TBL6 - Intrinsic Muscles, Nerves, and Arteries of Hand

Question 1

What are the muscles involved in flexion, extension, abduction, adduction & opposition of the thumb?

Answer 1

1) Extension: extensor pollicis longus, extensor pollicis brevis, and abductor pollicis longus
2) Flexion: flexor pollicis longus and flexor pollicis brevis
3) Abduction: abductor pollicis longus and abductor pollicis brevis
4) Adduction: adductor pollicis and 1st dorsal interosseous
5) Opposition: opponens pollicis

Question 2

What is the difference between adduction and opposition of the 1st digit?

Answer 2

1) Adduction - a movement of the thumb closer to the sagittal plane
2) Opposition - a complex movement, begins with the thumb in the extended position and initially involves abduction and medial rotation of the 1st meta carpal (cupping the palm) produced by the action of the opponens pollicis at the carpometacarpal joint and then flexion at themetacarpophalangeal joint (touch thumb to pinky)

Question 3

Relate the location of the abductor pollicis brevis, flexor pollicis brevis, opponens pollicis, & adductor pollicis muscles to each other on the anterior aspect of the thumb

Answer 3

First (deepest muscle): Adductor Pollicis muscles
Second: Flexor pollicis brevis
Third: Opponens pollicis
Fourth: Abductor Pollicis brevis

Question 4

What does the abductor digiti minimi do?

Answer 4

The abductor digiti minimi (one of three hypothenar muscles) contributes to abduction of digit 5

Question 5

What nerves innervate the thenar muscles? What nerves innervate the adductor pollicis?

Answer 5

1) The recurrent branch of median nerve (C8, T1) innervates the opponens policis, abductor pollicis brevis, the superficial head of the flexor pollicis brevis
2) The deep branch of ulnar nerve (C8, T1) innervates the deep head of the flexor pollicis brevis
3) The deep branch of ulnar nerve (C8, T1) innervates the oblique head, & the transverse head of the adductor pollicis

Question 6

What is the function of the thenar muscles? What is the function of the adductor pollicis?

Answer 6

1) The opponens pollicis: To oppose thumb, it draws 1st metacarpal medially to center of palm and rotates it medially
2) Abductor pollicis brevis: Abducts thumb; helps oppose it
3) The superficial and deep heads of the flexor pollicis brevis: Flex thumb
4) The oblique and transverse heads of the adductor pollicis: Adducts thumb toward lateral border of palm

Question 7

What innervates the 1st and 2nd lumbrical muscles? What innervates the 3rd and 4th lumbrical muscles? Where do these muscles attach proximally?

Answer 7

1) The 1st and 2nd lumbrical muscles are innervated by the median nerve (C8, T1)
2) The 3rd and 4th lumbrical muscles are innervates by the deep branch of ulnar nerve (C8, T1)
3) The lumbrical muscles attach proximally to the tendons of the FDP (flexor digitorum profundus)

Question 8

Where are the palmar and dorsal interosseous muscles located? Where do their tendons insert?

Answer 8

1) The palmar and dorsal interosseous muscles are located between the metacarpals
2) Their tendons insert into the extensor expansions

Question 9

What nerves innervate the interosseous muscles?

Answer 9

Deep branch of ulnar nerve (C8, T1) innervates all dorsal and palmar interosseous muscles

Question 10

What are the actions of the interosseous muscles at the 2nd, 4th, & 5th digits relative to the 3rd digit?

Answer 10

1) Dorsal interosseous muscles: Abduct 2nd–4th digits from axial line; act with lumbricals in flexing metacarpophalangeal joints and extending interphalangeal joints
2) Palmar interosseous muscles: Adduct 2nd, 4th, and 5th digits toward axial line; assist lumbricals in flexing metacarpophalangeal joints and extending interphalangeal joints; extensor expansions of 2nd–4th digits

Question 11

What is a similar insertion point between interosseous muscle tendons and tendons of the lumbrical muscles? What function does this serve?

