Casting Methods and Plantar Pressure

Journal of the American Podiatric Medical Association • Vol 96 • No 1 • January/February 2006 9

Custom-made foot orthoses are commonly used totreat a variety of foot and foot-related conditions.1

The literature describes many different types of cus-tom-made foot orthoses.2-5 However, the biomechani-

Casting Methods and Plantar PressureEffects of Custom-made Foot Orthoses on Dynamic Plantar Pressure Distribution

Nick A. Guldemond*Pieter Leffers, MSc†

Antal P. Sanders, MD, PhD‡Hans Emmen§

Nicolaas C. Schaper, MD, PhD||Geert H. I. M. Walenkamp, MD, PhD*

Foot orthoses are widely used to treat various foot problems. A literaturesearch revealed no publications on differences in plantar pressure distri-bution resulting from casting methods for foot orthoses. Four castingmethods were used for construction of orthoses. Two foam box tech-niques were used: accommodative full weightbearing method (A) andfunctional semiweightbearing method (B). Also, two suspension plastercasting techniques were used: accommodative casting (C) and functionalsubtalar joint neutral position (Root) method (D). Their effects on contactarea, plantar pressure, and walking convenience were evaluated. All or-thoses increased the total contact area (mean, 17.4%) compared withshoes without orthoses. Differences in contact areas between orthosesfor total plantar surface were statistically significant. Peak pressures forthe total plantar surface were lower with orthoses than without orthoses(mean, 22.8%). Among orthoses, only the difference between orthoses Aand B was statistically significant. Differences between orthoses for theforefoot were small and not statistically significant. The gait lines of theshoe without an insole and of the accommodative orthoses are more me-dially located than those of functional orthoses. Walking convenience inthe shoe was better rated than that with orthoses. There were no differ-ences in perception of walking convenience between orthoses A, B, andC. Orthosis D had the lowest convenience rating. The four casting meth-ods resulted in differences between orthoses with respect to contactareas and walking convenience but only slight differences in peak pres-sures. (J Am Podiatr Med Assoc 96(1): 9-18, 2006)

*Department of Surgery and Orthopaedics, University

Hospital Maastricht, Maastricht, the Netherlands.

†Faculty of Medicine, Department of Epidemiology, Maas-

tricht University, Maastricht, the Netherlands.

‡Department of Rehabilitation Medicine, University Hos-

pital Maastricht, Maastricht, the Netherlands.

§Smeets & Zonen Orthopedische Schoentechniek, Geleen,the Netherlands.

||Department of Internal Medicine, University HospitalMaastricht, Maastricht, the Netherlands.

Corresponding author: Nick A. Guldemond, Departmentof Surgery and Orthopaedics, University Hospital Maastricht,PO Box 5800, 6202 AZ Maastricht, the Netherlands.

cal premises of all foot orthoses are redirection offorces through the foot structure and distribution offorces over the contact area between the foot andthe device.1 Custom-made foot orthoses are derived

10 January/February 2006 • Vol 96 • No 1 • Journal of the American Podiatric Medical Association

from clinical evaluation and duplication of the footmorphology by use of an impression or molding tech-nique.1, 6 Numerous devices and methods have beendeveloped to duplicate the foot in a particular posi-tion: two-dimensional techniques such as pressuresheets and flatbed scanning and three-dimensional(3-D) techniques such as foam impressions, plastermolding, and digital scanning.1, 4, 7 The discussionabout which technique leads to “the best orthosis”for a particular condition has a long history andseems far from being settled.2, 8-12 In general, castingtechniques are used to construct either accommoda-tive or functional orthoses.1, 13

Custom-made accommodative foot orthoses aremainly used to accommodate deformities or to shiftpressure away from painful areas or areas that areprone to repeated ulceration.14-18 It is claimed thatthis pressure shift is accomplished by increasing thesurface area that accepts weightbearing forces sothat forces are more evenly distributed throughoutthe plantar area.1, 14, 18, 19 For this, the foot should bemolded in the position it assumes naturally duringweightbearing.1 If necessary, the grinding out of or-thosis material and cushioning are used to furtherprotect areas at risk.15, 17, 18 Both foam box impressionand plaster casting can be used for the production ofcustom-made accommodative foot orthoses.1, 15

