BIOMECHANICS-Hand Prostheses

By: John Poidevin

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Overview

• Hands• History of Prostheses• Current Developments• Need and Requirements• Foreseeable Future• Questions

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What are concidered Hands

• Appendages connected to the forearm

• Identifiable by opposible thumbs

• Only found in mammalian order of primates– Humans– Apes and Monkeys

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Importance of Hands

• Primary organ for physical interaction

• Dense collection of nerve endings

• Dominate area for pressure perception

• Controled by opposite side of the brain

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Make up of the Hand

• Bones– 8 Carpus– 5 Metacarpus– 14 Phalanges

• Distal• Middle• Proximal

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Make up of the Hand

• 27 Degrees Of Freedom (D.O.F)– 21 in fingers and thumb

• 4 for fingers• 5 for thumb

– 6 in wrist

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Control nerves

• Extrinsic control nerves– Radial– Deep redial– Ulnar– Median

• Intrinsic control nerves– Median– Ulnar

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Make up of the Hand

• Muscles– Extrinsic

• Flexor– Superficial anterior (4)– Deep anterior (2)

• Extensor– Superficial Posterior (5)– Deep Posterior (4)

– Intrinsic• Thenar (4)• Hypothenar (3)• Intermediate (3)

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History

• Originally made of leather and wood

• Roman General had a iron hand• Hook “hands”• German Knight Gotz Von

Berlichingen - “Robin Hood”

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Advancements in History

• 1500’s Ambroise Pare - “father of prosthetics”– Artificial joint

• Improved Medicine– Drugs and anesthesia

• Wars– Civil War– WWI– WWII

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Current hand prosthetics

• Mechanical– Cineplasty– Body-powered

• Advantages– Decent Feedback – Durable– Cheaper– Weight

• Disadvantages– Uncomfortable– Restrictive– Appearance

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Current hand prosthetics

• Electrical – Prosthetic Control by an EEG-

based Brain-Computer Interface– Myoelectric prostheses

• Advantages– Functionality– Appearance

• Disadvantages– Price– Weight– Recharge

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Prosthetic users preference

• Survey results– Increase of functionality

• Hand grasps• D.O.F

– Reduced weight– Better cosmetic appearance– Tactile feedback system

• Sensory feedback

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Common hand grasps

• Cylindrical Grasp• Precision grasp• Lateral grasp

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Importance of touch

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Hydraulic Hand Prostheses

• Flexible fingers• Fluidic actuators• Light weight frame• Microvalves• Micropump• Reservoir

• Controller / Interface

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Hydraulic Hand Prostheses

• Low power – Increased surface area – Oil fluidic actuators

• Light weight – External Gear pumps– Center of gravity

• Moveable thumb– 3 D.O.F

• Multiple hand grip

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Hydraulic Hand Prostheses

• Most used Hand grasps– Cylindrical Grasp– Precision grasp– Lateral grasp– Hook grasp– Index position

• 6 microvalves– 6 D.O.F

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Hydraulic Hand Prostheses

• Advantages– Increase in functionality– Reduced weight– Better cosmetic apperance

• Disadvantages– Control issues– Not for hard work– Leakage of hydraulic fluid

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Mechanomyography

• Mechanomyography (MMG)– Low frequency sound (5-50 Hz)

vibration produced by contracting muscles

– Mimics 2-site electromyograph(EMG)

• Non specific• Lacks skin impedance• Cheaper

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Mechanomyography

• Soft Silicone Socket– Embedded array of sensors

• Hard Socket– Battery pack

• EMG Emulator board– Reduced cost

• Otto-Bock

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Mechanomyography

• Trial run– Two participants– Three 30min visits

• Soft Silicon• Hard socket• Training

– Success• Relative to previous prosthetic• 88% and 71%

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Mechanomyography

• Advantages– Emulated electromyograph– Potential of multiple control– Heightened sensitivity

• Disadvantages– Extrinsic frequencies perceived– Lack of response under force– Use of emulator

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Direct Neural Feedback

• Need for referred sensations of touch and joint movement– Appropriate, discrete and graded

• Avoiding– whole never stimulation– Unrelated motion control

• Phantom hand– 80 % of amputees

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Direct Neural Feedback

• Solution– Peripheral nerve stump interface– Platinum-iridium wire

• Teflon insulate (30 cm long)– Planted in Medial nerve

• Fascicle • 1mm stimulus zone

– Amplified and listened to– Computer interface– Robotic hand control

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Direct Neural Feedback

• Future testing– Tactile and proprioceptive

• Strain gauge• Flexion/Extention

– Grip control and elbow position• Match forces• Match angles

– No visual assistance• Next would be Closed Loop

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Conclusion

• Hand Prosthetic – Come a long way– May new advancements

• D.O.F.• Control• Feedback

– Problems• Not a high need• Funding

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Questions?

www.geocites.com/kwenndb/prostheticluke 09 April 2004

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References

• Wu, Ying. Lin, John. Huang, Thomas S. “Analyzing and capturing articulated hand motion in image sequences.”,IEEE Trans Pattern Anal Mach Intell. 2005 Dec;27(12):1910-22.

• Kulley, Marlowe “Hand Prosthetics” April 28, 2003 http://biomed.brown.edu/Courses/BI108/BI108_2003_Groups/Hand_Prosthetics/index.html

• Langan, Ryan “Advanced Prostetic Hand Project” 2006, http://www.advancedprosthetichand.com/4436.html

• Wikipedia, Hand“”10 October 2006, en.wikipedia.org/wiki/Hand

• Guger, Christoph, Harkam, Werner, Hertnaes, Carin, Pfurtscheller, Gert “Prosthetic Control by an EEG-based Brain-Computer Interface (BCI)” viewed 2006 www.gtec.at/research/Publications/aaate.pdf

• Dhillon, Gurpreet Singh. Horch, Kenneth W. “Direct Neural Sensory Feedback and Control of a Prosthetic Arm” IEEE Transactions on Neural Systems and Rehabilitation Engineering, Vol, 13,No. 4, December 2005

• Pylatiuk, Christian. Schulz, Stefan. Kargov, Artem. Bretthauer, Georg “Two Multiarticulated Hydraulic Hand Prostheses”Artificial Organs 28(11):980-86, Blackwell Publishing, Inc.

• Silva, Jorge. Heim, Winfried. Chau, Tom. “Self-Contained Mechanomyography -Driven Externally Powered Prosthesis”Arch Phys Med Rehabil 2005;86:2066-70