Posterior Arm and Dorsum of Hand Flashcards
The common extensors of the hand attach where?
on the radial (lateral side) - especially the lateral epicondyle
What is the extensor retinaculum?
It’s a thickening of the antebrachial fascia in the distal forearm that binds down the extensor tendons as they pass intot he dorsum of the hand
it’s basicaly the dorsal version of the transverse carpal ligament.
What nerve passes from below the brachioradialis muscle and over the
extensor retinaculum to supply cutaneous innervation to the dorsum of the hand
The superficial branch of the radial nerve
How can you test radial nerve function in the hand?
You can’t really because the radial nerve (superficial branch) supplies the lateral dorsal hand, but there is so much overlap with the ulnar and medial nerve that you wouldn’t be able to
What are the three muscles to the thumb on the dorsal side?
extensor pollicis longus
abductor pollicis longus
estensor pollicis brevis
What anatomical structure is created between the tendons of the extensor policis longus, extensor pollicis revis, and abductor pollicis longus?
What vessel runs through it?
the anatomical snuff box
the radial artery
WHat are the extensors in the superficial group?
extensor carpi radialis longus
extensor carpi radialis brevis
extensor digitorum
extensor digiti minimi
extensor carpi ulnaris
Which superficial extensor attaches to the 2nd metacarpal?
To the 3rd metacarpal?
Extensor carpi radialis longus is on the 2nd
extensor carpi radialis brevis is on the 3rd
What superficial extensor attaches to the extensor expansion of the 5th finger.
The extensor digiti minimi
Which superficial extensor inserts into the dorsal side of the base of the 5th metacarpal to extend and adduct the hand?
the extensor carpi ulnaris
What are the 5 muscles in the dorsal deep group?
abductor pollicis longus
extensor pollicis brevis
extensor pollicis longus
extensor indicis
supintaor
Which deep muscle inserts into the extensor expansion of the 2nd finger (the index finger)?
the extensor indicis
Where does the supinator muscle take origin from and attach>
origin from the lateral epicondule, posterio ulna and adjacent ligaments
attaches on the posterior lateral and anterior surfaces of the proximal radius
What are the two outcropping muscles of the forearm?
the abductor policis longus and the extensor pollicis brevis (they cross over the tendons of the extensor carpi radialis longus nad brevis)
The posterior interosseous nerve is a continuation of what nerve? WHere does it come out? What does it supply?
It’s a continuation of the deep branch of the radial nerve
it comes out through the supinator
it supplies all the extensor muscles of the forearm
What does the posterior interosseous ARTERY branch off of? Where does it enter the posterior comparment?
It is a branch off te common interosseous artery that branched off th eulnar artery
It enters the posterior compartment under the supinator muscle
What muscles are the abductors of the digits?
the four dorsal interossei
(DABs)
they abduct the 2nd 3rd and 4th digits from the midline
Where do the dorsal interossei insert?
into the base of the proximal phalanx and the extensor hood.
What nerve innervates all the interossei muscles?
the ulnar nerve
THe extensor hood includes the insersion of tendons from which 2 differnt mucles?
the extensor tendonds of the lumbricales and interossei muscles
The tendon of the extensor digitorum splits over the proximal phalanx.
Where does the middle component go? Where do the two lateral compontents go?
Middle: inserts on the base of the middle phalanx
lateral: go laterally around the PIP joint and come back together to insert into the base of the distal phalanx
What joint do the lumbricals and interossei flex? Which do they extend? How?
THey flex the MP joint
They extend the DIP joints.
This is because they pull on the extensor hood
What does the radial collateral ligament of the elbow do?
It attaches the radius to the humerus
The radial collateral ligament of the elbow is continuous with what other ligament?
the annular ligament
What does the anular ligment do?
It’s a ligament that encircles the head of the radius
What does the ulnar collateral ligament of the elbow do?
It is located on the medial side of the elbow and attaches the ulna to the humerus
What artery pokes out between the radius and ulna to travel between them just superior to the interosseous membrane?
the posterior interosseous artery (which is off the ulnar artery)
In the wrist, what do the radial and ulnar collateral ligaments do?
