Anterior Forearm Flashcards
WHat are the two bones of the forearm? Which is medial and which is lateral?
the ulna (medial - pinky)
the radius (lateral - the thumb)
IDentify the structures
Where does the head of the readius articulate? WHat holds it in place?
It articulates with the radial notch of the ulna AND with the capitulum of the humerus
it’s held in position by the annular ligament
What membrane connects the radius and the ulna?
the interosseous membrane
Which forearm bone has the olecranon process at the upper end?
the ulna
What does the olecranon process articulate with?
the trochlea of the humerus
Which styloid process projects more ditally, the ulna or radius?
the radius
How do the forearm bones connect to the hand bones?
- the radius articulates with the scaphoid and lunate carpal bones
- the ulna is separated from the carpal bones by an articular disc
WHere does the medial cutaneous nerve of the foreamr arise?
Where does the lateral cutaneous nerve of the forearm arise?
medial = comes off the posterior cord of the brachial plexus
lateral = continuation of the musculocutaneous nerve
what does the brachioradialis attache?
proximally = lateral supracondular ridges of the humerus
distally = proximal to the styloid process of the radius
Thus, it crosses over the elbow joint, so it’s a flexor muscle.
What nerve innervates the brachioradiualis?
the radial nerve
After the radial nerve pierces the lateral intermuscular septum, what does it do?
It divides into superifcial and deep branches
the superficial branch is sensory and continues distally beneath the brachioradialis muscle
the deep branch pierces the supinator muscle and supplies motor fibers to extensor muscles of the forearm
What is the deep fascia thickening that serves to hold the flexor muscles in the carpal tunnel?
the transverse carpel ligament
also called the flexor retinaculum
What are the five muscles that compose the superficial group of forearm flexors?
- Pronator teres
- flexor carpi radialis
- palmaris longus
- flexor digitorum superficialis
- flexor carpi ulnaris
Protector teres flexes the carp in a radical way in his long palm. then flexes his superior digits and flings the carp to ulna.
Which 4 superficial forearm flexors are innervated by the median nerve?
Which is the only one innervated by the ulnar nerve?
the flexor carpi ulnarix is the only one supplied by the ulnar nerve
otherwise the pronator teres, flexor carpi radialis, palmaris longus, and the flexor digitorum superficialis are all innervated by the median nerve
The five muscles of the superficial flexors all have an origina hwere?
the medial epicondyle
Besides the medial epichondyle, where does the pronator teres originate? Where does it attach distally? What does this mean for its function?
It also takes origin on the ulnar head.
It attaches distally on the radius.
Because it originate on the ulnar side and attaches on the radial side, it can act as a pronator and flexor of the forearm
Where does the flexor carpi radialis attach distally?
to the base of the 2nd metacarpal
What does the palmaris longus attach to distally?
the palmar aponeurosis
Where does the flexor carpi ulnaris attach distally?
to the base of the 5th metacarpal
Where is the flexor digitorum superficialis located relative to the other 4 superficial forearm flexors?
deeper to them all (even though it’s called the superficialis)
Besides the medial epicondyle, where does the flexor digitorum superficialis take origin?
Where does it insert?
It takes origin fom the coronoid process of the ulna and the radius
it inserts on the middle phalange of the medial four digits
Of the superficial group, which one is the only one whose tendons pass through the carpel tunnel?
the flexor digitorum superficialis
there are 4 of them
The median nerve passes between the tendons of what 2 superficial flexors?
What does it do after that?
Between the flexor carpi radialis and the palmaris longus
It then passes through the carpal tunnel with the tendons fo the flexor digitorum superficialis (CARPEL TUNNEL SYNDROME)
What are the three muscles of the deep group of the forearm?
- Flexor digitorum profundus
- Flexor pollicis longus
- pronator quadratus
Where does the flexor digitorum profundus take origin?
Where does it insert?
Origin from the proximal portions of the anterior surface of the ulna and interocceous membrane.
The tendons pass through the carpal tunnel and hand to insert on the distal phalanx of the digits 2-5. (similar to the flexor digitorum superficialis)
How is the flexor digitorum profundus innervated?
- the median nerve (anterior interossous nerve) innervates the lateral half of the muscle - the part that goes to digits 2 and 3
- the ulnar nerve innervates innervates the medial half - the part that goes to digits 4 and 5
Where does the pollicis longus take origin? Insert?
Origin from the radial surface and adjacent interosseous membrane
attaches distally on the terminal phalanx of the thumb
What does the pronator quadratus do?
It attaches the distal radius and ulna and servies to pronate the radius
What nerve innervates both the flexor pollicis longus and pronator quadratus in the deep group?
the interosseous nerve (a branch of the median nerve)
What branch off the median nerve innervates the deep forearm muscles?
the anterior interosseous nerve
What two muscles does the median nerve pass sandwiched between through the forearm?
the flexor digitorum superficialis and the digitorum profundus
What is pronator syndrome?
When the pronator teres muscle compresses the medial nerve
after repetitive elbow motions such as chopping wood, sculling and cleaning fish
presents as chronic aching sensation localized to the forearm with pain occasionally radiating to the elbow
Where is the ulnar nerve located relative to the muscles of the forearm?
deep to the flexor carpi ulnaris
The brachial artery divides in the cubital fossa into what two arteries?
the ulnar and radial arteries
Where does the radial artery run relative to the muscles of the forearm?
