HAND Flashcards
Which nerves innervate the thenar and hypothenar eminences respectively?
Median and ulnar respectively
What shape do the lumbricals allow the hand to assume? Explain. Which nerve supply the 2 medial and 2 lateral lumbricals?
L shape: flexed metacarpophalangeal joints and extended interphalangeal joints
- Medial: ulnar
- Lateral: median
If there is loss of the lumbricals of the hand what shape would the hand assume? Explain why
Claw hand
- Metacarpophalangeal joints extended (cannot flex)
- Interphalangeal joints flexed (cannot extend)
How are the muscles of the hand subdivided?
Intrinsic and extrinsic:
- extrinsic → long flexors and extensors, muscle belly located on forearm
- intrinsic → smaller muscles located in hand itself
What is this muscle? What is it action? Refer to digits as in numbers. What is the nerve supply?
Flexor digitorum profundus: extrinsic hand muscle
Flexes distal interphalangeal joints of digits 2 to 5
→ supplied by median and ulnar nerves
Which nerve causes extension of the MCP joints? Via which muscle?
Radial nerve via extensor digitorum
Which nerves control wrist flexion and extension?
- Flexion: median and ulnar
- Extension: radius
Wrist deviation is seen in lesions involving which muscles? Explain what the deviation would be depending on which nerve is involved
Flexor muscles
Will deviate to ulnar side in medium lesions and radial side in ulnar lesions
A patient does this when attempting to make a fist. Where is the nerve lesion?
Median nerve: thumb, lateral fingers cannot flex, MCP extended
“Hand of benediction”
Wrist deviation in proximal vs distal lesions of median nerve
- More proximal: more likely to involve extrinsic flexors and cause ulnar deviation
- More distal: less likely to involve extrinsic flexors so unlikely to cause ulnar deviation
Someone presents with a superficial laceration to wrist. The thumb is immobilised but the sensation in thenar eminence is normal. Which nerve is involved? Explain why sensation is maintained
Recurrent motor branch of median nerve: superficial nerve near flexor retinaculum. Provides motor innervation to the thenar muscles →
- Flexor pollicis brevis
- Abductor pollicis brevis
- Opponents pollicis
A patient’s hand is like this at rest: what nerve is injured? Review the difference between this and the hand of benediction
Ulnar
Supracondylar fracture is most likely to cause injury to which a nerve?
Median
Fracture of which part of the humerus increases risk of ulnar damage?
Medial epicondyle fracture (funny bone)
