a comparison of plantar pressure in patients with diabetic foot ulcers using different hosiery

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The International Journal of Lower Extremity

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DOI: 10.1177/153473460200100305

2002 1: 174International Journal of Lower Extremity WoundsByron Blackwell, Roy Aldridge and Shirley Jacob

A Comparison of Plantar Pressure in Patients With Diabetic Foot Ulcers Using Different Hosiery

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BLACKWELL ET ALPLANTAR PRESSURE

A Comparison of Plantar Pressurein Patients With Diabetic Foot Ulcers

Using Different Hosiery

Byron Blackwell,* Roy Aldridge, PT, MS,* and Shirley Jacob, PhD

*Arkansas State University, Ark, USA, andSoutheastern Louisiana University, Hammond, La, USA

Abnormally high plantar pressure has been associated withthe development of foot ulcers in populations with diabetes.Improved foot care includes the use of hosiery (socks) as wellappropriate footwear. In this study, the Parotec System, anin-shoe plantar pressure measurement device, was used tomeasure the plantar pressure of the forefoot of 21 partici-pants. All patients were diagnosedwith diabetes and were as-

sessed while wearing a combination of either a diabetic soca dress sock, or no sock and the participants own shoe slipper. There were no statistically significant differences btween combinations of socks and footwear.

Key words: diabetes, ulcers, plantar pressures, hosiery

It is estimated that 16 million Americans suffer fromdiabetes. Among this population, an estimated 2.5million people (15%) will develop foot ulcers.1 Ap-proximately 14% to 24% of these patients will requirean amputation.1 It has also been estimated that 20% ofall diabetic admissions to hospitals are for foot prob-lems. Diabetes is the most frequent cause ofnontraumatic lower limb amputation in the UnitedStates each year, comprising more than 56,000amputa-tions.2 In 2002, the total cost of caring for persons with

diabetes inclusive of loss of productivity in the UnitedStates was estimated at $98 billion annually.2

Patients with foot ulcers localized to the plantar sur-face of their feet experience a 15 times higher overallrisk of amputation compared to nondiabetes.3 It hasbeen reported that diabetic neurotrophic ulcers areconfined almost exclusively to the plantar surfaces ofthe metatarsal heads and toes.4 Abnormal foot pressureis implicated in the etiology of foot ulcers. There is aneed to better manage this problem as well as to pre-vent it, as diabetes is projected to increase to involve 29million by the year 2050.5 The use of improved footcare programs and custom-made shoes is known to be

beneficial, leading to a 44% to 85% reduction in thrate of amputations.6

Neuropathic ulcers may be prevented in some ptients. This involves reduction of increased pressuperceived on plantar surfaces using specially designeshoes.7 The patient needing extra depth and occasionally rocker soles will need additional attention. as sucshoes can be unacceptable for everyday use.7 Adaptinthe hosiery is another step in helping the patient andreported to reduce plantar pressure.

Researchers have developed experimental hosierfor diabetic patients.8 The experimental hosiery hbeen shown to reduce the plantar pressure more effciently than typical hosiery.7 The purpose of this studwas to evaluate the impact of various socks (diabetic vnondiabetic [dress socks]) on the peak plantar pressumeasurements of persons with diabetes. The diabetsock (JOBST[Germany]) is composed of 100% cottowhereas the nondiabetic sock (basic Editions) is composed of 100% nylon. Plantar pressures were accepteas a measure of reduced risk of ulceration.

BACKGROUND STUDIES

Previous studies have used an optical pedbarography to collect the static and dynamic plantpressure under barefoot as well hosiery-protected foconditions. These studies examined subjects whiwalking barefoot as well as while wearing differen

174 LOWER EXTREMITY WOUNDS 1(3);2002 pp. 174178

Correspondence should be sent to: Roy Aldridge, PT, MS, PO Box

910, State University, AR 72467; e-mail: [email protected].

