VeteransAdministration

Journal of Rehabilitation Researchand Development Vol . 22 No . 3BPR 10—42 Pages 18—22

Walking casts : effect on plantar foot pressures

JAMES A. BIRKE, M.S. : DAVIS S . SIMS, JR., M.A. ; WILLIAM L. BUFORD, PH.D.Department of Physical Therapy and Rehabilitation Research,National Hansen's Disease Center, Carville, Louisiana 70721

Abstract — Pressure measurements were made atfour sites on the right foot of six normal subjects whilethey walked in a standard shoe, conventional paddedcast, total contact cast, and again in a shoe. Nodifferences in mean relative pressure were foundbetween the padded cast and the total-contact cast.Significant reductions in mean relative pressure werefound between the standard shoe and walking casts atthe first and third metatarsal head . This study sup-ported the use of walking casts in the management ofplantar ulcers . The effectiveness of the cast in reduc-ing plantar pressure was not found to be dependent onthe cast padding technique.

INTRODUCTION

Plaster walking casts have been used to pro-mote healing of neuropathic plantar ulcers inpatients with diabetes and Hansen's disease sincethe 1930's . Four rationales have been cited for theeffectiveness of walking casts in healing plantarwounds : 1) immobilization, minimizing stretch onthe healing wound site ; 2) reduction of footpressures by the total contact plaster fit;3) control and reduction of edema by the support-ing plaster cylinder ; and 4) protection fromfurther trauma by the hard plaster shell (1-4, 7,8, 12).

No data are available to support the rationalethat immobilization or protection from traumacontribute to the healing of plantar ulcers withina walking cast . Mooney and Wagner (9) reportedon the effectiveness of walking casts in decreas-ing edema in normal subjects and diabetic pa-tients . The strongest data, however, support therationale that walking casts promote healing of

ulcers by reduction of pressure . Recent studiesshow plantar ulcers develop at the areas ofmaximum pressure on the foot . The firstmetatarsal head is the most common site, and theremaining metatarsal heads are among the nextmost common sites of plantar foot ulceration inpatients with Hansen's disease and diabetes(6, 14, 15) . Pollard et al . (13) demonstrated thatconventional walking casts greatly reduce plantarfoot pressure and therefore promote healing atareas of high pressure.

Conventional casting techniques incorporateseveral inner layers of cotton padding to preventskin breakdown. In the 1960's Brand recom-mended the use of a total-contact cast usingminimal padding over bony areas only and acarefully molded inner plaster shell. The total-contact cast was thought to reduce pressure andfriction on the foot and to minimize loosening ofthe cast from gradual compression of the softcotton layers (5).

To date there are no data to support the use ofa total-contact cast or the effectiveness of onecast technique over another in reducing footpressures. A major reason has been the unavaila-bility of a suitable pressure transducer (11) . Weapproached this problem by using a thin, flexibletransducer, which has a minimal effect on the softtissue/device interface and provides a repeatablemeasurement of relative pressure.

The purpose of this study was to compare theeffect of a standard shoe, a conventional paddedcast, and a total-contact cast on plantar footpressures during walking. The hypothesis was

t

(

t

(

18

19

BIRKE et al . : Walking casts

tially in a standard shoe, conventional paddedwalking cast (PC), total-contact cast (TCC), andagain in the standard shoe . Subjects walked adistance of 23 meters on three consecutive trialsfor each treatment condition . An assistant wasused to pace subjects at their self-selected veloci-ty during all walking trials . Testing order of theTCC and PC was randomly assigned to eliminatesystematic error. The second cast was appliedimmediately after removal of the first . Castingtechniques differed primarily in the method usedto pad the foot and leg prior to applying plaster.Two rolls of 4-inch cotton webril were wrappedevenly over the foot and leg in the PC (Fig . 1).The TCC utilized 1/4 inch thick felt pads tapedover the malleoli, tibial crest, and dorsum of thefoot, and Scifoam (Contemporary Products,Corona, CA) placed over the toes (Fig. 2). Thetechnique of plaster application for the TCC hasbeen described previously (5) . Fiberglass resincasting tape (Scotchcast, 3M Center, St . Paul,MN) was used for reinforcement layers in bothcast techniques ; allowing patients to walk within

'UL1Conventional cast padding technique.

that a snug-fitting total-contact cast would pro-vide better contour to the foot and leg and resultin lower discrete foot pressures compared with aconventional cast.

