

Fusion of the outer cuneiform with its metatarsal occurs
occasionally at the plantar aspect. It is probably con-
genital. Pfitzner has seen it at seventeen and we at
nineteen.

Development. — Centres for the shafts of the meta-
tarsals appear towards the end of the third month of foetal
life. A pro.ximal epiphysis for the first and distal ones for
the others appear in the third year, fusing at about seven-
teen. Occasionally the metatarsals, especially the first,
have an epiphysis at each end.
Os Intermetatarseum. — This is an occasional wedge-shaped bone found on
the dorsal aspect of the foot, between the internal cuneiform and the first and second
metatarsals. It may articulate with all three, or with any of them, or be attached to
them by connective tissue. More often it is connected by bone with one of the three
neighbors, especially with the internal cuneiform, of which it mav seem to be a pro-
cess (Fig. 451). It is found in some form once in ten feet (Pfitzner).




Intermetatarsal bone fused \
right internal cuneiform



Fig. 452.





THE PHALANGES.

There are two for the great toe and three for each of the others. Although of
very different proportions, they present the features which have been described for
those of the hand, especially the shape of the articular sur-
faces. The first phalanx of the great toe is about as
long as that of the thumb and nearly twice as broad. There
is a tubercle for muscular insertion at each side of the pal-
mar aspect of the base. The terminal phalanx of the
great toe is also very massive. The first, or proximal, pha-
langes of the other toes diminish in length from within out-
ward. Those of the second row are so short as to be
almost cubical, although they are broader than thick. The
terminal, or distal, phalanges are very rudimentary.
Pfitzner" has shown that in about one-third of the cases the
terminal phalan.x of the little toe is fused with the middle
one, even before birth. Presumably they never were distinct
in the embryo. As he has found this condition in Egyptian
mummies, certain \-ery pessimistic views as to the degener-
ation in store for the human foot are probably unwarranted.

Sesamoid Bones. — Those of the first metatarso- pha-
langeal joint are large and constant ; those of the same joint
in the other toes very rare. The least uncommon are those
of the fifth toe, of which the inner sesamoid is found in 5.5
per cent, and the outer in 6.2 per cent. A sesamoid of the
interphalangeal joint of the great toe is found in 50.6 per
cent. (Pfitzner^).

Development. — The first nucleus to appear is that of
the distal phalanx of the great toe at the end of the third
foetal month. Those of the other distal phalanges, except the fifth, come some two
weeks later. The bones of the pro.ximal row seem to ossify rather later than the

' Arch, fiir Anat. und Entwick., 1890.
' Morph. Arbeiten, Bd. i.




Third distal
or ungual,
phalanx



Second, or
middle,
phalanx



First or
proximal,
phalanx



Phalanges of right second
toe, plantar surface.



THE PHALANGES.



433



distal ones, but this order is not constant. According to Bade,' the middle phalanges
have begun to ossify in the eighteenth week of foetal life, but we have found bone
wanting considerably later. The process of ossification in the fourth and tifth toes
is decidedly later than at the inner side of the foot. It does not begin in the middle
phalanx of the fifth till near term, and we have sometimes seen no sign of it in the

Fig. 453.









Ossification of bones of the foot. A. during sixth fcetai month: S, at eighth fcetal month; C at birth; D,
during first year ; £, between three and four years ; F, at about fifteen \ears. a, for shaft of metatarsals ; *, for cal-
caneum ■ c, for proximal phalanges; d, for distal phalanges ; e, for astragalus ;/, for middle phalanges; g-, for cuboid:
A. for external cuneiform ; i, for heads of metatarsal bones and base of first proximal phalanx ; j\ for base of first
distal phaianx ; k, for internal cuneiform ; /. for base of first metatarsal.



fifth, and even in the fourth at birth. Proximal epiphyses appear from the fourth to
the si.xth year, and fuse at about sixteen. The terminal phalanges have distal caps
like those of the hand. The fifth toe, according to Pfitzner, has the following pecu-
liarities : the proximal epiphysis of the second phalanx and the centre for the shaft
of the terminal one are wanting, the proximal epiphysis of the latter being greatly
exaggerated.

