Wrist and Hand

Wrist Radiocarpal Mid-carpal (intercarpal) maintain length-tension relationship for hand musculature

Distal Radius Facets Lateral (46%) scaphoid Medial (43%) lunate Inferior disk (11%) triquetrum

Radiocarpal Radius and Radioulnar disk (concave) Scaphoid (navicular), lunate, and triquetrum (proximal wrist bones)

Ligaments volar - thick, strong dorsal - thinner, fewer unique function extrinsic intrinsic

Ligaments Radiocarpal superficial deep

Ligaments Ulnocarpal complex meniscus homologue - radiotriquetral ligament triangular fibrocartilage - articular disk

Kinematics Extension distal carpals on fixed proximal carpals neutral (scaphoid-capitate close-packed)

Kinematics Extension scaphoid travels w/ distal carpals  450 ext. scaphoid & lunate close-packed  scaphoid travels w/ proximal carpals

Kinematics Flexion opposite extension

Hand Flexor Tendons surrounded by synovial sheaths reinforced by pulleys (5/3) minimize force/pressure prevent bowstringing

Flexor Tendons 60  900 of PIP flexion  40%  in tension in restraining pulley

Tendon Excursion and Pulleys

Tendon Excursion and Pulleys

Tendon Excursion and Pulleys Sliding of flexor/extensor tendons proximal jts. > distal joints FS > FP Flexors > extensors Extrinsics > intrinsics

Pulley Disruption Bowstringing  excursion at a joint  weakness at other joints

Pulley Disruption

Pulley Disruption

Balance of Power Extrinsic vs. Intrinsics Intrinsic -  clawing counteract extrinsics stabilize proximal phalanx tendons volar to AOR lumbricales critical for timing

Hand/Wrist Injuries CTD/RSI CTS inflammation in CT compressive neuropathy

Hand/Wrist Injuries Etiology of CTS forceful exertions repetitive*/prolonged activities awkward postures localized contact stresses vibration cold temp.

Carpal Fractures 80:20% load distribution between radius:ulna scaphoid (60-70%) hyperextension beyond 950 lunate

Finger Injuries Mallet Finger distal terminal tendon/slip rupture  flexion of DIP

Finger Injuries Boutonniere (Button-Hole) Deformity dorsal synovitis /capsular distension  thinning & lengthening of central tendon

Finger Injuries Boutonniere (Button-Hole) Deformity dorsal subluxation of proximal phalanx (PIP)  palmar displacement (dislocation) of lateral bands of long extensors  MCP /  PIP  DIP /

Finger Injuries Swan-Neck Deformity Flexor synovitis   flexor forces on MCP stretching of collateral ligaments and palmar plate at PIP

Finger Injuries Swan-Neck Deformity dorsal displacement of lateral bands of extensors  intrinsic tightening with MCP flexion  position of lateral bands  pull of extensor tendon  reciprocal DIP flexion

Finger Injuries Swan-Neck Deformity MCP   PIP /  DIP 

Thumb Injuries Gamekeeper’s/skier’s thumb MCP ulnar collateral ligament 20 to tensile loading (chronic or acute) excessive abduction/hyperextension

Thumb Injuries Bennett’s Fx fx subluxation of trapeziometacarpal joint intraarticular fx of 1st MET axial compression