Comparison of Plantar Pressures Distribution Patterns between Foot Orthoses Provided by

CAD-CAM and Foam Impression Methods

Emilie Ki Sum WaiMSc in Health Care (Health Technology)

SupervisorDr. Aaron Leung

Introduction

• Normal Values • Factors influence in plantar pressure

pattern • Foot Orthotics in Plantar Pressure

Measurement

Introduction- Normal Values• evaluate foot deformities : flatfoot,

clubfoot, hallux valgus, plantar fasciitis, callus formation and foot ulcers (diabetes mellitus)

• normative data is needed to provide a basic knowledge on plantar pressure.

• comparison with for the abnormal conditions of plantar pressure

Introduction – Normal Values• 30 healthy subjects • EMED-SF measuring system with a two-

step recording technique • smallest standard deviations of pressure

values • heel and the second and third metatarsal• → heel, central forefoot regions were

functionally the most stable areas of the foot during the stance

• greatest variations of pressure values• the mid-foot, the fifth metatarsal and the lesser

toes (Bryant et al. 2000)

Introduction- Normal Values

• 74 healthy volunteers • walk with a cadence of 100 steps/min• using Musgrave Footprint • foot image was divided into 6 plantar regions • greatest pressure

• second to fourth Metatarsal Heads (greater structure stability, act as main loading area)

• hallux• lowest pressure

• fifth metatarsal Head (Bennett and Duplock 1993)

Introduction

Factors influence plantar pressure pattern:

1. Walking speed2. Gender3. Type of foot and type of shoes

Introduction – walking speed

• Effects of different walking speed on plantar pressure

• Subjects: 20 normal subjects• walking on treadmill at 6 different speeds • Specific regions: hallux, the medial, central and

lateral forefoot and the heel• Conclusion:

• hallux and heel regions - highest pressures ( increased linearly with faster speeds)

• central and medial forefoot pressure (initially increased then become steady plateaued at faster speeds)

• lateral forefoot had the lowest peak pressure (decreased at faster speeds)

(Segal et al. 2004)

Introduction- Gender, foot types and types of shoes

• no gender differences plantar pressure or contact area -Men and women →subject group

(Murphy DF et al. 2005) (Soames RW ,1985)

• high arch, normal and low arch groups- high arch groupresult in least loading in mid-foot region and compensated by increasing loadings in the heel and forefoot regions.

(Rosenbaum et al. 1994)

• peak pressure, central metatarsals pressure and heel pressure - bare feet significant higher pressure then wearing shoes

(Burnfield JM et al. 2004) (Praet FE et al. 2003)

Introduction-Effect of Orthotics in Plantar Pressure measurement

• Four casting methods • foam box techniques in full weight-bearing and

Semi weight-bearing• suspension plaster casting techniques in full

weight-bearing and Semi weight-bearing• Concluded: the effects of different casting

methods on peak pressure and gait lines for accommodative and functional orthoses are almost the same

(Guldemond et al. 2006)

Introduction-Effect of Orthotics in Plantar Pressure Measurement

• Three Dimensional finite element analysis

• Custom-moulded soft insole reduced the peak pressure on the metatarsal and heel regions and increased the contact area

• Concluded: custom-moulded shape is more important in reducing the peak pressure rather then the material stiffness of insole

(Cheung et al. 2005)

Introduction

• Aim: 1. compare the plantar pressure

distribution pattern between foot orthoses generated by CAD-CAM and foam impression methods

2. provide additional reference on indication of appropriate orthoticintervention for different foot conditions

Methodology• Subjects: 5 males and 25 females

• Age 31.6 (22-55) • Height: 1.6m (1.5m-1.76m) • Weight: 56.4kg (44.0kg-71.8kg)

• Inclusion criteria: • No static foot deformity• No painful foot condition• Arch index within normal ( arch index=

0.21 <AI<0.26 )(Cavanagh PR et al. 1987)

MethodologyInstruments: •Novel PEDAR-mobile (Novel Gmbh, Munich, Germany) in-shoe plantar pressure measuring system

•Four different size insole sensors 2.6mm, 99 sensors using capacitance transducer•Frequency: 50 Hz•Calibration was done before data capture

Pedar mobile box

Pedar insole cables

Pressure sensing insole

Methodology

•The Swiss Comfort CAD-CAM foot orthotics system

Assessment stand

Analyzer

Vaccum system

former

Comfortsplinesoftware

Methodology•Materials

• Foam box• Insole materials

•Multiform•Multikork

~5mmAt the points of the heel centre and the toes

~5mmAt the points of the heel centre and the toes

~5mmEven thinkness

Thickness

3mm multiform + 20mm multikork

3mm multiform+ 2mm, 8mm multikork

3mm multiform+ 2mm multikork

Insoles materials:

CAD-CAMFoam impressionFlat insole

Methodology• Procedures

• Foot shape collection • Shape rectification• Insole fabrication• Measurement of plantar pressure• Data analysis

Methodology•Foot shape collection

•Weight and height of subjects were measured and recorded •Footprints were taken by using Harris-Mat footprint and arch index were calculated

(Cavanagh PR et al. 1987)

•Foot shape were taken by •Foam impression method•CAD-CAM method

•Partial weight-bearing •Sit on firm chair with hip

and knee flex in 90°•Subtalar joint in neutral position

Methodology

Shape rectification• Foam impression method

• Impressed foam impression box kit was filled with Plaster of Paris → positive model

