Forearm and Wrist Practice Quiz

Compression of the median nerve in the carpal tunnel affects which hand muscle(s)?

- Flexor pollicis brevis - Abductor pollicis brevis - Opponens pollicis --------------- The recurrent branch of the median nerve innervates the thenar compartment of the hand, including flexor pollicis brevis, abductor pollicis brevis, and opponens pollicis. So, if the median nerve was compressed, all of these muscles might be affected. The dorsal interossei, palmar interossei, and opponens digiti minimi are all muscles of the hand which are innervated by the deep branch of the ulnar nerve. Flexor pollicis longus is innervated by the median nerve, but it is a forearm muscle which is proximal to the carpal tunnel. Therefore, it would not be affected by compressing the median nerve in the carpal tunnel.

Supination of the hand and forearm would be diminished by loss of radial nerve function. But one very powerful supinator would remain intact and unaffected, namely:

Biceps brachii muscle ----------------- Biceps brachii supinates the arm, but it is not innervated by the radial nerve--instead, it is innervated by the musculocutaneous nerve. So, it would not be affected by a radial nerve injury. Brachialis is also innervated by the musculocutaneous nerve, but it is only involved with flexing the forearm--it is not a supinator. Brachioradialis flexes the elbow and assists in pronation and supination--it is innervated by the radial nerve and would be paralyzed after a radial nerve injury. Flexor carpi radialis is a flexor, not a supinator--it is innervated by the median nerve. Finally, supinator is innervated by the deep radial nerve.

The victim of multiple shrapnel wounds to the upper limb must have his forearm amputated at midlength. Because of concomitant damage in the patient's arm, the surgeon must ligate the main artery at some point. The best chance of saving collateral circulation to the stump of the forearm would be when the ligature is placed just below which of the following?

Bifurcation of the brachial artery ------------- The brachial artery bifurcates near the elbow. It forms two branches that become the radial and ulnar arteries. If these arteries were ligated after this bifurcation, there would be a chance at saving collateral circulation to the forearm because the ulnar artery might have already given off its common interosseous branch, which could carry blood to the forearm through the anterior and posterior interosseus arteries. Ligating near the beginning of the brachial artery would stop blood from flowing through the rest of the upper limb. Ligating near the origin of the deep artery, by the origin of the superior ulnar collateral artery, or near the origin of the inferior ulnar collateral artery might preserve enough collateral circulation to supply the elbow. However, there would not be collateral circulation to the forearm. For a better picture of these arterial connections, see Netter Plate 434.

After falling on the ice, it was determined that a patient had a Colles' fracture. Care must be taken to relieve tension on the broken distal end of the radius created by the pull of which muscle?

Brachioradialis --------------- The Colles' fracture is a fracture to the distal end of the radius. It usually occurs when someone tries to catch themselves from falling on an outstretched arm. So, you need to look in the answer choices for a muscle that inserts on the distal end of the radius. Brachioradialis inserts on the lateral side of the base of the styloid process of the radius, so this muscle could pull the broken piece of the radius out of place. This is why a cast over a Colles' fracture needs to extend up to the elbow--brachioradialis needs to be immobilized! Extensor carpi ulnaris inserts on the medial side of the base of the 5th metacarpal. Extensor carpi radialis longus inserts on the dorsum of the second metacarpal bone. Pronator quadratus extends between the distal ulna and radius-- it serves to pronate the hand. Although this muscle attaches to the broken part of the radius, it is not the most important muscle to stabilize following the injury. Extensor carpi radialis brevis inserts on the dorsum of the third metacarpal bone. So, none of the other muscles would pull on the distal piece of the radius as much as brachioradialis.

