The Hand
Which hypothenar muscle can abduct the little finger?
Abductor digiti minimi
What is the effect of a C8-T1 paralysis on the dorsal interossei muscles (i.e. how will the hand appear)?
Each finger is in contact with the finger or fingers beside it. This is because paralysis of the dorsal interossei has resulted in an inability to spread apart the index, middle, and ring fingers (you cannot abduct the fingers if the dorsal interossei is paralyzed!).
Which thenar muscle can flex the thumb?
Flexor pollicis brevis
The superficial palmar arch generally anastomoses in the lateral half of the palm with which branch of which artery?
The superficial branch of the radial artery
During each of the following movements, is there more contribution from the midcarpal joint or the wrist joint? >when the hand is flexed vs. >when the hand is extended
When the hand is *flexed* at the wrist, more movement occurs at the *midcarpal joint* than at the wrist joint. By contrast, when the hand is *extended* at the wrist, more movement occurs at the *wrist joint* than at the midcarpal joint.
This card shows a drawing of a coronal section of the bones and joints in the wrist region. The synovial cavity of the distal radioulnar joint is colored red. Observe that a disc of ___________ cartilage borders part of the distal radioulnar joint's synovial cavity.
disc of articular cartilage The radius and ulna articulate with each other, and the ulna also articulates with the articular disc at this joint.
In the palmar aspect of the wrist, there is a thickened band of deep fascia called the ________________________. This deep fascia overlies a tunnel-like space in the anterior part of the wrist that extends from the anterior forearm into the palm of the hand. This tunnel-like space is called the ____________________.
flexor retinaculum; carpal tunnel The flexor retinaculum is attached medially to the hamate and pisiform and laterally to the scaphoid and trapezium.
Read description of the cutaneous sensory nerve fibers distribution to the skin on the palmar and dorsal surfaces of the hand
see image of this distribution on the next slide
There are three main types of bones in the hand. The bones of the wrist are called _____________, the bones in the palm of the hand are called ________________, and the bones in the digits are called ________________.
wrist bones = carpals palm bones = metacarpals finger bones = phalanges
A severe injury to the ulnar nerve in the axilla, arm or forearm will cause which muscles to be paralyzed in the hand? What is the name of the hand abnormality that will result?
Adductor pollicis, the 3rd and 4th lumbricals, all the palmar (3) and dorsal interossei (4), abductor digiti minimi, flexor digiti minimi, and opponens digiti minimi --> 13 muscles in total! Hand abnormality = Claw Hand
For the following tendons that act on the fingers, say which motion each performs (and at which joint/s) and which spinal nerve provides the main innervation: Extensors >extensor digitorum >extensor indices >extensor digiti minimi Flexors >flexor digitorum superficialis >flexor digitorum profundus
Extensors (C7 and a little C8): >extensor digitorum (C7): extend the finger's proximal phalanx at its metacarpophalangeal joint, the finger's middle phalanx at its proximal interphalangeal joint, and the finger's distal phalanx at its distal interphalangeal joint >extensor indices (C7): same as above; but acts on index finger alone >extensor digiti minimi (C7): same as above, but acts on pinky alone Flexors (C8 and a little C7): >flexor digitorum superficialis (C8): flexes each middle phalanx at the proximal interphalangeal joint (PIP) >flexor digitorum profundus (C8): flexes each distal phalanx at the distal interphalangeal joint (DIP)
What is the first step of the Allen test?
Each artery is tested separately as follows: The patient is asked to make a tight fist. The making of a tight fist increases external pressure upon the capillary beds within the skin of the palm and thereby empties them of much of their blood content.
The Lumbricals The 4 lumbricals are numbered 1 through 4. >The 1st lumbrical is associated with the index finger, the 2nd lumbrical with the middle finger, the 3rd lumbrical with the ring finger, and the 4th lumbrical with the little finger. >Each lumbrical originates within the palm from one or two tendons of flexor digitorum profundus and inserts on the lateral side of a finger's extensor expansion. What motion do the lumbricals perform? The 1st and 2nd lumbrical are innervated by what nerve? The 3rd and 4th?
