Hand 1

Human hand is a complex structure of bones, arteries, nerves, ligaments, and tendons which

performs many functions. The primary function of the hand is prehension. For closing of hand it

requires coordinated movements of the joints in flexion. The forearm muscle is primary group

acted during most of the hand function. They are connected to the fingers by tendons which pass

through different channels.

Muscles involved in closing of hand

Extrinsic Muscles

Flexor digitorum profundus (FDP)

Flexor digitorum superficialis (FDS)

Flexor digiti minimi brevis.

Flexor pollicis longus

Extensor digitorum

Intrinsic Muscles

Lumbricals

Interossei

Adductor pollicis

Kinesiology and Kinetics of the hand

A powerful closing of the hand requires flexion of MP, PIP, and DIP joints, and

activation of FDP, FDP, and Interossei muscles. In contrast with finger flexors, wrist extensors

Hand 2

will work as a synergistic. The primary function of the extensor carpi radials brevis, extensor

digitorum help in maintains a powerful prehension. Placing the wrist in slight extension and

ulnar deviation increases the finger flexion strength, whereas wrist in flexion and radial deviation

decreases the wrist strength.

Mechanism of gripping

Torque

Grip

Shear Force

T = torque, S = total frictional or shear force, and D = handle diameter

T= S.D

Torque is dependent on handle diameter, large torque required for larger diameter.

Hand and Finger functions

A firm grip requires maximum output of extrinsic muscle torque. Whereas fine grip requires

more of the intrinsic muscles of the torque for fine-tune of the movements. There are different

types of handling.

Prehension handling:

Handle Diameter

Hand 3

Power grip

Precision handling

Cylindrical grip

Hook grip

Precision handling:

Pad-to-Pad prehension

Tip-to-Tip prehension (Precision pinch)

Pad-to-Side prehension (Power pinch)

Hand 4

Powerful grip (full hand prehension)

For powerful grip it requires fist position with flexion at all three joints of MP, PIP, and DIP

Example: holding the hammer, holding the bat.

Precision grip (finger-thumb prehension)

Hand 5

For fine precision there will flexion at PIP and DIP joints with one or two fingers

Example: Holding a ball, keeping the buttons.

Cylindrical grip

Hand 6

Finger tips towards the thumb

Example: holding a glass

Power Pinch (key pinch)

Hand 7

Stabilizing an object between the thumb and lateral border of index finger

The power pinch is formed by the activation of first dorsal Interossei and adductor pollicis.

Precision Pinch (tip-to-tip or pulp-to-pulp)

Hand 8

Object is hold between the thumb and index finger

Example: Holding a pen,

Hook grip

Hand 9

Holding the hook by partially flexing of PIP and DIP

Example: carrying luggage

References

Levangie, P.K., Norkin, C. C. (2001). Joint structure and function (3rd ed.). New Delhi: India.

Neumann, D.A. (2002). Kinesiology of the musculoskeletal system. Missouri: St. Louis.

Pennsylvania State University: Pennsylvania [Images]. Retrieved from: www.bsu.edu/.../hand

finger/ overview/overview.htm