A middle-aged woman comes to you complaining of pain on the lateral side of her right elbow, so severe that she holds her eating utensils in her left hand to eat. She says that she spent the weekend putting in a new garden plot and that it involved loosening and turning over a large area of grass sods with a garden fork. You find that the region just proximal to the lateral epicondyle of her humerus is painful to the touch. There is no sensory loss in her forearm or hand. You suspect a localized tearing of the origin of a muscle producing the equivalent of "tennis elbow." The muscle most likely involved is the:

Brachioradialis muscle ----------- Tennis elbow is usually caused by inflammation of the common extensor tendon on the lateral side of the forearm, but we know that that's not what happened here. Instead, the patient tore a muscle at its origin, near the lateral epicondyle of the humerus. Brachioradialis originates from the upper two-thirds of the lateral supracondylar ridge of the humerus, so this is the muscle that she probably tore. This also makes sense given her activities--brachioradialis flexes the elbow and assists in pronation and supination, so she would have been using this muscle while gardening. The common flexor tendon is associated with the medial epicondyle, not the lateral epicondyle. Extensor carpi radialis brevis and extensor digitorum take origin from the common extensor tendon, which attaches to the lateral epicondyle. This tendon would be inflamed in a classic case of tennis elbow, but the common extensor tendon is not the structure that was injured in this patient's case. Pronator teres takes origin from the common flexor tendon and the medial side of the ulna.

If the musculocutaneous nerve is severed at its origin from the brachial plexus, flexion at the elbow is greatly weakened but not abolished. What muscle remains operative and can contribute to flexion?

Brachioradialis muscle --------------- Brachioradialis is a muscle innervated by the radial nerve--it flexes the elbow and assists in pronating and supinating the arm. Brachialis, coracobrachialis, and both heads of biceps brachii are all muscles which flex the arm and/or forearm, but they are all innervated by the musculocutaneous nerve. These muscles would be denervated if the musculocutaneous nerve was severed at its origin from the brachial plexus.

Development of "tennis elbow" (lateral epicondylitis) involves the origin of which muscle?

Extensor carpi brevis muscle ------------- "Tennis elbow" is due to repetitive use of the superficial extensor muscles of the forearm. The pain is felt on the lateral epicondyle and radiates down the posterior surface of the forearm. With tennis elbow, the repeated flexion and extension of the wrist strains the attachment of the common extensor tendon, producing inflammation of the periosteum of the lateral epicondyle and the common extensor attachment of the muscles. The only muscle listed which takes origin from the common extensor tendon is the extensor carpi radialis brevis. So, that is the correct answer. (Extensor carpi ulnaris also takes origin from the common extensor tendon, so it might be responsible for some of the symptoms too.) None of the other muscles take origin from the common extensor tendon. Abductor pollicis longus originates from the middle one-third of the posterior surface of the radius, the interosseous membrane, and the mid-portion of posterolateral ulna. Anconeus originates from the lateral epicondyle of the humerus. Brachioradialis originates from the upper two-thirds of the lateral supracondylar ridge of the humerus--it is not a muscle from the common extensor tendon. Finally, triceps brachii is not really assoiciated with the lateral epicondyle or the common extensor tendon--this muscle attaches to the olecranon process of the ulna.

While going up for a rebound, a basketball player jams her middle finger against the ball. She experiences severe pain and the trainer notes that she can no longer extend the distal phalanx of the finger. The injury has avulsed (torn away from the bone) which structure from her distal phalanx to produce this condition?

Extensor expansions ------------ The extensor expansions are the expanded distal ends of the extensor tendons which wrap around the heads of the metacarpals and the bases of the proximal phalanges and insert on the bases of the middle and distal phalanges. These extensor expansions hold the extensor tendon in the middle of the digit and provide a place for the lumbricals and interossei to attach. If an extensor expansion was torn, the extensor tendon would not be held in place and a lumbrical would be torn from its attachment. This would impair extension at the joint. Extensor carpi radialis brevis and longus are involved with extending the wrist and abducting the hand. These muscles do not produce extension at the fingers. Extensor digiti minimi and extensor indicis help with extension at the 5th and 2nd finger, but they do not act at the third finger.

