Wednesday, 6 November 2013

WRIST BIOMECHANICS

ANATOMY OF THE WRIST


There are 8 carpal bones in wrist named as


Scaphoid, Lunate, Triquetrum, Pisiform, Trapezoid,  Trapezium, Capitate and Hamate.

(SHAM LAL TENDAY PAKA TENDAY TERAY CACHY HAIN)

KINAMETICS


Rows
There are two rows of bone in wrist joint are called proximal and distal.

Proximal made up of Scaphoid, Lunate, Triquetrum bone.
Distal row consists Trapezoid, Trapezium, Capitate, Hamate bone.

There are three columns in carpals

Central(flex/ext) column consists Lunate,Capitate,Hamate bone.
Lateral (mobile) is constructed by Scaphoid,Trapezoid,Trapezium bone.
Medial (rotation) made up of only a single bone Triquetrum.

Center of rotation of metacarpals is head of capitate

Radial deviation is a movement in which scaphoid flexes proximal pole goes dorsal “pulling” lunate into palmar flexion. where as in Ulnar deviation scaphoid extends proximal pole goes volar pulling lunate into dorsiflexion.

Triquetrohamate helicoid joint

Ulnar deviation : “low” position distal and dorsiflexed pulling lunate into dorsiflexion
Radial deviation : “high”position proximal and palmar flexed pulling lunate into palmar flexion

Forces Transmission


Principal force transmission is through capitate lunate and proximal pole of scaphoid 75% radius 25% ulna.

Three axes of motion

Flexion 90 degree
Extension 70 degrees

Flex/ext split between radiocarpal & midcarpal

Radial Deviation 20 degrees
Ulnar Deviation 50 degrees

Pronation 90 degree
Supination 90 degrees

Frykman Classification of Distal Radius

Extra Articular Fractures

Type-I : Trans Radial( with in 1 cm)
Type-II : Radius+Ulna+styloid

Treatment is Conservative with bellow elbow casting.

Intra Articular Fractures

Type-III    : RadioCarpal.
Type-IV   : RadioCarpal+UlnoStyloid.
Type-V    : RadioUlnar.
Type-VI   : RadioUlnar+Styloid.
Type-VII  : RadioCarpal,RadioUlnar.
Type-VIII : RadioCarpal,RadioUlnar+ Styloid.

Treatment is Conservative with above elbow casting as well as surgical.


Most Common site of fracture is Scaphoid Due to fall on hands.

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