The primary goal of a functional foot orthosis ismechanical control by alignment of the foot throughthe weightbearing phases of the gait cycle.1, 13 Pur-suant to this theory, the foot should be cast with thesubtalar joint held in the neutral position. Accordingto the original definition by Root et al,20 the subtalarjoint is in the neutral position when the foot is neithersupinated nor pronated. Simultaneously, the midtarsaljoint must be fully pronated to capture the angular re-lation between forefoot and rearfoot. From this angu-lar relationship, the forefoot type can be classified,and by cast modification, a correction of the align-ment can be induced.21 Although recent research dis-proved the theories about the subtalar joint neutralposition during the gait cycle,2, 10, 22-27 the related sub-talar joint neutral position plaster casting techniqueis still widely used for the construction of functionalfoot orthoses.1, 4, 8, 10, 21, 28 The use of compressible foamin the production of functional foot orthoses is con-troversial. Opponents argue that a foam box does notallow accurate modeling of the foot in the “correct”position.9, 11, 29 Supporters counter that no single tech-nique is superior for every condition and that foambox procedures are a good alternative to plaster cast-ing in many patients with an indication for a func-tional foot orthosis.2, 30

The aim of the present study was to quantify the

differences between custom-made foot orthoses madefrom foam impressions and plaster impressions re-garding contact area, plantar pressures, gait lines, andwalking convenience. This analysis was performedfor accommodative and functional foot orthoses. Thevariability of cast dimensions for different castingmethods has been evaluated in previous studies,6, 7, 31

but no publications assessing the differences be-tween casting methods regarding plantar pressuredistribution have been found.

Materials and Methods

Ten women (median ± SD age, 40 ± 8.4 years) withouta history of foot pathologies participated in the study.Body weight (median ± SD, 60.5 ± 10.1 kg) and height(median ± SD, 170 ± 7.4 cm) are given in Table 1 foreach participant. Four common casting methods wereused to obtain 3-D representations of each foot. Thechoice of these casting methods was based on a sur-vey of international literature databases1, 2, 4, 6-8, 15, 32-34

and on the results of a recent study in the Nether-lands.35 Two foam box impression methods, the ac-commodative full weightbearing method (method A)and the functional semiweightbearing subtalar jointneutral position method (method B), and two sus-pension plaster cast methods, the accommodativesuspension casting method (method C) and the func-tional suspension subtalar joint neutral position cast-ing technique (method D), were used.

In the accommodative full weightbearing method(A), the subject stood in a normal posture with onehand holding onto a bar. While the subject lookedstraight ahead, the orthopedic shoemaker lifted onefoot and guided it onto the foam box. The subjectpressed the foot until her body weight was evenlydistributed between both feet. The orthopedic shoe-

Table 1. Characteristics of the Ten Study Women

Subject Age Weight Height Walking Speed No. (years) (kg) (cm) (km/h)

1 32 51 157 3.52 35 65 179 4.03 45 56 161 3.54 46 66 175 5.05 40 60 169 5.06 42 59 167 3.47 19 61 171 4.08 42 54 159 4.09 32 84 178 4.0

10 40 78 178 4.5


maker pushed the subject’s toes down, and then thesubject lifted the foot straight up. This impression wasmade without any correction of foot alignment.15, 36

In the functional semiweightbearing subtalar jointneutral position method (B), the subject was posi-tioned in a chair with the hip and knee joints at 90°flexion. The foot was placed on the foam box, andthe orthopedic shoemaker pressed the subject’s footdown until the bottom of the box was reached whilemaintaining the foot sole parallel to the floor and therearfoot aligned in the subtalar neutral position.7

Hand pressure was applied to the dorsum of the mid-foot to prevent supination of the midtarsal joint dueto the reactive force of the foam.

In the accommodative suspension casting method(C), the subject was supine in a treatment chair withthe knee joint slightly flexed. A standard plaster wrapwas applied to the foot. The plaster was smoothedout around the contours of the foot while the footwas in a natural position. This position was held withthe ankle joint in the neutral position until the castwas dry.

