2.4.2. Anat Lab Tuesday - Forearm Flashcards
Name the purely sensory nerve that is located on the radial (lateral) side of the wrist. What part of the hand does this nerve provide sensation to?
Superficial branch of the radial nerve
Provides sensation to the radial side of the dorsum of the hand
Note: If injured, it can be extremely sensitive/irritable to the patient
Identify the labeled items:
- Flexor carpi radialis
- Palmaris longus
- Flexor carpi ulnaris
- Brachioradialis
List the superficial muscles of the anterior forearm (there are 4)
- Flexor carpi radialis
- Palmaris longus
- Flexor carpi ulnaris
- Brachioradialis
Identify the following structures:
(Note, this is an oblique view of the right forearm)
- Flexor digitorum superficialis
- Pronator teres
- Brachioradialis (cut and reflected)
- Flexor carpi radialis (cut and reflected)
- Radial artery
- Superficial branch of the radial nerve
- Radius
Identify the following structures:
- Flexor digitorum profundus
- Flexor pollicis longus
- Pronator quadratus
- Superficial flexor group - reflected
- Flexor digitorum profundus (index finger)
Identify the following structures:
- Flexor pollicis longus
- Median nerve
- Superficial branch of the radial nerve
- Ulnar nerve
- Flexor digitorum profundus
- Flexor carpi ulnaris tendon (cut)
Identify the following structures:
- Flexor digitorum profundus
- Flexor pollicis longus
- Pronator quadratus
- Flexor digitorum profundus (index finger)
Identify the following structures:
- Brachial artery
- Ulnar artery
- Radial artery
Identify the following structures.
Bonus - what nerve are you most worried about if this bone breaks in the middle?
Bonus Bonus - what are the symptoms of damage to that nerve in that area of the bone?
- Capitulum
- Trochlea
- Medial epicondyle
- Lateral epicondyle
- Coronoid fossa
Bonus: A mid-humeral fracture can be associated with damage to the radial nerve
Bonus Bonus: The characteristic clinical sign of radial nerve injury is WRIST-DROP. When the radial nerve is injured in the radial groove, the triceps is normally only weakened (because only the medial head is affected), and muscles in the posterior compartment of the forearm are paralyzed.
Identify the following structures:
- Medial epichondyle
- Lateral epicondyle
- Olecranon fossa
Identify the following structures (anterior view):
- Head of ulna
- Styloid process of ulna
- Ulnar tuberosity
- Coronoid process
- Ulnar interosseous border
- Styloid process of radius
- Radial tuberosity
Identify the following structures:
- Head of radius
- Radial tuberosity
- Styloid process of radius
- Interosseous border
What bone is this? Identify the numbered structures.
This is the ulna!
- Olecranon process
- Coronoid process
- Trochlear notch
Pronator teres:
Origin (2)
Insertion
Innervation
Main Action
Origin: Medial epicondyle of humerus and coronoid process of ulna
Insertion: Middle of lateral surface of radius (pronator tuberosity)
Innervation: Median Nerve (C6-C7)
Main Action: Pronates forearm and flexes elbow joint
Flexor carpi radialis:
Origin
Insertion
Innervation
Main Action
Origin: Medial epicondyle of humerus
Insertion: Base of 2nd and 3rd metacarpals
Innervation: Median nerve (C6-C7)
Main Action: Flexes and ABducts wrist joint
Palmaris Longus:
Origin
Insertion
Innervation
Main Action
Origin: Medial epicondyle of the humerus
Insertion: Distal half of flexor retinaculum and palmar aponeurosis
Innervation: Median nerve (C7-C8)
Main Action: Flexes wrist joint and tightens palmar aponeurosis
Flexor carpi ulnaris:
Origin (2)
Insertion (3)
Innervation
Main Action
Origin: 1) Humeral head: medial epicondyle of humerus
2) Ulnar head: olecranon and posterior border of ulna
Insertion: Pisiform, hook of hamate, and 5th metacarpal
Innervation: Ulnar nerve (C7-C8)
Main Action: Flexes and adducts wrist joint
Flexor digitorum superficialis:
Origin (2)
Insertion
Innervation
Main Action
Origin: 1) Humero-ulnar head: medial epicondyle of humerus, ulnar collateral ligament, and coronoid process of ulna
2) Radial head: superior half of anterior border of the radius
Insertion: Bodies of middle phalanges of medial four digits
Innervation: Median Nerve (C7, C8, T1)
Main Action: Flexes proximal interphalangeals (PIPs) of medial four digits; acting more strongly, it flexes metacarpophalangeal (MCPs) and wrist joint
Flexor digitorum profundus:
Origin
Insertion
Innervation (2)
Main Action
Origin: Proximal three quarters of medial and anterior surfaces of ulna and interosseous membrane
