Use of a durometer to measure the degree of skin induration in lipodermatosclerosis

Use of a durometer to measure the degree of skin induration in lipodermatosclerosis Marco Romanelli, MD,a and Vincent Falanga,MDb Pisa, Italy, and Miami,

Florida

Background: Chronic lipodermatosclerosis is characterized by indurated skin on the medial

aspect of the leg and is common around venous ulcers. The severity of induration of lipodermatosclerosis has been associated with poor ulcer healing. Clinical assessmentof lipodermatosclerosis presently relies on a clinical skin severity score adapted from studies of patients with systemic sclerosis. OQective: It would be desirable for prognostic reasons to develop an objective method for measuring skin hardness in lipodermatosclerosis. Methods: The degree of skin induration at the midpoint between the upper and lower margin of lipodermatosclerosis in 30 sequential nonselected patients with lipodermatosclerosis was assessedby a blinded observer’s clinical score and by quadruplicate determinations with a hand-held type 0 durometer. Skin induration on the medial aspect of the leg was similarly measured in five normal volunteers. Transcutaneous oxygen pressure was measured at the same sites, Results: A direct linear relation (r = 0.962) was found between skin severity scores and durometer readings (p < 0.01). A clinical skin score of 2 reflected a higher durometer reading compared with a skin score of 1 (p = 0.0016) and, similarly, higher durometer readings were found in skin score of 3 compared with score 2 skin (p = 0.0093). Transcutaneous oxygen pressure was uniformly reduced in lipodermatosclerosis (p < 0.02). Conclusion: The durometer is a reliable instrument for measuring skin hardness in patients with lipodermatosclerosis. It may be used to test the prognostic value of lipodermatosclerosis on ulcer healing. (J AMACAD DERMATOL 1995;32:188-91.)

Chronic lipodermatosclerosisis characterizedby hyperpigmentedinduratedskinon the medial aspect of the leg andis commonaroundvenousulcers.1Ulcersoften developandrecurwithin LDS, anda high degreeof skin induration hasbeen associatedwith poor ulcer healing.2Therefore accurate measurement of skin hardness in lipodermatosclerosis

may

be useful both in patient managementand in therapeutictrials in which a homogeneousgroup of patients is desirable. From the Department of Dermatology, University of Pisa School of Medicinea; and the Department of Dermatology and Cutaneous Surgery, University of Miami School of Medicine.b Supported in part by National Institutes of Health grants AR39658 AG10998 and the Dermatology Foundation of Miami. Accepted

for publication

Aug.

and

PATIENTS

18, 1994.

Reprint requests: Vincent Falanga, MD, Associate Professor of Dermatology and Medicine, University of Miami School of Medicine, Department of Dermatology and Cutaneous Surgery, Miami, FL 33101. Copyright 0190-9622/95

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@ 1995 by the American $3.00 + 0

16/l/59947

Academy

We havepreviouslyassessed skin hardnessin lipodermatosclerosis with a clinical skin severityscore adaptedfrom studiesof patientswith systemicsclerosis(scleroderma):0 = normal skin; 3 = maximal induration.With thesecriteria, we reportedthat ulcers surrounded by severe lipodermatosclerosis rarely heal.2However,there is a needfor more objective measurementof lipodermatosclerosis.Recently,we haveshownthe usefulnessand reliability of measuring sclerodermaskin hardnesswith a durometer,an engineeringinstrument widely employedto measurethe hardnessof metals, plastic, andother substances.3 We showthat the durometer can beusedto determinethe degreeof indurationin lipodermatosclerosis.

of Dermatology,

Inc.

AND METHODS

We prospectively examined patients with lipodermatosclerosis, with or without venous ulcers. All patients were sequential and nonselected, and all had clinical and laboratory evidence of venous insufficiency, as defined by the following criteria: presence of varicosities, hyperpig-

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Fig. 1. Durometer readings recorded at the center of the lipodermatosclerosis zone in patients with venous ulcers who had different skin scores and on the medial aspect of the leg of control subjects. Values on the y axis represent the mean ? SD of quadruplicate determinations. Cl, Control subjects; lEi,patients.

