Human Anatomy Vol 1

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UPPER LIMB

The articulating surface of trapezium is concave in

the sagittal plane and convex in the frontal plane.

The concavoconvex nature of the articular surfaces

permits a wide range of movements (Fig. 1.0.24).

[igoments

1 Capsular ligament surrounds the joint. In general,

it is thick but loose, and is thickest dorsally and

laterally.

Lateral ligament is broad band which strengthens

the capsule laterally.

The anterior ligament

The posterior ligaments are oblique bands running

downwards and medjally.

Relolions

Anteriorly: The joint is covered by the muscles of the

thenar eminence (see Figs 9.22).

Posteriorly: Long and short extensors of the thumb

(Figs. 10.32a and b).

Medially: First dorsal interosseous muscle, and the

radial artery (passing from the dorsal to the palmar

aspect of the hand through the interosseous space).

Laterally: Tendon of the abductor pollicis longus.

Blood Supply

Radial vessels supply blood to the slmovial membrane

and capsule of the joint.

Nerve Supply

First digital branch of median nerve supplies the

capsule of the joint.

Movemenls

Flexion and extension of the thumb take place in the

plane of the palm, and abduction and adduction at right

angles to the plane of the palm. In opposition, the thumb

crosses the palm and touches other fingers. Flexion is

associated with medial rotation, and extension with

lateral rotation at the joint.

Circumduction is a combination of different move-

ments mentioned. The following muscles bring about

the movements (Figs 10.31a to 10.32b).

t Flexion

2 Extension

3 Abduction

4 Adduction

5 Opposition

. Flexor pollicis brevis (see
Fig.9.1e)
' Opponens pollicis
o Extensor pollicis brevis
. Extensor pollicis longus (Figs
10.32a and b)
o Abductor pollicis brevis (see Fig.
9.79)
. Abductor pollicis longus
Adductor pollicis (see Fig. 9.22)
o Opponens pollicis (see Fig. 9.22)
. Flexpr pollicis brevis

Abduction

Adduction

Opposition

(d) (e)

Figs 10.31a to e: Movements of the thumb

The opposition is a sequential movement of

abduction, flexion, adduction of the 1st metacarpal with

simultaneous rotation. Opposition is unique to human

beings and is one of the most important movements of

the hand considering that this motion is used in almost

all types of gripping actions.

The adductor pollicis and the flexor pollicis longus

exert pressure on the opposed fingers.

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The synovial lining of the tendons of extensor