In the functional suspension subtalar joint neutralposition casting technique (D), as described by Rootet al,20 the subtalar joint was held in the neutral posi-tion while the midtarsal joint was fully pronatedagainst a stabilized rearfoot. This alignment wasmaintained until the cast was dry. Determination ofthe subtalar joint neutral position, by range checking,was carried out while the subject was nonweight-bearing. Body position and application of plasterwere identical to those in method C.

Following standardized construction proceduresand using identical materials, full-length orthoseswere made from the positive plaster casts. Plasterwas added to the positive casts to create a forefootplatform. No additional corrections, such as posts,medial arch fill, or heel-, lateral-, or medial-expansionplaster, were applied. Although a subtalar joint neu-tral position casting method was performed (methodD), we did not make a traditional “Root-style” func-tional orthosis. A three-layer construction was madeof 3-mm Nora Lunalastik and 8-mm Nora Lunasoft SL(Freudenberg GmbH, Weinheim, Germany), top andbottom, respectively, and 1.1-mm Rhenoflex 3208(Rhenoflex GmbH, Ludwigshafen am Rhein, Ger-many) as an internal reinforcement layer. Materialswith a relatively high stiffness were used to minimizethe influence of “cushioning” on plantar pressureloading. Considerable interclinician and intraclini-cian variability is reported regarding casting of thefoot.4, 12, 23, 31 For this study, all of the casts were madeby a single experienced orthopedic shoemaker (H.E.)to eliminate the interclinician source of variability.

All orthoses were evaluated with bare feet in stan-dard walking shoes (Durea Greenway; Durea Schoen-fabriek BV, Drunen, the Netherlands) (width H, outersole 63 Shore A) while walking on a treadmill. Sub-jects individually chose their preferred walking speed,which was kept the same for all subsequent measure-ments. Median ± SD walking speed was 4.0 ± 0.6 km/h(Table 1). The Pedar insole system (Novel, Munich,Germany) was used to measure contact area andplantar pressures. Data were recorded for approxi-mately 50 sec, with a frequency of 50 frames per sec-ond. Contact area and plantar peak pressure were es-timated by calculating the mean values across thereadings of 45 steps. This estimation was performedfor the total plantar surface and for 11 separate re-gions (Fig. 1). The contact area was determined bythe number of sensors activated during the rolloverprocess in a particular region.

To show contact area and peak pressure as a func-tion of time, contact time was standardized for step

Figure 1. Depiction of the 11 mask regions used.


duration (normalized to the longest contact time). Forthis standardization, percentage of contact time wasused instead of time itself. Because of the differentcalculation procedures, the maximum of the peakpressure values over time can be lower than the over-all peak pressure. For contact time–related variables,areas under the curve were calculated per step andwere subsequently averaged across all steps. The cen-ter of pressure was determined per frame. The centerof pressure corresponds with the virtual point of ap-plication of the resultant ground reaction force.37, 38

The path of the center of pressure from frame toframe composes the “gait line.” After standardizationof the pressure pattern dimensions (normalized forwidth and length), center-of-pressure coordinateswere averaged across all steps. Movements in thesagittal plane determine the location of the gait linealong the longitudinal axis. Displacements in thefrontal and transverse planes, eg, inversion and ever-sion of the subtalar joint, determine the location ofthe gait line along the mediolateral axis.

Subjects rated the walking convenience of each or-thosis on a 10-point scale. Statistical analysis was car-ried out using a software program (SPSS version 11.5;SPSS Science, Chicago, Illinois). Wilcoxon signedrank tests were performed for pairwise comparison.

Results

On visual inspection, each casting method resulted incharacteristic 3-D contours, with clear differencesbetween the orthoses (Figs. 2 and 3). The heel cupsof orthoses A and B were shallower than those of or-thoses C and D owing to heel-pad expansion, whichoccurs because of full and partial weightbearing dur-ing the casting process. Also, the arch supports dif-fered. Comparing orthoses A and D, in the sagittalplane the arches became more posteriorly located,whereas the elevation became more pronounced. Inthe frontal plane, the arches of orthoses C and D weresteeper than the arches of orthoses A and B. Thearches of orthosis B were more gently sloped and themost laterally extended.

