Kinesiology, NTUPT

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The Hand

Functions of the Hand
Structure of the Hand
Kinematics of the Hand
Muscle Actions at the Hand
Grasp Patterns

Objectives： After studying this topic, the students will be able to

To identify hand articulations, including joint types, articular shapes, and the surrounding tissues
To describe joint mobility and stability of the hand
To distinguish the saddle joint from the one-degree-of-freedom and other two-degree-of-freedom joints
To understand the characteristics of two joint muscles and prehension patterns of the hand

Neumann DA (2002). Hand. In Neumann DA: Kinesiology of the Musculoskeletal System: Foundations for Physical Rehabilitation. Philadelphia: Mosby. Chapter 8, pp. 194-241
Smith LK, Weiss EL, Don Lehmkuhl L (eds, 1996). Brunstromm's Clinical Kinesiology, 5th ed. Philadelphia: FA Davis. Chapter 6, pp. 180-222.
Barr AE et al. (2001). Biomechanics of the wrist and hand. In Nordin M & Frankel VH (eds): Basic Biomechanics of the Musculoskeletal System. Philadelphia: Lippincott Williams & Wilkins. Chapter 14, pp.358-387

Functions of the Hand

to manipulate delicate fine motions

to complete powerful grasp tasks

to support or transfer force for changing positions

to serve as an sensory organ for perception of the surroundings

to help to express emotions

Joint Structure of the Hand

Joints at the hand

5 carpometacarpal joints (CMC)

3 intermetacarpal joints (IMC)

5 metacarpophalangeal joints (MCP)

4 proximal interphalangeal joints (PIP)

5 distal interphalangeal joints (DIP)

composed of 19 bones, 5 digital rays, 29 muscles, and 14 joints (Note: In Neumann's book, he claims of 19 articulation by including 5 CMC articulations)

Digital ray

to indicate the entire chain of the digit that is composed of

metacarpal

proximal phalanx

middle phalanx

distal phalanx

Note: phalanges = more than 1 phalanx

5 fingers

thumb = 1^st

index = 2^nd

middle finger = 3^rd

ring finger = 4^th

little finger =5^th

5 digital rays

1^st ray： thumb + 1^st metacapral

2^nd ray： index + 2^nd metacapral

3^rd ray： middle finger + 3^rd metacapral

4^th ray： ring finger + 4^th metacapral

5^th ray： little finger + 5^th metacapral

First carpometarcarpal (1^st CMC) joint

proximal component： two trapezii

trapezoid

trapezium

distal component： first metacarpal base

joint type： saddle joint

motions：

flexion/extension： concave first metatarsal base moving on convex trapezii

abduction/adduction： convex first metatarsal base moving on concave trapezii

DOF = 2

close-packed position： full opposition

Other CMC joints

2^ndCMC： 2^nd metacapral on trapezoid (principal), trapezium, and capitate

3^rdCMC： 3^rdmetacarpal on capitate

4^thCMC： 4^thmetacarpal on hamate (principal) and capitate

5^thCMC： 5^thmetacarpal on hamate

function： to allow the hand to fit around any object, e.g. holding a ball

Joints at the hand

Metacarpophalangeal (MCP) joint

proximal component： head of the metacarpal bone

distal component： base of the proximal phalanx

joint type： condyloid joint

motion：

flexion/ extension： concave proximal phalangeal base moving on convex metacarpal head

abduction/ adduction： concave proximal phalangeal base moving on convex metacarpal head

DOF = 2

Joints at the hand

Proximal interpalangeal (PIP) joint

proximal component： head of the proximal phalanx

distal component： base of the middle phalanx

joint type： hinged joint

motion：

flexion/ extension： concave middle phalangeal base moving on convex proximal phalangeal head

DOF = 1

Joints at the hand

Distal interpalangeal (DIP) joint

proximal component： head of the middle phalanx

distal component： base of the distal phalanx

joint type： hinged joint

motion：

flexion/ extension： concave distal phalangeal base moving on convex middle phalangeal head