It goes to the radial side and runs under the brachioradialis with the sueprficial branch of the radial nerve
It’s the artery that’s present in the wrist lateral fo the tendon of the flexor carpi radialis - common site for taking a pulse
Where does the ulnar branch of the brachial artery pass in relation to the forearm muscles?
it passes posteriorly to go between the superficial muscles and the deep muscles. It then joins the ulnar nerve as they pass distally to enter the palm of the hand
What is a major branch off the ulnar artery?
the interosseous artery
What does the common interosseous artery divide into?
the anterior and posterior interosseous arteries
What does the anterior interosseous nerve do?
It joins the anterior interosseous nerve and passes distally between the flexor digitorum profundus and the flexor pollicis longus.
What does the posterior interosseous artery do?
It passes above the interosseous membrane to supply blood to the posterior comparement (extensor comparement) of the forearm.
What bursa is usually affected in busitis of the elbow?
What will cause this?
What are the two other potential bursitises of the elbow?
The subcutaneous olecranon bursa
repeated and excessive pressure and friction of the elbow causes the bursa to become inflamed
It’s also calle dstudents elbow, miners elbow, dar thrower’s elbow, etc.
The other two include subtendinous olecranon bursitis (excessive friction between triceps tendons and olecranon) and bicipitoradial bursitis
What is abulsion of the medial epicondyle?
How doe sit happens?
in a fall that causes severe abduction of the extended elbow, the traction on the ulnar collateral ligament pulls the medial epicondyle distally
This happens in children and means the epihpysis for the medial epicondyle may not fuse with the distal end of the humerus until up to age 20
In dislocation of the elbow joint, which way do the bones go relative to each other?
How does dislocation often happen?
The ulna and radius are driven posteriorly
the distal end of the humerus is driven through the weak anterior part of the fibrous layer sof the joint capsule.
This often happens when kids fall and catch themselves with their hands when their elbows are flexed
In ulna and radius fractures, where does the fracture usually occur?
Why does the fracture of one bone often lead to dislocation of the joint?
Fractures will usually occur in the middle third of the bones
dislocation of the neraest joint will often occur because the two bones are held together so firmly by the interosseous membrane
What is hte most common fracture of the forearm?
Where does it happen and who does it often happen to?
A colles fracture of the forearm, which is a complete transverse fracture of the distal 2cm of the radius
It occurs in forced dorsiflexion of the hand, usually as the result of trying to ease a fall by outstretching the upper limb
usually in females over 50 with osteoporosis
it causes a dinner form deformity
Which forearm bone is more subject to fx due to elbow trauma and which one to wrist trauma?
ulna = elbow trauma
radius = falling on hands
What is a reverse Colle’s fracture called?
A Smith’s fracture.
the distal radius is displaced anteriorly instead of posteriorly.
Usually caused by a fall on the dorsum of the hand with the wrist flexed
What happens when the median nerve is severed at the elbow?
You lose the ability to flex the proximal interphalangeal joints of the 1-3 digits and it’s weakened in the 4-5 digits.
Flexion of the distal interphalangeal joints of the 2-3 digits is also lost.
When someone attempts to make a fix, the 2nd and 3rd fingers remain partically extended in a “hand of benediction”
What happens when the anterior interosseous nerve is injured?
You get paralysis of the flexor digitorum profundus and flexor pollicis longus.
When the patient attempts to make the okay sign, it looks more like a pinch than a circle
Why might you erroneously conclude that the median nerve hasn’t been damaged when it has?
Somtimes communications occur between the median and ulnar nerves of the forearm, so even with a complete lesion of the median nerve, some muscle may not be paralyzed
WHat is cubital tunnel syndrome?
When the ulnar nerve is compressed in the cubital tunnel formed by the tendinous arch joining the humeral and ulnar heads
What causes a claw hand deformity?
distal lesion of the ulnar nerve - they can’t flex the 4th and 5th digits at the DIP joints when trying to make a fist.
What happens in ulnar canal syndrome (guyon’s tunnel syndrome)?
the ulnar nerve is compressed as it asses through the ulnar canal
you get hypoesthesia in the medial one and a half fingers and weakness in the intrinsic muscles of the hand.
WHat happens in handlebar neuropathy?
people who ride bikes with their hands in extended position puts pressure ont he hooks of their hamates, which compresses their ulnar nerves
it results in sensory loss on the medial side of the hand and weakness of the instrinsic hand muscles
What causes a volkmann’s contracture?
interruption of blood flow in the brachial artery
you get ischemic necrosis of the muscles, and the necrotic tissue is replaced by fibrous scar tissuees what causes the involved muscles to be permanently shortened, causing a flexion deformity called volkmann’s deformity
If there is high division of the brachial artery into the radial and ulnar arteries, what happens to the median nerve
it will pass between them down the arm
What can be an issue if someone has a superficial ulnar artery?
A superficial ulnar artery will descend superficial to the flexor muscles and the pulsations can be felt and seen.
This means it is often mistaken for a vein and if you try to take a blood draw or give intravenous injections, you can damage the artery and produce bleeding. If a certain drug is put in an artery is may be fatal.
