Theory 15- Forearm and hand

What are the five flexor muscles that originate at the medial humeral epicondyle?

1. Pronator teres 2. Flexor carpi radialis 3. palmaris longus 4. flexor carpi ulnaris 5. Flexor digitorum superficialis

What are the forearm flexors anatomical actions?

14 G 2. Biceps brachii m.: flexion and supination 14 G 3. Brachialis m.: flexion only (ulnar insertion) 15 A 1. Pronator teres m.: flexion and pronation 15 B 1. Brachioradialis m.: flexion and pronation or supination Benefits: stability and options forforces that can be applied to the hand Brachioradialis m. is "the beveragecarrying muscle;" it keeps you fromspilling by pronation or by supination

Which two muscles of the thumb are innervated, all or in part, by the ulnar nerve?

Adductor pollicis muscle (all), flexor pollicis brevis muscle (half)

Which muscles acting on the thumb are affected?

All of adductor pollicis muscle, part of flexor pollicis brevis muscle

Which palmar interosseous muscles and which dorsal interosseous muscles are affected?

All palmar interosseous muscles. All dorsal interosseous muscles

What allows supination and pronation of the radial head?

Annular ligament

What muscle inserts on the radial tuberosity of the radius?

Biceps brachii muscle

What fan of tendon separates them from the depth of the brachial artery?

Bicipital aponeurosis of biceps brachii

Name its partner, which attaches to the coronoid process of the ulna.

Brachialis muscle

Which two nerve roots are involved in lower brachial plexus injury?Do nerve fibers in those two roots terminate relatively proximal in the upper limb, or relatively distal in the upper limb?

C8 and T1. Distally.

Which of these two would you expect to present with signs and symptoms in the hand only?

Carpal tunnel syndrome

What movement of the forearm at the elbow occurs to stretch the biceps brachii?

Extension of the forearm at the elbow

What is the number of the one of those four muscles that is listed individually on the anatomy study list?

First

What tendon is outside the main compartment of the tunnel on the radial side, stopping at the base of the hand?

Flexor carpi radialis muscle

All of the major contents passing through the main compartment of the carpal tunnel reach the digits. What tendon is entirely outside the carpal tunnel on the ulnar side, reaching the base of the hand but not accessing the digits directly?

Flexor carpi ulnaris muscle

What group of four tendons is located relatively superficially in the carpal tunnel?

Flexor digitorum superficialis muscle

Which two of the four lumbrical muscles are affected if that nerve is severely lacerated at the wrist?

Fourth digit lumbrical, fifth digit lumbrical

Teres minor:

Internal rotation and abduction of the arm at the shoulder joint

Which two "median nerve muscles" of the hand are not thenar muscles?

Lumbrical muscle of second digit, lumbrical muscle of third digit (first and second lumbricals)

Key sign

Supposedly, the normal way to grasp a key is with thumb opposition and flexion of the interphalangeal joint of the thumb This is a median n. behavior (flexor pollicis longus m. and intrinsic hand muscles) Substitution: if the median n. or its muscles are not functional, the patient will grasp the key with a pinching adduction movement of the thumb that uses a familiar ulnar n. muscle

If the passive range of motion in internal rotation of the arm at the shoulder joint is greater when the arm is in an adducted position and less when the arm is in an abducted position, which rotator cuff muscle is likely to be unable to stretch fully?

Teres minor

The "hand of benediction" or "pope's hand" occurs when the patient cannot actively flex the second and third digits of the hand. Why does this appearance indicate a nerve lesion proximal to the wrist?

The innervations of the flexor digitorum superficialis and profundus muscles are in the forearm, so the lesion cannot be far distal to the elbow

What does antecubital mean?

The useful term "antecubital vein" means any vein of the cubital fossa that is used for venipuncture

Are muscles that act on the hand or the digits certain to be affected in a case of lower brachial plexus injury?

Yes

Do any digits have all of their skin surfaces served by a single one of the three nerves of the hand?

Yes

If there are motor deficits caused by lower brachial plexus injury, will muscles innervated by the median nerve be affected?

Yes

What ligament holds the radial head in place against the radial notch of the proximal ulna?

