The hand Flashcards
Essentially, what is the whole function of the upper limb devoted to
“The whole function of the upper limb is devoted to the hand – the rest of the limb allows the hand to grasp objects and manipulate them via four fingers and the opposing thumb”
List the names of the thumb and digits
Thumb Index finger Middle finger Ring finger Little finger
Sumamrise the bones of the wrist and hand
The Radius The Ulna The Carpus (carpal bones); The metacarpal bones The phalanges
What are the proximal row of carpal bones from lateral to medial
Scaphoid (boat shaped)
Lunate (crescent shaped)
Triquetrum (three sided)
Pisiform (sesamoid bone in the tendon of the flexor carpi ulnaris)
What are the distal row of carpal bones from lateral to medial
Trapezium (irregular) - thumb
Trapezoid (four sided) - index finger
Capitate (has a head) - middle finger
Hamate (has a hook) - little and ring fingers
Summarise the articulation of the distal radius and ulna in the wrist joint
The distal ends of the radius and ulna articulate with the proximal row of carpal bones, with the exception of pisiform (a sesamoid bone).
Radius – articulates with scaphoid and lunate
Ulna – doesn’t directly articulate with the carpal bones, it articulates with an articular disc
What separates the anterior and posterior compartments of the forearm?
The interosseous membrane separates the anterior and posterior compartments, and is a site of attachment for muscles in the forearm.
Describe what is meant by the carpal arch
The carpal bones do not lie in a flat plane; rather, they form an arch, whose base is directed anteriorly (Fig. 7.92). The lateral side of this base is formed by the tubercles of the scaphoid and trapezium. The medial side is formed by the pisiform and the hook of the hamate.
The flexor retinaculum attaches to, and spans the distance between, the medial and lateral sides of the base to form the anterior wall of the so-called carpal tunnel. The sides and roof of the carpal tunnel are formed by the arch of the carpal bones.
Essentially, the lateral and medial carpal bones have prominences which give it a gutter shape- important for the formation of the carpal tunnel but also provides bony attachments for the flexor retinaculum.
What are the key features of the proximal row of carpal bones
The pisiform is a sesamoid bone in the tendon of the flexor carpi ulnaris and articulates with the anterior surface of the triquetrum.
The scaphoid has a prominent tubercle on its lateral palmar surface that is directed anteriorly.
What are the key features of the distal row of carpal bones
The trapezium articulates with the metacarpal bone of the thumb and has a distinct tubercle on its palmar surface that projects anteriorly.
The largest of the carpal bones, the capitate, articulates with the base of metacarpal III.
The hamate, which is positioned just lateral and distal to the pisiform, has a prominent hook (hook of hamate) on its palmar surface that projects anteriorly.
How many metacarpals are related to each digit and name them
Each of the five metacarpals is related to one digit:
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Metacarpal I is related to the thumb.
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Metacarpals II to V are related to the index, middle, ring, and little fingers, respectively
What does each metacarpal consist of
Each metacarpal consists of a base, a shaft (body), and distally, a head.
Describe the articulations of each metacarpal
All of the bases of the metacarpals articulate with the carpal bones; in addition, the bases of the metacarpal bones of the fingers articulate with each other.
All of the heads of the metacarpals articulate with the proximal phalanges of the digits. The heads form the knuckles on the dorsal surface of the hand when the fingers are flexed.
Describe the structure of the phalanges
The phalanges are the bones of the digits (Fig. 7.92):
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The thumb has two—a proximal and a distal phalanx.
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The rest of the digits have three—a proximal, a middle, and a distal phalanx.
Each phalanx has a base, a shaft (body), and distally, a head.
Describe the articulations of the phalanges
The base of each proximal phalanx articulates with the head of the related metacarpal bone.
The head of each distal phalanx is nonarticular and flattened into a crescent-shaped palmar tuberosity, which lies under the palmar pad at the end of the digit.
Summarise the fascia of the hand
Palmar fascia (fibrous and dense) Palmar Aponeurosis Fibrous digital sheaths (wrap round bones of digits and the tendons that run with the bone)
Summarise the palmar aponeurosis
overlies the long flexor tendons of the hand
proximally continuous with the flexor retinaculum
distally continuous with the fibrous digital sheaths
thought to be an extension of the palmaris longus tendon- which touches down onto the floor of the flexor retinaculum- which crosses the carpal tunnel
However the palmar aponeurosis is still present even in the absence of the palmaris longus tendon
Provides a thick protection for the vessels, nerves and tendons running through it
What is the palmaris aponeurosis, describe its structure
The palmar aponeurosis is a triangular condensation of deep fascia that covers the palm and is anchored to the skin in distal regions
The apex of the triangle is continuous with the palmaris longus tendon, when present; otherwise, it is anchored to the flexor retinaculum. From this point, fibers radiate to extensions at the bases of the digits that project into each of the index, middle, ring, and little fingers and, to a lesser extent, the thumb.
