Sievert: Forearm and Posterior Hand Flashcards
What are the three joints of the fingers?
MP: metacarpo-phalangeal between metacarpals and proximal phalanx
PIP: proximal interphalangeal between between proximal and middle phalanx
DIP: distal interphalangeal between middle and distal phalanx
Are there muscles associated with the posterior hand?
No muscles, just tendons of muscles of the forearm that are crossing the wrist.
How many phalanges are associated with each finger? How many are associated with each thumb?
3 for each finger: distal, middle, and proximal
2 for each thumb: distal and proximal
How many metacarpals are associated with each hand?
5
This is an apparatus that runs across the phalanges, giving off a central band and two lateral bands that come together and attach to the distal phalanx
extensor hood
When you pull on the extensor hood, what happens to tension in the central and lateral bands? What happens when you attach an extensor tendon to the hood?
When you pull on the hood, you cause increased tension in both of these bands. Attaching an extensor tendon to the hood causes extension at the PIP and DIP joints.
On which side of the extensor hood is the extensor tendon attached?
dorsal side
What do extensor tendons do?
Cause extension of all of the joints
The MP, PIP, and DIP joints can be acted on individually in the anterior hand digits. However, what happens to these joints when the extensor digitorum contracts?
Because of the arrangement of the extensor hood, all of these joints are extended at the same time in any single digit when the extensor digitorum contracts
The long extensor tendon gives off a central band. Where does this go? It also gives off a lateral band. Where does this go?
central band goes to the base of the middle phalanx; lateral band to distal phalanx
What do the lumbricals and interossei do?
extend interphalangeal joints
flex metacarpophalangeal joints
What does the flexor digitorum profundus do?
flexes the distal interphalangeal joint (DIP)
What does the flexor digitorum superficialis do?
flexes the PIP
Can you make a tight fist without the extendor tendons at the wrist?
No
T/F: Tendons passing through the compartments must be protected from wear by a synovial tendon sheath.
True
In the anterior and posterior forearm, when long muscles and their tendons cross into the wrist into the base of the metacarpals, what must they pass under?
the retinaculum
What is the purpose of the retinaculum?
It is a dense CT sheath that holds the tendons in place. It keeps the tendons nice and tight and prevents bow-stringing.
There is a retinaculum on the posterior side called the (blank) retinaculum, which corresponds to the (blank) retinaculum on the anterior side.
extensor; flexor
What allows tendons to slide smoothly beneath the retinaculum without causing damage to the tendons?
tubes filled with synovial fluid
Not a part of any muscle, it is a band around tendons that holds them in place. Its function is mostly to stabilize a tendon.
retinaculum
In which portion of the hand, dorsum or anterior side, are there more tendon sheaths? Can these sheaths become infected?
On the dorsum of the hand, tendon sheaths are more numerous. They can become infected.
Where do most posterior forearm muscles arise from?
from the common extensor tendon off of the lateral epicondyle or the supracondylar ridge of humerus
Which posterior forearm muscles DO NOT arise from the lateral epicondyle or supracondylar ridge?
3 thumb muscles (arise from radius, ulna, interosseus membrane)
extensor indices
supinator
All posterior forearm muscles are innervated by this nerve.
radial nerve (mostly deep branch)
How many muscles are there to the thumb? The fingers? The wrist? Muscles that don’t cross at the wrist?
THREE!
What does the snuffbox form between?
two extensor tendons: most posterior is the extensor pollicis longus, anterior: extensor pollicis brevis and abductor pollicis longus** most lateral (these two tendons run together)
What is it important to consider when thinking about the actions of the thumb?
The thumb is not in the same place as the fingers - it is 90 degrees from the plane of the fingers.
Describe abduction and adduction of the fingers. What is unique about the middle finger?
Abduction is moving away from the middle finger, while adduction is moving toward the middle finger. Middle finger can ONLY abduct in both directions.
In what plane do you flex and extend the fingers? On what axis is this motion occurring?
sagittal plane; transverse axis
On what plane do you flex and extend the thumb? On what axis is this motion occurring?
coronal plane; AP axis
What is adduction of the thumb? What’s abduction?
thumb moving close to the midline (palm); thumb moving away from midline
What’s extension of the thumb?
Hitchhiker thumb!