2002 Sage Publications

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support hosiery.7,9 The investigation presented in thisreport was limited to the dynamic plantar pressuremeasurements using an in-shoe measurement device(Parotec System[Germany]). The device allows 24 in-dependent measurement sites. The diabetic sock(JOBST), dress sock,and no-sock (barefoot)conditionswere examined with patients using a slipper and their

own shoe.Veves et al9 studied the pressure-reducing effects of

socks worn by athletes. In another study, 27 patientswere studied using a computerized optical pedobaro-graph. Three footsteps on each side were recorded un-der 3 conditions: barefoot, wearing the patients ownhosiery, and wearing the experimental patented pad-ded hosiery.9 It was reported that the special hosierydesigned for diabetic patients was more efficient in re-ducing plantar pressure.9

Veves et al7 studied the durability of these speciallydesigned socks and reported plantar pressures of531.702 kPa, 234.459 kPa, and 343.35 kPa obtained at

baseline, 3-month follow-up, and 6-month follow-up,respectively. Socks were washed regularly during thestudy. The study demonstrated the pressure reductionafforded by hosiery at different time periods.

METHODS AND MATERIALS

Twenty-one subjects (10 men, 11 women) with amean age of 57.4 years (20 to 83 years) were recruitedfrom the communityand previous diabetic foot studiesto participate in this study, which was approved by theinstitutional review board at Arkansas State Univer-sity. Prior informed consent was obtained from all par-

ticipants. All participants were diabetic by definition(5 type I, 16 type II). Eighteen participants (85.4%) hada previous history of, or complained of, foot complica-tions. These included perceived loss of feeling of hot/cold (4), discoloration (1), edema (7), burning (3), pain(8), tingling (5), cramping(3), bunions (2), callusforma-tion (7), ulceration (3), loss of protective sensation (9),and amputation (2). However, if an open ulceration waspresent at the time of testing or if the participant hadsuffered an amputation, data from that extremity wereexcluded. At the time of data collection, 2 (9.5%) par-ticipants had an amputation (1 below-knee and 1 re-moval of the third and fourth phalanges) and 1 (4.76%)

participant had an open ulcer. Patients with bilateralfrank ulcers were excluded from the study.Patients walked a distance of 6 m wearing a control-

ler unit weighing 0.907 kg around their waist. Theywore a 3-mm thick collecting insole in each shoe, liftedtheir legs while seated for 1 second to calibrate the de-

vice, and stood without support for 10 seconds to colect staticmeasurements. Each patient (n = 18)repeatethe walk. The following procedure was repeated on aparticipants. The first step was an oral explanation andemonstration of the collection procedures while thsubject sat in view of the testing path. After history taing, body weight (using an electrical scale) and sho

size were measured. Sensation was tested with thSemmes-Weinstein monofilament(5.07 g), and the fopulse was palpated by the examiner. All informatiowasrecorded on the intake form and filed in individufolders.

Patients were asked to participate in 3 trials of eacof the 6 conditions using a repeated-measures desigbased on previous pilot studies by the group. Theconditions were wearing (1)nosock with slipper, (2)nsock with the patients own shoe, (3) dress sock witslipper, (4) dress sock with the patients own shoe, (diabetic sock with slipper, and (6) diabetic sock witthe patients own shoe. Each trial consisted of the p

tient walking on a hard, level surface for a predetemined distance while wearing one of the 6 combintions of hosiery and shoe.

All participants completed three 6-m trials per condition while fitted with the Parotec-Systems data colection device, which was attached to a belt and worabout the waist. The pressure sensor pads were placedirectly under the hosiery or foot and directly abovthe insole of either the patients own shoe or slippedepending on the combination of support and hosierThe sensor pads were connected to the data collectiodevice by wires.Participants were given a verbalexplnation and demonstration of the procedure.

Patients were instructed to lift their feet off thground for 3 seconds while seated in order to calibrathe device. After calibration, patients stood with thefeet together at the starting point of their walk for seconds whilethestaticsignals were collected. The ptients were then asked to walk normally at a constanspeed while plantar pressure measurements were rcorded. Along with the collection of the dynamic platarpressure measurements, thetime andthe total number of steps during the distance covered were collecteto ensure that a consistent speed and number of stepwere taken with each trial. After walking, patients rturned to the computer, where they sat in a chair whi

the dataweredownloaded intotheindividuals file. Ptientswere permittedto recover before performing a rpeat walk. All data for each participant were collecteon the same day by the same researcher, with the timof day being dependent on a mutual agreement btween the schedules of the participant and examiner

