Kinematic Effects of Sloped Kinematic Effects of Sloped Surfaces on Shank Angle Surfaces on Shank Angle for Persons with Drop Footfor Persons with Drop Foot

Kristin Carnahan, MSPO 2008Kristin Carnahan, MSPO 2008

Dr. Robert Gregor, AdvisorDr. Robert Gregor, Advisor

April 9, 2008April 9, 2008

22

IntroductionIntroduction

Drop Foot: passive equinus or Drop Foot: passive equinus or excessive ankle plantarflexion in excessive ankle plantarflexion in swing phase (Perry)swing phase (Perry)

Orthotic TreatmentOrthotic Treatment– Traditional: Ankle Foot Orthosis Traditional: Ankle Foot Orthosis

(AFO) (AFO) – Alternative: Functional Electrical Alternative: Functional Electrical

Stimulation (FES) of peroneal Stimulation (FES) of peroneal nervenerve

http://www.alimed.com

33

Functional Electrical Functional Electrical Stimulation (FES)Stimulation (FES)

Peroneal Nerve Stimulators Peroneal Nerve Stimulators (PNS)(PNS)– First described in 1961 by First described in 1961 by

LibersonLiberson– Must control timing of stimulation Must control timing of stimulation

want stimulation at toe off want stimulation at toe off

Types of PNS RegulatorsTypes of PNS Regulators– Heel sensor (Liberson 1961)Heel sensor (Liberson 1961)– EMG sensors (Lyons 2002)EMG sensors (Lyons 2002)– ““Natural” sensor – sural nerve Natural” sensor – sural nerve

(Haugland 1995)(Haugland 1995)– Tilt sensor (Dai et al, 1996)Tilt sensor (Dai et al, 1996)

http://www.walkaide.com

44

Tilt SensorTilt Sensor

Dai et al, 1996

Dai et al, 1996

Start Stim

55

Shank Angle & Phases Shank Angle & Phases of Gaitof Gait

Heel Strike

(Initial Contact)

Mid-Stance Toe-off

(Pre-swing)

S=0S(-) S(+)

66

PurposePurpose

Describe differences in shank angle Describe differences in shank angle when walking on inclined/declined when walking on inclined/declined surfaces compared to a flat surfacesurfaces compared to a flat surface

Determine if tilt sensor FES control is Determine if tilt sensor FES control is reliable on inclined/declined surfaces.reliable on inclined/declined surfaces.

77

HypothesisHypothesis

Shank angleShank angle at toe off at toe off will be will be significantly differentsignificantly different on on inclined/declined surfaces compared inclined/declined surfaces compared to a flat surface.to a flat surface.

Dai et al, 1996

88

Methods: SubjectsMethods: Subjects

Inclusion criteria:Inclusion criteria:– Unilateral drop footUnilateral drop foot– Own and use a Walk AideOwn and use a Walk Aide– Over 18 years of ageOver 18 years of age

n=7n=7– Gender: 3 Female , 4 maleGender: 3 Female , 4 male– Average Age: 59.04 yrs (STD=11.42)Average Age: 59.04 yrs (STD=11.42)– Dx: 4 Multiple Sclerosis, 2 CVA, 1 TBIDx: 4 Multiple Sclerosis, 2 CVA, 1 TBI– Time using Walk Aide: 2 mos to 2 yrsTime using Walk Aide: 2 mos to 2 yrs

99

Methods: Methods: ProtocolProtocol

Vicon motion analysis Vicon motion analysis systemsystem

Standard Lower Standard Lower Extremity marker setExtremity marker set

Walk Aide setup “as is”Walk Aide setup “as is” Walking speed self-Walking speed self-

selectedselected

1010

Methods: EquipmentMethods: Equipment

Flat surfaceFlat surface Two stationary Two stationary

rampsramps– WoodWood– Modular DesignModular Design– 8’ Length8’ Length– 4.84.8o o and 9.6and 9.6oo

ResultsResults

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Shank Angle at Toe OffShank Angle at Toe Off

0

10

20

30

40

50

60

-10 -5 0 5 10

Grade of Slope, degrees

Shank Angle, degrees

Subject 1

Subject 2

Subject 3

Subject 4

Subject 5

Subject 6

Subject 7

1313

0

10

20

30

40

50

60

-10 -5 0 5 10

Grade of Slope, degrees

Shank Angle, degrees

Shank Angle at Toe OffShank Angle at Toe Off

* indicates significant difference from 0 degree condition (p<0.05)

* *

1414

ConclusionConclusion

HypothesisHypothesis– Shank angle at toe off Shank angle at toe off ISIS significantly significantly

different (lower) on different (lower) on inclined surfacesinclined surfaces compared to a flat surface.compared to a flat surface.

HypothesisHypothesis– Shank angle at toe off Shank angle at toe off IS NOTIS NOT

significantly different on significantly different on declined declined surfacessurfaces compared to a flat surface. compared to a flat surface.

1515

Discussion: Shank Discussion: Shank AngleAngle Key Finding:Key Finding: Shank angle at toe off Shank angle at toe off

is significantly reduced for both is significantly reduced for both inclined surfaces compared to a inclined surfaces compared to a flat surface.flat surface.

Clinical Application:Clinical Application: Does this Does this affect stimulation?affect stimulation?