Each lumbrical can flex its finger at the metacarpophalangeal joint and extend its finger at the interphalangeal joints (like a small child does when s/he learns to wave goodbye). The 1st and 2nd lumbricals are innervated by the median nerve, and the 3rd and 4th lumbricals are innervated by the deep branch of the ulnar nerve.
Which hypothenar muscle can flex the little finger at its metacarpophalangeal joint?
Flexor digiti minimi
How are the dorsal interossei, the lumbricals, and the palmar interossei all related to one another in terms of location?
From the back of the hand to the palm they are stacked in this order: Dorsal interossei Lumbricals Palmar interossei
What occurs when innervation from C8 and T1 is totally lost?
In instances in which all the C8 and T1 nerve fibers in the lower trunk are lost (Fig. D), the *complete denervation of the lumbrical in each finger results in hyperextension of the finger at its metacarpophalangeal joint (due to the activity of the extensor muscles acting across the metacarpophalangeal joint)*. The hyperextension of each finger at its metacarpophalangeal joint stretches the flexor digitorum profundus and superficialis tendons in the finger to the extent that the tendons can no longer accommodate full extension of the finger at its interphalangeal joints. *Consequently, the finger becomes flexed at its interphalangeal joints.*
See a radiograph of the hand that highlights the carpometacarpal joint (a synovial joint) of the thumb. In the carpometacarpal joint of the thumb, which bone of the wrist articulates with the first (i.e. the thumb's) metacarpal?
In the carpometacarpal joint of the thumb, the trapezium articulates with the base of the 1st metacarpal.
This card shows a drawing of a coronal section of the wrist region in which the synovial cavity of the wrist joint is colored yellow. In the wrist joint, the distal end of the radius and the articular disc of the distal radioulnar joint articulate with which three bones of the wrist? Which is left out?
In the wrist joint, the *distal end of the radius and the articular disc* of the distal radioulnar joint articulate with the *scaphoid, lunate, and triquetrum.* Observe that the pisiform does not contribute an articular surface to the wrist joint.
The muscles which may be partially or completely paralyzed by excessive traction on the lower parts of the brachial plexus include the upper limb muscles whose sole or major innervation is provided by C8 and/or T1 nerve fibers. If significant damage is sustained by both C8 and T1 nerve fibers, the most important muscular actions compromised or lost by such damage are those of the ???
Intrinsic hand muscles This is because C8 and T1 are the only spinal nerves that provide innervation for not only the intrinsic hand muscles innervated by the deep branch of the ulnar nerve but also the intrinsic hand muscles innervated by the median nerve.
Adductor pollicis What motions does the adductor pollicis perform? What is its innervation and spinal nerves?
It can both adduct and flex the thumb. It is innervated by the *deep branch of the ulnar nerve* and receives nerve fibers from C8 and T1 only.
BLOOD SUPPLY TO THE HAND The blood supply of the hand is mainly provided by two arterial arches which course through the palm of the hand called what?
The superficial palmar arch and the deep palmar arch Whereas the superficial palmar arch lies anterior to the tendons of flexor digitorum profundus and superficialis, the deep palmar arch lies posterior to these tendons
Which hypothenar muscle can oppose the little finger?
Opponens digiti minimi The opposition action of opponens digiti minimi flexes and laterally rotates the 5th metacarpal at its carpometacarpal joint. This action deepens the hollow of the palmar surface of the hand
Which thenar muscle is the sole prime mover for opposition of the thumb (sweeping the thumb over the palm)?
Opponens pollicis
Which thenar muscle can abduct the thumb?
Abductor pollicis brevis
In addition to the 3 muscles of the thenar eminence, what is the last intrinsic muscle of the hand that acts on the thumb?
Adductor pollicis Adductor pollicis is not considered to be a thenar muscle.
The carpals (wrist bones) are traditionally divided into two rows (a proximal row and a distal row) of four carpals each. Proceeding from the most lateral carpal to the most medial carpal in the proximal row (that is, the row nearest the distal ends of the radius and ulna), the carpals of the proximal row (4) are named what? The carpals of the distal row (4) are named what?