Insertion: Bases of distal phalanges of medial four digits
Innervation: 1) Medial Part: Ulnar nerve (C8-T1)
2) Lateral Part: Median Nerve (C8-T1)
Main Action: Flexes distal interphalangeals (DIPs) of medial four digits; assists with flexion of wrist joint
Flexor pollicis longus:
Origin
Insertion
Innervation
Main Action
Origin: Anterior surface of radius and adjacent interosseous membrane
Insertion: Base of distal phalanx of thumb
Innervation: Anterior interosseous nerve from median (C8-T1)
Action: Flexes interphalangeal (IP) joints of 1st digit (thumb) and assists flexion of wrist joint
Pronator quadratus:
Origin
Insertion
Innervation
Main Action
Origin: Distal fourth of anterior surface of ulna
Insertion: Distal fourth of anterior surface of radius
Innervation: Anterior interosseous nerve from median (C8-T1)
Main Action: Pronates forearm; deep fibers bind radius and ulna together
Which way does the palm face when the radius spins into pronation?
Palm faces down
Which way does the palm face when the radius spins into supination?
Palm is up
Which bone is the forearm rotates, and which bone in the forearm cannot rotate?
Explain the function of the stationary bone and the motion of the rotating bone.
The radius rotates, and the ulna does not.
The proximal ulna is like a big crescent wrench that grips the humerus at the elbow, allowing the elbow to move like a big hinge.
The radius spins in an arc around the stable ulna.
The “head” of the ulna is on which end of the bone? (Proximal or distal)
Distal
What are the two pivot points of the forearm?
What type of joints are they?
The two pivot points are the proximal and distal radioulnar joints.
They are synovial joints, and must be normal in order to allow the spinning to occur.
If a patient’s proximal and/or distal radioulnar joints are not normal, what won’t they be able to do?
They will not be able to perform pronation and supination movements
The radius contributes more to the _____ joint,
while the ulna contributes more to the _____ joint
The radius contributes more to the wrist (radiocarpal) joint
The ulna contributes more to the elbow joint
Which bone in the forearm does not directly contact bones in the wrist?
The ulna does not directly contact the bones in the wrist, but it moves via the triangular fibrocartilage complex and the articular disc that are positioned at the end of the ulna
What is the function of the anular ligament?
It encircles/stabilizes the radial head while the radius “spins” around the ulna in supination and pronation
The dorsal radial tubercle (Lister’s tubercle) acts as a “pulley” for which tendon?
The extensor pollicis longus (EPL)
Which tubercle does the extensor pollici longus (EPL) use as a “pulley”?
What is the resulting motion of this “pulley system”?
The dorsal radial tubercle, also called Lister’s tubercle
Allows elevation of the thumb
What does the pulley system between Lister’s tubercle and the Extensor Pollicis Longus tendon unfortunately predispose the tendon to, and why?
Predisposes the tendon to rupture in rheumatoid arthritis and in fractures of the distal radius
This is due to the inflammation and friction that can develop at Lister’s tubercle as the tendon makes its turn toward the thumb. This can wear the tendon down.
Where is the most common location for a radius fracture to occur?
The distal radius
Which artery is located in the “anatomical snuff box”?
The radial artery (passes diagonally from the anterior surface of the radius to the dorsal surface of the hand)
Describe the course of the ulnar artery through the forearm.
Descends inferomedially and then directly inferiorly, deep to superficial (pronator teres and palmaris longus) and intermediate (flexor digitorum superficialis) layers of flexor muscles to reach medial side of forearm; passes superficial to flexor retinaculum at wrist in ulnar canal to enter hand
Which artery does the common interosseous artery originate from, and where does it branch off?
The ulnar artery in the cubital fossa, distal to bifurcation of brachial artery
What two arteries originate as terminal branches of the common interosseous artery?
Describe their courses in the forearm.
The two arteries are the anterior interosseous artery and the posterior interosseous artery.
The anterior interosseous passes distally on the anterior aspect of the interosseous membrane to the proximal border of the pronator quadratus; it then pierces the membrane and continues distally to join the dorsal carpal arch on the posterior aspect of the interosseous membrane.