' Arch, fiir Mik. Anat., Bd. Iv., 1900.
28



434



HUMAN ANATOMY.
Fig. 454-



I ostero inferior surface of calcaneum



Groove for tendon of.
flexor longus halhicis



Sustentaculum lal



Scaphoid ^^

Tibialis postic.

External cuneilorm
Middle cuneiform
Internal cuneiform

Tibialis anticus



First metatarsal.



Sesamoid boni



Abductor and Hexor

brevis hallucis
Adductores obliguus
et transversus



Flexor longits hallu




Bones of right foot, plantar aspect.



BONES OF THE FOOT.



435



Fig. 455.



Ttndo Achilhs
Bursal surface



Lateral articular surface for fibul
Groove ior peroneus long



Groove iox peron.
Extensor brevis digits



Groove for peroneus /on^.



Groove iorjiexor iotigus halluc



Superior articular surface of
astragalus



Peroneus tert.



Fourth dorsal interosse.



Extensor brevis digitorum

Extensor longus digitorum




External cuiieifornr
Middle cuneiform
Internal cuneiform



First metatarsal



First dorsal inter



Extefisor brevis hallucis



Extensor longus hallucis



Bones of right foot, dorsal aspect.



436 HUMAN ANATOMY,



PRACTICAL CONSIDERATIONS.

The union of the foot with the leg at a right angle, while necessitated by the
erect attitude of man, makes it essential that the bones of the foot shall be so shaped
and united that they may aflord a basis for both support and propulsion, all pre-
hensile function being sacrificed to those ends. Accordingly, we find the tarsus
proportionately much larger, both it and the metatarsus stronger, and the pha-
langes much smaller and less mobile than the corresponding parts of the hand.
The strength of the foot and its comparative freedom from injury, in spite of its con-
stant exposure to traumatisms of various grades of severity, are due to the arrange-
ment of its component bones into the form of an arch, which is well adapted not only to
sustain weight and to provide leverage for motion, but also to resist and distribute
e.xcessive force received, as in falls upon the feet. The posterior pillar of the arch,
composed of the os calcis and the hinder portion of the astragalus, has but one joint
— the calcaneo-astragaloid — with a very limited range of motion. The action of the
calf muscles upon the heel is thus applied to the elevation of the hinder pillar with
the least possible expenditure of force, as there are no unnecessary movements
between their point of insertion and the ankle-joint.

The anterior pillar beginning at the top of the astragalus — the summit of the
arch — may be said to include practically most of the foot anterior to the ankle and to
separate naturally into ( i ) a larger and stronger inner division consisting of the neck
and head of the astragalus, the scaphoid, the three cuneiforms, and the three inner
metatarsals ; and ( 2 ) a weaker and smaller outer division composed of the cuboid
and the remaining metatarsals.

The anterior pillar thus secures in the wide surface of the distal extremities of
the metatarsal bones a broad basis of support ; its inner division carries most of the
weight, and is enabled to do this by the thickness and strength of the metatarsal bone
of the great toe and by the parallelism of the latter with the great toe ; its outer
division bears less weight, but supports the inner division laterally and broadens the
surface in contact with the ground. The normal foot thus rests directly upon the os
calcis and the anterior e.xtremities of the metatarsals, the outer side of the foot aiding
more in preserving balance than in carrying weight.

An imperfect transverse arch — including the scaphoid, cuboid, and cuneiforms —
adds to the elasticity of the foot and aids the main arch in affording a pressure-free
area for the plantar vessels and nerves. Both arches depend for their integrity not
only upon the shape of the bones-, but also upon the fasciae, ligaments and tendons,
and to some extent upon the small plantar muscles. Still another transverse arch is
formed by the bases of the metatarsal bones, and a third, but less distinct one, by
their heads.

Perhaps the most accurate conception of the foot mechanically is as a semi-dome
(Ellis), the whole dome being completed in well-shaped feet when the inner borders
are approximated.

The epiphysis of the os calcis occupies the posterior rounded extremity of the
bone, and has inserted into it the tendo Achillis. No positive clinical evidence of
separation exists, but it is probable that the X-rays will show that in young persons
lesions heretofore supposed to be fractures of the os calcis from muscular action are
actually epiphyseal disjunctions.

