tecnologie robotiche per la neuroriabilitazione dell'arto ...l-exos system overview l-exos...

Tecnologie Robotiche per la Neuroriabilitazione dell'Arto Superiore in Realtà Virtuale

Giovanni Greco

PERCRO, Scuola Superiore Sant’Anna, Pisa

Summary

Arm rehabilitation: introduction

L-Exos system overview

Clinical protocol Reaching task Free motion task constrained to a circular trajectory Task of object manipulation

Therapy results

Clinical results

Future work

Arm rehabilitation

Several research studies have recently focused on the development of robotic interfaces and on the use of Virtual Reality technologies for neurorehabilitation

New technologies allow to overcome some of the major limitations manual assisted movement training suffers from lack of repeatability lack of objective estimation of rehabilitation progress high dependence on specialized personnel availability

VR-based rehabilitation protocols may significantly improve the quality of rehabilitation by offering strong functional motivations to the patient, who can therefore be more attentive to the movement to be performed

Several arm rehabilitation robotic devices, both cartesian and exoskeleton-based, have been developed in the last 10 years

Advantage:

robotic-aided therapy allows a higher level of improvement of motor control if compared to conventional therapy

positive effects of Virtual Reality on rehabilitation, which enhances cognitive and executive functions of stroke patients by allowing them to receive enhanced feedback on the outcome of the rehabilitation tasks he/she is performing

VR can provide an even more stimulating videogame-like rehabilitation environment when integrated with force feedback devices, thus enhancing the quality of the rehabilitation

Arm rehabilitation


L-Exos (Light Exoskeleton) system is a 5-DoF arm exoskeleton installed at the Neurorehabilitation Unit of the University of Pisa, where it has been used in schemes of robotic assisted VR-based rehabilitation with chronic stroke patients

L-Exos is a force feedback exoskeleton for the right human arm, is designed to apply a controllable force of up to 100 N at the center of the user’s hand palm, oriented along any spatial direction and it can provide active and tunable arm weight compensation

Performance Feedback Online and Offline Performance Scoring

Motion facilitation gravity compensation to facilitate movement in various goal directed

movements linear gain of amplification from hand movement to VR representation

Error Feedback Visual Force feedback with active guidance and virtual fixtures

Task Feedback Performance in task execution (scoring)


Overall integration set-up

The picture shows the three-axial force sensor integrated at the handle

The structure of the L-Exos is open, the wrist being the only closed joint, and can therefore be easily wearable by post-stroke patients with the help of a therapist

In order to use the L-Exos system for rehabilitation purposes, an adjustable height support has been created

The L-Exos device has been integrated with a projector used to display on a wide screen placed in front of the patient different virtual scenarios in which to perform rehabilitation exercises

The VR display is therefore a mono screen in which a 3D scene is rendered

Three Virtual Rehabilitation scenarios have been developed using the XVR Development Studio


Clinical protocol

A pilot study was carried out at the Santa Chiara Hospital involving 9 subjects with the main objective of validating the implemented therapeutic schemes and generally of evaluating the robot aided therapy with the L-Exos system

The protocol consisted of 3 one-hour rehabilitation sessions per week for a total of six weeks (i.e., 18 therapy sessions)

Each rehabilitation session consisted in 3 different VR mediated exercises

Clinical protocol

The patients enrolled for the testing

Patient Sex

Age Event year Type of stroke

Site of stroke Fugl-Meyer score (66)

Ashworth score

1 M 72 2003 Hemorrhagic temporo-parietal, cortical-subcortical left side 52 22

2 M 79 2005 Hemorrhagicposterior portion of the left lateral ventrical roof

with an extension corresponding to the semioval center

36 39

3 M 37 2004 Hemorrhagic nucleo-capsule-radiata left side 37 17

4 F 42 1988 Hemorrhagic midbrain-thalamus left lesion 12 24

5 M 58 2006 Hemorrhagicintra-parenchymal lenticular-capsular left

collection57 9

6 M 69 2004 Ischemic extensive lesion in the left parietal side 56 10

7 M 58 2002 Hemorrhagic temporo-parietal left side 43 15

8 M 68 2004 Ischemic parieto-occipital, cortical-subcortical left side 12 21

9 M 70 2005 Hemorrhagic temporo-parietal left side 17 15

Different fixed targets are displayed as gray spheres disposed on a horizontal row

When one of the fixed targets is activated, a straight trajectory connecting the starting point and the final target is displayed

The patient is instructed to actively follow the position of a yellow marker, whose motion is generated along the line connecting the start and end points