THey join the carpal bones with the radius and ulna respecitvely
What are the clinical symptoms of medial nerve palsy (proximal) and why do they occur?
- atrophy of thenar eminene (because the median nerve supplies the recurrent median nerve to supply the thenar muscles)
- Thum laterally rotated and adducted (the radial nerve supplies the abductors and medial rotators of the thumb)
- Loss of thumb flexion (the median nerve innervates the flexor pollicis longus)
- Loss of flexion at 2nd and 3rd PIP joints (lost median inneration of the flexor digitorum superficialis)
- Loss of flexion at the 2nd and 3rd DIP joints (lost median innervation of the flexor digitorum profundus)
- Weakened flexion of 2nd and 3rd MP joints (lost median innervation of the 1st and 2nd lumbricals)
What is the general name for what the hand looks like in medial nerve palsy (proximal)?
hand of benediction
What are the clinical characteristics of a median nerve injury (distal)?
- paresthesia in the lateral three and a half giners (abnormal sensation in the medial nerve)
- No loss or abnormal sensation in the palm (because the palmar cutaneous branch of the median nerve passes above the carpal tunnel)
- Loss of coordination and strength in the thumb (loss of innervation by the recurrent branch of the median nerve - no nerve supply to the thenar muscles)
- Difficulty in utilizing the thumb in gripping things
- Weakened flexion of 2nd and 3rd MP joints (lost median nerve innervation of the 1st and 2nd lumbricals)
- Phalen test is positive due to compression of the median nerve in the carpal tunnel
What is a nother name for distal median nerve injury?
carpal tunnel syndrome
What clinical signs will appear in ulnar nerve palsy (proximal)?
- loss of flexion at 4th and 5th DIP joints (lost innervation of the medial flexor digitorum profundus by the ulnar nerve)
- Loss of flexion at the 4th and 5th MP joint (loss of innervation of the 3rd and th lumbricals by the ulnar nerve)
- Inability to extend the IP joints when attempting to straighten the fingers (loss of innervation of the 3rd and 4th lumbricals and interossei)
- Hypoesthesia and parasethsia in little finger and ulnar half of ring finger
- Atrophy of interossei muscles (loss of innervation by the ulnar nerve)
- Weakness of thumb adduction (loss of innervation of the adductor pollicis by the ulnar nerve)
What is the general term for the hand that comes with ulnar nerve palsy (proximal)
claw hand
What is another term for DISTAL ulnar nerve palsy?
Ulnar canal syndrome or Guyon tunnel syndrome
What are the clinical signs of guyon tunnel syndrome
- NO loss of flexion at the 4th and 5th DIP joints (flexor digitorum profundus innervation by the ulnr nerve is still intact)
- Loss of flexion at the 4th and 5th MP joint (No innervation of 3rd and 4th lumbicals by the ulnar nerve)
- Inability to extend the IP joints when attempting to straighten fingers (no innervation of the 3rd and 4h lumbricals and interossei by the ulnar nerve)
- Hypoesthesia and paresthesia in little finger and ulnr half of ring finger (loss of sensory innervation by th eulna rnerve)
- Atrophy of the interossei muscles (no innervation by ulnar nerve)
- Weakness of thumb adduction (loss of innervation of adductor pollicis by ulnar nerve)
- Ability fo flex unaffected - no radial deviation of hand (unlike in a proximal ulnar nerve palsy)
Injury to what nerve will result in wrist drop?
radial nerve
you get an inability to extend the wrist and fingers at the MP joint because there is a loss of innervation of extensor muscles by the radial nerve
What will cause subluxation and dislocation of the radial head? What is this called?
When the head of the radius is pulled out of the anular ligament by upward pulling (usually parents liftin kid by the arms)
also called nursemaid’s elbow
What causes mallet finger?
avulsion of the extensor tendon from the distal phalanx when the extensor tended is contracted and the distal phalanx is forcibly flexed
without the extensor tendon, the phalanx will be help in a flexed position because of th eunopposed action of the flexor digitorum profundus
this is what happens when you jamm your finger sliding into a base in baseball.