METHOD

Capacitive pressure transducers (Hercules Or-thoflex Data System, Allegany Ballistics Lab,Cumberland, MD) 2 mm thick and L5 cm indiameter were taped to the first metatarsal head(MTH), third MTH, fifth MTH, and plantar heelof the right foot of six normal subjects . The footwas then covered with a cotton stockinette,which remained undisturbed during the studyTransducers were calibrated according to themanufacturer's instructions prior to testing eachsubject. Pressure measurements were made us-ing a four-channel capactive impedance bridgeamplifier (Hercules Orthoflex Data System) andan oscillographic recorder (Beckman Type RMDynagraph Recorder, Beckman Instruments,Schaller Park, IL) while subjects walked sequen-

FIGIJTotal-contact cast padding technique .

20

Journal of Rehabilitation Research and Development Vol . 22 No . 3 July 1985

FIGURE 3Standard placement of walking heel at 40 percent of heel-to-toe length.

30 minutes after application . Walking heels wereattached to the bottom of the casts at a point 40percent of the distance from heel to toe (Fig . 3).

Relative pressure was measured in millimetersof peak-to-peak chart deflection for 36 steps foreach treatment condition . The middle distance ofthe best two walking trials was used for analysis.Mean relative pressure was calculated for each ofthe four treatment conditions at all transducersites. An analysis of variance was used to deter-mine whether treatment differences were signifi-cant within each site . Duncan's New MultipleRange Test was used for post hoc analysis oftreatment means (10).

RESULTS

Analysis of variance (Table 1) of mean relativepressure during walking was significant at the

TABLE 1Analysis of variance of

ielative pressureby site

Source DF SS MS F

1st MTH

treatments 3 3,040 1,010 13 .57*error 20 1,490 74 .6total 23 4,530

3rd MTH

treatments 3 2,820 939 33 .47*error 20 561 28 .1total 23 3,380

5th MTH

treatments 3 128 42.7 2 .99terror 20 285 14.3total 23 413

Heel

treatments 3 342 114 3 .011error 20 750 37 .9total 23 1,100

* P < 0 .001 t P > 0.05 MTH = metatarsal head,DF = degrees of freedom ; SS = sum of squares, MS = meansquares, F = f ratio

first MTH and third MTH . Duncan's test wasperformed to establish which treatment differed.A significance level of 0 .05 was used for compari-sons . No difference was found between paddedand total-contact casts or between initial and finaltrials walking in a shoe (Figs . 4-7). Significantdifferences were found between the mean rela-tive pressure walking in shoes compared withcasts . Pressure was reduced in casts 84 percentat the third MTH and 75 percent at the firstMTH, as compared with shoes (Fig . 8). Althoughnot statistically significant, relative pressure atthe fifth MTH and heel showed reductions of35 percent and 25 percent, respectively.

DISCUSSION

This study demonstrates the effectiveness ofwalking casts in reducing foot pressure in apopulation of normal individuals . These findingssupport the rationale that walking casts promotehealing of neuropathic plantar ulcers by redis-tributing the forces on the bottom of the foot . Thepresent findings as well as those of Pollard and

21

BIRKE et al . : Walking casts

RELATIVE PRESSURE

RELATIVE PRESSURE(mm chart deflection)

(mm chart deflection)

-ascs)

Shoe

TCC TCC

Shoe

PC

PC

Shoe

Shoe

FIGURE 4Mean relative pressure at the 1st metatarsal head for eachof 4 walking trials.

associates (13) show greater pressure reductionat the first and third MTH as compared to thefifth MTH and heel . Further study is needed todetermine if the rate of healing using walkingcasts is dependent on the ulcer location.