mentation, irregularly shaped ulcerations on the medial aspect of the leg, and venous reflux by Doppler flow studies. In addition, arterial insufficiency was excluded in all patients by Doppler examination.4 Clinical scoring for hardness was done at a skin site midway between the upper and lower margin of lipodermatosclerosis by a blinded observer using published criteria for a skin severity score2: 0 = normal, 1 = minimal, 2 = moderate, 3 = maximal hardness. This scoring system is based on one widely used for assessingskin hardness in patients with systemic sclerosis (scleroderma).5 Patients were excluded if the center of lipodermatosclerosis was in or within 5 cm of the area of ulceration. Control measurements were made on the medial aspect of the leg of persons without evidence of venous disease. Durometer

hardness testing

Durometer testing of skin hardness was done as described in a previous article in this JOURNAL, in which there is a photograph of the durometer.3 We used a Rex durometer Max-hand model 1700 without a foot attachment (Rex Gauge Co., Inc., Glenview, Ill.). This instrument is the international standard for measurement of hardness of plastic, rubber, and other nonmetallic material. Model 0, as used in this study, is for soft materials such as animal tissue, in which the amount of creep is minimal. Considerations regarding creep have been previously outlinecL3 The durometer is provided with a calibrated gauge that registers linearly the relative degree of hardness. This feature is the result of a spring-loaded interior that senseshardness by application of an indentation load on the specimen. At the bottom of the durometer that is held by gravity against the skin, there is a

small dull inferior indentor that is retractable and is responsible for the measurements registered on the gauge. For measurements, the durometer was used at 25” C and rested by gravity against the skin; four consecutive readings were taken at the same site. Between readings, the durometer was reset to 0. Measurements were made with the patients supine, and muscle tension or contraction of the lower extremity was avoided by placing the extremity over a pillow or several layers of gauze. The investigator performing the durometer measurements was not aware of the skin severity score assigned to each patient. Transcutaneous

oxygen pressure

Measurements of transcutaneous oxygen pressure (tcPo2) at the same site assessedfor induration were made in 15 sequential patients and in the control subjects. The skin was stripped with tape 20 times to remove excess scale before application of the tcPoz sensor. Measurements were made as previously described with the patient supine and with an oxygen monitor (model TCM-3, Radiometer, Copenhagen, Denmark).6 The sensor temperature was set at 44” C and calibration was performed before each measurement. Readings of tcPo2 were taken after a 15minute equilibration period. Statistical

analysis

The mean of quadruplicate determinations for each patient and control was used for analysis. The nonparametric Mann-Whitney two-sample test was used to compare between patients and controls and between patients with different skin severity scores.The least-square linear regression analysis was used to compare tcPO2 measure-

190

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Journal of the American Academy of Dermatology February 1995

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Fig. 2. Relation between tcPo2 measurements and durometer readings (scattergram) or clinical severity score (inset). Measurements of tcPo2 were taken at the center of lipodermatosclerotic skin and on the medial aspect of the leg of control subjects.

merits with durometer readings. In all cases, statistical significance was defined asp lessthan 0.05. Thep values were not calculated in those instances in which data were insufficient. RESULTS

We assessed 30 patientswith lipodermatosclerosisandfivenormalpersons(controlsubjects).Venous ulcerswere presentin 20 of the patients.The mean ageof the patientswas 63 years( k 7 years[ S.D.]) and that of control subjects was 62 +- 6 years (p = 0.6882).Therewere 15men and 15womenin the patient group and threemen and two women in the control group. Durometerreadingsobtainedwith four consecutive determinationson the samesite in eachsubject differedby lessthan 5%. Fig. 1 showsthe durometer readingsfor patients and control subjectscontrasted with their skin severityscore.Normal control subjectsuniformly receiveda skin severityscoreof 0. Comparedwith normal skin in control subjects, increasedskin severityscoreswere associatedwith higher durometer readings(p < 0.01). This direct relationbetweenclinical scoresanddurometerreadings was linear (r = 0.9621).No differencesin durometer readingswere found betweenthe patients with isolated lipodermatosclerosisand those who also had a venousulcer. Fig. 1 showsthat the durometerwasable to differentiatebetweenincreased levelsof skin hardness.Thus a skin severityscoreof 2 reflecteda higher durometerreadingthan that of