Describe the two types of fibres found in the palmar aponeurosis and describe the structures that run beneath it
Transverse fibers interconnect the more longitudinally arranged bundles that continue into the digits.
Vessels, nerves, and long flexor tendons lie deep to the palmar aponeurosis in the palm.
Summarise the fibrous digital sheaths
contain the flexor tendons and their synovial sheaths
What is another name for the flexor retinaculum
Transverse carpal ligament.
Name the compartments of the hand
Hypothenar compartment ( digiti minimi- medial prominence as a result of the muscles which act on the little finger).
Central compartment
Thenar compartment ( part of palm close to the thumb- prominence of muscles which act on the thumb- thenar eminence of small intrinsic muscles of the thumb).
Adductor compartment
Which structures form the compartments of the hand
Fibrous septa
Septa – medial and lateral
Septa ; from palmar apponeurosis to
medially : to little finger metacarpal (from medial border of palmar aponeurosis)
laterally : to middle finger metacarpal (from lateral border of palmar aponeurosis).
What structures do septa form within the hand
Channels that contain various structures e.g. long flexors passing from the wrist into the digits and also contain vessels.
Describe the two spaces that the septae in the hand create
Thenar space- anterior to adductor compartment but posterior to lateral border of central compartment
Midpalmar space- posterior to central compartment- not very expansive
These spaces are important in the spread of infection in the hand
Summarise the muscular anatomy of the region
Anterior compartment of the forearm (revision) Superficial compartment Deep compartment Posterior compartment of the forearm (revision) Intrinsic muscles of the hand thenar compartment adductor compartment hypothenar compartment interossei and lumbricals
What is the key role of the forearm muscles
The hand and wrist are operated by “remote control” by the forearm muscles
The forearm muscles attach at the distal humerus as well as the radius and ulna
Flexors (and pronators) anteriorly
Extensors (and supinators) posteriorly
How else can the forearm muscles be functionally divided
As well as flexor and extensor functions, forearm muscles acting on the hand can be divided functionally into:
Muscles acting across the wrist - the “carpi” muscles.
Muscles acting on the digits – the “digitorum” muscles and long muscles of thumb, index finger (extensor) and little finger
List the muscles in the superficial anterior compartment of the forearm
Pronator teres (PT) Flexor carpi radialis (FCR) Palmaris longus (PL) Flexor digitorum superficialis (FDS) Flexor carpi ulnaris (FCU)
List the muscles in the deep anterior compartment of the forearm
Flexor digitorum profundus (FDP) Flexor pollicis longus (FCP) Pronator quadratus (PQ)
What is the proximal attachment for all the muscles in the superficial anterior compartment of the forearm
Common flexor origin (at the medial epicondyle of the humerus)
Which muscles of the anterior compartment do not cross the wrist
Pronator quadratus and pronator teres
State the 12 muscles in the posterior compartment of the forearm
Supinator Brachioradialis Abductor pollicis longus (APL) Extensor pollicis longus (EPL) Extensor pollicis brevis (EPB) Extensor indicis (EI) Extensor digitorum (ED) Extensor digiti minimi (EDM) Extensor carpi radialis longus (ECRL) Extensor carpi radialis brevis (ECRB) Extensor carpi ulnaris (ECU) Extensor retinaculum (not a muscle)
What is a common attachment for most of the muscles in the posterior compartment of the forearm
Common extensor origin (just distal to the lateral epicondyle)
Which muscles have their proximal attachment on the ulna as opposed to the common extensor tendon
Abductor pollicis longus (APL) Extensor pollicis longus (EPL) Extensor pollicis brevis (EPB) Extensor indicis (EI)
Name all the intrinsic muscles of the hand
Thenar · Abductor pollicis brevis (APB) · Flexor pollicis brevis (FPB) · Opponens pollicis (OP) Hypothenar · Abductor digiti minimi (ADM) · Flexor digiti minimi (FDM) · Opponens digiti minimi (ODM) Adductor · Adductor pollicis (AP) Interossei and Lumbricals · Palmar interossei · Dorsal interossei · Lumbricals
Ultimately, what movements are the lumbricals responsible for
Flexion of metacarpophalangeal joint (MCP)
Extension of the interphalangeal joints (IPJs)
Ultimately, what movements are the palmar and dorsal intraossei responsible for
PAD & DAB
Palmar = ADduction of the fingers
Dorsal = ABduction of the fingers
Describe the proximal and distal attachments of the abductor pollicis muscle and its main function
