The Hand Flashcards
What do intrinsic and extrinsic muscles of the hand actually mean?
Intrinsic muscles: The muscles that move the hand originate from the hand itself
Extrinsic muscles: The muscles that move the hand originate outside the hand in the forearm
Function of intrinsic muscles
Fine movement
Function of extrinsic muscles
Power
Try the following movements with the THUMB: Abduction Adduction Extension Flexion Opposition Reposition
Picture
What different kinds of grips are there? Give examples of each
Power:
Prehensile - cylindrical grip (holding a racket), light tool grip (like a push pen), sphere grip (tennis ball)
Non prehensile - hook grip
Precision - key pinch, sphere pinch (inspecting an apple), fine pinch (index and thumb crab), plate (passing over the book)
What is the clinical symptom of a radial nerve injury?
Wrist drop
No extension of wrist or digits (unopposed action of FDS and FDP)
Weak flexion at DIP joint from intrinsic muscles of the hand
What are precision grips?
When objects are held between the tip of the thumb and 1,2 or 3 fingers
What muscles are involved in precision grips?
Intrinsic muscles cooperate with the long flexor and extensor muscles
From what age can precision grips happen?
9 months
Causes of radial nerve injury
Known as Saturday night palsy
Cause: radial nerve in armpit or upper arm compressed or stretched
Usually due to falling asleep with arm hanging
In infants: prolonged pressure of inferior arm by pelvic brim
Symptoms: wrist drop
Symptoms of radial nerve palsy in infants
Wrist drop
Inability to extend thumb and MCP of all digits
Weak extension of elbow
General symptom of radial nerve injury
Wrist drop
What is an example of a High Median Nerve injury? What are the symptoms?
Hand of benediction
Loss of flexion in MCP in digits 23
Loss of flexion in PIP in digits 123
Loss of flexion in DIP in digits 23
Weak PIP flexion in digits 45 (ulna innervates FDP and FCU)
What is an example of a low median nerve injury? Symptoms
Carpal tunnel syndrome
Any condition reducing size of carpal tunnel causing compression of median nerve
Progressive loss of coordination and strength in thumb
What muscles are involved in a ulna nerve injury?
Clawhand
Flexor carpi ulnaris Medial half of FDP Medial two All interossei (palmar and dorsal) Adductor pollicis
Symptoms of a ulna nerve injury?
Thumb abducted and extended with distal phalanx flexed
First two fingers fully extended, DIPs slightly flexed
Medial 2 fingers hyperextended at MCP joints but flexed at DIP joints
What is the difference between a high ulnar lesion and low ulnar lesion?
High lesion - both intrinsic hand and FDP weak (clawing is milder)
Low lesion - only the intrinsic muscles are weak making the clawing more severe
Called the Ulnar paradox
Where is the most common site of ulnar nerve injury?
Medial epicondyle of the humerus
What percentage of nerve lesions to the upper limb include the ulnar?
27%
What is high ulnar nerve palsy called?
Cubital tunnel syndrome
High: all muscles lost
Example of low ulnar nerve palsy?
Guyon’s canal syndrome
Low = FDP pulls digit 4 and 5 into flexion
What is another name for the knuckles?
Metacarpophalangeal joint
MCP
What movements can occur at the MCP joints
Flexion
Extension
Abduction
Adduction
What movements occur at PIP and DIPs?
Flexion and extension
What is the opposition of the thumb?
Thumb touching any of the other fingers
What is abduction of the thumb?
When thumb is at right angles to the palm
What is flexion of the thumb?
Thumb to palm
What is extension of the thumb
Flat out
Opposite of flexion
Where do the flexors of the forearm originate from?
Medial epicondyle
Where do the extensors of the forearm originate from?
Lateral epicondyle
