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

5/10/2013 The Hand • The effector organ of the upper limb • The sensory receptor • The hand and brain — an interactive unit 3 4 1

5/10/2013 5 6 Hand Mechanics Fibonacci Series 3 Elements Interaxial finger length ~ • Motor � 10 (2,3,5) • Transmission Ratio of 1:1.618 � • Application PIP joint exactly at � mathematic center The logarithmic spiral is � the only curve that does not change its shape as it grows. 7 8 2

5/10/2013 Hand Function As a Unit Prehension - M Mo ov ve em me en nt ts s i in n P Pr re eh he en ns si il le e - • • w wh hi ic ch h a an n a ab bs st tr ra ac ct t • Fundamental requisite is that is s s se ei iz ze ed d a an nd d h he el ld d i the object should be held pa p ar rt tl ly y o or r w wh ho ol ll ly y securely w wi it th hi in n t th he e c co om mp pa as ss s o of f t th he e • Stability is a pre-requisite h ha an nd d N No on n- -p pr re eh he en ns si il le e - - M Mo ov ve em me en nt ts s i in n • Two major components • • w wh hi ic ch h n no o g gr ra as sp pi in ng g or o r s se ei iz zi in ng g b bu ut t � Precision ob o bj je ec ct ts s a ar re e � Power m ma an ni ip pu ul la at te ed d b by y pu us sh hi in ng g o or r l li if ft ti in ng g p • 9 10 11 12 3

5/10/2013 The baboon (above) is a quadripedal monkey that has become The gorilla (above) is an ape with an arm-swinging terrestrial. weight on his knuckles. Note that the gorilla ’ ’ s arms are ’ ’ ancestry, and when he walks quadripedally he takes his much longer than his legs. 13 14 The Architecture For grasping the hand must change shape. The arches running in different directions: Transversely Longitudinally Obliquely 15 16 4

5/10/2013 The Hallowing of the Palm The functional role of the carpometacarpal joints 17 18 19 20 5

5/10/2013 Digital Positioning • The functional anatomy of the MP joint – Condyloid joints -2 degrees of freedom – Assymetry of the – “ Force nucleus ” at joint metacarpal heads 21 22 23 24 6

5/10/2013 The Thumb The Thumb � 5 bone structures � 4 joints � 5 degrees of opposition for freedom 25 26 “ Intercalated Bone ” Principle Landsmeer “ intercalated bone. ” • Digit functions as a multi- joint system with an • Complete independence of the MCP and PIP joints • 3 muscle system controls this system 27 28 7

5/10/2013 Digital Positioning Digital Positioning Distal Phalanx • The functional anatomy of the • Paramount feature of PIP joint: hominid hand (tool user) • Broad ungual tuberosity – Hinge joints -1 degree of freedom • Defined proximal and distal ungual pulp – Center of axis of digital • Passive hyperextension not motion altered by change of digital – Changing orientation of axis position of flexion due to joint asymmetry 29 30 8

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