The Hand The effector organ of the upper limb The sensory - - PowerPoint PPT Presentation

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The Hand

• The effector organ of the

upper limb

• The sensory receptor
• The hand and brain — an

interactive unit

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Fibonacci Series

• Interaxial finger length ~

10 (2,3,5)

• Ratio of 1:1.618
• PIP joint exactly at

mathematic center

• The logarithmic spiral is

the only curve that does not change its shape as it grows.

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Hand Mechanics

3 Elements

• Motor
• Transmission
• Application

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Hand Function As a Unit

• P

Pr re eh he en ns si il le e

• M

Mo

• v

ve em me en nt ts s i in n w wh hi ic ch h a an n a ab bs st tr ra ac ct t i is s s se ei iz ze ed d a an nd d h he el ld d p pa ar rt tl ly y

• r

r w wh ho

• l

ll ly y w wi it th hi in n t th he e c co

• m

mp pa as ss s

• f

f t th he e h ha an nd d

• N

No

• n

n-

• p

pr re eh he en ns si il le e

• M

Mo

• v

ve em me en nt ts s i in n w wh hi ic ch h n no

• g

gr ra as sp pi in ng g

• r

r s se ei iz zi in ng g b bu ut t

• b

bj je ec ct ts s a ar re e m ma an ni ip pu ul la at te ed d b by y p pu us sh hi in ng g

• r

r l li if ft ti in ng g

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Prehension

• Fundamental requisite is that

the object should be held securely

• Stability is a pre-requisite
• Two major components

Precision Power

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13 The gorilla (above) is an ape with an arm-swinging ancestry, and when he walks quadripedally he takes his weight on his knuckles. Note that the gorilla’ ’ ’ ’s arms are much longer than his legs. 14

The baboon (above) is a quadripedal monkey that has become terrestrial.

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The Architecture

The arches running in different directions: Transversely Longitudinally Obliquely For grasping the hand must change shape.

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The Hallowing of the Palm

The functional role of the carpometacarpal joints

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Digital Positioning

• The functional

anatomy of the MP joint

– Condyloid joints -2 degrees of freedom – Assymetry of the metacarpal heads – “Force nucleus” at joint

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5 bone structures 4 joints 5 degrees of opposition

for freedom

The Thumb The Thumb

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“Intercalated Bone” Principle

• Digit functions as a multi-

joint system with an “intercalated bone.”

• Complete independence of

the MCP and PIP joints

• 3 muscle system controls

this system Landsmeer

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• The functional anatomy of the

PIP joint: – Hinge joints -1 degree of freedom – Center of axis of digital motion – Changing orientation of axis

• f flexion due to joint

asymmetry

Digital Positioning Digital Positioning

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Distal Phalanx

• Paramount feature of

hominid hand (tool user)

• Broad ungual tuberosity
• Defined proximal and distal

ungual pulp

• Passive hyperextension not

altered by change of digital position

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