MSK 4 - Upper Limbs Flashcards
The muscles in the posterior forearm are organized into 3 functional groups which are what?
- *1) Muscles that extend and abduct or adduct the hand at the wrist joint
2) Muscles that extend the medial four digits
3) Muscles that extend or abduct the thumb**
Muscles that extend and abduct or adduct the hand at the wrist joint:
what are they?
Extensor carpi radialis longus
Extensor carpi radialis brevis
Extensor carpi ulnaris
What is the action of extensor carpi radialis longus and brevis on the wrist joint?
What other action are they involved with the help of flexor carpi radialis?
They both extend and abduct the wrist joint
They cause radial deviation of the wrist
Muscles that extend the medial four digits:
what are they?
what is the function of the extensor digitorum and where does it arise?
Is an extensor of the fingers and of the wrist and arises from common extensor origin on the lateral epicondyle of the humerus
As its fleshy muscle belly runs distally it ducks under the extensor retinaculum, and divides into 4 tendons for the fingers – very similar to FDS and FDP in Lesson 3
Spread (abduct) your fingers to see the tendons of extensor digitorum on the dorsum of your hand
a
Abductor pollicis longus
b
Extensor pollicis brevis
c
Extensor pollicis longus
Muscles that extend or abduct the thumb:
what are they?
Abductor pollicis longus (APL)
Extensor pollicis brevis (EPB)
Extensor pollicis longus (EPL)
(pollicis means going to the thumb)
what is the supinator?
What is the action of supinator?
This muscle envelops the neck and the proximal part of the shaft of the radius, covering it completely, except on its medial side
Supination of the forearm when the elbow is extended, accessory role to biceps when the elbow is flexed and the forearm supinated
a
Radial Nerve
b
Extend medial 4 digits at MCP joints
c
Extension and abduction
d
Extension and abduction
e
Flexes elbow when forearm in neural and stabilizes elbow during rapid flexion or extension
f
Extension and ulnar deviation of the wrist
g
Supinates forearm
h
Extends 5th finger at MP joint
Radial Nerve in the Posterior Forearm:
As the radial nerve leaves the cubital fossa it gives off a ____ and ________ branch
deep
superficial
what is the deep brach of the radial nerve and its function?
The deep branch (also known as the posterior interosseus nerve), is the main motor nerve of the extensors of the forearm.
It runs deep to the supinator muscle eventually piercing it to enter the extensor compartment of the forearm
what is the superficial branch of the radial nerve and its function?
The superficial branch is purely sensory and distributed to skin on the dorsum of the hand. As it branches at the cubital fossa it runs deep to brachioradialis and enters the hand passing over the anatomical snuff box
what is A and what is B? (ignore writing)
A = Superficial terminal branch
B = Posterior interosseous nerve (deep terminal nerve)
what is the arterial supply of the posterior forearm?
The arterial supply is complex network of arterial anastomosis including:
- The posterior interosseus artery arising from the ulnar artery
- The recurrent interosseous artery – a branch of the above.
These are of minor note with wide ranging anatomical variation
The venous supply follows the above and again is of limited use in learning in detail
Similar to the palmar aspect of the hand, the dorsum of the hand has a number of structures transmitting through it to reaching their terminal destination of the digits
Proximally an extensor retinaculum exists providing what?
stability and a tunnel for the extensor tendons, which are wrapped in synovial sheaths
Clinical: Ganglion (Synovial Cyst)
what is it?
Non-tender cysts can grow on the synovial sheaths found on the back of the hand
These are often more inconvenient than functionally limiting and can be removed surgically…if hitting them with a bible doesn’t work! (NB this is not recommended)
Dorsal venous arches:
The cephalic vein lies as the ______ continuation of the dorsal venous arch running proximally.
The basilic vein lies as the ______ continuation of the dorsal venous arch.
lateral
medial
As the extensors of the thumb approach their attachments, they become long tendons passing on the radial side of the arm, forming the boundaries of what?
the anatomical snuff box
what is the anatomical snuff box?
A shallow depression on the lateral aspect of the wrist when the thumb is extended fully
a
Extensor retinaculum
b
Radial artery
c
Abductor pollicis longus
d
Extensor pollicis brevis
e
Extensor pollicis longus
Anatomical Snuffbox Boundaries:
Medial border (1 tendon)
Extensor pollicis longus
Anatomical Snuffbox Boundaries:
Lateral Border (2 tendons)
Abductor pollicis longus and Extensor pollicis brevis
Anatomical Snuffbox Boundaries:
Floor (2 carpal bones)
Scaphoid and trapezium
Which artery can you feel pulsating on its floor? (anatomical snuff box)
radial artery
a
Posterior interosseous nerve (deep motor branch of the radial nerve)
b
Extension of thumb distal interphalangeal joint
c
Extension of proximal phalanx of thumb
d
Abduct and extension of thumb
Clinical: Distal Forearm Fractures
Distal forearm fractures make up a large percentage of broken bones following a mechanical fall – e.g. hand stretched out to cushion impact.
These can be classified into different names according to their clinical findings on x-ray.
Whata re the different ones?
Colle’s Fracture (shown x-ray)
This is a common fracture of the distal radius in which there is anterior displacement (movement) of the shaft of the radius on the distal aspect of the bone
This is known as a dinner fork deformity and is caused by falling onto an extended wrist.
A Smith’s Fracture is the reverse of this, in which there is posterior displacement of the radius on the distal aspect of the bone.
This is cause by falling onto a flexed wrist, or by a direct blow to the forearm
is a Colles or Smiths fracutre more common?
COlles fracture
what is the most fractures carpal bone?
scaphoid
how does a scaphoid fracutre occur?
This has a similar mechanism of injury to a Colle’s fracture, but more often occurring in the elderly
what are the symptoms of a scaphoid fracture?
The pain from this fracture is felt during palpation of the anatomical snuff box.
If left there is a risk of malunion of the bone, or avascular necrosis
The latter is due to bone death (necrosis), as on fracturing the bone, the blood supply from the radial artery has been interrupted
The Dorsal Digital (Extensor) Expansion:
what is it?
The four extensor digitorum tendons flatten to form extensor expansions.
On attaching to the proximal, middle and distal phalanx there is a number of ligaments which converge and diverge. Therefore, making the extensor insertion a complex interaction of tendon and ligaments
what is the shape, structure and location of each extensor expansion?
Each extensor expansion is a triangular tendinous aponeurosis that wraps around the dorsum and sides of the head of the metacarpal and base of the proximal phalanx
a
Middle Conjoint Tendon
b
Oblique Interosseus Fibres
c
Common extensor tendon of the extensor apparatus/extensor digitorum tendon
d
Proximal phalanx
e
Terminal conjoined extensor tendon
f
Lumbrical
g
Interosseous muscle
Once distal to the proximal phalanx, a number of ligaments stabilise the extensor expansion. These include what?
the tendinous fibres of the interossei and lumbrical muscles
The main tendons which insert distally are the middle and terminal conjoint tendons. Where do they insert?
The middle onto the base of the middle phalanx, and terminal onto the base of the distal phalanx respectively
Which muscles attach onto the extensor expansion?
- lumbricals of the hand
- Extensor indicus/digitorum muscle
- Dorsal interossei of the hand
- Flexor pollicis longus and brevis