YESYES

1616

% Dorsiflexion in % Dorsiflexion in SwingSwing

R2 = 0.9959

0.00

20.00

40.00

60.00

80.00

100.00

-10 -5 0 5 10

Grade of Slope, degrees

% DF in Swing

1717

Limitations and Future Limitations and Future ResearchResearch LimitationsLimitations

– Short ramps Short ramps limited strides observed limited strides observed– Did not directly monitor performance of Did not directly monitor performance of

Walk AideWalk Aide

Future ResearchFuture Research– Monitor operation of the FES device on Monitor operation of the FES device on

different sloped surfaces.different sloped surfaces.– If stimulation is reduced on sloped If stimulation is reduced on sloped

surfaces, determine if this is detrimental to surfaces, determine if this is detrimental to patients.patients.

– Smart sensors? Smart sensors? Cikajlo et al, 2008 Cikajlo et al, 2008

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ReferencesReferences

Perry J, editor. Perry J, editor. Gait Analysis: Normal and Pathological Gait Analysis: Normal and Pathological FunctionFunction, 1, 1stst Ed. Thorofare, NJ: SLACK Incorporated; 1992. Ed. Thorofare, NJ: SLACK Incorporated; 1992.

Lieberson WT, Holmquest HJ, Scott D, and Dow M. Functional Lieberson WT, Holmquest HJ, Scott D, and Dow M. Functional electrotherapy in stimulation of the peroneal nerve electrotherapy in stimulation of the peroneal nerve synchronized with the swing phase of gait in hemiparetic synchronized with the swing phase of gait in hemiparetic patients. patients. Archives of Physical Medicine and Rehabilitation Archives of Physical Medicine and Rehabilitation 1961;42:101-105.1961;42:101-105.

Lyons GM, Sinkjaer T, Burridge JH, and Wilcox DJ. A review of Lyons GM, Sinkjaer T, Burridge JH, and Wilcox DJ. A review of portable FES-based neural orthoses for the correction of drop portable FES-based neural orthoses for the correction of drop foot. foot. IEEE Transactions on Neural Systems and Rehabilitation IEEE Transactions on Neural Systems and Rehabilitation EngineeringEngineering 2002;10:260-279. 2002;10:260-279.

Haugland MK and Sinkjaer T. Cutaneous whole nerve Haugland MK and Sinkjaer T. Cutaneous whole nerve recordings used for correction for footdrop in hemiplegic man. recordings used for correction for footdrop in hemiplegic man. IEEE Transactions on Biomedical EngineeringIEEE Transactions on Biomedical Engineering 1995;3:307-317. 1995;3:307-317.

Dai R, Stein RB, Andrews BJ et al. Application of tilt sensors in Dai R, Stein RB, Andrews BJ et al. Application of tilt sensors in functional electrical stimulation. IEEE Transactions on functional electrical stimulation. IEEE Transactions on Rehabilitation Engineering 1996;4:63-72.Rehabilitation Engineering 1996;4:63-72.

Cikaljo I, Matjacic Z, Bajd T. Efficient FES triggering applying Cikaljo I, Matjacic Z, Bajd T. Efficient FES triggering applying Kalman filter during sensory supported treadmill walking. Kalman filter during sensory supported treadmill walking. Journal of Medical Engineering & TechnologyJournal of Medical Engineering & Technology 2008;32:133-144. 2008;32:133-144.

Questions?Questions?

http://www.vimeo.com/

Special Thanks Special Thanks to:to:Dr. Robert GregorDr. Robert GregorDr. Teresa SnowDr. Teresa SnowTodd Clay, CPOTodd Clay, CPOMatthew Nelson, Matthew Nelson, CPOCPOPaula Katz, CPOPaula Katz, CPOMolly Cooper, CPOMolly Cooper, CPO

2020

Step Length vs SpeedStep Length vs Speed

R2 = 0.7706

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 0.2 0.4 0.6 0.8 1 1.2

Speed, m/s

Step Length, m

2121

Shank Angle at Toe OffShank Angle at Toe Off

0

10

20

30

40

50

60

1 2 3 4 5 6 7

Subject

Shanke Angle, degrees

Flat 4.8deg Up 9.6deg Up

2222

Shank Angle at Heel Shank Angle at Heel StrikeStrike

-25

-20

-15

-10

-5

0

5

10

-10 -5 0 5 10

Grade of Slope, degrees

Shank Angle, degrees

Subject 1

Subject 2

Subject 3

Subject 4

Subject 5

Subject 6

Subject 7

2323

Shank Angle at Heel Shank Angle at Heel StrikeStrike

-25

-20

-15

-10

-5

0

5

10

-10 -5 0 5 10

Grade of Slope, degrees

Shank Angle, degrees

* * *

* indicates significant difference from 0 degree condition (p<0.05)

2424

% Dorsiflexion in % Dorsiflexion in SwingSwing

R2 = 0.8358

0.00

20.00

40.00

60.00

80.00

100.00

-10 -5 0 5 10

Grade of Slope, degrees

% DF in Swing

2525

OutlineOutline

Introduction/BackgroundIntroduction/Background PurposePurpose HypothesisHypothesis MethodsMethods ResultsResults DiscussionDiscussion