Reaching task

The patient is asked to move freely along a circular trajectory where it is constrained by an impedance control

Position, orientation and scale of the circular trajectory can be changed online

No guiding force is applied to the patient’s limb when he/she is moving within the given trajectory, along which the patient is constrained by means of virtual springs

Free motion task

The patient is asked to move cubes to arrange them in a order decided by the therapist (e.g. putting together the fragments of one image)

The device is controlled with a direct force control

By pressing a button on the handle the patient can decide to select which cube wants to move or to release it. Collisions are simulated to perceive all the contact forces during the simulation

Object manipulation

Therapy results

Reaching task

Typical path followed by a patient during the reaching task

The cumulative error for each task has been chosen as being the most significant metric to analyze reaching data

Reaching task

Significant improvements in the average fitting curves from Week 1 to Week 6 are recognizable

Free motion task

Total time required to complete a full circular path was the quantitative parameter used to assess patient improvement for the constrained motion task

Results: 3 of the patients report no significant decrease of the completion

time from Week 1 to Week 6 3 patients report a decrease of about 50% in the task completion

time 3 patients report a decrease of about 70%

Free motion task

Sample data from Patient 3 allow to visualize a typical trend which has been found in the patients reporting improvements in the motion constrained exercise

Object manipulation

No quantitative data has been computed for the last proposed task

Completion time was not significant to evaluate patient performance improvements due to the high variability in the task difficulty among different therapy sessions initial cube disposition was randomly chosen by the control PC accepted amount of cube misalignment amount of time spent in trying to perform fine movements to

reduce such misalignment

Clinical results

Clinical results

Standard clinical evaluation scales:

Fugl-Meyer scale

Modified Ashworth scale

Range Of Motion (ROM)

Fugl-Meyer scale

The scale is used for the evaluation of motor function, of balance, and of some sensation qualities and joint function in hemiplegic patients

The Fugl-Meyer assessment method applies a cumulative numerical score to 50 items, for a total of 100 points, each item being evaluated in a range from 0 to 2

33 items concern upper limb functions, for a total of 66 points, and are used for the clinical evaluation

Fugl-Meyer scale

The results obtained by a Fugl-Meyer assessment were carried out before and after robotic therapy

Every patient reported an increment ranging from 1 to 8 points


Modified Ashworth scale is the most widely used method for assessing muscle spasticity in clinical practice and research

Its items are marked with a score ranging from 0 to 5, the greater the score, the greater being the spasticity level

Only patients with modified Ashworth scale values ≤ 2 were admitted to this study


Improvement index defined for each value of the Ashworth scale:

+1: decrement of one step +2: decrement of two steps +3: decrement of three steps -1: increment of one step

The total improvement index has been computed for each patient

A mean improvement of 6.2 points in the overall improvement index has been found

Range Of Motion

Range Of Motion is the most classical and evident parameter used to assess motor capabilities of impaired patients

The therapy with the L-Exos has beneficial effects on the maximum range of motion both for joints directly employed when performing the therapy exercises and for joints not directly exercised by the rehabilitation exercises (e.g. wrist) and blocked in a fixed position during the therapy

Correlation between clinical measurements and robotic performance measurements

We have conducted preliminary analysis to confirm that robotic measurements correlate well with clinical scales (see next slide)

An important aspect to be considered is the: Distance from event (acute, sub-acute and chronic patient) Level of impairment at the enrollment (low, moderate, severe)

These two variables should be considered in the tuning of therapy and accelerators on the patient, and will affect significantly the outcome of the therapy.

Example of clusterization of patients according to motor impairment

Per

form

ance

mea

sure

d in

the

exec

utio

n of

re

achi

ng a

ssis

ted

by th

e ro

bot a

t the

en

rollm

ent

Fugl-Meyer Score at the enrollment

Severe impairment

Moderate impairment

Low impairment

Rob

ot m

easu

rem

ent

Clinical measurement

R=0.47, p<0.05

Elbow velocity profile

In a healthy subject we expect to have a profile of the angle aperture velocity for elbow or shoulder joints with two peaks, corresponding to the forward and backward movement in a reaching movement, like what it is reported in this figure.

Levin, M.F., Interjoint coordination during pointing movements is disrupted in spastic hemiparesis. Brain, 1996. 119(1): p. 281.

In a similar way we can define a parameter called T-angle, from the plot of the angle velocity vs. angle displacement for each joint. In a healthy subject with good joint coordination it should look like a CIRCLE.

