Human Anatomy Vol 1

UPPER LIMB

occurs in the plane of palm (Fig. 9.25) in contrast to the

movement of thumb where abduction occurs at right

angles to the plane of palm (Fig.9.26). Note that

movement of the middle finger to either medial or

lateral side constitutes abduction. Also note that the

first and fifth digits do not require dorsal interossei as

they have their own abductors.

Testing of Some lntrinsic Muscles

a. Pen/pencil test for abductor pollicis breais: Lay the hand

flat on a table with the palm directed upwards. The

patient is unable to touch with his thumb a pen/

pencil held in front of the palm (Fig.9.27).

b. Test for opponens pollicis: Request the patient to

touch the proximal phalanx of Zndto 5th digits with

the tip of thumb.

c. The dorsal interossei are tested by asking the subject to

spread outthe fingers againstresistance. As indexfinger

is abducted one feels 1st dorsal interosseous (Fig. 9.28).

d. The palmar interossei and adductor pollicis are tested

by placing a piece of paper between the fingers,

between thumb and index finger (Fi9.9.29) and

seeing how firmly it can be held (Fig. 9.30).

e. Froment's sign, or the book test which tests the

adductor pollicis muscle. When the patient is asked

to grasp a book firmly between the thumb and other

fingers of both the hands, the terminal phalanx of

the thumb on the paralysed side becomes flexed at

the interphalangeal joint (by the flexor pollicis longus

which is supplied by the median nerve) (Fig. 9.31).

Abductor digiti minimi

(a) (b)

Figs 9.24a and b: (a) The dorsal interossei muscles, and (b) palmar interossei muscles

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f. The lumbricals and interossei are tested by asking

the subject to flex the fingers at the metacarpo-

phalangeal joints against resistance.

Dissection

Deep to the lateral two tendons of flexor digitorum

profundus muscle, note an obliquely placed muscle

extending from two origins, i.e. from the shaft of the

third metacarpal bone and the bases of 2nd and 3rd

metacarpal bones and adjacent carpal bones to the

base of proximal phalanx of the thumb. This is adductor

pollicis. Reflect the adductor pollicis muscle from its

origin towards its inseftion (Fig. 9.22).

ldentify the deeply placed interossei muscles. ldentify

the radial artery entering the palm between two heads

of first dorsal interosseous muscle and then between

two heads of adductor pollicis muscle turning medially

to join the deep branch of ulnar artery to complete the

deep palmar arch (Fig. 9.32). ldentify the deep branch

of ulnar nerue lying in its concavity. Carefully preserve

it, including its multiple branches. Deep branch of ulnar

nerve ends by supplying the adductor pollicis muscle.

It may supply deep head of flexor pollicis brevis also.

Lastly, define four small palmar interossei and

four relatively bigger dorsal interossei muscles (Figs 9.23

and 9.24a and b).

Second