The method of padding in walking ea : ' had noeffect on the pressure distribution ove electedareas on the bottom of the foot in fi le

;,tion. The influence of time could not 'since pressure measurements were made1 hour after cast application . .A PC may haysless effective in reducing foot pressure over Cdue to looseness from compression of the cottonpadding. Shear stress (friction) may also bereduced in a snug-fitting TCC . Since thetransducers used in this study only measurednormal stress (pressure), further investigation isneeded to determine whether friction is de-creased in a TCC . Measurement system unrelia-bility was a potential source of error that wouldhave limited the ability to detect differencesbetween casts . This is an unlikely explanation forthe results obtained since initial and final walks inthe standard shoe did not differ significantly atany site .

FIGURE 5Mean relative pressure at the 3rd metatarsal head for eachof 4 walking trials .

RELATIVE PRESSURE(mm chart deflection)

Shoe

TCC

PC

Shoe

it the 5th metatarsal head for each

22

Journal of Rehabilitation Research and Development Vol . 22 No . 3 July 198

letMTH

3rdMTH

RELATIVE PRESSURE(mm chart deflection)

es)

Shoe

TCC

I ERE„

W ION

cn

p<® .Cal

p<0 .501

es)

PC

5thMTH N .S.

Shoe

Heel

N .S.

FIGURE 7Mean relative pressure at the heel for each of 4 walkingtrials.

CONCLUSIONS

Within the limitations of this study it is possi-ble to conclude that 1) walking casts are effectivein reducing pressure at the first and third ZVITHand 2) there is no difference in the pressuredistribution between padded and total-contactcasts.

REFERENCES

1. ANDERSEN JG: '11-eatment and prevention of plantarulcers . Lep Rev 35: 251-258, 1964.

2. ANGEL JC: The mechanism of the healing cast. Ortho-pedic Seminars, University of Southern California,Department of Orthopedic Surgery, Rancho LosAmigos Hospital 4 : 17, 174-179, 1973 . .

3. BAUMAN JH, GIRLING JP, BRAND PW : Plantar pres-sures and trophic ulceration. J Bone J Surg 45B: 652-673, 1963.

4. BRAND PW : The insentitive foot. In: Disorders of theFoot, vol . II, MH Jahss (ed .). Philadelphia, PA:Saunders, 1982, p. 1266-1286.

5. COLEMAN WS, BRAND PW, BIRKE JA: The total con-tact cast—A therapy for plantar ulceration of theinsensitive foot . J Am Pod Assoc 74 : 548-552, 1984.

6. CTERCLEKO GC, DHANENDRAN M, HUTTON WS, LE-QUESNE LP : Vertical forces acting on the foot of

FIGURE 8Reduction of pressure while walking in casts compared withwalking in shoes for each of 4 transducer sites.

diabetic patients with neuropathic ulcertation . Br~ JSurg 68 : 609-14, 1981.

7. HELM PA, WALKER SC, PULLUIM G: Total contactcasting in diabetic patients with neuropathic footulcerations . Arch Phys Med Rehabil 65 : 691-693.

8. LANG-STEVENSON Al, SHARRARD WJW, BETTS RP,DUCKWORTH T: Neuropathic ulcers of the foot . J BoneJ Surg 67B : 438-442, 1985.

9. MOONEY V, WAGNER W: Neurocirculatory disordersof the foot . Clin 03, ' , to` Relnto c F : 's 122: 53-61, 1977.

10. OTT L : An Iris o - . .

to

s 11 Methods andData Analysis .

nont, CA: Wadsworth, 1977,p . 392-407.

11. PATTERSON RP, SV: The accuracy of electricaltransducers for thf me al : : er•lent of pressure appliedto the skin . IEEE Biomed Eng 26 : 450-456,1979.

12. POLLARD JP, LEQUESNE LP : Method of healingdiabetic forefoot ulcers . Br Med J 286 : 436-437, 1983.

13. POLLARD JP, LEQUI SNE LP, TAPPIN JW: Forcesunder the foot . J Bic , ?d Eng 5 : 37-40, 1983.

14. PRING JD, Cr -11 y N: A N: Simple plantar ulcerstreated by below-knee plaster and moulded doublerocker plantar shoe . Lepr Rev 53 : 261-264, 1982.

15. SODERBERG G: Follow-up of application of plaster-of-paris casts for noninfected plantar ulcers in fieldcondition, Lepr Rev 41 : 184-190, 1970 .