Table 2 gives the mean plantar contact areas ofthe total foot and of subregions for the shoe withoutan insole and for shoes with each of the four or-thoses. Compared with the shoe without an insole,the orthoses increased the total contact area by 17.4to 24.0 cm2 (mean, 21.5 cm2; 17.4%). The medial mid-foot region was mainly responsible for this increase:10.2 to 14.7 cm2. Differences in contact areas be-tween orthoses A and D, B and C, B and D, and C andD for total plantar surface and for the medial midfootwere statistically significant (P ≤ .015). The differ-

ences between orthoses A and B and orthoses A andC were not statistically significant (P ≥ .057). The in-crease in contact area in the metatarsal regions wasnil or very small. Figure 4A shows the total plantarcontact area as a function of contact time. For theinitial phase of the rollover process, the curves werethe same, whereas during the push-off phase, the dif-ferences between shoes without and with orthosesare considerable. The total area under the curve forthe shoe without an insole is smaller than those forthe four orthoses (P ≤ .001). The differences betweenorthoses A and B, B and C, and B and D were fairlysmall but statistically significant (P ≤ .048). The dif-ference between orthoses and no orthoses is clearestin the medial midfoot region (Fig. 4B). The areasunder the curve for all four orthoses were greaterthan that for the shoe without an insole (P ≤ .001).Comparing the orthoses, there were statistically sig-nificant differences between orthoses A and C, A andD, B and C, and B and D (P ≤ .048).

Peak pressure for the total plantar surface with theorthoses was 6.7 to 8.1 N/cm2 (mean, 7.4 N/cm2; 22.8%)lower than without an orthosis (P ≤ .001) (Table 3).Comparing the orthoses with each other, only the dif-ference between orthoses A and B (24.2 versus 25.6N/cm2) was statistically significant (P = .008). Thegreatest mean reduction by orthoses was achieved inthe third metatarsal region (8.0 N/cm2; 28.6%). Differ-ences between orthoses for all regions of the fore-foot were equal to or smaller than 1.0 N/cm2, andnone were statistically significant (P ≥ .083). Thelargest difference between orthoses is found in thelateral heel region (2.5 N/cm2). Compared with theshoe-only condition, all orthoses increased peakpressures in the toe regions. The largest differencebetwen orthoses was 2.0 N/cm2 for the big toe and1.5 N/cm2 for the lesser-toes region. Only the differ-ence between orthoses B and D for the big-toe regionwas statistically significant (P = .003). For the lesser-toes region, differences between orthoses A and Dand between orthoses B and D were statistically sig-nificant (P ≤ .006).

Figure 5 shows peak pressure as a function of con-tact time. With respect to the total plantar surface, allorthoses resulted in a clear reduction in peak pres-sures during the contact time (Fig. 5A). Areas underthe curve for the orthoses were smaller than that forthe shoe without an insole (P ≤ .001). The differencesin peak pressure between orthoses are small (Fig.5A). Differences in areas under the curve for the or-thoses were not statistically significant (P ≥ .351). Forthe lesser-toes region, the areas under the curve withorthoses were greater than that for the shoe withoutan insole (P ≤ .001) (Fig. 5B). The differences between


Figure 3. Lateral views of orthoses made by castings on the right foot for one subject using methods A, B, C, andD. In the sagittal plane, the arches of orthoses A to D became more posteriorly located, while the elevation be-came more pronounced.

Method A

Method C

Method B

Method D

Figure 2. Right angular views of digitalized (Faculty of Industrial Design Engineering, University of Technology,Delft, the Netherlands) surfaces of orthoses made by castings on the right foot for one subject using methods A, B,C, and D. The heel cups of orthoses A and B were shallower than those of orthoses C and D owing to heel-pad ex-pansion. In the frontal plane, the arches of orthoses C and D were steeper than those of orthoses A and B. Thearches of orthoses made by method B were more gently sloped and the most laterally extended.