• Modification of toe piece →flatten toe platform • Smoothed by sand paper and allowed to dried

up

• CAD-CAM method• Toes section was modified to become a flat

platform • The foot shape adjusted shallower through the

ComfortSpline software on in order to prepare rooms for the covering

Methodology•Insole Fabrication

•Foam impression method- vacuum moulding•CAD-CAM method- former•Flat Insole

Methodology• Foam Impression method• CAD-CAM method• Flat insole

Methodology• Plantar pressure measurement

• Foot orthoses fitted with 1cm heel height and laced sport shoes

• Pedar insole sensor with correct size was select

• zero setting• Walked along 10m pathway with his/her

walking speed• Each trial- more then 10 steps• 3 successful trial taken in

each condition• Conditions were taken in randomly

Methodology• Data Analysis

• Pedar multi-mask evaluation was used • Divided into 8 regions

1. Heel region2. Medial mid-foot region3. Lateral mid-foot region4. Medial forefoot region5. Mid-forefoot region6. Lateral forefoot region7. Hallux8. Other toes

Methodology• Parameters

• Peak Pressure• Maximum force• Pressure time integral• Contact area

• SPSS statistical software (version 11.0) • One-way ANOVA tests• post hoc Tukey

Result• Peak Pressure

Peak Pressure in Eight Foot Regions

0

5

10

15

20

25

30

35

Heel Medialarch

Lateralarch

Medialfore-foot

Midforefoot

Lateralforefoot

Big toe Toe

Prss

sure

(N/c

m2 )

Flat Insole

CAD-CAMprovidedorthosis

FoamImpressionprovidedorthosis

Result

•Peak Pressure- flat insole

Result

•Peak Pressure- CAD-CAM provided orthosis

Result•Peak Pressure- Foam impression provided orthosis

Result• Peak Pressure

Flat insole CAD-CAM Form impression

Result

• Maximum forceMaximum Force in Eight Foot Regions

0

100

200

300

400

500

600

Heel Medialarch

Lateralarch

Medialfore-foot

Midforefoot

Lateralforefoot

Big toe Toe

Forc

e (N

)

Flat Insole

CAD-CAMprovidedorthosis

FoamImpressionprovidedorthosis

Result• Maximum force

Maximum Force of a subject

0

100

200

300

400

500

600

0 12 24 36 48 60 72 84 96

Percentage of stance (%)

Forc

e (N

)

Flat insole

CAD-CAMprovidedorthis is

foamimpress ionprovidedorthos is

Result• Pressure-time integral

Pressure-time Integral in Eight Foot Regions

0

1

2

3

4

5

6

7

Heel Medialarch

Lateralarch

Medialfore-foot

Midforefoot

Lateralforefoot

Big toe Toe

Pres

sure

-tim

e In

tegr

al (N

/cm2 s

) Flat Insole

CAD-CAMprovidedorthosis

FoamImpressionprovidedorthosis

Result• Contact Area

Contact Area in Eight Foot Regions

0

5

10

15

20

25

30

35

40

45

Heel Medialarch

Lateralarch

Medialfore-foot

Midforefoot

Lateralforefoot

Big toe Toe

Con

tact

Are

a (c

m2 )

Flat insole

CAD-CAMprovidedorthosis

FoamImpressionprovidedorthosis

Discussion

• Comparing among flat insole and total contact insole (CAD-CAM and foam impression)• Medial arch support in total contact

insole contributed in • ↓ Peak pressure and maximum force in

heel• ↑ peak pressure and maximum force in

medial arch region• ↑ pressure-time integral in medial arch

region• ↑ total contact area and area in medial arch

region

Discussion• Comparing among insoles provided

by CAD-CAM and foam impression method• ↓ peak pressure and pressure-time

integral in mid forefoot region in CAD-CAM provided orthosis

• compression force was applied on the dorsum of mid foot in foam impression method

• →transverse arch collapsed • Not in CAD-CAM → neutral metatarsal

support during scanning

Discussion• Comparing among insoles provided

by CAD-CAM and foam impression method• ↑ contact area in medial arch region in

CAD-CAM• Foam impression method

• Difficult to control subject’s foot • Applied force• Keep foot in subtalar neutral

Discussion

• Casting method and technique• Casting method and technique affected

the outcome of the insoles• semi-weight bearing condition are

different• percentages of weight-bearing in foam

impression method were higher than CAD-CAM method

• contact area of CAD-CAM insole was significant higher than the foam impressed insole

Discussion

• Suggested Guideline by selection of CAD-CAM and Foam Impression Methods• both methods can decrease heel

pressure and increase medial arch support

=>plantar fasciitis

Discussion• Suggested Guideline by selection of CAD-

CAM (Swiss Comfort) and Foam Impression Methods• CAD-CAM provided orthosis: reduced peak

pressure and pressure-time integral in mid forefoot → callus or pain in 2nd and 3rd MTH

• CAD-CAM provided orthosis: hallux valguswhich associated with flatfeet / forefoot varusand flatfeet which associated forefoot / hindfoot structural disorder => foot alignment is easily control

Conclusion

• Total contact insole provided by both methods can redistribute peak pressure and maximum force from heel to medial mid foot area

• Swiss Comfort CAD-CAM System could provide similar result as the foam impression method did

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Acknowledgements

• Dr. Aaron Leung, my supervisor• Mr. Daniel Lo, my Hospital

Department Manager • Mr. Denis Wong, my service in-

charge• Mr. Noel Kwong, my colleagues• All my subjects

Thank you