LOWER EXTREMITY WOUNDS 1(3); 2002 175

PLANTAR PRESSURE



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RESULTS

The Parotec System records 24 separate sensors,

but for the purpose of the study, datafrom sensors relat-ing to forefoot alone (17 to 24) were considered. Eachtrial consisted of data collected on 5 steps. Therefore,each mean value of the 3 trials represented 15 individ-ual steps for the particular condition of sock/no sockand shoe/slipper. Data of each individual participatingwere entered into Sigma Stat (US) for data analysis us-ing 1-way repeated-measures analysis of variance.

Table 1 represents the statistical analysis of themeanplantar pressure (kPa) measurements of the forefoot re-gion taken during the 6 combinationsused in thestudy.Figure 1 shows the descriptive statistics of the meanplantar pressure of the forefoot for each of the 6 vari-

ables used in the study.Data analysis of the forefoot region plantar pressuremeasurementsproducedno statisticallysignificant dif-ferences between any of the 6 combinations in thestudy. One-way repeated-measures analysis of vari-ance revealed that the plantar pressure measurementsunder the area of the metatarsal heads between the 6combinations in the study were not statistically signifi-cant. These are presented in tabular form in Table 2.

Analysis of variance of the plantar pressure mea-surements recorded under the toes (sensors 21 to 24)were also run for the 6 combinationsin the study. A sta-tistically significant difference (p = .0195) was shownbetween 5 of the combinations. The slipper combinedwith no sock had significantly lower pressure than theother 5 combinations. Because these data were non-normally distributed, a Friedman repeated-measuresanalysis of variance on ranks was used to evaluate themeasurements under the phalanges/toes. Table 3shows the descriptive data of the phalanges/toes taken

during the 6 combinations used in the study. One-warepeated-measures analysis of variance was used to dtermine differences between the 6 combinations mesured by sensor 20, which was located under the firmetatarsal head. Again, no statistically significant diferences were detected.

These measurements suggest that the diabetic socdidnot significantly decreasethe plantar pressuremesurement with either the shoe or the slipper.

DISCUSSION

The aim of this study was to determine differencbetween hosiery used by diabetic patients using platar pressure measurements as an objective risk assesment for foot ulcer occurrence/prevention. Two diffeent types of hosiery (socks) were compared to a n

socks condition in this study to measure plantar presure obtained with different footwear. Lower plantpressure or the ability to lower a high value is considered useful in reducing the risks of forefoot ulcers ipersons with diabetes. This study showed that the dibetic sock (JOBST) was not different from the othtypes of hosiery in reducingplantar pressure. Howeveit was observed that the slipper/no sock combinatiowas associated with significantly less pressure undthe metatarsal heads. This interesting observation mahave implications for persons with diabetes in Chineand South Asian societies, where slippers arworn outwith the household and where diabetes increasing.

For those persons who have diabetes, finding means of dispersing and relieving this abnormal presure can be the difference between having healthy feand having complications that could lead to a signifcantly increased risk of amputation. Many simple ations can be taken as a preventative means in caring f

176 LOWER EXTREMITY WOUNDS 1(3); 2002

BLACKWELL ET AL

Table 1. Plantar Pressure Measurements (kPa)of the Forefoot Region (Sensors 17 to 24)

Taken During the 6 Combinations (N = 21)

Combination Mean SD SEM

Slipper with no sock 1123.5 256.0 55.9

Slipper with diabetic sock 1148.9 266.7 58.2Slipper with dress sock 1161.4 289.4 63.2Shoe with no sock 1091.9 232.3 50.7Shoe with diabetic sock 1143.5 241.3 52.7Shoe with dress sock 1129.5 230.9 50.4

NOTE: One-way repeated-measures analysis of variance showed nosignificant difference between the 6 combinations; F = 0.562, p =.729. Power of the performed test with = .05 is 0.0496

Table 2. Plantar Pressure Measurements (kPa)of the Metatarsal Heads (Sensors 17 to 20)Taken During the 6 Combinations (N = 21)


Slipper with no sock 195.3 60.7 13.2

Slipper with diabetic sock 182.1 72.6 15.8Slipper with dress sock 187.1 72.1 15.7Shoe with no sock 171.5 43.7 9.5Shoe with diabetic sock 176.4 42.0 9.1Shoe with dress sock 177.8 38.7 8.4

NOTE: One-way repeated-measures analysis of variance showed nsignificant difference between the 6 combinations; F = 0.933, p.463. Power of the performed test with = .05 is 0.0496.