The epiphyses of the remaining bones of the foot have but little surgical interest.
The first metatarsal, like that of the thumb, has its epiphysis at the proximal end,
and to that extent resembles a phalanx. The other four metatarsals have their epiph-
yses at the distal ends. All the phalangeal epiphyses are at the proximal ends.
In the metatarso-phalangeal joints the synovial membrane is in close relation to the
epiphyseal lines ; in the phalangeal joints it is not. A knowledge of these facts may
occasionally be useful in cases of disease or injury limited to a particular bone.

Fract2ire of the bones of the tarsus is rare, e.xcept as a result of crushing injuries
or of falls from considerable heights. If the bones of the anterior pillar are broken,
it is usually by direct violence, as the numerous joints and ligaments of this region
render it so elastic, and so diffuse forces applied, as in jumps or falls, as effectually to



PRACTICAL CONSIDERATIONS : THE FOOT BONES. 437

prevent fracture. The bones of the posterior pillar are broken in both ways. In
falls the astragalus is apt to break about its neck, — the weakest portion ; or if the
foot is strongly dorsiflexed, the anterior articular edge of the tibia may act as a
wedge and split it across. The os calcis may be broken between the astragalus and
the ground, — compression fracture ; or it may be broken behind the insertion of the
inferior calcaneo-scaphoid ligament, the anterior arch being flattened by the fall, but
the ligament resisting rupture. A few cases of fracture of the sustentaculum tali have
been reported, the foot having been in forcible inversion, the lesser process (susten-
taculum) being broken off against the edge of the astragalus. In each case this was
followed by eversion and sinking of the inner border of the foot (valgus), the support
given by the internal articulating surface to the astragalus having been removed.

Of the metatarsal bones, the first, although the strongest, is most frequently broken
because it carries so large a proportion of the body weight and because it receives an
undue share of the violence in falls associated with eversion of the foot. The fifth
comes next in frequency because of its exposed position on the outer side of the foot
and the added violence in cases of inversion.

Dislocation of separate bones, especially of the astragalus, is rare. It is always
the result of the application of considerable crushing force, is usually associated with
other injuries, and is influenced but little by anatomical factors.

Disease of the bones of the foot, and especially tuberculous disease of the tarsus,
is common because of : (i) the frequency of traumatism ; (2) the exposure to cold
and damp and the scanty protection afforded by the superjacent tissues; (3) the
remoteness from the centre of circulation and the dependent position of the part,
both favoring congestions ; (4) the preponderance of cancellous tissue in the bones ;
and (5) the difficulty in securing perfect rest, especially after minor injuries, which
are those most often followed by tuberculous osteitis. It affects most frequently those
bones that bear most of the weight of the body, — the os calcis, the head of the
astragalus, and the base of the first metatarsal. It is more likely to remain localized
when situated in the os calcis or in the hinder part of the astragalus ; in the anterior
portions of the tarsus the number and complexity of the synovial cavities (often
intercommunicating) tend to prolong and to spread the disease. In disease of the
tarsal bones — excepting the astragalus, to which no muscle is attached — the tendon
sheaths in the vicinity may be involved by direct extension from the periosteum.

Any metatarsal bone may be involved in cases of ' ' perforating ulcer, ' ' the situa-
tion of the latter being determined usually by the degree of pressure upon the sole in
cases in which anaesthesia is already present ; hence the frequency with which the first
metatarsal is involved in this disease.

Excision of the separate bones has frequently been performed, especially of the
astragalus and os calcis.

Landmarks. — On the inner side of the foot can be felt : («) the ridge between
the inner and posterior surfaces of the os calcis ; ((5) the tubercle of the os calcis ; (^)
the sustentaculum tali, one inch directly below the tip of the malleolus ; (^) from one-
half to three-quarters of an inch in front of the latter the head of the astragalus, very
noticeable in flat-foot ; {e) from one-half to three-quarters of an inch more anterior
the prominent tuberosity of the scaphoid, the space between it and the sustentaculum
being filled by the inferior calcaneo-scaphoid ligament and the tibialis posticus tendon ;
from the tuberosity the tendon may be traced to the back of the inner malleolus ;
(/) the internal cuneiform ; (^) the base (one and a half inches in front of the
scaphoid tuberosity), the shaft, and the expanded head of the first metatarsal ; (^)



Online LibraryGeorge A. (George Arthur) PiersolHuman anatomy : including structure and development and practical considerations (Volume v.1) → online text (page 53 of 135)