Answer 11

1) Like the interosseous muscle tendons, the tendons of the lumbrical muscles insert into the extensor expansions
2) Simultaneous contraction of the two muscle groups flexes the MCP joints and extends the IP joints of the fingers

Question 12

Compare sensory distributions of the median and ulnar nerves on the palmar aspect and dorsum of the hand

Answer 12

1) The ulnar nerve branches into the pinky and medial side of the fourth digit
2) The median nerve branches into the lateral side of the fourth digit in addition to digits 1-3

Question 13

Where does the palmar cutaneous branch of the median nerve pass through in relation to the carpal tunnel & ligament?

Answer 13

The palmar cutaneous branch of the median nerve arises proximal to the carpal tunnel and courses anterior to the palmar carpal ligament into the central palm

Question 14

Define the distribution of the superficial radial nerve on the dorsum of the hand

Answer 14

Radial nerve, superficial branch:

1) Origin: Arises from radial nerve in cubital fossa
2) Course: Courses deep to brachioradialis, emerging from beneath it to pierce the deep fascia lateral to distal radius
3) Distribution: Skin of the lateral (radial) half of dorsal aspect of the hand and thumb, the proximal portions of the dorsal aspects of digits 2 and 3, and of the lateral (radial) half of digit 4

Question 15

How does median nerve injury near the elbow affect the ability to make a fist?

Answer 15

1) When the median nerve is severed in the elbow region, flexion of the proximal interphalangeal joints of the 1st–3rd digits is lost and flexion of the 4th and 5th digits is weakened
2) The ability to flex the metacarpophalangeal joints of the 2nd and 3rd digits is affected because the digital branches of the median nerve supply the 1st and 2nd lumbricals. Thus, when the person attempts to make a fist, the 2nd and 3rd fingers remain partially extended (“hand of benediction”)

Question 16

How does injury of the anterior interosseous nerve alter the ability to make the “okay” sign?

Answer 16

1) When the anterior interosseous nerve is injured, the thenar muscles are unaffected, but paresis (partial paralysis) of the flexor digitorum profundus and flexor pollicis longus occurs
2) When the person attempts to make the “okay” sign, opposing the tip of the thumb and index finger in a circle, a “pinch” posture of the hand results instead owing to the absence of flexion of the interphalangeal joint of the thumb and distal interphalangeal joint of the index finger

Question 17

Where is the ulnar nerve most commonly injured and how is the ability to flex the wrist or make a fist altered? Where does paresthesia occur after the injury?

Answer 17

1) Ulnar nerve injury occurs most commonly where the nerve passes posterior to the medial epicondyle of the humerus
2) An injury to the nerve in the distal part of the forearm denervates most intrinsic hand muscles. Power of wrist adduction is impaired, and when an attempt is made
to flex the wrist joint, the hand is drawn to the lateral side by the FCR (supplied by the median nerve) in the absence of the “balance” provided by the FCU
3) After ulnar nerve injury, the person has difficulty making a fist because, in the absence of opposition, the metacarpophalangeal joints become hyperextended, and he or she cannot flex the 4th and 5th digits at the distal interphalangeal joints when trying to make a fist

Question 18

What are the sensory and motor deficits after injury of the superficial or deep branches of the radial nerve?

Answer 18

1) The radial nerve is usually injured in the arm by a
fracture of the humeral shaft. This injury is proximal to the motor branches to the long and short extensors of the wrist from the (common) radial nerve, and so wrist drop is the primary clinical manifestation of an injury at this level
2) Severance of the deep branch of the radial nerve results in an inability to extend the thumb and the metacarpophalangeal (MP) joints of the other digits
3) Loss of sensation does not occur because the deep branch of the radial nerve is entirely muscular and articular in distribution
4) When the superficial branch of the radial nerve, a cutaneous nerve, is severed, sensory loss is usually minimal. Commonly, a coin-shaped area of anesthesia occurs distal to the bases of the 1st and 2nd metacarpals. The reason the area sensory loss is less than expected is the result of the considerable overlap from cutaneous branches of the median and ulnar nerves

Question 19

How do cubital tunnel syndrome and Klumpke paralysis alter the ability to flex the wrist or make a fist? Where do the lesions produce paresthesia?