Proximal- Tubercles of scaphoid and trapezium and adjacent flexor retinaculum
Distal- Proximal phalanx and extensor hood of thumb
Function- Abducts thumb at metacarpophalangeal joint
Describe the proximal and distal attchments of the flexor pollicis brevis and its function
Proximal- Tubercle of the trapezium and flexor retinaculum
Distal- proximal phalanx of thumb
Function- Flexes thumb at metacarpophalangeal joint
Describe the attachments of the pollicis opponens and its function
Proximal- Tubercle of trapezium and flexor retinaculum
Distal- Lateral margin and adjacent palmar surface of metacarpal I
Function- Medially rotates the thumb (brings it to the little finger)
What are all the thenar muscles innervated by
Recurrent branch of median nerve (C8-T1)
Describe the attachments of the adductor pollicis
proximal- Transverse head—metacarpal III; oblique head—capitate and bases of metacarpals II and III
Distal- Base of proximal phalanx and extensor hood of thumb
Describe the function and innervation of the adductor pollicis
innervation- Deep branch of ulnar nerve (C8, T1)
Function -adducts thumb
Describe the attachments and function of the abductor digiti minimi
Proximal- Pisiform, the pisohamate ligament, and tendon of flexor carpi ulnaris
Distal- Proximal phalanx little finger
Function- Abducts the little finger at the MCP
Describe the attachments and function of the opponens digit minimi
Proximal- Hook of hamate and flexor retinaculum
Distal- Medial aspect of metacarpal V
Function- Laterally rotates metacarpal V
Describe the attachments and function of the flexor digit minimi
Proximal- Hook of the hamate and flexor retinaculum
Distal- Proximal phalanx of little finger
Function- Flexes little finger at MCP
Describe the innervation of muscles in the hypothenar compartment
Deep branch ulnar nerve (C8-T1)
Describe the attachments of the lumbricals
Proximals- Tendons of flexor digitorum profundus
Distal- Extensor hoods of index, ring, middle, and little fingers
Describe the innervation and function of the lumbricals
Innervation- Medial two by the deep branch of the ulnar nerve; lateral two by digital branches of the median nerve
Function- Flex metacarpophalangeal joints while extending interphalangeal joints
Describe the two different types of lumbricals
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The medial two lumbricals are bipennate and originate from the flexor digitorum profundus tendons associated with the middle and ring fingers and the ring and little fingers, respectively.
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The lateral two lumbricals are unipennate muscles, originating from the flexor digitorum profundus tendons associated with the index and middle fingers, respectively.
The lumbricals pass dorsally around the lateral side of each finger, and insert into the extensor hood (Fig. 7.104). The tendons of the muscles are anterior to the deep transverse metacarpal ligaments.
Explain why the function of the lumbricals is so unique
The lumbricals are unique because they link flexor tendons with extensor tendons. Through their insertion into the extensor hoods, they participate in flexing the metacarpophalangeal joints and extending the interphalangeal joints.
Describe the attachments of the dorsal interossei muscles and its function
Proximal- Adjacent sides of metacarpals
Distal- Extensor hood and base of proximal phalanges of index, middle, and ring fingers
Function- Abduction of index, middle, and ring fingers at the metacarpophalangeal joints
Describe the attachments of the palmar interossei muscles and its function
Proximal- Sides of metacarpals
Distal- Extensor hoods of the thumb, index, ring, and little fingers and the proximal phalanx of thumb
Function- Adduction of the thumb, index, ring, and little fingers at the metacarpophalangeal joints
Describe the innervation of the interossei muscles
Deep branch of ulnar nerve (C8, T1)
Summarise the dorsal interossei muscles
Dorsal interossei are the most dorsally situated of all of the intrinsic muscles and can be palpated through the skin on the dorsal aspect of the hand (Fig. 7.100). There are four bipennate dorsal interosseous muscles between, and attached to, the shafts of adjacent metacarpal bones (Fig. 7.100). Each muscle inserts both into the base of the proximal phalanx and into the extensor hood of its related digit.
Where are the dorsal interossei muscles situated
The tendons of the dorsal interossei pass dorsal to the deep transverse metacarpal ligaments:
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The first dorsal interosseous muscle is the largest and inserts into the lateral side of the index finger.