A B ShoeMethod AMethod BMethod CMethod D

Figure 4. Contact area curves for the whole plantar surface (A) and the medial midfoot region (B). Note the differ-ent square centimeter scales used in parts A and B.

Con

tact

Are

a (c

m2 )

130 -120 -110 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 -0 -

0 10 20 30 40 50 60 70 80 90 100

Total Contact Time (%)

Con

tact

Are

a (c

m2 )

24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 -0 -

0 10 20 30 40 50 60 70 80 90 100


Table 3. Peak Pressure by Region and Method

Mean Difference:Peak Pressure (mean ± SD) (cm2) A–D versus Shoe

Region Shoe Method A Method B Method C Method D (cm2)

Big toe 18.7 ± 4.7 20.7 ± 3.7 22.0 ± 5.1 20.9 ± 4.6 20.0 ± 3.7 2.2Lesser toes 10.0 ± 2.5 13.9 ± 2.7 14.3 ± 3.1 13.6 ± 3.5 12.8 ± 2.2 3.7Metatarsal 1 23.3 ± 5.7 19.9 ± 3.0 20.6 ± 3.1 20.7 ± 3.5 20.7 ± 3.1 –2.8Metatarsal 2 26.7 ± 5.9 20.9 ± 3.1 21.3 ± 3.1 20.8 ± 3.4 21.1 ± 3.5 –5.7Metatarsal 3 28.0 ± 7.5 19.8 ± 3.7 19.8 ± 4.1 20.0 ± 4.6 20.4 ± 4.8 –8.0Metatarsal 4 22.6 ± 4.7 17.4 ± 3.0 16.4 ± 3.3 17.1 ± 3.5 17.1 ± 3.1 –5.6Metatarsal 5 10.0 ± 2.5 10.4 ± 2.8 10.3 ± 2.3 10.2 ± 2.6 10.3 ± 2.8 0.3Medial midfoot 6.5 ± 3.0 9.2 ± 3.2 10.5 ± 2.1 9.3 ± 1.9 10.1 ± 2.4 3.3Lateral midfoot 10.7 ± 2.4 10.0 ± 2.2 9.9 ± 1.7 9.2 ± 1.9 10.0 ± 2.3 –0.9Medial heel 20.6 ± 3.3 14.7 ± 2.2 12.7 ± 1.7 13.2 ± 1.9 14.4 ± 1.5 –6.9Lateral heel 19.3 ± 5.1 14.7 ± 3.2 12.7 ± 2.8 12.5 ± 2.5 12.3 ± 1.9 –6.3

Total foot 32.3 ± 5.6 24.2 ± 2.2 25.6 ± 2.5 25.1 ± 2.7 24.9 ± 2.3 –7.4

Table 2. Contact Area by Region and Method

Mean Difference: Contact Area (mean ± SD) (cm2) A–D versus Shoe

Region Shoe Method A Method B Method C Method D (cm2)

Big toe 9.8 ± 2.1 9.9 ± 2.0 10.0 ± 1.9 10.0 ± 1.7 9.9 ± 1.6 0.1Lesser toes 11.6 ± 2.9 13.0 ± 2.5 12.5 ± 2.7 12.4 ± 2.6 12.5 ± 2.8 1.0Metatarsal 1 9.4 ± 1.5 9.8 ± 1.5 9.9 ± 1.6 9.8 ± 1.7 9.9 ± 1.6 0.5Metatarsal 2 6.8 ± 1.0 6.9 ± 0.7 6.9 ± 0.7 6.9 ± 0.7 6.9 ± 0.7 0.1Metatarsal 3 8.4 ± 1.7 8.5 ± 1.9 8.5 ± 1.9 8.5 ± 1.9 8.5 ± 1.9 0.1Metatarsal 4 6.2 ± 1.0 6.2 ± 1.0 6.2 ± 1.0 6.2 ± 1.0 6.2 ± 1.0 0.0Metatarsal 5 5.0 ± 0.8 5.2 ± 0.7 5.2 ± 0.7 5.2 ± 0.7 5.2 ± 0.7 0.2Medial midfoot 5.5 ± 2.0 19.5 ± 4.9 20.2 ± 4.7 18.3 ± 4.1 15.7 ± 5.1 12.9Lateral midfoot 19.7 ± 3.9 24.2 ± 2.5 24.1 ± 2.2 23.6 ± 2.3 22.4 ± 3.3 3.9Medial heel 17.2 ± 4.0 18.0 ± 4.1 18.1 ± 4.2 18.1 ± 4.2 18.1 ± 4.1 0.9Lateral heel 20.5 ± 7.7 21.5 ± 7.9 21.6 ± 7.9 21.6 ± 7.9 21.5 ± 7.9 1.1