The tendons on the dorsal side of the wrist are held in place by a thickening of the antebrachial fascia called the:

Extensor retinaculum ------------------- The extensor compartment is on the dorsal surface of the arm. The tendons of the muscles from this compartment pass onto the dorsal side of the wrist by crossing under the extensor retinaculum. The bicipital aponeurosis is the membranous band that runs from the biceps tendon across the cubital fossa and merges with the antebrachial fascia over the forearm flexor muscles. An extensor expansion wraps around the head of a metacarpal and the base of the proximal phalanx to hold the extensor tendon in place on the digit. The interosseous membrane connects the radius to the ulna, and the palmar carpal ligament is a thickening of the antebrachial fascia over the palmar surface of the wrist. The palmaris longus and ulnar neurovascular bundle pass deep to the palmar carpal ligament, and the flexor retinaculum lies deeper and more distal, forming the carpal tunnel.

Interruption of the median nerve in the cubital fossa affects what movement(s) of the thumb?

Flexion and opposition ------------- The recurrent branch of the median nerve innervates the thenar compartment of the hand. This nerve innervates opponens pollicis, which opposes the thumb, and flexor pollicis brevis, which helps to flex the thumb. So, disrupting the median nerve would impair both flexion and opposition of the thumb.

In an attempt to commit suicide by slashing the ventral side of the wrist, the two tendons of the flexor digitorum superficialis located most superficially were completely severed. What movement would be affected?

Flexion of the PIP joints of digits 3 and 4 --------------- When cutting the ventral side of the wrist, the first tendons cut would be the tendons of flexor digitorum superficialis. These tendons help flex the metacarpophalangeal and proximal interphalangeal joints, but not the distal interphalangeal joints. Flexor digitorum profundus (which has deeper tendons) is responsible for flexing the distal interphalangeal joints. To understand the next part of the question, look at Netter plate 443. The tendons of flexor digitorum superficialis are arranged in a packet with two superficial tendons and two deeper tendons. The tendons that go to fingers 3 and 4 are superficial, while the ones to finger 2 and 5 are underneath. So, the tendons to fingers 3 and 4 will be cut, impairing flexion of the proximal interphalangeal joints of digits 3 and 4.

If the tendon of palmaris longus were transected, what movement would be affected?

Flexion of the wrist ------------ Palmaris longus is a small muscle in the anterior compartment of the arm--it flexes the hand at the wrist and tightens the palmar aponeurosis. If this tendon was cut, it would be more difficult to flex the wrist. Flexor pollicis longus flexes the MP and IP joints of the thumb. Flexor digitorum profundus and superficialis flex the proximal IP joints of digits 2, 3, 4, and 5. Extensor carpi ulnaris, extensor carpi radialis longus and extensor carpi radialis brevis all extend the wrist.

The pulse of the radial artery at the wrist is felt immediately lateral to which tendon?

Flexor carpi radialis -------------- The radial artery runs on the radial side of the wrist, lateral to the tendon of flexor carpi radialis. So, the radial pulse will be felt immediately lateral to this tendon. Remember--the radial artery enters the wrist on the anterior side. This means that the extensor tendons, which are on the posterior side of the wrist, will not be involved with the radial artery! The tendons for flexor digitorum profundus and superficialis are found more towards the center of the wrist, not on the wrist's lateral side. These tendons cross under the flexor retinaculum to reach the hand.

If the medial epicondyle of the humerus is fractured and the nerve passing dorsal to it is injured, which muscle would be most affected?