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The second and third dorsal interossei insert into the lateral and medial sides, respectively, of the middle finger.
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The fourth dorsal interosseous muscle inserts into the medial side of the ring finger.
In addition to generating flexion and extension movements of the fingers through their attachments to the extensor hoods, the dorsal interossei are the major abductors of the index, middle, and ring fingers, at the metacarpophalangeal joints
What is important to remember about abduction and adduction of the little finger
The middle finger can abduct medially and laterally with respect to the long axis of the middle finger and consequently has a dorsal interosseous muscle on each side. The thumb and little finger have their own abductors in the thenar and hypothenar muscle groups, respectively, and therefore do not have dorsal interossei.
Summarise the palmar interossei muscles
The three (or four) palmar interossei are anterior to the dorsal interossei, and are unipennate muscles originating from the metacarpals of the digits with which each is associated
The palmar interossei adduct the thumb, index, ring, and little fingers with respect to a long axis through the middle finger. The movements occur at the metacarpophalangeal joints. Because the muscles insert into the extensor hoods, they also produce complex flexion and extension movements of the digits
Describe each of the palmar interossei muscles
The first palmar interosseous muscle is rudimentary and often considered part of either the adductor pollicis or the flexor pollicis brevis. When present, it originates from the medial side of the palmar surface of metacarpal I and inserts into both the base of the proximal phalanx of the thumb and into the extensor hood. A sesamoid bone often occurs in the tendon attached to the base of the phalanx.
The second palmar interosseous muscle originates from the medial surface of metacarpal II and inserts into the medial side of the extensor hood of the index finger.
The third and fourth palmar interossei originate from the lateral surfaces of metacarpals IV and V and insert into the lateral sides of the respective extensor hoods.
Like the tendons of the dorsal interossei, the tendons of the palmar interossei pass dorsal to the deep transverse metacarpal ligaments
Describe the two heads of the adductor pollicis muscles converge and describe its role in gripping
The two heads converge laterally to form a tendon, which often contains a sesamoid bone, that inserts into both the medial side of the base of the proximal phalanx of the thumb and into the extensor hood
The adductor pollicis is a powerful adductor of the thumb and opposes the thumb to the rest of the digits in gripping
When is the action of the abductor pollicis brevis most apparent
The abductor pollicis brevis abducts the thumb, principally at the metacarpophalangeal joint. Its action is most apparent when the thumb is maximally abducted and the proximal phalanx is moved out of line with the long axis of the metacarpal bone
What may the tendon of the flexor pollicis brevis containn
The tendon often contains a sesamoid bone.
Why is the rotation of the little finger much less apparent than that of the thumb
The opponens digiti minimi rotates metacarpal V toward the palm; however, because of the simple shape of the carpometacarpal joint and the presence of a deep transverse metacarpal ligament, which attaches the head of metacarpal V to that of the ring finger, the movement is much less dramatic than that of the thumb
List the different ranges of motion possible in the thumb and describe the muscles involved
Abduction
APL, APB
Adduction
Adductor pollicis, first dorsal interosseous
Extension
EPL, EPB, APL
Flexion
FPL, FPB
Opposition
Opponens pollicis
Summarise the arrangement of the interossei and relate this to the movements they produce
Arranged along the axial line of the hand- which runs through the middle metacarpal
Dorsal- tendons attach to side towards axial line- abduct
Palmar- tendons attach away from axial line- adduct
Why is adductor pollicis in a different compartment to the other pollicis muscles?
It is innervated by the ulnar nerve whereas the thenar muscles are all innervated by the median nerve
How many lumbricals, dorsal interossei and palmar interossei are there?
