MS - Anat & Phys (Hand)

Question 1

Explain how the muscles of the hand interact at rest.

Answer 1

At rest, a balance exists between the extrinsic flexors and extensors of the hand, as well as the intrinsic muscles of the hand - particularly the lumbrical muscles (flexion of MCP, extension of DIP and PIP joints)

Question 2

In what kinds of lesions is “clawing” best seen? What is the mechanism behind this?

Answer 2

“Clawing” - seen best with DISTAL lesions of median or ulnar nerves. Remaining extrinsic flexors of the digits exaggerate the loss of lumbricals => fingers extend at MCP, flex at DIP and PIP joints

Question 3

In what kind of lesions are hand deficits (e.g., clawing) less pronounced? In what context do deficits present in this case?

Answer 3

Deficits less pronounced in PROXIMAL lesions; deficits present during voluntary flexion of digits

Question 4

Use your hand to show the physical sign of “ulnar claw”. What is the location of the lesion if a patient presents this way? In what context(s) would this sign appear?

Answer 4

“Ulnar claw” - see p. 415 in First Aid 2014 for visual; Distal ulnar nerve; Extending fingers/at rest

Question 5

Use your hand to show the physical sign of “Pope’s blessing”. What is the location of the lesion if a patient presents this way? In what context(s) would this sign appear?

Answer 5

“Pope’s blessing” - see p. 415 in First Aid 2014 for visual; Proximal median nerve; Making a fist

Question 6

Use your hand to show the physical sign of “Median claw””. What is the location of the lesion if a patient presents this way? In what context(s) would this sign appear?

Answer 6

“Median claw” - see p. 415 in First Aid 2014 for visual; Distal median nerve; Extending fingers/at rest

Question 7

Use your hand to show the physical sign of “OK gesture” (with digits 1-3 flexed). What is the location of the lesion if a patient presents this way? In what context(s) would this sign appear?

Answer 7

“OK gesture” (with digits 1-3 flexed) - see p. 415 in First Aid 2014 for visual; Proximal ulnar nerve; Making a fist

Question 8

How is the hypothenar versus thenar eminence affected, if at all, in median versus ulnar nerve lesions?

Answer 8

Atrophy of the thenar eminence (unopposable thumb => “ape hand”) can be seen in median nerve lesions, while atrophy of hypothenar eminence can be seen in ulnar nerve lesions

Question 9

What nerve innervates the Thenar muscles? Give 3 examples of such muscles.

Answer 9

Thenar (median) - Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis

Question 10

What nerve innervates the Hypothenar muscles? Give 3 examples of such muscles.

Answer 10

Hypothenar (ulnar) - Opponens digiti minimi, Abductor digiti minimi, Flexor digiti minimi brevis

Question 11

Draw the palm of the hand, shading in the hypothenar versus thenar eminence.

Answer 11

See p. 415 in First Aid for visual at bottom left of page

Question 12

What functions do the Thenar versus Hypothenar muscle groups perform?

Answer 12

Both groups perform the same functions: Oppose, Abduct, and Flex; Think: OAF (same as names in each group: Thenar (median) - Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis; Hypothenar (ulnar) - Opponens digiti minimi, Abductor digiti minimi, Flexor digiti minimi brevis)

Question 13

What hand muscles abduct versus adduct the fingers?

Answer 13

Dorsal interosseous muscles - abduct the fingers; Palmar interosseous muscles - adduct the fingers; Think: “DAB = Dorsals ABduct & PAD = Palmars ADduct”

Question 14

What functions do the lumbrical muscles have?

Answer 14

Lumbrical muscles - flex at the MCP joint, extend PIP and DIP joints