Wrist into

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

2 primary articulations

1. Radiocarpal joints
2. Midcarpal joints

Terminology / directional terms

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

Osteology

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

Osteology: Distal Forearm

DORSAL

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

Osteology: Distal Forearm

PALMAR

• Proximal attachments of wrist capsule & thick palmar radiocarpal ligaments

Osteology: Distal Forearm
• distal articular surface of the radius

• 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

Osteology: Carpal Bones (proximal)

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

Osteology: Carpal Bones (distal)

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

Osteology Proximal Bones: scaphoid

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

Osteology Proximal Bones: Lunate

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

Osteology Proximal Bones: Triquetrum

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

Osteology Proximal Bones: Pisiform

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

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

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

Osteology Distal Bones: trapezoid

Nothing to notes

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!

Osteology: The carpal tunnel

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

Arthrology: Radiocarpal

Between ulnar+radius and triquerium+lunate+scaphoid

Arthrology: Midcarpal

Between finger bones and hamate+capitate+trapezoid+trapezium

Arthrology: Intercarpal

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

Arthrology: Intercarpal (ligaments)

Arthrology: Intercarpal (extrinsic ligaments)

Arthrology: Intercarpal (intrinsic ligaments)

Osteokinematics

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

Arthrokinematics: flexion + extension (limp+back wrist)

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

Arthrokinematics: ulnar + radial deviation

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

"Double V" ligaments with ulnar+radial deviation

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

Primary Muscular Actions

attach distally within the carpus; act on the wrist only

Secondary Muscular Actions

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

Muscular actions map

Muscular Actions: Wrist Extensors Muscles

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

Muscular Actions: Wrist Extensors in action

• 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

Muscular Actions: Wrist Flexors muscles

• 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

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

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

Muscular Action: Radial Deviations

• 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)

Muscular Action: Ulnar Deviations

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