Human Anatomy Vol 1

Table 2.3: Differences between metacarpals and meta-

tarsals

Chorocleristics of lndividuol Melocorpol Bones

1st a. It is the shortest and stoutest of all metacarpal
bones (Fig. 2.38a).
b. The base is occupied by a convexo-concave
articular surface for the trapezium.
c. The dorsal surface of the shaft is uniformly
convex (Fig. 2.38b).
d. The head is less convex and broader from side
to side than the heads of other metacarpals. The
ulnar and radial corners of e palmar surface
show impressions for sesamoid bones.
e. The first metacarpal bone is rotated medially
through 90' relative to the other metacarpals.
As a result of this rotation, the movements of
the thumb take place at right angles to those of
other digits.

BONES OF UPPER LIMB

f. It does not articulate with any other metacarpal

bone.

2nd The base is grooved from before backwards. The

medial edge of the groove is larger.

3rd The base has a styloid process projecting up from

the dorsolateral corner.

4th The base has two small oval facets on its lateral side

for the third metacarpal, and on its medial side it

has a single elongated facet for the 5th metacarpal.

Sth The base has an elongated articular strip on its

lateral side for the 4th metacarpal. The medial side

of the base is nonarticular and bears a tubercle.

Side Delerminoiion

The proximal, distal, palmar and dorsal aspects of each

metacarpal bone can be made out from what has been

stated above. The lateral and medial sides can be

confirmed by the following criteria.

laearpal

1st The anterolateral surface is larger than the

anteromedial (Fig. 2.38b).

2nd a. The medial edge of the groove on the base is

b.

3rd a.

b.

C.

4th a.

b.

5th a.

b.

deeper than the lateral edge.

The medial side of the base bears an articular

strip which is constricted in the middle.

The styloid process is dorsolateral.

The lateral side of the base bears an articular

strip which is constricted in the middle.

The medial side of the base has two small oval

facets for the 4th metacarpal.

The lateral side of the base has two small oval

facets for the 3rd metacarpal.

The medial side of the base has an elongated

articular strip for the Sth metacarpal.

The lateral side of the base has an elongated

articular strip for the 4th metacarpal.

The medial side of the base is nonarticular and

has a tubercle.

Moin Atlochments

The main attachments from shaft of metacarpals is of

palmar and dorsal interossei muscles. Palmar interossei

arise from one bone each except the 3rd metacarpal

(Fig.2.38a). Dorsal interossei arise from adjacent sides

of two metacarpals (Fig. 2.38b). The other attachments

are listed below.

Metacdrpal

1st a. Ttre opponens pollicis is inserted on the radial

border and the anterolateral surface of the shaft

(Fig.2.38a).

The abductor pollicis longus is inserted on the

lateral side of the base (Fig. 2.38a).

The first palmar interosseous muscle arises from

the ulnar side of the base (Fig. 2.38a).

$etacarpal

1. The head and shaft are
   prismoid


2. The shaft is of uniform
   thickness


3. The dorsal suface of
   the shaft has an elongated,
   flat triangular area


4. The base is irregular

Metatarsal

1. The head and shaft are
   flattened from side to
   side


2. The shaft tapers distally


3. The dorsal surface of
   the shaft is uniformly
   convex


4. The base appears to be
   cut sharply and obliquely

tt

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o

CL

CL

f

co

Fo

U}o)

b.

Ulnar nerve

Carpal tunnel

Triquetral

Scaphoid

Figs 2.37a to c: (a) Normal position of nerves, (b) dislocation

of lunate leading to carpal tunnel syndrome, and (c) Ape-like

deformity of the hand

c.