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the feet using the simple acronym KEEP: know the diease, exercise, eat right, and wear proper footweaMany factors go into selecting the proper footweaShoes should provide proper archsupport, pressurerlief, and a large toe box; in many cases, a wide shoe cabe found. Never should a person with diabetes amblate, whether inside or out, without wearing some kinof shoe (not sandals). Footwear involves notonly sho

but also the wearing of socks. White socks are preferble because any form of wound that appears can be eaily noticed by the stains of the exudate on the whisock. High plantar pressures should be avoided usindesigned footwear and hosiery. Boulton10 has also su

LOWER EXTREMITY WOUNDS 1(3); 2002 177

PLANTAR PRESSURE

0

200

400

600

800

1000

1200

1400

1600

1800

PlantarPressure

(kPa)

Minimum 659.01 636.64 679.03 738.2 743.8 714.37

Maximum 1647.3 1759.17 1662.33 1770.11 1763.86 1715.6

Mean 1091.919 1143.5138 1129.5048 1123.54 1148.8905 1161.3643

Shoe with no

sock

Shoe with

diabetic sock

Shoe with

dress sock

Slipper with no

sock

Slipper with

diabetic sock

Slipper with

dress sock

Fig. 1. Mean plantar pressure values (kPa) of the forefoot (sensors 17 to 24) for each of the 6 variables used in the study.

Table 3. Plantar Pressure Measurements (kPa)of the Phalanges/Toes (Sensors 21 to 24)

Taken During the 6 Combinations (N = 21)


Slipper with no sock 85.6 52.7 11.51Slipper with diabetic sock 105.2 54.2 11.84Slipper with dress sock 103.3 64.1 13.99Shoe with no sock 101.5 40.6 8.85Shoe with diabetic sock 109.5 43.3 9.45Shoe with dress sock 104.6 46.0 10.03

NOTE: Theslipperwith no sockcombination hadsignificantly lowerplantar pressure than the other 5 combinations; F= 2.84, p = .0195.Power of the performed test with = .05 is 0.6018.



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gested the importance of evaluating plantar pressuresregularly.

REFERENCES

1. Cavanagh PR, Buse JB, et al. The AmericanDiabetesAssociation,Inc. Diabetes Care 1999;22:1354-60.

2. American Diabetes Association. About us. Retrieved January 12,2002, from http://www.diabetes.org/main/health/body_care/foot/foot_care.jsp.

3. Boulton AJM, Betts RP, Franks CI, et al. The natural history offoot pressure abnormalities in neuropathic diabetic subjects. Diabe-tes Res 1987;5:73-7.

4. Boulton AJM, Bowker JH, Gadia M, et al. Use of plaster casts inthe management of diabetic neuropathic foot ulcers. Diabetes Care1986;9:149-52.

5. Boyle JP, HoneycuttAA, Narayan KMV, et al.Projectionof diabtes burden through 2050: impact of changing demography and dease prevalence in the US. Diabetes Care 2001;24:1936-40.

6. Bild DE, Selby JV, Sincock P, et al. Lower extremity amputatiin people with diabetes: epidemiology and prevention. Diabetes R1987;5:73-7.

7. Veves A, MassonEA, Fernando DJS, et al. Studies of experimetal hosiery in diabetic neuropathic patients with high foot pressurDiabetic Med 1990;7:324-6.

8. Herring KM,Richie DH.Friction blisters andsockfibercompotion: a double-blindstudy. J Am PodiatrMedAssoc 1990;80(2):63-7

9. Veves A, Masson EA, Fernando DJS, et al. Use of experimenpadded hosiery to reduce abnormal foot pressures in diabetic neropathy. Diabetes Care 1989;12:653-5.10. Boulton AJM. The diabetic foot. Med Clin North A1988;72:1513-31.

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