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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)
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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 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
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