Flexor carpi ulnaris ---------------- The nerve passing dorsal to the medial epicondyle of the humerus is the ulnar nerve. In the forearm, the ulnar nerve innervates flexor carpi ulnaris and the ulnar side of flexor digitorum profundus. So, flexor carpi ulnaris would be most affected if the ulnar nerve was disrupted. What other symptoms might you see? Paralysis of hand muscles (except for the thenar compartment and the first two lumbricals) and numbness over the ulnar 1.5 digits in the hand! The extensor muscles (extensor digitorum and extensor carpi ulnaris) are in the posterior compartment of the forearm--they are innervated by the radial nerve. Flexor digitorum superficialis is innervated by the median nerve only. Although the ulnar side of flexor digitorum profundus would be impaired following the injury, the radial side of flexor digitorum profundus would still be innervated by the median nerve.

What muscle is supplied by both the median and ulnar nerves?

Flexor digitorum profundus --------------- The radial half of flexor digitorum profundus is supplied by the median nerve, while the ulnar half of flexor digitorum profundus is supplied by the ulnar nerve. The ulnar nerve also supplies flexor carpi ulnaris in the anterior forearm. (Remember--the ulnar nerve is the 1 1/2 nerve--it supplies 1 1/2 muscles in the anterior forearm, and it supplies cutaneous innervation to 1 1/2 fingers on the ulnar side of the hand!) Flexor digitorum superficialis, flexor pollicis longus, and pronator quadratus are innervated by the median nerve.

What muscle is innervated by branches of both the median and ulnar nerves?

Flexor digitorum profundus muscle ---------------- The median and ulnar nerve both innervate flexor digitorum profundus. Flexor carpi ulnaris is innervated by the ulnar nerve only. Flexor digitorum superficialis and flexor pollicis longus are innervated by the median nerve. Pronator quadratus is innervated by the anterior interosseus nerve, which is a branch of the median nerve.

A worker doing repetitive lifting develops an inflammation in the tendon of origin of the extensor carpi radialis brevis muscle, commonly called "tennis elbow". The focal point of pain would most likely be near which palpable bony landmark?

Lateral epicondyle of the humerus ----------- The extensor carpi radialis brevis muscle originates from the common extensor tendon off the lateral epicondyle of the humerus. So, an injury to this tendon would result in pain near the lateral epicondyle. Tennis elbow is due to the repetitive use of superficial extensor muscles of the forearm--the pain is often felt at the lateral epicondyle and it radiates down the posterior surface of the forearm. None of the other bony landmarks are associated with the common extensor tendon, although the medial epicondyle is the origin of the common flexor tendon.

When falling on an outstretched hand, the most commonly dislocated carpal bone is the

Lunate ----------- It is fairly common for the lunate to be dislocated anteriorly--this injury may result from a fall on an extended wrist. The lunate may be pushed out of its place on the floor of the carpal tunnel and move toward the palm of the wrist. This dislocation may compress the median nerve and lead to carpal tunnel syndrome. Also remember: scaphoid, the lateral bone in the proximal row of carpals, is frequently fractured when someone falls on an outstretched wrist! Capitate, hamate, and trapezoid are not commonly injured in these falls.

The anterior interosseous is a branch of which nerve?

Median nerve -------------- The anterior interosseous nerve is a branch of the median nerve that provides motor innervation to the deep muscles in the flexor compartment, including flexor pollicis longus, the radial half of flexor digitorum profundus, and pronator quadratus. The other related nerve to think about is the posterior interosseous nerve, which is the terminal branch of the deep radial nerve. It provides sensory innervation to the wrist area.

During an industrial accident, a sheet metal worker lacerates the anterior surface of his wrist at the junction of his wrist and hand. Examination reveals no loss of hand function, but the skin on the thumb side of his palm is numb. Branches of which nerve must have been severed?

Median nerve ---------------- The median nerve provides sensory innervation to the skin of the radial 3.5 fingers of the palm. So, the patient's loss of cutaneous sensation is suggestive of a median nerve injury. The location of the injury also implies that there has been an injury to the median nerve--this nerve enters the hand by crossing under the flexor retinaculum on the anterior side of the wrist. The lateral and medial antebrachial cutaneous nerves provide cutaneous innervation to the anterior side of the forearm--the symptoms here are not consistent with an injury to these nerves. The radial nerve innervates the radial side of the dorsum of the hand but does not innervate the palmar side of the hand. The ulnar nerve innervates the medial (ulnar) side of both the dorsum and palm of the hand.

