Biomech Exam #2: Wrist Flashcards


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1

Wrist into

  • 8 carpal bones
  • Act as a “spacer” between the forearm and the hand

2

2 primary articulations

  1. Radiocarpal joints
  2. Midcarpal joints

3

Terminology / directional terms

  1. Palmar & volar = anterior
  2. Dorsal = posterior

4

Osteology

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  1. Distal forearm
  2. Carpal bones
  3. Carpal tunnel

5

Osteology: Distal Forearm

DORSAL

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  • several grooves & raised areas that stabilize tendons coursing to the wrist/hand
  • Example: Dorsal(Lister’s)Tubercle => separates the ECRB from the EPL

6

Osteology: Distal Forearm

PALMAR

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  • Proximal attachments of wrist capsule & thick palmar radiocarpal ligaments

7

Osteology: Distal Forearm
• distal articular surface of the radius

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  • concave in both ML & AP directions
  • Two important boney configurations
    • Medial (ulnar) angulation of ~25 degrees = “ulnar tilt”
    • Palmar angulation of ~10 degrees = “palmar tilt”
  • ulnar deviation & flexion > radial & extension

8

Osteology: Carpal Bones (proximal)

  • scaphoid, lunate, triquetrum, pisiform
  • Joined “loosely”

9

Osteology: Carpal Bones (distal)

  • Bound tightly = stable base for articulation with metacarpal bones
  • trapezium, trapezoid, capitate, hamate

10

Osteology Proximal Bones: scaphoid

  • Most fractured
  • • Greek for “boat duetoit’sdistalroundedsurface(likeahull)
  • Has a tubercle
  • Articulateswithbothproximal&distalrow
  • Scapholunateligamentisimportant;morelater

11

Osteology Proximal Bones: Lunate

  • most instable; 2nd most fractured
  • Latinfor“moon”

12

Osteology Proximal Bones: Triquetrum

  • 3rd most fractured! • “triangle bone
  • Easily palpated with radial deviation

13

Osteology Proximal Bones: Pisiform

  • shaped like pea
  • EmbeddedwithinthetendonofFCU;sesamoid bone
  • Attachmentforotherligaments
  • Easytopalpate!

14

Osteology Distal Bones: capitate

  • largest of all carpals
  • Latin for “head”
  • Stable anchor at the base of the third metacarpal = longitudinal stability of hand; axis for all wrist motion

15

Osteology Distal Bones: Trapezium

  • Articulates with thumb; saddle joint.
  • Has a tubercle
  • Along with tubercle of scaphoid; serves as attachment point for transverse carpal ligament

16

Osteology Distal Bones: trapezoid

Nothing to notes

17

Osteology Distal Bones: hamate

  • Articulates with base of 4th & 5th = allows for cupping motion of hand
    • Has a hook = medial attachment for the transverse carpal ligament!

18

Osteology: The carpal tunnel

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  • Thick band = transverse carpal ligament
  • Palmar cavity made by carpal bones and transverse CL
  • Restrains enclosed tendons from springing out (anteriorly)

19

Arthrology: Radiocarpal

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Between ulnar+radius and triquerium+lunate+scaphoid

20

Arthrology: Midcarpal

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Between finger bones and hamate+capitate+trapezoid+trapezium

21

Arthrology: Intercarpal

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  • synovial plane joints that connect the carpal bones
  • 3 sets/rows of joints

22

Arthrology: Intercarpal (ligaments)

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23

Arthrology: Intercarpal (extrinsic ligaments)

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24

Arthrology: Intercarpal (intrinsic ligaments)

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25

Osteokinematics

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  • 40 flexion
  • 40 extension
  • 10 radial deviation
  • 30 ulnar deviation

26

Arthrokinematics: flexion + extension (limp+back wrist)

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  • ROLL + SLIDE = same direction
  • concave + convex
  • limp wrist forward (extension) OPPOSITE with flexion
    • dorsal radiocarpal ligaments slacken + parlmar RC lig is tight

27

Arthrokinematics: ulnar + radial deviation

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  • roll + slide = same direction of deviation
  • concave-convex
  • waving motion

28

"Double V" ligaments with ulnar+radial deviation

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  • Upper V shape = medial + lateral of palmar intercarpal ligament
  • Lower V shape = palmar ulnocarpal+ palmar radiocarpal ligaments

29

Primary Muscular Actions

attach distally within the carpus; act on the wrist only

30

Secondary Muscular Actions

cross the carpus and attach to the digits = act on wrists & hand

31

Muscular actions map

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32

Muscular Actions: Wrist Extensors Muscles

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  • Extensor Carpi Radialis Longus
  • Extensor Carpi Radialis Brevis
  • Extensor Carpi Ulnaris
  • (Extensor digitorum // finger extension + torque at wrist)
  • Extrinsic finger extensors

33

Muscular Actions: Wrist Extensors in action

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  • extrinsic finger flexors contract (Fl. digit.sup+ profundus) and fex fingers but creates wrist flexion torque
  • carpi radialis brevis BLOCK wrist flexion tendency (caused by finger flexor muscles)
  • => wrist extensor maintains good length+flex fingers better

34

Muscular Actions: Wrist Flexors muscles

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  • Flexor Carpi Radialis
  • Flexor Carpi Ulnaris
  • Palmaris Longus
    • Absent in 10-15% of people
  • (Extrinsic finger flexors): produce more torque than wrist muscles, depending on wrist position

35

RIGHT CARPAL TUNNEL: Cross sectional area, position, and length of moment arms (muscles that cross wrist @capitate head level)

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  • each muscle's moment arm for a particular action is equal to the perpendicular distance between the axis and the muscle tendon's position

36

Muscular Action: Radial Deviations

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  • 15% more torque than ulnar
  • Extensor carpi radialis brevis+Longus (ECRB & ECRL)
  • extensor pollicis longus + brevis (EPL & EPB)
  • flexor carpi radialis (FCR)
  • abductor pollicus longus (AbPL)
  • flexor pollicis longus (FPL)

37

Muscular Action: Ulnar Deviations

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  • extensor carpi ulnaris (ECU)
  • flexor digitorum profundus and superficialis (FDP & FDS)
  • extensor digitorum (ExDigi)