What are three posterior forearm thumb muscles, that do not arise from the lateral epicondyl and supracondylar ridge?
abductor pollicis longus
extensor pollicis brevis
extensor pollicis longus
Which muscle to the thumb is more toward the anterior surface and most lateral? This muscle goes to the base of the metacarpal and crosses 1 joint.
abductor pollicis longus
Which muscle to the thumb runs along the same line as the abductor pollicis longus, goes to the proximal phalanx, and crosses 2 joints?
extensor pollicis brevis
Which muscle to the thumb goes to the distal phalanx and crosses 3 joints?
extensor pollicis longus
again, list the three tendons that make up the anatomical snuffbox.
abductor pollicis longus
extensor pollicis brevis
extensor pollicis longus
What are the contents of the anatomical snuffbox. List them.
radial artery
base of 1st metacarpal
styloid process of the radius
crossing of dorsal digit branches of the radial nerve
What happens to the radial artery at the anatomical snuffbox?
It is the place where this artery turns to gain access to the dorsum of the hand - where the artery courses from the anterior to the posterior side (you can feel a pulse here)
What are the three forearm muscles that go to the digits?
extensor digitorum
extensor digiti minimi
extensor indicis
Which of the muscles to the digits comes from the lateral epicondyl and divides into four tendons (to index, middle, ring, and little finger)
extensor digitorum
Which of the muscles to the digits is a tendon just for the little finger - might aid in sipping a cup of tea like a snob.
extensor digiti minimi
Which muscle to the digits is a tendon for the index finger that arises similarly to the muscles of the thumb?
extensor indices
Besides providing the digits with movement, what else do the muscles of the digits do?
assist in wrist extension
List the three muscles to the wrist
extensor carpi radialis longus
extensor carpi radialis brevis
extensor carpi ulnaris
How many muscles that act on the wrist joint are on the radial side? Which arises the highest on the supracondylar ridge? Where do both of the radial muscles attach to? Where does the muscle on the ulnar side attach?
2 muscles on the radial side (longus and brevis); extensor carpi radialis longus arises from highest point; radial side muscles attach to base of first and second metacarpals; extensor carpi ulnaris attaches to base of metacarpal on ulnar side
What do the muscles to the wrist do?
These muscles assist in abduction/adduction and are extensors of the wrist (work in conjunction with flexors on the anterior side)
3 posterior forearm muscles that don’t cross the wrist joint.
anconeus
brachioradialis
supinator
What is unique about the brachioradialis muscles?
It is a posterior compartment muscle innervated by a posterior compartment nerve that performs an anterior compartment function (flexion of elbow)
This muscle is a powerful flexor of the elbow, and is considered the friendly muscle, because it is used in handshakes to maintain a semi-prone-semi-supinated position.
brachioradialis
What does the supinator muscle wrap around? What does it “point to” on the anterior side? What does it do to the radius? What is another muscle that supinates?
The supinator wraps around the radius, and points to the pronator on the anterior side. It rolls the radius. The two heads of the biceps are also supinators.
This nerve provides innervation to all muscles in the posterior compartment and plays a big role in cutaneous innervation of the dorsum of the hand.
Radial nerve
Two branches of the radial nerve are superficial and deep. What does the deep nerve innervate? Is it sensory or motor? What does the superficial nerve innervate?
deep innervates most of the muscles in the forearm, and is only motor. The superficial is sensory and ends in the hand as cutaneous branches to the fingers.
What happens if there is damage to the deep radial nerve?
Just a motor loss, but no sensory loss
If the radial nerve is damaged high up before coursing over the elbow joint, what muscle can lose innervation?
triceps
There is a thin strip of skin supplied by the radial nerve on the posterior forearm. What are the medial and lateral sides supplied by?
medial is supplied by medial antebrachial cutaneous (from medial cord) and the lateral is supplied by the lateral antebrachial cutaneous
What is the medial antebrachial cutaneous nerve a branch of? What is the lateral antebrachial cutaneous a CONTINUATION of?
the medial cord; the musculocutaneous nerve
Which fingers does the median nerve supply? What fingers does the ulnar nerve supply?
3.5 fingers: the thumb, index, middle, and half of ring finger. 1.5 fingers: little and half of ring finger.
what happens if there is damage to the radial nerve? What does damage high in the arm cause? What does damage to the nerve in the forearm mostly affect?
varying effects depending on location; wrist drop, weak or absent wrist/digit extension, no extension at elbow, decreased grip strength; in forearm will affect wrist and digit extensors
T/F: Trauma in the forearm can cause swelling which may be restricted by fascial compartments. This can cause elevated pressure in the compartment and subsequent damage to all structures due to blood flow impairment.