a skin scoreof 1 (p = 0.0016), and, similarly, a higher durometer measurementwas observedin score3skincomparedwith score2 skin(p < 0.0093). Measurementsof tcPo2 were made at the skin sitesevaluatedfor indurationin the control subjects and in 15 consecutivenonselectedpatients. The scattergramin Fig. 2 showsan inverseand statistically significant relation (r2 = 0.431; p = 0.0079) between-tcPozmeasurementsand durometerreadingsin both patientsandcontrolsubjects.The tcPo2 measurementswerealsocomparedwith the clinical severityscoresof patientsandcontrol subjects(Fig. 2, inset). Only oneof the patientshad a clinical score of 3 (tcPo2, 14 mm Hg); thereforeour statistical evaluationis confinedto comparingcontrol subjects with patientshaving clinical scoresof 1 and 2. The amount of oxygenmeasurableat the skin surface was indirectly relatedto the degreeof skin induration. Thus control subjectshad a higher tcPoz than patientswith a clinical scoreof 1 (p = 0.0159)or 2 (p = 0.0034).However,tcPo2valuescould not separate patientswith clinical scoresof 1 and 2 (p = 0.0763). DISCUSSION

We foundthat durometerreadingswerehigherin patientswhoseaffectedskinwasjudgedblindly to be more indurated.Moreover,measurementswith the durometer were highly reproduciblein the same subject and in persons with the same degree of skin

induration.This more objectivemethod to measure

Journal of the American Academy of Dermatology Volume 32, Number 2, Part 1

the extent of lipodermatosclerosisshouldbe useful clinically and in studiesof venousulcers,in which a homogeneouspopulationis desirable.With a clinical severityscore,we havepreviouslyreportedthat patientswhosevenousulcers are surroundedby a high degreeof induration have a more prolonged healingtime.2The useof a durometerin future prospectivestudies may be helpful in confirming the prognosticvalue of lipodermatosclerosis. Attempts to measureobjectively the degreeof skin hardnessin other conditions,particularly scleroderma, have included skin biopsies,7ultrasonography,* skin elastometers,9> lo magnetic resonance imaging,’ 1andmeasurementsof tcPo2.l2The drawbacksof thesemethodsare that they requireeither considerableexperienceor expensiveequipment. Skin biopsiesare an invasiveprocedureand are not practical for sequentialmeasurements.The durometeris uniquein its simplicity and easeof use,aswe havealreadyshownin measuringskin induration in scleroderma.3The medial aspectof the leg,which is the usual location of lipodermatosclerosis,is well suitedfor durometermeasurements.However,areas of skin immediatelyoverlyingboneor tendonswould likely give spuriouslyhigh readings. In this study we also found that tcPo2 readings were lower in indurated skin than in normal skin. This observationconfirms previousreports of low tcPo2 in patients with lipodermatosclerosisand thosewith scleroderma.2tl2 Most likely, low tcPo2 readingsreflect poor diffusion of oxygen through denseand thickenedskin. However,it appearsthat a low tcPo2 cannot differentiatebetweendifferent degreesof hardness.Thus we found similar tcPo2 readingsin patientswith lipodermatosclerosiswith

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clinical scoresof 1 and 2. Considerableoverlapin tcPo2 measurementswere also found in patients with scleroderma and different degreesof skin hardness.l2

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Falanga V, Bucalo B. Use of a durometer to assess skin hardness. J AM ACAD DERMATOL 1993;29:47-5 1. Falanga V. Venous ulceration. J Dermatol Surg Oncol 1993;19:764-71. Kahaleh MB, Sultany CL, Smith EA, et al. A modified scleroderma skin scoring method. Clin Exp Rheumatol 1986;4:367-9. Romanelli M, Katz MH, Alvarez AF, et al. The effect of topical nitroglycerin on transcutaneous oxygen. Br J Dermatol 1991;124:354-7. Rodnan GP, Lipinski E, Luksick J. Skin thickness and collagen content in progressive systemic sclerosis and localized scleroderma. Arthritis Rheum 1979;22: 130-40. Myers SL, Cohen JS, Sheets PW, et al. B-mode ultrasound evaluation of skin thickness in progressive systemic sclerosis. J Rheumatol 1986;13:577-80. Bjerring P. Skin elasticity measured by dynamic admittance: a new technique for mechanical measurements in patients with scleroderma. Acta Derm Venereol Suppl (St&h) 1985;120:83-7. Ballou SP, Mackiewicz A, Lysikiewicz A, et al. Direct quantitation of skin elasticity in systemic sclerosis. J Rheumat01 1990;17:790-4. Richard S, Querleux B, Bittoun J, et al. In vivo proton relaxation times analysis of the skin layers by magnetic resonance imaging. J Invest Dermatol 1991;97:120-5. Silverstein JL, Steen VD, Medsger TA Jr, et al. Cutaneous hypoxia in patients with systemic sclerosis (scleroderma). Arch Dermatol 1988;128:1379-82.