Session 29 - The Palm of the Hand

Question 1

Which carpal bone is most prone to fracture? What complication may result if a
fracture of this bone is missed?

Answer 1

Scaphoid

Fracture can disrupt blood supply to proximal part leading to avascular necrosis of this area

Question 2

What is the cutaneous distribution of the median, ulnar and radial nerves in the
hand? Which regions of skin would you test to assess these nerves?
Pg 17

Answer 2

 Median: the palmar surface of the lateral side of the hand. The palmar
surface of the lateral 3 ½ digits. The skin over the dorsum of the distal
phalanges of the lateral 3 ½ digits.

o Test = palmar surface of the middle finger

 Ulnar: the palmar and dorsal surfaces of the medial side of the hand and
the medial 1 ½ digits.

o Test = medial border of the hand

 Radial: the dorsal surface of the lateral side of the hand. The skin over the
dorsum of the lateral 3 ½ digits as far as the DIP joint.

o Test = dorsum of the hand, lateral aspect

Question 3

In which regions of the hand would you assess dermatomes C6, C7 and C8?

Answer 3

 C6: lateral part of palm of hand - thumb
C7: middle finger
 C8: medial border of the hand

Question 4

Which muscles comprise the thenar eminence? Which nerve innervates them?

Answer 4

Flexor pollicis brevis (FPB)

Abductor pollicis brevis (APB)

Opponens pollicis (OP)

Innervation = recurrent branch of the median nerve.

Question 5

How would you test the function of the interosseous muscles?

Answer 5

Test
Abduction - dorsal interossei
Adduction - palmar interossei of
the fingers

Question 6

How would a patient present if they injured their median nerve at their wrist? In
comparison, how would a median nerve injury at the elbow present?

Answer 6

Median nerve injury at the wrist results in weakness / paralysis of the
muscles innervated by the nerve distal to the wrist i.e. the thenar
eminence muscles and the lateral two lumbricals.

Median nerve injury at the elbow results in weakness / paralysis of the
muscles innervated by the nerve distal to the elbow i.e. all the anterior
forearm muscles (except for FCU and the medial / ulnar half of FDP),
the thenar eminence muscles and the lateral two lumbricals

Question 7

A patient with carpal tunnel syndrome has normal sensation over the lateral side
of their palm. Why is this?

Answer 7

Compression of median nerve in carp tun gives:
Sensory disturb - Palmar aspect of lateral 3 1/2 digits (these branches leave distal to the carpal tunnel)

Lateral palm also innervated by median but nerves pass over carpal tunnel so aren’t affected of compression of the medial nerve in the carpal tunnel

Question 8

Which muscles would be affected by an ulnar nerve injury in the mid-forearm?

Answer 8

Most of small muscles of the hand

(adductor pollicis, the hypothenar eminence muscles, the medial two
lumbricals and all the interossei)

Question 9

Which muscles would NOT be affected by an ulnar nerve injury in the mid-forearm?

Because branches of the Ulnar have already been given off

Answer 9

FCU

Ulnar/Medial half of FDP