Wednesday, November 18

• Orthoses : passive, powered• Hand movers• Ankle rehabilitators• Walking Lab

AFO adjustable for PF correction

DAAJ

Knee stability in an AFO

Standard MetalAFO: 375 in. lbs.

60% reductionIn Quad torque

Types of ankle bracing

More types

Powered Gait OrthosesHydraulic Actuation (Seireg et al 1981)• Five DOFs (2 at hip, 1 at knee, 2 at ankle)• Good and simple design and analysis• Bulky and unusable because of the current state of technology

• linear DC motor (Ruthenberg et al 1997) 4 bar linkage and CAM system• One DOF run by a Battery pack and control system • Mechanized hip and knee with cam-modulated linkage for knee function• Peak power usage ~ human walking• May be a practical means for paraplegic gait?

Powered ankle

• http://www.ossur.com/prosthetics

• http://www.ossur.com/bionictechnology/propriofoot

Functional Electrical Stimulation

• Can re-animate paralyzed muscles• External or internal electrodes• User triggered with switches. How else?• Most are open loop, but reflexes not

necessary for rhythmic motions. • Problem because cutaneous nerves are

stimulated first. Also larger motoneurons have lower threshold.

Functional Arm Orthoses

See also pp. 319 yellow

FES

Correcting muscle Atrophy

• Atrophy is the loss of muscle mass

• Present methods for preventing atrophy– Myoplasty

– Myodesis

– Implantable devices

Continuation of Class 5 on muscles

Muscle Characteristics

• Irritability– ability to respond to a stimulus

• Conductivity– propagate a stimulus

• Contractility– ability to modify length (shorten)

• Adaptability– ability to change structure

Time scale(All or none)

Elasticity

Muscle adaptation

• Two types : fast and slow• or twitch and tonic• white and red• Interchangeable

• Fibers extend full length of • muscle

Bion (Loeb et al.) • BIONs are individually

addressable, single channel stimulators that can be injected in or near muscles and nerves to treat paralysis, spasticity and other neurological dysfunctions. BIONs receive power and digital commands from an externally worn RF transmitter coil and generate precisely timed, current-regulated electrical stimulus pulses.

System for functional electrical stimulation

Prototypes of Bion2 have sensing capability for acceleration, & proximity.

Non-polarizable

High surface area

Galvani discovery of electricity

The BION™

• A system using BIONs consists of a personal computer, a transduction coil, and the associated implantable BIONs

• A computer can control up to 256 BIONs at a time

• What are present uses for the BION?• 560 KHz carrier, need 20 Hz stim• E Storage in body’s capacitance

Flow Charts of BION OperationImplantable Device

Comparison of Std. FES and the BION™ System

• Battery Powered• Switch to turn power on or

off

• Not battery powered• External computer

controls BION™

activation

Similarities

Differences

• Both use magnetic fields to activate the implants• Both are used to stimulate muscle contraction

Implantable FES

BION™

Idea for Bion in Preventing Atrophy

• Currently bions are controlled by an outside source, the personal trainer

• Goal would be to have the body control the computer that controls the bions.

• The trick would be creating a component that would be able to sense/detect an action potential along the severed nerve and use that signal to activate the bions.

Some Applications• Shoulder Subluxation

• Hand assist devices

• Without a glove• May be difficult for a

paralytic hand to don.

Ankle Exercisor

• Drop foot is due to central paralysis; injury, I.e. PTT; osteoarthritis; Charcot foot.

Range of Motion Ankle Rehabilitator

• An inverted joystick interface to computer.

Rehabilitation Engineering

Linking virtual to real world