SOME LOVERS TRY POSITIONS THAT THEY CANT HANDLE From most lateral to most medial, the carpals of the proximal row are named *scaphoid, lunate, triquetrum, and pisiform*. In the wrist, pisiform lies anterior to triquetrum. Proceeding from the most lateral carpal to the most medial carpal of the distal row, the carpals of the distal row are named *trapezium, trapezoid, capitate, and hamate*. The images of trapezium and trapezoid partially overlap each other in an AP radiograph of the hand.
The deep palmar arch generally anastomoses in the medial half of the palm with which branch of which artery?
The deep branch of the ulnar artery
The Palmar Interossei How many are there?
3! The 3 palmar interossei are numbered 1 through 3. The 1st palmar interosseous is associated with the medial side of the index finger, the 2nd palmar interosseous with the lateral side of the ring finger, and the 3rd palmar interosseous with the lateral side of the little finger. Each palmar interosseous originates from the metacarpal of a finger. The tendon of insertion passes anterior to the side of a finger's metacarpophalangeal joint before inserting onto the same side of the finger's extensor expansion
Upon entering the palmar aspect of the hand, the median nerve gives rise to the nerves that innervate ___ (#) of the intrinsic muscles of the hand.
5
Review: Which spinal nerve controls each one of these movements? >Abduction of the arm at the shoulder >Flexion of the forearm at the elbow >Extension of the forearm at the elbow >Flexion of the fingers >Abduction of the fingers
>Abduction of the arm at the shoulder: C5 >Flexion of the forearm at the elbow: C6 >Extension of the forearm at the elbow: C7 >Flexion of the fingers: C8 >Abduction of the fingers: T1
What action do each of the tendons that travel through the carpal tunnel perform? >flexor pollicis longus >flexor digitorum superficialis >flexor digitorum profundus
>flexor pollicis longus: flexes the thumb at its only interphalangeal joint >flexor digitorum superficialis: flexes each finger at the proximal interphalangeal joint (PIP) >flexor digitorum profundus: flexes each finger at the distal interphalangeal joint (DIP)
How many muscles (called the intrinsic hand muscles) lie exclusively within the hand? What nerve innervates the majority of these muscles (13 of them)? What nerve innervates the other 5 muscles?
All except 5 of the intrinsic hand muscles are innervated by a branch of the ulnar nerve called the *deep branch of the ulnar nerve.* The 5 remaining intrinsic hand muscles are innervated by the *median nerve*
Where is the midcarpal joint? Which bones of the wrist contribute surfaces to it? Which one does not?
All of the carpals, except for pisiform, contribute articular surfaces to the midcarpal joint.
Emergency room tests of median and ulnar nerve supply to the intrinsic hand muscles: How is the median nerve supply to the intrinsic hand muscles tested? The ulnar nerve supply?
Median nerve: A quick test of the median nerve's motor supply within the hand is to request the patient to touch the base of the little finger with the tip of the thumb. This maneuver cannot be executed if opponens pollicis is paralyzed. Ulnar nerve: A quick test of the ulnar nerve's motor supply within the hand is to request the patient to clench a piece of paper tightly between the middle and ring fingers as you attempt to dislodge the paper. The paper cannot be tightly clenched between the fingers if the palmar and dorsal interossei are paralyzed.
The flexor retinaculum borders the carpal tunnel ________________, while the carpals of the wrist border the carpal tunnel medially, posteriorly, and laterally.
anteriorly
In the hand, how can we test the: >median nerve supply >ulnar nerve supply >superficial radial nerve supply
A quick test of the integrity of median nerve supply is to ascertain whether the patient can sense a probe lightly applied to the palmar surface of the index finger. A quick test of the integrity of ulnar nerve supply is to ascertain whether the patient can sense a probe lightly applied to the palmar surface of the little finger. And a quick test of the integrity of superficial radial nerve supply is to ascertain whether the patient can sense a probe lightly applied to the dorsal, or posterior, surface of the skin fold between the bases of the thumb and index finger.
Which spinal nerve fibers provide the nerves that serve these intrinsic hand muscles?
C8 and T1 Thus a severe lower brachial plexus injury will affect these muscles!
See how a hand appears/what happens to the hand when the thenar eminence muscles are paralyzed What is this appearance of the hand often called?