Total foot 123.8 ± 11.5 147.2 ± 12.7 147.8 ± 12.0 145.1 ± 11.5 141.2 ± 13.6 21.5


orthoses A and B and between orthoses B and Dwere statistically significant (P ≤ .029). In the metatar-sal 3 region, peak pressure is lower with orthosesthan without (P ≤ .001) (Fig. 5C). Differences in areasunder the curve for the four orthoses were not statis-tically significant (P ≥ .263).

Figure 6 shows the gait lines. All orthoses pro-duced shorter gait lines than the shoe without an in-sole. The gait lines for the shoe without an insole andorthoses A and C are more medially located com-pared with those for orthoses B and D.

The effect on walking convenience is shown inFigure 7. The shoe without an orthosis was betterrated than those with orthoses (P ≤ .05). The shoewithout an insole had the highest mean score forwalking convenience: 7.7. Method A was secondbest, with a mean score of 6.8. Methods B and C hadan equal mean score of 6.3. Method D had the lowestscore: 4.7 (P ≤ .004). There were no statistically sig-

B

Pea

k P

ress

ure

(N/c

m2 )

0 10 20 30 40 50 60 70 80 90 100


A

Pea

k P

ress

ure

(N/c

m2 )

0 10 20 30 40 50 60 70 80 90 100


32 -30 -28 -26 -24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 -0 -

C

Pea

k P

ress

ure

(N/c

m2 )

0 10 20 30 40 50 60 70 80 90 100


32 -30 -28 -26 -24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 -0 -

Figure 5. Peak pressure curves for the whole plantarsurface (A), the lesser-toes region (B), and the meta-tarsal 3 region (C).

32 -30 -28 -26 -24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 -0 -

ShoeMethod AMethod BMethod CMethod D

Figure 6. Depiction of the locations of gait lines foundwith each method and the shoe alone.

Shoe

Method A

Method B

Method C

Method D


nificant differences in walking convenience amongorthoses A, B, and C (P ≥ .206).

Discussion

We compared the effects of four commonly usedcasting methods for the production of accommoda-tive and functional foot orthoses on plantar pressureand walking convenience in ten women with normalfeet. Visual inspection of arch height and geometryshowed clear differences among the orthoses madeaccording to the four casting protocols.

Comparison Between Shoe and Orthoses

All four casting techniques produced increased totalcontact areas and lower peak pressures during walk-ing. The medial midfoot region contributed most tothe increase in total contact area. The largest pressurereduction was in the central forefoot. All casting tech-niques caused higher pressures under the toes. Thiswas also found by Redmond et al39 and Chen et al.40

An increase in the total contact area is often usedas a surrogate measure for pressure reduction or re-distribution. Total contact area would be appropriateas an “effect parameter” while standing still or inrigid rocker shoes, where the foot is more or less im-mobilized. However, while walking in flexible shoes,the effective contact area changes in size and loca-tion during the rollover process. The effective con-tact area is located under the forefoot during thepush-off phase, where the highest forces are acting.41-43

Therefore, contact area enlargement in the midfootregion cannot be effective in reducing pressure dur-

ing push-off. Because even without orthoses the fore-foot is almost completely loaded during rollover, ac-cording to the area enlargement concept, not muchpressure reduction is to be expected. Gait lines endedmore posteriorly in shoes with the tested orthoses,which indicates a posterior transfer of peak pressureor an increase in the contact area in a posterior di-rection during push-off. A somewhat larger increasein contact area might be expected by using more de-formable or compliant cushioning materials.14, 17

Good walking convenience is important for accep-tance of an orthotic device. Walking conveniencewas better rated in the shoe without an orthosis. Apossible explanation for this finding is that the par-ticipants did not have a chance to get accustomed tothe orthoses.