Lumbricals – 4
Dorsal interossei – 4
Palmar interossei - 3
With relation to the attachments of the palmar interossei- explain why the middle finger remains still while the other fingers adduct
Palmar interossei are attached to the extensor expansion away from the axial line (there is no palmar interossei attached to the middle finger)
The cause adduction of the fingers whilst the middle finger remains still
What are the two groups of tendons in the hand
Anterior tendons
Posterior tendons
Summarise the anterior tendinous anatomy of the hand
Fibrous digital sheath
Osseo-fibrous tunnels
In the tunnels run the long flexor tendons and their synovial sheaths
Annular and cruciform pulleys
Outline the passage of the four FDP and FDS tendons
FDP and FDS tendons pass in the carpal tunnel beneath the flexor retinaculum
…enter a common synovial sheath
…enter a digital synovial sheath, within its own fibrous digital sheath
Little finger and thumb sheaths continuous
Then the tendons going to the middle three fingers enter digital synovial sheaths
FDS splits around FDP
FDS to middle phalanx, FDP to distal phalanx (FDP travels further than FDS)
Describe how the little finger and thumb sheaths are different to the other three fingers
Their digital synovial sheaths are continuous with the common synovial sheath
Describe the structure of the fibrous digital sheaths
After exiting the carpal tunnel, the tendons of the flexor digitorum superficialis and profundus muscles cross the palm and enter fibrous sheaths on the palmar aspect of the digits (Fig. 7.98). These fibrous sheaths:
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begin proximally, anterior to the metacarpophalangeal joints, and extend to the distal phalanges;
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are formed by fibrous arches and cruciate (cross-shaped) ligaments, which are attached posteriorly to the margins of the phalanges and to the palmar ligaments associated with the metacarpophalangeal and interphalangeal joints; and
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hold the tendons to the bony plane and prevent the tendons from bowing when the digits are flexed.
Within each tunnel, what are the tendons surrounded by
Within each tunnel, the tendons are surrounded by a synovial sheath. The synovial sheaths of the thumb and little finger are continuous with the sheaths associated with the tendons in the carpal tunnel
Describe the ligaments of the fibrous digital sheaths
Tough ligamentous structures (anular and cruciate ligaments) hold tendon close to digit Palmar ligaments (thickened plates) at joint regions Efficiently holds tendon close to the digits- so when digits move- you don't get bowing of the tendons.
Describe how the arrangement of the digital fibrous sheaths, synovial sheaths and osseo-fibrous sheaths.
The entire thing is an osseo-fibrous sheath
This contains digital fibrous sheaths, which, in turn, contain synovial sheaths
Summarise the posterior tendinous anatomy of the hand
Extensor retinaculum (not as tough as flexor)
Synovial tendon sheaths
Inter-tendinous bands
Extensor expansions
Lumbricals and interossei attach to the expansions
Extensor digitorum, EI, EDM
Describe the formation of the extensor hoods
The tendons of the extensor digitorum and extensor pollicis longus muscles pass onto the dorsal aspect of the digits and expand over the proximal phalanges to form complex “extensor hoods” or “dorsal digital expansions” (Fig. 7.99A). The tendons of the extensor digiti minimi, extensor indicis, and extensor pollicis brevis muscles join these hoods.
Describe the structure of the extensor hoods
Each extensor hood is triangular, with:
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the apex attached to the distal phalanx,
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the central region attached to the middle phalanx (index, middle, ring, and little fingers) or proximal phalanx (thumb), and
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each corner of the base wrapped around the sides of the metacarpophalangeal joint—in the index, middle, ring, and little fingers, the corners of the hoods attach mainly to the deep transverse metacarpal ligaments; in the thumb, the hood is attached on each side to muscles.
What structures attach to the extensor hoods
In addition to other attachments, many of the intrinsic muscles of the hand insert into the free margin of the hood on each side. By inserting into the extensor hood, these intrinsic muscles are responsible for complex delicate movements of the digits that could not be accomplished with the long flexor and extensor tendons alone.
In the index, middle, ring, and little fingers, the lumbrical, interossei, and abductor digiti minimi muscles attach to the extensor hoods. In the thumb, the adductor pollicis and abductor pollicis brevis muscles insert into and anchor the extensor hood.
Describe the importance of the extensor hoods
Because force from the small intrinsic muscles of the hand is applied to the extensor hood distal to the fulcrum of the metacarpophalangeal joints, the muscles flex these joints (Fig. 7.99B). Simultaneously, the force is transferred dorsally through the hood to extend the interphalangeal joints. This ability to flex the metacarpophalangeal joints, while at the same time extending the interphalangeal joints, is entirely due to the intrinsic muscles of the hand working through the extensor hoods. This type of precision movement is used in the upstroke when writing a t
What is important to remember about the FDP tendons
Goes to distal phalanx- but needs to become superficial to do so and so needs to pierce the FDS
What is the function of the digital synovial sheaths
To lubricate the tendons and to prevent friction when they move
How can the forearm muscles exert a lot of power
Attach to proximal parts of the forearm- to prevent muscles bulking at the wrist- also allowing for finer control of hand movements.
Describe the type of skin found on the palms and soles
Plantar-palmar skin- thick- no hair
Histologically- outer dead layer (cornified layer)- much thicker- needs protection as it is exposed to a lot of physical insult.