Called *ape hand* Thumb becomes laterally rotated excessively at the carpometacarpal joint. Thenar eminence becomes flattened due to atrophy.
Entrapment or compression of the median nerve as it travels through the carpal tunnel can produce damage due to mechanical injury and/or ischemia. In cases of insidious onset, pain of the thumb, index finger and middle finger, as well as sensory deficits on the palmar surfaces of these digits are usually the *typical initial neurological symptoms.* MOTOR DEFICITS OCCUR *AFTER* THESE SENSORY DISTURBANCES. A condition which produces these sensory and motor issues is called __________________.
Carpal tunnel syndrome
Most brachial plexus injuries involve either an injury to the upper parts of the plexus or an injury to the lower parts of the plexus. An injury to the lower part of the plexus (C8 and T1) will result in a motor deficit called what? What type of accident results in this injury?
Klumpke's palsy Most severe lower brachial plexus injuries produce Klumpke's palsy. The mechanism of injury that most commonly produces Klumpke's palsy is excessive traction on the lower parts of the brachial plexus. Instances in which such an injury is sustained include accidents in which a person falling from a significant height grasps at some object to break the fall and in the process hyperabducts the arm.
The Lumbricals (contd) The lumbricals are the only upper limb muscles whose chief action is to flex each finger at its _________________ joint. The lumbricals are innervated by nerve fibers that arise from ____ and ____ only, with the majority arising from ____.
Metacarpophalangeal joint; C8 and T1 with T1 predominance. Under normal, resting conditions, the activities of the muscles identified here in slide 20 keep the phalanges of the fingers only partially flexed at their metacarpophalangeal and interphalangeal joints
How do the normal resting positions of the phalanges of a finger become distorted if a person suffers a lower brachial plexus injury in which there is loss of C8 and T1 nerve fibers in the lower trunk of the brachial plexus?
Of the muscles that can flex or extend the phalanges of a finger, the extensor muscles (extensor digitorum, extensor indicis, and extensor digiti minimi) are weakened the LEAST by a loss of nerve fibers in the lower trunk of the brachial plexus because the majority of the nerve fibers that innervate these muscles are C7 nerve fibers that extend through the middle trunk of the brachial plexus. In contrast, the flexor muscles (flexor digitorum profundus, flexor digitorum superficialis, and the lumbricals) are weakened the most because the majority of the nerve fibers that innervate these muscles are either C8 or T1 nerve fibers. In each finger, the lumbrical suffers the greatest loss of innervation because it is innervated by C8 and T1 nerve fibers only; the flexor digitorum muscles retain some of their innervation via C7 nerve fibers.
Common cutaneous sensory nerve fiber distribution - image
Palmar surface of the lateral three and a half fingers/digits: supplied by a branch of the median nerve AFTER it passes through the carpal tunnel Palmar surface of the lateral 2/3rds of the palm: supplied by a branch of the median nerve BEFORE it passes through the carpal tunnel
_____ is the spinal nerve that provides most of the nerve fibers to the muscles that abduct the fingers (the dorsal interossei and abductor digiti minimi) and the muscles that adduct the fingers (the palmar interossei).
T1 Therefore, T1 is the spinal nerve that provides most of the nerve fibers that control abduction and adduction of the fingers at their metacarpophalangeal joints.
During each of the following movements, is there more contribution from the midcarpal joint or the wrist joint? >abduction of the hand vs. >adduction of the hand
The *midcarpal joint* provides almost all the carpal movements for *abduction* of the hand The *wrist joint* provides almost all the movements for *adduction* of the hand.
THE INTRINSIC HAND MUSCLES See the 6 ways/groups we can divide the 18 muscles of the hand into
The 18 intrinsic hand muscles can be divided into 6 groups: >the 4 lumbricals >the 4 dorsal interossei >the 3 palmar interossei >the 3 muscles of the thenar eminence >adductor pollicis >the 3 muscles of the hypothenar eminence.
What is the Allen test? How is it done? What is it used for?
