forearm, ulna & radius Flashcards
what is the forearm?
the part of the arm that extends from the elbow to the wrist
What are important landmarks of the radius?
- head
- neck
- radial tuberosity
- roughening for attachment of pronator teres
- radial styloid process
what are important landmarks on the ulna?
- olecranon
- trochlear notch
- coronoid process
- radial notch
- tuberosity of ulna
- interosseus border
- ulnar styloid process
what is the interosseous membrane of the forearm?
- acts as an extrinsic ligament and links the ulna and radius
- assists the proximal and distal radioulnar joints
describe the proximal radioulnar joint
- synovial pivot joint
- articulation between the radial head and the radial notch of the ulna
- pivot joint - supination (holding a bowl of soup) and pronationof the forearm
where is the proximal radioulnar joint located?
- immediately distal to the elblow joint
- enclosed within the same elbow joint capsule
which important ligament holds the radial head in place?
the annular radial ligament - forms a collar around the joint
describe the distal radioulnar joint
location, articulations, type etc
- the distal radioulnar joint is located just proximal to the wrist joint
- articulation between the head of ulna, ulnar notch of radius and the triangular fibrocartilaginoius disc
what is the function of the triangular fibrocartilaginous disc in the distal radioulnar joint?
*** binds radius and ulna together **
* **separates **the distal radioulnar joint from the wrist joint
what is pronation of the forearm?
- the **rotation of the radius and hand around an immobile ulna **
- the ulna remians almost stationary and the radius rotates around it
what is colles’ fracture?
- complete fracture of the radius bone of the forearm close to the wrist
- results in a posterior displacement of the radius
- can happen due to a fall on an outstretched hand
what is smith’s fracture?
- a fracture of the distal end of the radius caused by a fall on the back of the hand
- results in anterior (volar) displacement of the fractured segment
note you only ever hear volar in relation to hand and wrsit injuries
what 2 nerves innervates the anterior compartment of the forearm?
- median nerve
- ulnar nerve
into what 2 categories are the anterior muscles of the forearm divided into?
- superficial
- feep
what are the superficial anterior muscles of the forearm?
- pronator teres (PT)
- flexor carpi radialis (FCR)
- palmaris longus (PL)
- Flexor digitorum superficialis (FDS)
- flexor carpi ulnaris (FCU)
what are the deep muscles of the anterior compartment of the forearm?
- flexor digitorum profundus (FDP)
- flexor pollicis longus (FPL)
- pronator quadratus (PQ)
what is the common origin for the anterior muscles of the forearm?
- medial humeral epicondyle (the flexor origin)
where does the pronator teres muscle insert onto?
- lateral border of radius (remember the roughening ofnthe bone)
- median nerve
where does the flexor carpi radialis (FCR) insert onto & what nerve innervates this muscle ?
- base of 2nd and 3rd metacarpal
- median nerve
where does the palmaris longus muscle insert onto & what nerve innervates this muscle?
- inserts onto palmar aponeurosis
- innervated by the median nerve
where does the flexor carpi **ulnaris ** insert onto and what nerve innervates this muscle?
- base of the 5th MC
- ulnar nerve
where does the flexor digitorum superficialis ( FDS) muscle insert onto and which nerve innervates this muscle?
- inserts onto the phalanges
- innervated by the median nerve
where does the flexor digitorum profundus (FDP) originate and insert onto?
deep muscles
- O: ulna
- I: distal phalanges of digits
what nerves innervates the flexor digitorum profundus muscle?
- median and ulnar nerve
where does the flexor pollucis longus (FPL) muscle originate and insert onto?
- O: anterior radius
- I: distal phalanx pollux (thumb)
what nerve innervates the flexor pollicis longus muscle?
medial nerve
where does the pronator quadratus muscle originate and insert onto & what nerve innervates it?
- O: ulna (distal)
- I: radius (distal)
- innervated by median nerve
Describe the pathway of the median nerve
- runs between the 2 heads of the pronator teres muscle
- runs deep to the flexor digitorum superficialis
- supplies most of the anterior forearm
through what branch, does the median nerve supply the deep muscles of the anterior compartment of the forearm?
the anterior interosseous branch
describe the pathway of the ulnar nerve
- posterior to medial humeral epicondyle
- runs between the 2 heads of fcu
- supplies FCU and half of FDP
where is the brachial artery located in the forearm?
medial to biceps tendon
what is the common extensor origin for the muscles of the posterior forearm?
- lateral humeral epicondyle
how are the posterior forearm muscles divided into categories ?
- 4 groups of 3 muscles
- radial
- thumb/pollux
- digital
- other
**
what does the radial group of posterior forearm muscles consist of?
- brachioradialis
- extensor carpi radialis longus
- extebsor carpi radialis brevis
what muscles are in the thumb/pollux group of the posterior forearm muscles?
- extensor pollicis longus
- extensor pollicis brevis
- abductor pollicis longus
what does the digital group of the posterior forearm muscles contain?
- extensor digitorum
- extensor digiti minimi
- extensor indicis
what does the ‘other’ group of the posterior forearm muscles contain?
- extensor carpi ulnaris
- anconeus
- supinator
where does the brachioradialis originate and insert onto?
- o: lateral supracondylar ridge
- I: radial styloid
where does the extensor carpi radialis longus muscle originate and insert onto?
- O: lateral supracondylar ridge
- I: 2nd metacarpal
where does the extensor carpi radialis brevis originate and insert onto?
- O: common origin (medial humeral epicondyle)
- I: 3rd metacarpal
where does the extensor digitorum originate and insert into?
- O: common origin (medial humeral epicondyle)
- I: extensor expansions
what is the origin and insertion of the extensor digiti minimi muscle?
- O: common origin - medial humeral epicondyle
- I: extensory expansion 5th digit
what is the origin & insertion of the extensor indicis muscle?
- O: distal ulna and IO (interosseus) membrane
- I: extensor expansion 2nd digit
where does the extensor pollucis longus muscle originate and insert onto?
- O: distal ulna and IO membrane
- I: pollux
where does the extensor pollicis brevis originate and insert onto?
- O: distal radius and IO membrane
- I: pollux
where does the abductor pollicis longus muscle originate and insert onto?
- O: radius, ulna and io membrane
- I: 1st metacarpal
what is the anatomical snuff box?
- triangular depression found on the lateral aspect of the dorsum of the hand
what are boundaries of the anatomical snuff box?
- medial border - tendon of the extensor pollicis longus
- lateral border - tendon of the extensor pollicis brevis and abductor pollicus longus
- floor - carpal bones - scaphoid & trapezium
- roof - cephalic vein and raial nerve
what is the most commonly fractured carpal bone?
the scaphoid
what is the typical moi for a scaphoid fracture?
falling on an outstretched hand
what is a complication of a scaphoid fracture?
AVN
where does the anconeus originate and insert onto?
- O: common origin - lateral epicondyle of humerus
- inserts onto the olecranon and ulna
where does the extensor carpi ulnaris originate and insert onto?
‘other’ group
- O: common origin and ulna
- I: 5th metacarpal
where does the supinator muscle originate and insert onto?
note 2 heads
- O: lateral epicondyle of the humerus (superficial head)
- O: ulnar head (deep)
- I: proximal radius
what muscles are involved in pronation of the forearm & what nerve innervates these muscles ?
- pronation teres - median nerve
- pronator quadratus- median nerve
what muscles are involved in supination of the forearm & what nerve innervates these muscles ?
- biceps brachii - NB - musculocutaneous
- supinator - radial nerve