Annular ligament of radius

What are the three extensor carpi muscles that cross the wrist joints?

Extensor carpi radialis longus Extensor carpi radialis brevis Extensor carpi ulnaris

Why can't the annular ligament attach directly to the radius?

Radius has to be free to rotate in supination and pronation

What makes the carpal tunnel?

flexor retinaculum and carpal bones. Carpal bones are: hamate, capitate, trapezoid, trapezium

What four nerves cross the elbow joint?

1. Median nerve 2. Ulnar nerve 3. Radial nerve 5. Lateral antebrachial cutaneous nerve.

What are the median nerve muscle innervations in the hand? What is the visible appearance of the hand when these muscles are denervated due to median nerve injury at the wrist? This condition is sometime called "ape hand" because a chimpanzee's hand has a very small thumb with weak muscles.

Abductor pollicis brevis, opponens pollicis, superficial part of flexor pollicis brevis, lumbricals of second and third digits. Wasting of the thenar eminence

In a typical upper brachial plexus injury, what is the posture of the arm (abducted or adducted, etc.)?

Adducted, internally rotated

Is the radial nerve anterior to the lateral epicondyle of the humerus or posterior to it?

Anterior

All of the muscles you could name for question "e" are in one compartment; name it.

Anterior compartment

If all of these movements are combined and brought to the limit of range of motion, what other muscles will be stretched at the shoulder joint?

Anterior deltoid, pectoralis major, coracobrachialis muscles

Where is the interosseous insertions?

Base of the proximal phalanx and extensor expansion

What other major structures are at the same depth as the brachial artery?

Brachial vein, median nerve. (If there is a relatively proximal terminal branching of the brachial vessels, the radial and ulnar arteries and veins will be present in the cubital fossa.)

What does the combination of the two movements in "c" and "d" (or "f" and "g") mean for the muscles you named in question f?

Brachialis will be stretched more than pronator teres will be stretched

What are the movements of the bracioradialis muscle?

Brachioradialis m. does not cross the wrist joints, so its actions arelimited to flexion, pronation and supination of the forearm at the elbow

Which two roots of the brachial plexus are involved in upper brachial plexus injury?

C5 and 6

What are the innervation of the extensor carpi radialis muscles?

C6 and C7

Tell me about the lumbrical muscles?

Covert proximal flexion to distal extension force of the knuckles. 1. They originate from flexor digitorum profundus tendons 2. They pass anterior to metacarpophalangeal joints, so they have a flexion action there 3. They insert on extensor expansions, so they have interphalangeal extension action

Don't stop there with your testing. Define the limits of the deficits by evaluating the health of neighboring structures that you do not expect to be injured. Give two examples.

Cutaneous innervation (i.e., sharp object sensation) on the lateral side of the fourth digit, or on the third digit; opposition of the thumb; etc. These will be normal if only the ulnar nerve is impacted by the injury

Which four interosseous muscles are easily identified on the dorsal side of the hand? These muscles take origin from both bones of their intermetacarpal space, so very little of the other muscle in the same space will be visible.

Dorsal interosseous muscles

Is any part of the skin of the dorsum of the hand and digits served by the median nerve?

Dorsal side of second, third and fourth digits distally

Is any part of the skin of the dorsum of the hand and digits served by the ulnar nerve?

Dorsum of hand medially and of fingers four and five

What movement of the arm at the shoulder occurs to stretch the biceps brachii?

Extension or abduction of the arm at the shoulder, or both together

What extensor muscle on the radial side will you use to prevent your whole hand from flexing? What extensor muscle on the ulnar side? (Don't use much extensor digitorum, because you want your fingers to be able to flex.)

Extensor carpi radialis muscles. Extensor carpi ulnaris muscle

Subscapularis:

External rotation and abduction of the arm at the shoulder joint

Which of that patient's fingers will be the primary focus of your cutaneous sensory testing?

Fifth digit

How far distal to the site of injury might you get and still detect dysfunction of the motor neurons in the relevant nerve?

First dorsal interosseous muscle on the lateral side of the hand

Between which two bones is this particular interosseous muscle located? If you see arrows for that one muscle on the exploration exam, be specific--include the number.

