comparison of shoe insole materials in pressure relief - copy

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Prosthetics and Orthotics International, 1986, 10, 135-138A comparison of shoe insole materialsin plantar pressure relief

C . L E B E R a n d P . M . E V A N S K IDepartment of Orthopaedic Surgery, New York University Medical Center

AbstractA clinical study was performed to evaluate theeffectiveness of seven shoe insole materials andtheir ability to relieve areas of high plantarpressure. The following materials were tested:Latex foam, Plas tazote R , D y n a f o a m R , Orthofe l t , PPT R , S p e n c o R , and M olo R . Twenty-sixpatients with areas of high plantar pressure weretested using each of these m aterials . The Ha rrisand Beath footprint ing technique was used tomeasure plantar pressure. I t was found that theaverage pressure of a clinically painful plantararea was 398.15kN/m 2. All insole materialstested decreased this pressure, with averagesranging from 186.33kN/m 2 to 286.35kN/m 2.PPT, Plastazote and Spenco were the mosteffective products tested.

IntroductionAre as of increased planta r pressure have beenclearly linked to foot pain and discomfort(Godfrey et al, 1967; Silvino et al, 1980).Increased pressure is also responsible for skinbreakdown in the denervated foot such as inHansen ' s d isease and diabet ic neuropathy(Bau ma n et al , 1963; McD owell and E nn a,1974). Attempts to reduce this high plantarpressure have produced a wide variety of shoeinsoles which can be inserted into footwearbetwe en th e shoe sole and the p lantar surface ofthe foot.Because of the great number of products

clinically available, there is a need forexperimental data to determine which productsare most effective. This study was undertaken tocompare seven materials commonly used toreduce p lantar pressure . The s tudy measuresmaxim um pla ntar pressures using the Harris andBea th (1947) footprint techn ique which enabledboth quanti tat ive and quali tat ive results to becompi led .

Materials and methodsDescription of materials testedSeven produc ts were evaluated a nd are brieflydescribed below.PlastazoteR is a foam ed p olye thylen e of closedcell construction. I t is mouldable, bouyant andno n-to xic . Plastazote is widely used inorthopaedics as a foot orthosis for protectionagainst pressure points . I t can be laminated toother materials for increased reinforcement.

Three densit ies are available. The mediumdensity was tested.Latex foam is a cellular rubber of open cellconstruction (absorbs water) . I t is washable,odourless and can be cemented to otherma terials . Latex foam has a long history of use inorthopaedics as a footwear insole and castpadding.DynafoamR is a polyvinyl chloride foamcompound. I t is odourless and water resistant ,and quickly forms an impression of the foot.Ortho felt is a resilient fabric composed of ablend of cotton and wool, with a relatively lowtensile strength. Felt is widely used for castpadding and pressure rel ief pads in shoes.Spenco R is a neoprene sponge product withnitrogen-induced closed cells which is coveredwith a multistretch nylon fabric on one sid e. It isresistant to decay and odour. Spenco is said toabsorb vert ical forces, torq ue , and fore, aft, andlateral shear. I t is designed to preventneuropathic and rheumatoid ulcerat ions and ismarketed for athletes to prevent bl isters andcallosities (Spence and Shields, 1968).Molo R is a combination of latex, jels , leather,cork and other products which are incorporatedinto a rubbery sheet . Under continued pressureMolo forms an impression of the foot. It isresistant to moisture and can be joined toanother subs tance .PPTR is an open cell, porous, firm foammaterial which relieves local pressure. It ismarketed as a "high-energy absorbingsubstance" that wil l not "bottom out" under the

forces of pressure, shock and shear.All correspondence to be addressed to Dr. P. M.Evan ski, 530 First Av enu e, Suite 5D, New Yo rk,N. Y. 10016.

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13 6 C. Leber and P. M. EvanskiAll materials tested were one-eighth inchthick and can usually be added to a shoe withoutmaking it too tight to wear comfortably.*Measurem ent of plantar pressuresPlantar pressures were recorded using theversion of the Harris and B eath footprint ing matmanufactured by Berkem ann Lab ora tor ies and

available through Apex Foot ProductsCorpo ra t ion , Englew ood, N .J . For de ta il s of i tsuse and quantificat ion of the recorded pressu re,see Harris and Beath (1947) and Silvino et al(1980).Twen ty-six patie nts were studie d, 16 male an d

