The Thumb

combined ____ joint ________ and _______ produces _______ joint reposition

CMC extension adduction CMC

Extends first CMC joint in plane of palm. Its name reflects the fact that it produces frontal plane motion in anatomical position. Innervated by the radial nerve.

abductor pollicis longus

The ___________ is a prime _________ of the CMC joint because its line of force passes anterior (palmar) to the joint's mediolateral axis of rotation. This muscle can also extend the CMC joint of the thumb.

abductor pollicis longus

The ________ acts in synchrony with any action of the thenar muscles. Its activity stabilizes the first metacarpal so that the thenar muscles do not produce movement at the first CMC joint. Since this muscle also produces radial deviation of the wrist, the ___________may also act to prevent wrist motion.

abductor pollicis longus extensor carpi ulnaris

extrinsic muscles of the thumb

abductor pollicis longus extensor pollicis brevis extensor pollicis longus flexor pollicis longus

The adductor pollis causes __________and __________. It is used in functional activities like _______ or ______.

adduction flexion pinching with thumb and index finger using scissors

Depending on the CMC's initial position, can flex the MP joint. Can assist with IP extension through its attachment to the thumb's extensor mechanism. Innervated by the ulnar nerve

adductor pollicis

Forms bulk of "web space" between 1st & 2nd metacarpals.

adductor pollicis

The trapezium is ________ in the plane of CMC abduction/adduction.

concave

Attaches proximally to radius, then attaches to base of proximal phalanx. Crosses the wrist, CMC, and MP joints.

extensor pollicis brevis

The ___________ extends the MCP and CMC joints of the thumb.

extensor pollicis brevis

The tendons from these muscles form the anatomical snuffbox's radial border and produce wrist flexion.

extensor pollicis brevis abductor pollicis longus

Attaches proximally to ulna, and crosses wrist, CMC, MP, and IP joints. Can assist with adduction of first MP joint, because its tendon can lie on that joint's ulnar side.

extensor pollicis longus

Only muscle that extends IP joint directly; other muscles attach to thumb's extensor mechanism. Innervated by radial nerve.

extensor pollicis longus

The ________ extends the IP, MCP, and CMC joints of the thumb. This muscle also causes adduction. Its actions are necessary for reposition.

extensor pollicis longus

The tendons from this muscle forms the anatomical snuffbox's ulnar border and produces wrist extension.

extensor pollicis longus

What are the primary extensors of the thumb at the IP joint?

extensor pollicis longus abductor pollicis brevis

Rapid extension of the thumb's IP joint involves the _____________, and is often accompanied by palpable activity in the __________muscles.

extensor pollicis longus thenar

Attaches on the radial side of the second metacarpal and the proximal half of the ulnar side of the first metacarpal. Attaches on the radial side of the base of the second proximal phalanx (index finger) and the extensor expansion.

first dorsal interosseous

the flexor pollicis brevis is responsible for __________ the ___________ joint of the thumb

flexing MCP

Attaches to thumb's distal phalanx. Only muscle that crosses IP joint on flexor side. Innervated by median nerve

flexor pollicus longus

The thumb's MP and CMC joints flex and extend in a plane _____________________

parallel to the palm

extension is also known as _____________ because the thumb moves toward ___________

radial abduction the hand's radial side

Attaches proximally to trapezium, trapezoid, and capitate. Crosses two joints; flexes CMC and MP joints. Innervated by both ulnar and median nerves.

radial head of flexor pollicis brevis

The _________ of the _________ is usually classified as the first palmar interosseous.

ulnar head flexor pollicis brevis

Attaches proximally to first metacarpal. Attaches distally to proximal phalanx and the extensor mechanism; crosses only first MP joint. Innervated by ulnar nerve.

ulnar head of flexor pollicis brevis

Attaches to the trapezium and to base of the first proximal phalanx. Contributes to IP extension because its fibers attach to the extensor mechanism of the thumb.

Abductor Pollicis Brevis

The abductor pollicis brevis crosses the ______ and ______ joints.

MCP CMC

Why can you not passively rotate the CMC joint when you place it in full opposition or reposition?

These are the CMC joint's close packed positions. In these positions, the capsular fibers are maximally elongated and taut, preventing CMC rotation.