First metacarpal, second metacarpal

When they are recruited to move the fingers, what action do those two muscles ( Flexor digitorum superficialis muscle and Flexor digitorum profundus muscle) exert on the whole hand at the wrist?

Flexion

The name of the pronator teres muscle makes one of its actions obvious. What is the other anatomical action of the pronator teres on the forearm at the elbow?

Flexion of the forearm at the elbow

What action do the brachialis and biceps brachii muscle share?

Flexion of the forearm at the elbow

What is the brachialis muscle only significant anatomical action on the forearm at the elbow?

Flexion of the forearm at the elbow

What are the ulnars nerve muscles?

Flexor carpi ulnaris muscle and ulnar half of flexor digitorum profundus muscle

What flexor muscle reaches the distal phalanx, applying flexion force there, too?

Flexor digitorum profundus muscle

What group of four tendons is located more deeply in the carpal tunnel? What other tendon is with them there?

Flexor digitorum profundus tendon. Flexor pollicis longus tendon

Name a muscle with a somatic motor nerve supply that could be diminished by nerve impingement between the two heads of pronator teres, but that would not be affected directly by nerve impingement within the carpal tunnel.

Flexor digitorum superficialis m., flexor pollicis longus m., etc.

The first four questions here serve one story, and the last six serve a different one. What muscle allows you to flex the proximal interphalangeal joints of your fingers while leaving the distal interphalangeal joints relaxed (so your fingertips can wiggle or extend to put the finger pad flat on the table)?

Flexor digitorum superficialis muscle

What muscle has the hole or gap? What bone is its insertion? What muscle passes through? What bone is its insertion?

Flexor digitorum superficialis. Middle phalanx of second, third, fourth or fifth digit Flexor digitorum profundus. Distal phalanx of second, third, fourth or fifth digit

What ligament makes the anterior border of the carpal tunnel?

Flexor retinaculum

Tell me about adduction of the thumb?

Grasping a piece of paper with pollical adduction (thumb to the third finger) The paper bends nicely without creasing because the thumb is flat (extended metacarpophalangeal and interphalangeal joints) Adductor pollicis m., ulnar n

A prominent feature of the hamate bone is deep to that nerve at the wrist. What part of the hamate bone is this?

Hamulus; it is right there on the study list

What tissue type is in the radial head of a young child?

Hyaline cartilage

What tissue types are in the adult radial head?

Hyaline cartilage, bone

Anatomy gives you the map of your patient's health and disease; for clinical practice you need the clock or calendar that is provided by knowledge of natural history of disease. Many peripheral nerve lesions get worse over time without care; in such cases sensory symptoms usually precede motor signs. (Sensory nerve processes are more vulnerable than the axons of motor neurons.) If the muscles are affected, too, the condition is more severe. What does it mean to say paresis precedes atrophy?

If a muscle disease or a motor neuron disease process is getting worse over time, the affected muscles will be weak before atrophy is visibly recognizable. Atrophy develops over a period of days and weeks after acute nerve injury; paresis (or paralysis) will be evident as soon as a nerve is injured

If the passive range of motion in external rotation of the arm at the shoulder joint is greater when the arm is in an adducted position and less when the arm is in an abducted position, which part of the subscapularis muscle may be less able to stretch than the other part of it?

Inferior part of subscapularis muscle

Supraspinatus is hard to stretch. Describe the movements or positions that stretch each of the other three rotator cuff muscles. Infraspinatus:

Internal rotation of the arm at the shoulder joint

To identify other muscles that might be causing the range of motion pattern in question c above, we will look for other muscles that share the anatomical actions of subscapularis. What are those actions? What muscles also have those actions?

Internal rotation, adduction Pectoralis major muscle, latissimus dorsi musclea.

In fact, no ligament attaches to the head of the radius. What ligament attaches to the shaft of the radius?

Interosseus membrane of forearm

Although this objective emphasizes veins, it can be used to anchor a potential theory exam item that combines vessels and nerves at the elbow. The cephalic vein in the forearm is not an ideal vein for venipuncture because a cutaneous nerve accompanies it. Name that nerve.