The Allen test is a physical test which can determine whether the ulnar and radial arteries are each a chief source of blood supply to a patient's hand. In the critical care setting, an arterial line is sometimes put into the radial artery near the wrist to monitor blood pressure and blood gases. The Allen test must be performed prior to placing the arterial line in the radial artery. The reason for the absolute necessity for performing the Allen test is because the ulnar and radial arteries are not always each a chief source of blood supply to the hand. If, for example, the ulnar artery cannot adequately supply a patient's hand in the absence of supply by the radial artery, and the patient's radial artery becomes blocked following the placement of an arterial line, the patient's hand would no longer receive adequate blood supply.
What nerve and what three tendons are transmitted through the carpal tunnel?
The carpal tunnel transmits the median nerve and the insertion tendons of three anterior forearm muscles (flexor pollicis longus, flexor digitorum superficialis, and flexor digitorum profundus) from the anterior forearm into the palmar aspect of the hand
The Palmar Interossei cont'd What is the innervation of these muscles? Nerve fibers? What movements do they control (acronym = PAD)? How would paralysis of these muscles affect the hand?
The collective actions of the palmar interossei can be presented by the acronym PAD. Starting with the fingers abducted, each Palmar interosseous can ADduct its finger. Each palmar interosseous can also flex the finger at its metacarpophalangeal joint and extend the finger at its interphalangeal joints (like the dorsal interossei and the lumbricals). The palmar interossei are all innervated by the deep branch of the ulnar nerve and receive nerve fibers from C8 and T1 only. Paralysis of the palmar interossei results in an inability to squeeze the fingers together along their sides.
The Dorsal Interossei Muscles The 4 dorsal interossei are numbered 1 through 4. The 1st dorsal interosseous is associated with the lateral side of the index finger, the 2nd dorsal interosseous with the lateral side of the middle finger, the 3rd dorsal interosseous with the medial side of the middle finger, and the 4th dorsal interosseous with the medial side of the ring finger. Each dorsal interosseous had two heads of origin; the heads originate from the contiguous surfaces of two adjacent metacarpals. The two heads have a common tendon of insertion that passes anterior to the side of a finger's metcarpophalangeal joint before inserting onto the same side of the finger's extensor expansion. What is the innervation of these muscles? Nerve fibers? What movements do they control (acronym = DAB)?
The dorsal interossei are all innervated by the deep branch of the ulnar nerve and receive nerve fibers from C8 and T1 only The collective actions of the dorsal interossei can be described by the acronym DAB. Starting with the hand in the anatomical position, *each Dorsal interosseous can ABduct its finger (spread the fingers apart). Each dorsal interosseous can also flex the finger at its metacarpophalangeal joint and extend the finger at its interphalangeal joints (like the lumbricals)*. DORSAL INTEROSSEI ARE SEEN ON THE POSTERIOR HAND
see image of the back and front of the dermatome man's arms and hands ... which spinal nerves supply which parts of the hands?
The drawings in slide 45 show the spinal nerves that provide cutaneous sensory nerve fibers to the skin of the hand's digits. C6 provides most of the sensory innervation to the skin of the thumb, C7 provides most of the sensory innervation to the skin of the index, middle, and ring fingers, and C8 provides most of the sensory innervation to the skin of the little finger.
What is the second step of the Allen test?
The examiner applies pressure to both the ulnar and radial arteries at their palpation sites in the anterior forearm. This significantly blocks the blood flow into the palmar arches.
What is the last step of the Allen test?
The examiner releases the pressure on one artery and ascertains whether color is restored to the palmar surface within 2 to 4 seconds. The return of color indicates that the artery is a chief source of blood supply to the hand. The average velocity of blood flow in a capillary is 1 mm/sec, and the average length of blood capillary is 1 mm. Consequently, a subcutaneous blood capillary bed emptied of much of its blood content should, under normal conditions, become filled with blood within about 2 seconds after blood supply is restored. The entire test is then repeated with the other artery to ascertain that both arteries are supplying the palmar arches
The Hypothenar Eminence What is it? What three muscles make it up and what are their actions? What is the innervation of these muscles?
The hypothenar eminence is the mound of soft tissue in the palm of the hand that overlies the 5th metacarpal. The 3 muscles of the hypothenar eminence (abductor digiti minimi, flexor digiti minimi, and opponens digiti minimi) form most of the substance of the hypothenar eminence. The 3 muscles of the hypothenar eminence are all innervated by the deep branch of the ulnar nerve and receive nerve fibers from C8 and T1 only. The hypothenar muscles consist of a muscle that can abduct the little finger, a muscle that can flex the little finger at its metacarpophalangeal joint, and a muscle that can oppose the little finger.