Comparison Between Orthoses

Foam box methods resulted in larger contact areasthan plaster methods. This was at least partly due tothe soft-tissue expansion that occurred during loadingin the foam box. Given that maximizing the contactarea is the main purpose of accommodative orthoses,it is surprising that the functional foam box methodresulted in somewhat larger contact areas. Also,whereas the four casting methods led to clearly differ-ent orthotic contours and differences in contact area,the corresponding peak pressures were virtually thesame: for clinically important regions in the forefootregion, the differences were no greater than 1.0 N/cm2.The gait lines, or the center-of-pressure paths, offunctional orthoses were similar and were more lat-erally located than the gait lines of accommodativeorthoses. This finding is in accordance with the objec-tive of functional orthoses: the change in the center ofpressure reflects the redirection of forces. The lateralshift of the center of pressure with functional or-thoses was also found by Sloss44 and Scherer and So-biesk,45 who postulated that the lateral shift indicatesa reduction in pronation and greater foot stability. Alateral shift of the center of pressure may also be de-sirable when the center of pressure is too far medial-ly deviated without orthoses.44 Kirby46, 47 and Fuller48

described the possible implications of the center ofpressure in relation to the spatial location of the sub-talar joint axis: altering the center-of-pressure paththrough orthoses might curatively adjust the internalstress on foot structures. The meaning of the center-of-pressure path to foot function and orthoses thera-py is not fully understood, but it is claimed that thecenter of pressure is a promising parameter for thebiomechanical analysis of foot-orthoses therapy.12, 38, 49

Walking convenience was better rated in orthoses

Rat

ing

10 -

9 -

8 -

7 -

6 -

5 -

4 -

3 -

2 -

1 -

0 -

7.7 ± 1.4

6.8 ± 1.46.3 ± 1.5

6.3 ± 1.7

4.7 ± 1.8

Figure 7. Walking convenience rated on a 10-pointscale. Scores are given as mean ± SD.

Shoe Method A Method B Method C Method D


that were made by foam box casting than by plastercasting. This finding is probably due to the more “nat-ural” curvatures that are the result of weightbearingduring foam box casting. The use of alternative mate-rials or cast corrections might lead to different peakpressures or ratings for walking convenience, but wethink that the rank order of these outcomes would besimilar to that found in this study.

The effects of different casting methods on peakpressure and gait lines for accommodative and func-tional orthoses are virtually the same. In addition,walking convenience was better rated for orthosesmade using foam box techniques. The combinationof these results indicates that foam box techniquesgive the best results. Future research should provewhether this is also true for patients with an indica-tion for custom-made functional or accommodativefoot orthoses.

Conclusion

Each casting method resulted in characteristic 3-Dcontours. Compared with the shoe without an insole,all orthoses reduced peak pressures. The four castingmethods resulted in differences between orthoseswith respect to contact area but only slight differ-ences in peak pressure. The gait lines were differentbetween accommodative and functional orthoses,but foam box and plaster casting did not lead to dif-ferent gait lines. Foam box casting is preferable forthe construction of accommodative and functionalorthoses because it is easier to use, quicker, cleaner,and less expensive and because it leads to betterwalking convenience.

Acknowledgment. Carlo Colla of Livit Orthopae-dics in Maastricht and Bert Donders and LambertKlaus of the Centre for Health Science and TechnicalTrades in Nieuwegein for information about castingtechniques; our colleagues at the Department ofPhysiotherapy at University Hospital Maastricht forthe use of their facilities; Joris Vergeest, PhD, andWolf Song, PhD, of the University of Technology,Faculty of Industrial Design Engineering in Delft, forscanning the orthoses; and Durea Schoenfabriek BVin Drunen for providing the shoes free of charge.This study was supported by Smeets & Zonen Ortho-pedische Schoentechniek in Geleen.

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Documents

Casting Methods and Plantar Pressure