Lateral antebrachial cutaneous nerve (lateral cutaneous nerve of the forearm)

What muscles that act on the arm at the shoulder are functional to produce the posture you described in "c" above?

Latissimus dorsi muscle (it has a lot of C8 in its nerve supply)

Relative to the more massive biceps brachii and brachialis muscles, the brachioradialis muscle is weak. But try comparing the brachioradialis muscle to the other forearm muscles. Its cross-sectional area and distance from the axis of rotation of the elbow suggest that, among the forearm muscles, brachioradialis is the most powerful forearm flexor.

Life is full of balances like that

What other muscles will be stretched at the elbow joint?

Mainly brachialis and supinator muscles

What other muscles will be stretched by the movement between the two forearm bones?

Mainly brachioradialis muscle, maybe also pronator teres because it has pretty good elbow flexion action.

What are the ulnar nerve muscle innervations in the hand? What is the visible appearance of the hand when these innervations are lost due to injury at the wrist? What is this called?

Many. Visible atrophy of hypothenar eminence, intermetacarpal spaces and web of hand. Claw hand

What two ligaments stabilize the elbow?

Medial collateral and lateral humeroulnar ligament

What is on the deep side of the flexor digitorum superficialis muscle?

Median n. on deep side of flexor digitorum superficialis m. At the wrist, it is medial to the flexor digitorum superficialis tendon In the middle of the cubital fossa Between two heads of pronatorteres m. Proximal to the carpal tunnel it is very superficial

The contrast between carpal tunnel syndrome and pronator teres syndrome is good. What nerve passes between the two heads of the pronator teres muscle, and is vulnerable to irritation there?

Median nerve

What, then, is the tenth structure passing from the forearm to the hand through the carpal tunnel?

Median nerve

A patient presents with inability to flex his index finger and middle finger (second and third digits); he also shows weakness in abducting and opposing his thumb. Which nerve do you suspect to be injured, and at what location?

Median nerve lesion proximal to the elbow because that would include denervation of the flexor digitorum muscles and the flexor pollicis longus muscle

What nerve goes "right up the middle" of the cubital fossa? c. What major vessel is lateral to that nerve? Lateral to that is the biceps brachii tendon.

Median nerve. Brachial artery

Name the nerve in the arm that ends with a cutaneous branch that passes near the lateral side of the biceps brachii tendon. What is the name of that cutaneous nerve? The fourth nerve is buried a little more lateral than that. Name it.

Musculocutaneous nerve. Radial nerve

Are muscles that act on the arm at the shoulder certain to be affected in a case of lower brachial plexus injury?

No

Are muscles that act on the hand certain to be affected in a case of upper brachial plexus injury?

No

If there are motor deficits caused by lower brachial plexus injury, will muscles innervated by the axillary nerve be affected?

No

If there are motor deficits caused by lower brachial plexus injury, will muscles innervated by the musculocutaneous nerve be affected?

No

Is there a major artery or vein in the carpal tunnel?

No

The arrangement of the thumb flexor muscles is remotely similar to the arrangement of the finger flexor tendons that we just described. Explain.

On the flexor aspect of the thumb, the flexor pollicis longus tendon is embraced by the two heads of the flexor pollicis brevis muscle

What muscles that act on the arm at the shoulder are paralyzed?

Pectoralis major muscle, biceps brachii muscle, coracobrachialis muscle, deltoid muscle, rotator cuff muscles

We have discussed three of four "quadrants" of the elbow (a nerve and vessels in the anteromedial quadrant, one nerve in the posteromedial quadrant, two nerves in the anterolateral quadrant). Which of the four quadrants has no major nerve?

Posterolateral quadrant

What movement within the forearm occurs to stretch the biceps brachii?

Pronation of the radius relative to the ulna

What are the median nerves muscles?

Pronator teres m. Palmaris longus m. Flexor digitorum superficialis m. Flexor carpi radialis m. Radial half of flexor digitorum profundus m. Flexor pollicis longus m. Pronator quadratus m.

Comparing pure and logical cases of pronator teres syndrome and carpal tunnel syndrome, which will have more proximal signs and symptoms?

