metatarsal
Any of the five long bones of the foot
(hind feet in quadrupeds), which collectively make up the metatarsus. They
are analogous to the metacarpals of the
hand. The metarsals articulate at one end with the tarsals
(ankle bones) and at the other with the phalanges
(toe bones).
Osteology of the metatarsals (Gray's
Anatomy, 1918)
The metatarsals are numbered from the medial side (ossa metatarsalia I.-V.);
each presents for examination a body and two extremities.
Common characteristics of the metatarsal bones
The body is prismoid in form, tapers gradually from the tarsal to the phalangeal
extremity, and is curved longitudinally, so as to be concave below, slightly
convex above. The base or posterior extremity is wedge-shaped, articulating
proximally with the tarsal bones, and by its sides with the contiguous metatarsal
bones: its dorsal and plantar surfaces are rough for the attachment of ligaments.
The head or anterior extremity presents a convex articular surface, oblong
from above downward, and extending farther backward below than above. Its
sides are flattened, and on each is a depression, surmounted by a tubercle,
for ligamentous attachment. Its plantar surface is grooved antero-posteriorly
for the passage of the flexor tendons, and
marked on either side by an articular eminence continuous with the terminal
articular surface.
Characteristics of the individual
metatarsal bones
The first metatarsal bone (os metatarsale I; metatarsal
bone of the great toe)
The first metatarsal bone is remarkable for its great thickness, and
is the shortest of the metatarsal bones. The body is strong, and of
well-marked prismoid form. The base presents, as a rule, no articular
facets on its sides, but occasionally on the lateral side there is
an oval facet, by which it articulates with the second metatarsal.
Its proximal articular surface is of large size and kidney-shaped;
its circumference is grooved, for the tarsometatarsal ligaments, and
medially gives insertion to part of the tendon of the Tibialis anterior;
its plantar angle presents a rough oval prominence for the insertion
of the tendon of the Peronĉus longus. The head is large; on its plantar
surface are two grooved facets, on which glide sesamoid
bones; the facets are separated by a smooth elevation. |
|
The second metatarsal bone (os metatarsale II)
The second metatarsal bone is the longest of the metatarsal bones,
being prolonged backward into the recess formed by the three cuneiform
bones. Its base is broad above, narrow and rough below. It presents
four articular surfaces: one behind, of a triangular form, for articulation
with the second cuneiform; one at the upper part of its medial surface,
for articulation with the first cuneiform; and two on its lateral
surface, an upper and lower, separated by a rough non-articular interval.
Each of these lateral articular surfaces is divided into two by a
vertical ridge; the two anterior facets articulate with the third
metatarsal; the two posterior (sometimes continuous) with the third
cuneiform. A fifth facet is occasionally present for articulation
with the first metatarsal; it is oval in shape, and is situated on
the medial side of the body near the base. |
|
The third metatarsal bone (os metatarsale III)
The third metatarsal bone articulates proximally, by means of a triangular
smooth surface, with the third cuneiform; medially, by two facets,
with the second metatarsal; and laterally, by a single facet, with
the fourth metatarsal. This last facet is situated at the dorsal angle
of the base. |
|
The fourth metatarsal bone (os metatarsale IV)
The fourth metatarsal bone is smaller in size than the preceding;
its base presents an oblique quadrilateral surface for articulation
with the cuboid; a smooth facet on the medial side, divided by a ridge
into an anterior portion for articulation with the third metatarsal,
and a posterior portion for articulation with the third cuneiform;
on the lateral side a single facet, for articulation with the fifth
metatarsal. |
|
The fifth metatarsal bone (os metatarsale V)
The fifth metatarsal bone is recognized by a rough eminence, the tuberosity,
on the lateral side of its base. The base articulates behind, by a
triangular surface cut obliquely in a transverse direction, with the
cuboid; and medially, with the fourth metatarsal. On the medial part
of its dorsal surface is inserted the tendon of the Peronĉus tertius
and on the dorsal surface of the tuberosity that of the Peronĉus brevis.
A strong band of the plantar aponeurosis
connects the projecting part of the tuberosity with the lateral process
of the tuberosity of the calcaneus. The plantar surface of the base
is grooved for the tendon of the Abductor digiti quinti, and gives
origin to the Flexor digiti quinti brevis. |
|
Articulations
The base of each metatarsal bone articulates with one or more of the tarsal
bones, and the head with one of the first row of phalanges. The first metatarsal
articulates with the first cuneiform, the second with all three cuneiforms,
the third with the third cuneiform, the fourth with the third cuneiform
and the cuboid, and the fifth with the cuboid.
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