Attaches proximally to radius and ulna. Its distal attachment to the base of the first metacarpal is palpable at the gap on the proximal end of the first metacarpal shaft.

abductor pollicis longus

the anatomical snuff box is a landmark for the true axis of the wrist, the _________

capitate

The trapezium is ________ in the plane of CMC flexion/extension.

convex

close packed position of the first IP joint

extension

close packed position of the first MCP joint

extension

close packed position of the first CMC joint

extreme opposition or reposition

The tendon of this muscle "splits into 2 heads.

flexor pollicis brevis

In which extrinsic thumb muscle does passive force develop as a result of passive wrist extension?

flexor pollicis longus

The _______ provides flexion to the IP, MCP, CMC and wrist.

flexor pollicis longus

Rapid flexion of the thumb's IP joint involves the __________, and is often accompanied by palpable activity in the ______________.

flexor pollicis longus abductor pollicis longus

the abductor pollicis longus, extensor pollicis brevis, and the flexor pollicis longus all _______ deviate and ________ the wrist

radially flex

During CMC flexion/extension, the metacarpal rolls and glides in ________ directions.

the same

The opponens pollicis only crosses the ________ joint. Its oblique fibers __________, _________, and ________ the CMC joint which _________ the thumb to the other digits.

CMC abduct flex rotate oppose

combined ____ joint ________ and _______ produces _______ joint opposition

CMC flexion abduction CMC

intrinsic muscles of thumb

abductor pollicis brevis adductor pollicis first dorsal interosseous flexor pollicis brevis opponens pollicis

Which muscles make up the thenar eminence? What innervates them?

abductor pollicis brevis flexor pollicis brevis opponens pollicis median nerve

Fibers from which muscles insert into the first digit's extensor mechanism? Which nerves innervate each?

abductor pollicis brevis-median adductor pollicis-ulnar ulnar head of flexor pollicis brevis/first palmar interosseous-ulnar extensor pollicis longus-radial

Activity in the __________counters flexor pollicis longus's tendency to flex the CMC joint in the plane of the palm.

abductor pollicis longus

the abductor pollicis brevis causes __________ of the IP joint because it attaches into the _______________ of the thumb

extension extensor expansion

Which wrist muscles assist a tenodesis grip if the patient has innervation to them?

extensor carpi radialis brevis extensor carpi ulnaris

Which wrist muscles are required for a tenodesis grip?

extensor carpi radialis longus

To move the thumb without also moving the wrist, the snuffbox muscles must act in a synergy with the __________ or ___________.

extensor carpi ulnaris flexor carpi ulnaris

Full and strong opposition consists of _______, ________, and ________.

flexion abduction medial rotation

In which extrinsic finger muscles does passive force develop as a result of passive wrist extension?

flexor digitorum profundus flexor digitorum superficialis

The opponens pollicis has a line of pull to _______ rotate the thumb towards the fingers.

medially

The __________ of the ___________ attaches proximally to capitate and to base of third metacarpal. Attaches distally to base of first phalanx base and to extensor mechanism.

oblique head adductor pollicis

Activity in the ____________counters the extensor pollicis longus's tendency to extend the first CMC joint or adduct it in a plane perpendicular to the palm.

opponens pollicis

Attaches proximally to trapezium and flexor retinaculum. Attaches distally to shaft of first metacarpal. Crosses only CMC joint.

opponens pollicis

If you palpate at the base of first metacarpal while performing gentle lateral prehension, which muscle are you palpating?

opponens pollicis

During CMC abduction/adduction, the metacarpal rolls and glides in ________ directions.

opposite

What kinds of patients might need to use a passive or tenodesis grip?

patients with C6 quadriplegia whose wrist extensors are innervated but their fingers and thumb are not

The thumb's MP and CMC joints abduct and adduct in a plane ____________________

perpendicular to the palm

Using any of the extrinsic thumb muscles _________ deviates the wrist.

radially

the extensor pollicis longus _________ deviates and ________ the wrist

radially extends

the abductor pollicis longus ___________ deviates and ________ the wrist

radially flexes

the extensor pollicis brevis __________ deviates and _________ the wrist

radially flexes

The __________ of the ___________ attaches proximally to shaft of 3rd metacarpal and distally to base of 1st phalanx.

transverse head adductor pollicis

the axis for thumb abduction and adduction passes through the ________

trapezium

the axis for thumb flexion and extension passes through the ________

trapezium