A boy fell onto a sharp object and cut his deep radial nerve as it emerged from the supinator muscle. The artery joining it at this point was also injured. The injured artery is the:

Posterior interosseous artery ------------- The deep radial nerve emerges from the supinator muscle and runs in the deep layer of the posterior forearm. It runs next to the posterior interosseous artery, which, along with the anterior interosseous artery, is a branch of the common interosseous artery. The common interosseous artery comes off the ulnar artery to give these two branches that supply the deep arm on the anterior and posterior sides. The ulnar and radial arteries are branches of the brachial artery that run down the ulnar and radial sides of the anterior arm.

Structures within the carpal tunnel include which bursa?

Radial and ulnar bursa

A patient is severely limited in extension at the wrist joint after several months in a cast following a Colles fracture. Which joint would be especially important in therapy to regain full extension?

Radiocarpal joint ------------ The radiocarpal joint is the joint commonly known as the wrist joint--it is a condyloid (oval) type of synovial joint that allows for flexion and extension, abduction and adduction, and circumduction. A Colles fracture is a fracture of the distal end of the radius--this is why this sort of break would limit movement between the radius and carpals. The carpometacarpal joint is found between the distal row of carpals and the metacarpals--these joints are mobile for the thumb and little finger, allowing extension, flexion, abduction, and adduction. However, the carpometacarpal joints are quite immobile for the middle three fingers. The distal radioulnar joint is located between the distal ends of the radius and ulna--this joint allows the radius and ulna to rotate around each other during pronation and supination. The midcarpal joint is located between the proximal and distal row of carpals--this joint is important for flexion and extension of the hand. As for the "ulnocarpal joint," the ulna does not articulate with the carpal bones--it articulates with the distal end of the radius only.

The function of the posterior interosseous nerve is:

Sensory to the wrist joint -------------- The posterior interosseous nerve is the sensory continuation of the deep radial nerve, distal to its motor branches to the extensor muscles (this is at odds with how the posterior interosseous nerve is considered clinically, that is, it is considered synonymous with the deep radial) . It reaches the wrist joint and carpal bones for proprioceptive sense from these structures. Brachioradialis is innervated by the radial nerve, and extensor carpi ulnaris is innervated by the deep radial nerve. There are no parasympathetic nerves in the forearm, and sensory innervation from the dorsum of the forearm is carried by the radial nerve.

After suffering a gunshot wound to the forearm, it was determined that the posterior interosseous nerve was severed. What function was lost?

Sensory to the wrist joint ------------------ The posterior interosseous nerve is the sensory continuation of the deep radial nerve, distal to its motor branches for the extensor muscles. It reaches the wrist joint and carpal bones for proprioceptive sense from these structures. Brachioradialis and extensor carpi radialis longus are innervated by the radial nerve, and extensor carpi radialis brevis is innervated by the deep radial nerve. Flexor digitorum superficialis is innervated by the median nerve. There are no parasympathetic nerves in the limbs or body wall.

In an industrial accident, the artery passing lateral to the pisiform bone is cut. This artery is the

Ulnar artery ------------- The ulnar artery runs on the medial side of the wrist, near pisiform and hamate. It supplies most of the blood to the superficial palmar arterial arch in the hand, but gives a deep ulnar branch to complete the deep palmar arch in the hand. The radial artery runs on the lateral side of the wrist, near scaphoid and trapezium. It supplies most of the blood to the deep palmar arterial arch, but gives off a superficial palmar branch of the radial artery which completes the superficial palmar arch in the hand. The superficial and deep palmar arches are found more distal in the hand, near the heads and bases of the metacarpal bones, respectively.