Wrist B&B

Question 1

name the proximal and distal wrist bones

Answer 1

proximal: scaphoid, lunate, triquetrum, pisiform (moving thumb to pinkie) [Scathing Lunatics Try Pirating…]

distal: trapezium, trapezoid, capitate, hamate (moving thumb to pinkie) [… Trapping Treasure & Capturing Honor]

Question 2

what is the most commonly fractured carpal bone and how does this typically occur?

Answer 2

scaphoid (proximal wrist bone), classically fractured via FOOSH injured - falling on an out-stretched hand

complications - avascular necrosis, nonunion

Question 3

describe why avascular necrosis is a complication of scaphoid bone fracture

Answer 3

scaphoid receives blood from radial artery (palmar and dorsal branches), which supply distal bone - proximal portion relies on retrograde flow

if bone is fractured, avascular necrosis may occur at proximal bone … this may cause nonunion (failure of bone to heal)

Question 4

which wrist bone is susceptible to dislocation and why?

Answer 4

lunate is attached to the radius - if there is trauma/fall, other wrist bones are forced backwards but lunate will be displaced towards the palm

may compress carpal tunnel and cause median nerve dysfunction

Question 5

carpal tunnel syndrome is entrapment of the ____ nerve in the carpal tunnel, which is found between the carpal bones and ________ ligament

Answer 5

carpal tunnel syndrome is entrapment of the MEDIAN nerve in the carpal tunnel, which is found between the carpal bones and transverse carpal (flexor retinaculum) ligament

Question 6

where will a patient with carpal tunnel syndrome experience pain and paresthesia?

Answer 6

entrapment of median nerve —> sensory loss to lateral fingers near thumb but NOT thenar eminence (as this is supplied by a small branch that does not enter carpal tunnel)

if symptoms progress, motor function of thumb (thenar muscles) and flexion/extension of lateral fingers (lumbricals) will be affected

Question 7

what is dialysis-related amyloidosis and for what syndrome of the hand does this put patients at risk?

Answer 7

amyloid deposits form from beta2 microglobulin (component of MHC I) because they cannot be effectively removed by dialysis

deposit in bones, joints, tendons —> carpal tunnel syndrome

Question 8

Which two maneuvers can be used to diagnose carpal tunnel syndrome?

Answer 8

1. Tinel’s sign: patient extends wrist, physician taps over thumb side of wrist - tingling in distribution of median nerve is positive sign
2. Phalen maneuver: patient flexes wrist and holds for a minute - tingling in distribution of median nerve is positive sign

Question 9

Tinel’s sign

Answer 9

patient extends wrist, physician taps over thumb side of wrist

tingling in distribution of median nerve is sign of carpal tunnel syndrome

Question 10

Phalen maneuver

Answer 10

patient flexes wrist and holds for a minute

tingling in distribution of median nerve is sign of carpal tunnel syndrome

Question 11

what structures make up Guyon’s canal?

Answer 11

aka ulnar canal

roof formed by palmar fascia, floor formed by transverse carpal ligament (which makes the roof of the carpal tunnel)

Question 12

what are the clinical consequences of Guyon’s Canal Syndrome? (3)

Answer 12

aka ulnar canal syndrome

—> loss of abduction and adduction (interossei muscles)
—> motor loss to little and ring finger (hypothenar muscles, medial two lumbricals)
—> sensory loss to side of little finger

common in bicyclists from direct pressure on handlebars

Question 13

A patient presents to their physician complaining of weakness of the little and ring finger on their R hand, as well as sensory loss to the side of their little finger. They state they are otherwise healthy, and go for long bike rides every morning. What is likely going on?

Answer 13

Guyon’s canal syndrome: aka ulnar canal syndrome

—> loss of abduction and adduction (interossei muscles)
—> motor loss to little and ring finger (hypothenar muscles, medial two lumbricals)
—> sensory loss to side of little finger

common in bicyclists from direct pressure on handlebars

Question 14

Greenstick fracture

Answer 14

pediatric fracture that does not extend through the width of the bone - the bone is bent (because pediatric bones are not as dense)

often occurs in distal radius from trauma (FOOSH injury - fall on out-stretched hand)

Question 15

Torus fracture

Answer 15

aka “buckle fracture”

pediatric fracture due to axial force trauma (force into end of bone) - bone crunches in on itself

occurs in distal metaphysis (most porous section)

Question 16

most common cause of median nerve injury

Answer 16

carpal tunnel syndrome - most common among post-menopausal women