True
Anterior and posterior compartments of the forearm are surrounded by an investing fascia. If you have injury to this tissue, edema can result and lead to pressure build up. This can compress the artery and vein and restrict blood flow and venous return, leading to ischemia. What is the treatment for compartment syndrome?
make large slits in the investing fascia to relieve the pressure
This is a large branch off of the brachial artery that mimics the course of the radial nerves by wrapping around the spiral groove of the humerus
profunda brachii
After passing anterior to the elbow joint, the brachial artery divides into what two branches? These two arteries continue all the way down to the anterior forearm.
radial and ulnar arteries
This is a branch off of the ulnar artery, which divides into an anterior and posterior branch and runs inside the interosseus membrane
interosseus artery
T/F: There are significant anastomoses around the elbow joint providing great collateral flow.
True
Down beyond the wrist, there are many anastomotic connections between the radial and ulnar arteries. What can the radial artery be used for? What test is important to do before removing the radial artery?
radial artery can be used for bypass surgery, and you need to know if there is good collateral flow because it varies. If you have a dominant radial artery supplying the hand, you will not want to take this and leave hand with poor blood flow. Allen test can be performed to tell (looks at capillary bed reperfusion)
Two palmar arches of the arteries of the hand? There is collateral flow between the arches, but which provides most blood to the digits? What are exceptions to this?
superficial and deep palmar arches; superficial arch provides most blood to digits, except the index finger and thumb
What does the musculocutaneous nerves supply?
anterior arm muscles (motor branches)
forearm (lateral cutaneous nerve)
The median nerve supplies muscular branches to all forearm anterior compartment muscles except for which two?
flexor carpi ulnaris
medial two heads of flexor digitorum profundus (middle and ring finger)
What does the ulnar nerve supply?
muscular branches to forearm (1.5 muscles: flexor carpi ulnaris
medial two heads of FDP) and hand, cutaneous branches to hand
Cutaneous innervation of median nerve?
3.5 digits
What does the radial nerve supply?
posterior arm muscles
posterior cutaneous nerve of forearm
What does the radial nerve supply in the arm and forearm? In regards to cutaneous innervation?
innervates all muscles in posterior compartment; inntervates 3.5 digits on posterior surface of hand
- Nice place to attach muscles
- Maintains integrity of radius and ulna – allows them to rotate around each other
- Referred to as middle radial ulnar joint
- Has a particular orientation of fibers – designed to get tighter when you fall on your hand
interosseus membrane
3 tendons of the wrist; which is most prominent and is absent in some people?
flexor carpi ulnaris
flexor carpi radialis
palmaris longus ** most prominent
List 5 superficial forearm muscles that arise from the medial epicondyl and are attached by a common flexor tendon
- pronator teres
- flexor carpi radialis
- palmaris longus
- flexor digitorum superficialis
- flexor carpi ulnaris
From an anatomical position, is the radius lateral or medial?
lateral
How many anterior compartment muscles are there? How many are superficial vs deep?
8; 5 superficial, 3 deep
Where do the deep anterior compartment muscles arise from? What are they?
interosseus membrane or radius and ulna; flexor pollicis longus, flexor digitorum profundus, and pronator quadratus
What is the order of tendon, artery, and nerve that is significant in regards to the biceps tendon?
biceps tendon: brachial artery: radial nerve (lateral to medial)
This deep anterior compartment muscle courses into the thumb
flexor pollicis longus
This deep anterior compartment muscle gives off four tendons, one to each finger
flexor digitorum profundus
This deep anterior compartment muscle is a pronator
pronator quadratus
List two pronators
pronator terres
pronator quadratus
What are the 3 wrist flexors?
palmaris longus
flexor carpi ulnaris
flexor carpi radialis
What are 3 finger flexors? Which is most deep?
flexor digitorum superficialis
flexor pollicis longus
flexor digitorum profundus** deep
T/F: Long tendons to the fingers split to attach to the base of the proximal phalanx and then the base of the distal phalanx. These tendons have to be held down to prevent bow-stringing.
True
What does the interosseus artery arise from?
the ulnar artery