Cirstea, Levin et al., Interjoint coordination dynamics during reaching in stroke, Exp Brain Res (2003), 151:298-300

Angulardisplacement

Angularvelocity

Joint velocity in reaching

T-angles

Data acquisition and analysis

The kinematic and electromyographic recordings were carried out when the subject performed the motor task: the 8-channel integrated Elite-BTS system was used; 6 electromyographic channels were dedicated to cameras for the kinematic analysis of the movements.

The motor task was repeated 18 times at different speeds and to 3 different position target: 3 times was called the patient to operate at normal speed and 3 times at their maximum possible speed to reach 3 target position placed according to [1].

Movement features (high severity)

0 0.5 1 1.5 2 2.5 3

90

t (sec)

Ang

le (°

)

Elbow angle at normal velocity after rehabilitation

-20

0

20

Vel

ocity

(°/s

)

0 1 2 3 4 5 6 7 8

82

84

86

88

t (sec)

Ang

le (°

)

Elbow angle at normal velocity before rehabilitation

-10

-5

0

5

10

Vel

ocity

(°/s

)

50 55 60 65 70 75 80 85 90 95 100-60

-40

-20

0

20

40

60

80

100

angle (°)

velo

city

(°/s

)


outwardinward

50 55 60 65 70 75 80 85 90 95 100-60

-40

-20

0

20

40

60

80

100

angle (°)ve

loci

tà (°

/s)


outwardinward

FM<20


T-angles

0 2 4 6 8 10 12 14

100

t (sec)

Ang

le (°

)


-50

0

50

Vel

ocity

(°/s

)

0 1 2 3 4 5 6 7 8

100

t (sec)

Ang

le (°

)


-50

0

50

Vel

ocity

(°/s

)

70 80 90 100 110 120 130 140 150-100

-80

-60

-40

-20

0

20

40

60

80

100

120

angle (°)

velo

city

(°/s

)


outwardinward

70 80 90 100 110 120 130 140 150-100

-80

-60

-40

-20

0

20

40

60

80

100

120

angle (°)

velo

cità

(°/s

)


outwardinward

20<FM<50


T-angles

Movement features (medium severity)

0 0.5 1 1.5 2 2.5 3 3.5 4

100

t (sec)

Ang

le (°

)


-200

0

200

Velo

city

(°/s

)

0 0.5 1 1.5 2 2.5 3 3.5

70

80

90

100

110

t (sec)

Ang

le (°

)


-150

-100

-50

0

50

100

150

Vel

ocity

(°/s

)

50 60 70 80 90 100 110 120 130

-100

-50

0

50

100

angle (°)

velo

city

(°/s

)


outwardinward

50 60 70 80 90 100 110 120 130

-100

-50

0

50

100

angle (°)

velo

cità

(°/s

)


outwardinward

50<FM<66


T-angles

Movement features (low severity)

Movement analysis of patients

The amount of cocontraction of agonist-antagonist muscles during the outward movement was quantified via a cocontraction index (CI), calculated as the ratio of the corresponding RMS values. For the biceps-triceps couple the index was estimated on the

time interval located between the starting instant of the wrist movement and the maximum velocity instant during the outward movement.

– For the carpal extensor-flexor couple the index was estimated on the time interval located between the starting instant of the elbow angle variation and the instant of maximum velocity during the elbow opening phase.

Muscle activation

Conclusions

The L-Exos system has been successfully clinically tested in a study involving chronic stroke patients with upper limb motor impairments

Most of the patients enthusiastically report major subjective benefits in Activities of Daily Life after robotic treatment

Qualitative subject feedback is strongly supported by the clinical analyses which definitely underline significant improvements in clinical metrics deriving from robotic-mediated rehabilitation therapy

Conclusions

This shows a general set-up of the integrated system, with force sensors, including one EMG sensor placed on the biceps to monitor on-line activation during movement, in the conditions of robot assisted movement

Future workOverall integration set-up

Performance evaluation

Aalborg, April, 2009 SKILLS General Meeting

INITIAL EMG/KINESIOLOGICAL EVALUATION

INITIAL CLINICAL ASSESSMENT

FINAL EMG/KINESIOLOGICAL EVALUATION

FINAL CLINICAL ASSESSMENT

INTERMEDIATE EVALUATION

Tecnologie Robotiche per la Neuroriabilitazione dell'Arto Superiore in Realtà Virtuale

Giovanni Greco

PERCRO, Scuola Superiore Sant’Anna, Pisa

tecnologie robotiche per la neuroriabilitazione dell'arto ...l-exos system overview l-exos...

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