Pronator teres syndrome

Do nerve fibers in those two roots terminate relatively proximal in the upper limb, or relatively distal in the upper limb?

Proximal

Tell me about the anatomical snuff box?

Radial a. in the snuffbox (palpable pulse) Scaphoid bone is the floor of the snuffbox "Longus, brevis, longus" muscles

In the forearm and cubital fossa, what is the depth of the cephalic vein, median cubital vein and basilic vein?

Superficial fascia

Which branch of the radial nerve crosses the wrist? The location of this nerve is something to know for the exploration exam. What two functions (distinct neural functional modalities) does it serve in the hand?

Superficial radial nerve. General sensory, sympathetics

What action does the bicep brachii get by attaching to the radius and not the ulna?

Supination of the radius relative to the ulna

Whose radial head is much more easily deformed such that it can slip distally away from the ligament that encircles it?

The child

Loss of lumbrical function may cause the affected fingers to assume a position opposite to the anatomical actions of the lumbricals. What is that position?

The paralyzed position is metacarpophalangeal extension and interphalangeal flexion

How would you differentiate claw hand from pope's hand with muscle tests in a physical examination?

The patient with pope hand can extend the fourth and fifth digits effectively, but he or she cannot flex the second and third digits. The patient with claw hand can flex the second and third digits, but he or she cannot extend the fourth and fifth digits forcefully

If there are motor deficits caused by lower brachial plexus injury, will muscles innervated by the radial nerve be affected?

This is less likely

Tell me about the palmar and interosseous muscles?

Three palmar and four dorsal interosseous muscles PAD - Palmar interosseous mm. adductDAB - Dorsal interosseous mm. abduct Third digit has two dorsal interosseous musclesThe second muscle abducts laterally and the third muscle abducts medially

A patient comes into the office unable to extend her ring finger and pinky finger (fourth and fifth digits) fully. Which nerve do you suspect to be injured?

Ulnar nerve

If your patient (a golfer, perhaps) fractures the hamulus of the hamate bone, you will want to assess the function of the nerve passing by there. Name the nerve again.

Ulnar nerve

Next story. The "claw hand" deformity can result when the nerve that innervates most of the intrinsic hand muscles is severely damaged. What nerve is that?

Ulnar nerve

What nerve innervates all of the interosseous muscles?

Ulnar nerve

Which nerve is the only major nerve that passes posterior to the elbow joint (posterior to an epicondyle of the humerus)?

Ulnar nerve

Which of the two major nerves serving the palmar side of the hand does not utilize the carpal tunnel?

Ulnar nerve

What nerve is on the superficial via the medial side of the wrist?

Ulnar nerve and artery

If so, which nerves are devoted to which individual digits?

Ulnar nerve of the fifth digit

. Are the fingertips served primarily by ventral nerves, or by the dorsal nerve of the hand?

Ventral nerves (median and ulnar nerves)

A patient presents with a longstanding history of carpal tunnel syndrome. What motor signs or symptoms would you expect to result from the patient's nerve injury? What sensory symptoms would you anticipate?

Weak opposition of the thumb; poorly controlled extension of the second and third digits (lumbrical paresis). Paresthesia of the tips of the first second and third digits; sensory innervation of the palm may be spared.

If there are motor deficits caused by lower brachial plexus injury, will muscles innervated by the ulnar nerve be affected?

Yes

Will abducting and adducting the fingers be a good test for the nerve's ability to convey motor signals?

Yes, both will be good tests to use, with weakness indicating nerve injury

The branch of the median nerve that supplies the skin of the palm branches proximal to the carpal tunnel and then passes superficial to the flexor retinaculum. So in a case of pure carpal tunnel syndrome, the cutaneous innervation of the skin of the palm is not affected. Is the skin of the thumb and some of the fingertips affected? If so, which fingertips?

Yes. Second digit, third digit, lateral half of fourth digit

a. 19 total intrinsic muscles; 14.5 are innervated by the ulnar nerve. b. How many intrinsic hand muscles for the radial nerve? c. How many intrinsic hand muscles for the median nerve?

b. 0 c. 4.5