Answer 19

1) The ulnar nerve may be compressed (ulnar nerve entrapment) in the cubital tunnel formed by the tendinous arch joining the humeral and ulnar heads of attachment of the FCU. The signs and symptoms of cubital tunnel syndrome are the same as an ulnar nerve lesion in the ulnar groove on the posterior aspect of the medial epicondyle of the humerus
2) Injuries to inferior parts of the brachial plexus (Klumpke paralysis) are much less common. Inferior brachial plexus injuries may occur when the upper limb is suddenly pulled superiorly—for example, when a person grasps something to break a fall, or a baby’s upper limb is pulled excessively during delivery. These events injure the inferior trunk of the brachial plexus (C8 and T1), and may avulse the roots of the spinal nerves from the spinal cord. The short muscles of the hand are affected, and a claw hand results

Question 20

What are typical causes of Carpal tunnel syndrome? Where do paresthesias, hypothesia, or anesthesia occur in the syndrome and which motor functions of the thumb are lost or weakened?

Answer 20

1) Carpal tunnel syndrome results from any lesion that significantly reduces the size of the carpal tunnel or, more commonly, increases the size of some of the nine structures or their coverings that pass through it (e.g., inflammation of synovial sheaths)
2) Fluid retention, infection, and excessive exercise of the fingers may cause swelling of the tendons or their synovial sheaths
3) The median nerve is the most sensitive structure in the tunnel. The median nerve has two terminal sensory branches that supply the skin of the hand; hence paresthesia (tingling), hypoesthesia (diminished sensation), or anesthesia (absence of sensation) may occur in the lateral three and a half digits
4) The palmar cutaneous branch of the median nerve arises proximal to, and does not pass through, the carpal tunnel; thus sensation in the central palm remains unaffected. The nerve also has one terminal motor branch, the recurrent branch, which serves the three thenar muscles

Question 21

What does the ulnar artery become in the hand? Which branch of this artery is continuous with the radial artery?

Answer 21

The ulnar artery continues as the superficial palmer arch and also supplies the deep palmar arch, which is a continuation of the radial artery

Question 22

What do the common palmar digital arteries do? Name the branch of the radial artery that generates the digital arteries of the thumb

Answer 22

1) Common palmar digital arteries branch off of the superficial palmar arterial arch to supply digits 2-5
2) Princeps pollicis is a continuation of the radial artery at the thumb. It descends on palmar aspect of 1st metacarpal; divides at base of proximal phalanx into two branches that run along sides of thumb

Question 23

Where is the best place to stop bleeding after laceration of the palmar arches?

Answer 23

1) Bleeding is usually profuse when the palmar (arterial) arches are lacerated. It may not be sufficient to ligate only one forearm artery when the arches are lacerated, because these vessels usually have numerous communications in the forearm and hand and thus bleed from both ends
2) To obtain a bloodless surgical operating field for treating complicated hand injuries, it may be necessary to compress the brachial artery and its branches proximal to the elbow (e.g., using a pneumatic tourniquet). This procedure prevents blood from reaching the ulnar and radial arteries through the anastomoses around the elbow

Question 24

What causes Raynaud syndrome and if it becomes a chronic condition, how is it treated?

Answer 24

1) Intermittent bilateral attacks of ischemia of the digits, marked by cyanosis and often accompanied by paresthesia and pain, is characteristically brought on by cold and emotional stimuli. The condition may result from an anatomical abnormality or an underlying disease. When the cause of the condition is idiopathic (unknown) or primary, it is called Raynaud syndrome (disease)
2) When treating ischemia resulting from Raynaud syndrome, it may be necessary to perform a cervicodorsal presynaptic sympathectomy (excision of a segment of a sympathetic nerve) to dilate the digital arteries