The posterior interosseous passes to the posterior aspect of the interosseous membrane, giving rise to recurrent interosseous artery; it then runs distally between superficial and depp extensor muscles, supplying both; it is replaced distally by the anterior interosseous artery.
What three structures separate the flexor compartment from the extensor compartment?
What is their surgical significance?
The interosseous membrane, the radial artery and the subcutaneous medial border of the ulna.
they are useful guides in planning surgical incisions because no important nerves cross these structures.
What are the general clinical findings of a median nerve injury?
Injury causes a predictable pattern of sensory loss in the hand:
- numbness to the radial-sided 3 1/2 digits
- loss of thumb opposition (the ability to raise the thumbtip up away from the palm in order to touch the fingertips)
Explain how the nerve branches that are proximal and distal to a nerve injury are affected.
Any branches that departed the nerve proximal to the injury will still function.
Any branches distal to the injury will not function.
What are the general clinical findings of an anterior interosseous nerve injury?
Injury causes loss of tip-to-tip pinch between the thumb and index finger.
What are the general clinical findings of an ulnar nerve injury?
Injury causes a predictable pattern of sensory loss in the hand:
- Numbness to the ulnar-sided 1 1/2 digits
- Loss of coordination of the hand due to loss of the function of the intrinsic muscles of the fingers (muscles that originate and insert within the hand)
What are the general clinical findings of a radial nerve injury?
- Injury causes “wrist drop” (due to the loss of the wrist extensor muscles), which causes loss of power grip, since the fist cannot be raised up to assume its power-grip position
- Causes a predictable pattern of sensory loss (numbness) to the radial-sided dorsal skin of the hand
What are the general clinical findings of an injury to the superficial branch of the radial nerve?
Injury causes a predictable pattern of sensory loss over the back (dorsum) of the thumb and 1st webspace on the radial side.
What are the general clinical findings of an injury to the deep branch of the radial nerve?
This nerve is renamed the posterior interosseous nerve after it pierces the supinator muscle on the dorsal/extensor side of the forearm
Injury causes loss of full extension of the central digits (the patient cannot fully open their hand)
For extremity incisions, is it better to have latitudinal or longitudinal ones? Why?
Longitudinal because the vessels and nerves run in this direction; there is less danger of transecting them
The posterior (extensor) compartment paradoxically contains one flexor muscle.
What is the muscle, what is it innervated by, and what joint does it flex?
The brachioradialis muscle is innervated by the radial nerve (just like all of the extensors in the posterior compartment). It is considered a flexor of the elbow joint.
True or False: If nerves are microscopically repaired after a laceration injury, they can fully recover and function as the did before the injury occurred.
FALSE!!!!
Nerves, even if microscopically repaired, never regain full function once they are transected. They can, however, under optimal circumstances, recover from certain compression type injuries. But after a laceration, the injured nerves can only regenerate up to a point and are never the same as before the injury.
Name the two branches that the radial nerve branches into in the lateral cubital fossa.
What does these two nerves do?
1) The superficial branch of the radial nerve is sensory to the skin over the dorsum of the thumb and radial-sided digits.
2) The deep branch of the radial nerve is RENAMED the posterior interosseous nerve after piercing the supinator muscle distal to the elbow on the extensor surface of the forearm. The posterior interosseous nerve motors the extensors of the forearm.
Why is it easier for some infections to rapidly spread between the hand and forearm (especially synergistic (flesh-eating) infections)?
Fascial septae divide the forearm into anterior (flexor) and posterior (extensor) compartments. These compartments do not communicate with those of the arm, but do continue into the hand. This makes it easier for infections to spread between the hand and forearm.
Define “synergistic infection.”
What do they cause?
What are the clinical symptoms?
How do you treat them?
BONUS: What organisms are the usual culprits? (2)
Synergistic infection: infections that are due to two or more organisms that work together to spread rapidly by elaborating enzymes (collagenases) that dissolve collagen and by destroying tissue as they spread.
They cause rapidly-spreading necrosis that can become life threatening within HOURS and are considered surgical emergencies.
Clinical symptoms include pain and tachycardia (rapid heart rate) and sometimes elaborate gas in the soft tissues, which is seen on imaging and/or felt as “crepitance” - a crunchy or bubbly feel to the soft tissues when palpated.
Treatment: These infections must be immediately opened and debrided aggressively and packed open until the infection has resolved. Intravenous antibiotics are also administered.
BONUS: Microaerophilic streptococcus and anaerobic staphylococcus