DOF = 1

Joints at the hand

Arches of the hand

longitudinal arch

composed of 4 digital rays and carpals

central pillar： 2^nd and 3^rd digital rays

proximal transverse arch

composed of distal carpal rows

apex： capitate

covered with flexor retinaculum to form carpal tunnel

distal transverse arch

composed of 5 metacarpal rows

apex： 3rd metacarpal heads

muscles to maintain the arches

Intrinsic muscles are primarily responsible for maintaining the configuration of the three arches

interossei, dorsal and palmar

lumbricals

thenar muscles

hypothenar muscles

adductor pollicis

Functional position of the hand

MCP joint： 45º of flexion

PIP joint： 30º of flexion

DIP joint： slight flexion

Kinematics of the Hand

Osteokinematic movements

CMC flexion/ extension

ROM： 1 > 5 > 4 > 3 or 2

to help cupping the hand

MCP flexion/ extension： 0 ~ 110º of flexion and varying extension

MCP abduction/ adduction： defined using the longitudinal axis of the middle finger as the midline

PIP or DIP： flexion/ extension

thumb movements (Neumann 2002, p. 197)

flexion： the movement of the palmar surface of the thumb in the frontal plane across the hand

extension： the movement that returns the thumb to its anatomic position from flexion

abduction： the forward movement of thumb away from the plane of the hand

adduction： the movement that returns the thumb to its anatomic position from abduction

opposition： the movement of the thumb across the palm, making direct contact with the tip of any of the fingers

reposition： the movement that returns the thumb to its anatomic position from opposition

Arthrokinematic movements

articular surface

first CMC joint： saddle (concave on convex for flexion/ extension and convex on cave for abduction/ adduction)

MCP joints： concave on convex condyloid joint

PIP nad DIP joints： concave on convex hinged joint

volar/ dorsal glide with flexion/ extension of the MCP, PIP, and DIP joints

radial/ ulnar glide with abduction/ adduction of the MCP joint of the thumb, index, and middle fingers

ulnar/ radial glide with abduction/ adduction of the MCP joint of the thumb, index, and middle fingers

Factors checking motion

finger flexion limited by

long finger extensors

finger extension limited by

palmar plate

transverse metacarpal ligament

collateral ligament

long finger flexors

Muscles at the Hand

Digital flexor pulley system

composed of 5 annular ligaments + 3 cruciform ligaments to hold the underlying tendons at a fixed distance to the phalanges (constant moment arm) gliding mechanism of long flexors digital tendons were wrapped by tendon sheath which contains synovial fluid
vaginal ligament serves as a pulley to fix tendon to joint surface and prevent bowstring phenomenon

Extensor mechanism

synonym: extensor assembly extension hood： composed of the central tendon of the long extensor, the lumbricals, and the interosseus muscles
central slip to base of middle phalanx lateral bands to distal phalanx at MCP joint extensor digitorum communis extends proximal phalanx lumbricals and interosseus flexes proximal phalanx at PIP joint all tendons extends middle and distal phalanges

Tenodesis

wrist flexion with hand opening

wrist flexors activate to maintain an optimized length of extrinsic finger extensors and to neutralize excessive wrist extension created by extrinsic finger extensors

wrist extension with hand closure

wrist extensors activate to maintain an optimized length of extrinsic finger flexors and to neutralize excessive wrist flexion created by extrinsic finger flexors

active insufficiency vs. passive insufficiency

Grasp Patterns

Power grip： for strength

cylindrical grasp the entire palmar surface of the hand grasping around a cylindrical-shaped object muscle involved：finger flexors, intrinsic muscles, and thumb flexors and abductors e.g. grasping a baseball bat or a hammer
spherical grasp cupping the thenar and hypothenar eminences with varying degrees of finger flexion muscle involved： finger flexors, especially from 4^th or 5^th digits, and interossei e.g. holding a ball
hook grasp gripping like a hook formed by flexed fingers without the thumb involvement usually a static nature for a period of time muscle involved: flexor digitorum profundus e.g. carrying a suitcase
conoid grasp cone-shaped grasp with the apex at the ulnar side of the palm e.g. using a knife or other tools