10 fem ale, ran ging in age from 25 to 71 years. Allpatients complained of forefoot pain on weight-bearing and all showed areas of increased

pressure under one or more metatarsal headswhen tested with the Harris and Beathtechnique .Footprints of the 26 patients were initiallyrecorded without orthotic material . Subsequentfootprints were recorded for each patient testingeach of the materials described above.The material to be tested was placedunderneath the recording paper which wasunder the Harris mat. W hen a subject s teppedon the mat the pressure recorded representedthe interface between the foot and the insolematerial which is where plantar pressureredistr ibution occurs.Footprints using each insole material werecom pared to the patient 's control footprint , anda general category of effectiveness was assignedto each product by the overall improvement

observed. The following three categories wereused: most reduction in plantar pressure, somereduction, least reduction.

* All products, except PPT, were purchased from theEneslow-Apex Shoe Co rpora t ion, 200 Fores t Av enue ,Englewood, N.J. 07630. PPT was obtained fromProfessional Protective Technology, Inc. , 21 EastIndustry Court , Deer Park, N.Y. 11729

Fig. 1. Footp rints recorded using the Harr is and Beath footprinting mat and various orthotic m aterials de mo nstratean area of increased pressure under the first metatarsal head; left, with least effective material, centre, with moreeffective material, and right, with most effective material.


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Estimation of pressure was made for eachfootprint using a calibration curve (Silvino et al,1980). Mean pressure values were thencalculated for each product and for the control.Nu me rical data was eva luate d for significance bya two-way analysis of variance.Results

Th e seven materials were divided into generalcategories of effectiveness by the overallapp earan ce of the footprints . Tho se that showedthe most reduction in plantar pressure werePlas tazote , Spenco, and PPT. Those tha tshowed some reduction were Dynafoam andMolo. Those that showed the least reductionwere Ortho fel t and Latex foam.Figure 1 dem onstrate s an examp le of the threecategories of effectiveness. The estimated footpressures appear in Table I . The mean value of

pressure under the clinically painful metatarsalhead was 398.15kN/m 2 without any insolematerial . When the various products were usedthe mea n pres sure at the painful site rang ed from286.35kN/m 2 with Latex foam to 186.33kN/m 2with PPT. This represented a decrease inpressure of 28 percent and 53 percentrespectively.Two -way ana lysis of varianc e disclosed that allseven products were significantly different fromcontrol at the p


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138 C. Leber and P. M. Evanskistrength or special uses. The relief of pressure bythese compound materials has not been studiedand is an area where more research is needed.

It has been demonstrated that differencesexist between commercially available productsin their ability to relieve high plantar pressureand this information can be of great value inprescribing footwear insoles for the manypatients suffering from pain or pressure-inducedlesions of the feet.Acknowledgements

The authors wish to acknowledge the editorialassistance of Beatrice Pasternak.

REFERENCESB A U M A N , J. H., B R A N D , P. W. (1963). Measurementof pressure between foot and shoe. Lancet 23March, 629-632.B A U M A N , J. H., GIRLING , J. P., B R A N D , P. W. (1963).Plantar pressures and trophic ulceration: anevaluation of footwear. J. Bone Joint Surg. 45B,652-673.

CAMPBELL, G. , N E W E L L , E. , M C L U R E , M. (1982).Compression testing of foamed plastics and rubbersfor use as orthotic shoe insoles. Prosthet. Orthot.Int. 6, 48-52.G O D F R E Y , C. M. , L A W S O N , G. A., S T E W A R T , W. A.(1967). A method for determination of pedalpressure changes during weight-bearing:preliminary observations in normal and arthritic

feet. Arthritis Rheum. 1 0 ( 2 ) , 135-140.HARRIS, R. I. , BEATH , T. (1947). Army footsurveyan investigation of foot ailments inCanadian soldiers. Ottawa, Canada: NationalResearch Council of Canada. ( N . R . C . #1574).M C D O W E L L , F. , E N N A , C. D. (1974). Surgicalrehabilitation in leprosy. Baltimore M D : Williams& Wilkins.SILVINO , N., E V A N S K I , P. M. , W A U G H , T. R. (1980).The Harris and Beath footprinting mat: diagnosticvalidity and clinical use. Clin. Orthop. 1 5 1 , 2 6 5 - 2 6 9 .S P E N C E , W. R., S H I E L D S, M. N. (1968). Prevention ofblisters, callosities and ulcers byabsorption of shearforces. J. Am. Podiatry Assoc. 58 , 428434.

comparison of shoe insole materials in pressure relief - copy

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