What are the major branches of the superficial palmar arch and what do they supply?
The major branches of the superficial palmar arch are the *digital arteries* that supply the fingers
What is the third step of the Allen test?
The patient is asked to unclench the fist, exposing the blanched pallor of the palmar surface
Description of the image from the last card
The photograph shows a woman's left hand in which all the intrinsic hand muscles are paralyzed and atrophied; the muscles atrophied following their denervation. Th One of the more prominent features of the woman's hand is that all 4 fingers are hyperextended at their metacarpophalangeal joints and fully flexed at their interphalangeal joints. This combination of hyperextension at the metacarpophalangeal joints and full flexion at the interphalangeal joints is *due to the paralysis of all 4 lumbricals*. Lumbricals get paralyzed --> extensors are thus able to take over and will hyperextend the metacarpophalangeal joints --> this then causes hyperflexion of the interphalangeal joints as the flexors are too stretched out.
What are the three regions of a single metacarpal (palm bone) called?
The proximal end of each metacarpal is called its base. Its distal end is called its head. The midregion of each metacarpal is called its shaft.
Which artery is the deep palmar arch a direct continuation of?
The radial artery in the hand The radial artery gives rise to a superficial branch upon entering the hand, and then curves medially through the palm as the deep palmar arch
What is the specific branch of the median nerve that innervates the muscles of the thenar eminence? What spinal nerve roots feed it?
The recurrent branch of the median nerve. The recurrent branch arises from the median nerve distal to the carpal tunnel. It first curves forward and laterally and then backward as it approaches the thenar muscles. The recurrent branch of the median nerve transmits nerve fibers from C8 and T1 only.
The Thenar Eminence What is it? What three muscles make it up and what are their actions? What is the innervation of these muscles?
The thenar eminence is the mound of soft tissue in the palm of the hand that overlies the 1st metacarpal. The 3 muscles of the thenar eminence (abductor pollicis brevis, flexor pollicis brevis, opponens pollicis) form most of the substance of the thenar eminence. The muscles of the thenar eminence are all innervated by the *median nerve*. You should take note at this point that you now know the 5 intrinsic muscles of the hand that are innervated by the median nerve: *the 1st and 2nd lumbricals and the 3 muscles of the thenar eminence.* The muscles of the thenar eminence consist of a muscle that can abduct the thumb, a muscle that can flex the thumb, and a muscle that can oppose the thumb.
What are the three regions of a single phalanx (finger bone) called? How many phalanges are in each digit? What are the names of each phalanx in a digit?
The thumb has only 2 phalanges: a proximal phalanx and a distal phalanx. Each finger has 3 phalanges: a proximal phalanx, a middle phalanx, and a distal phalanx. The proximal end of each phalanx is called its base; its distal end is called its head. The midregion of each phalanx is called its shaft.
The superficial palmar arch is the direct continuation of which artery in the hand? Where does the deep palmar arch originate?
The ulnar artery The ulnar artery enters the hand by passing superficial to the flexor retinaculum. *The ulnar artery gives off a deep branch (NOT THE DEEP PALMAR ARCH, ANOTHER DEEP BRANCH) immediately distal to the flexor retinaculum, and then curves laterally through the palm as the superficial palmar arch.*
The ulnar nerve DOES NOT travel through the carpal tunnel... where does it travel? Where does it split into two branches and what are these branches names? What does each branch innervate?
The ulnar nerve extends from the anterior forearm into the hand by extending distally superficial to the flexor retinaculum. Upon entering the palm of the hand, the ulnar nerve divides into two branches: a deep branch and a superficial branch. The deep branch gives rise to the nerves that innervate 13 of the intrinsic muscles of the hand; the superficial branch gives rise to cutaneous sensory nerves.
Which major artery of the thumb arises from the radial artery in the hand? Which major artery of the index finger arises from the radial artery in the hand?
Thumb: princeps pollicis Index finger: radialis indicis
