Hardness of Plantar Skin in Diabetic Neuropathic Feet

Hardness of Plantar Skin in Diabetic Neuropathic Feet Alberto Piaggesi, Marco Romanelli, Elena Schipani, Fabrizio Campi, Antonio Magliaro, Fabio Baccetti, and Renzo Navalesi

ABSTRACT To evaluate if skin hardness in diabetic neuropathic feet was increased and if its eventual modifications could be correlated to the severity of neuropathy, we studied a group of diabetic outpatients with and without neuropathy. Patients, selected among those who were attending their routine screening for diabetic neuropathy at our diabetologic clinic, were divided into two groups according to the presence (ND1) or absence (ND2) of diabetic neuropathy with the criteria of the S. Antonio Consensus Conference on Diabetic Neuropathy. Patients then underwent an evaluation of vibration perception threshold (VPT) by means of a biotesiometer, measurement of skin hardness (DMT) by means of a durometer, and transcutaneous oxygen tension (TcPO2) determination. VPT was determined at allux (VPTA) and external malleolus (VPT-M), DMT was measured at heel (DMT-H), at medial (DMT-M) and lateral (DMT-L) midfoot, and at posterior midcalf (DTM-C) as a control site; TcPO2 was evaluated at dorsum (TcPO2-D) and at medial midfoot (TcPO2-M), respectively. All measurements were performed on the nondominant side with the patients supine.

Patients were compared with age and gendermatched healthy volunteers (Controls), who underwent the same evaluations in the same order. ND1 patients showed higher values of VPT than ND2 and Controls, both at first toe and at malleolus analysis of variance (ANOVA) p , 0.01), as well of DMT in all the three sites explored (ANOVA, p , 0.01). Moreover, ND1 showed no difference in DMT among the sites, while both in ND2 and in controls DMT-M was significantly (p , 0.05) lower than DMTH and DMT-L. No difference among the three groups were observed in TcPO2 measurements, and no difference in DMT-C was observed either. A significant correlation was observed between DMTH and VPT-M (r2 5 0.516) and between DMT-M and VPT-A (r2 5 0.624) in ND1 patients. Skin hardness was diffusely increased in ND1 patients, and this increase strongly correlates with the severity of neuropathy. Simple, noninvasive determination of skin hardness could identify patient at potential risk to develop neuropathic foot ulcers. (Journal of Diabetes and Its Complications 13; 3: 129–134, 1999.)  1999 Elsevier Science Inc.

INTRODUCTION

autonomic component of peripheral nerves.1 One of the key events in the pathogenetic pathway to neuropathic ulceration is hyperkeratosis, which develops in areas of increased pressure. Although orthostatic stress has been claimed to be the major responsible of hyperkeratosis, other factors, such as nonenzymatic glycation and autonomic dysidrosis are suspected of being involved in the pathogenesis of skin hardening.2 Recently, a new and easy method to assess skin hardness, durometry, was developed and applied to various skin pathologies, such as hypertrophic scars, dermatosclerosis, lymphedema, with interesting results.3

P

eripheral polyneuropathy is one of the major risk factors of foot ulcers in diabetic patients, through a multifactorial pathogenetic sequence that involves motor, sensitive, and

Department of Metabolic Diseases (A.P., E.S., F.C., F.B., R.N.), and Department of Dermatology (M.R., A.M.), University of Pisa, Pisa, Italy Reprint requests to be sent to: Dr. Alberto Piaggesi, U.O. Malattie del Ricambio e Diabetologia, Azienda Ospedaliera Pisana, Cisanello, Via Paradisa 2, 56100 Pisa, Italy. Journal of Diabetes and Its Complications 1999; 13:129–134  1999 Elsevier Science Inc. All rights reserved. 655 Avenue of the Americas, New York, NY 10010

1056-8727/99/$–see front matter PII S1056-8727(98)00022-1

130

PIAGGESI ET AL.

J Diab Comp 1999; 13:129–134

The Durometer (Rex Gauge Co., Inc., Glenview, IL) is the international standard for hardness measurement of various nonmetallic materials, from rubber to plastic, wood etc. Model 0, as used in this study, is suitable for soft material such as animal tissues, in which there is a minimal amount of creep.4 The durometer shows the relative degree of tissue hardness on a linear calibrated gauge as the result of a spring-loaded interior that senses hardness by applying an indentation load on the specimen. Determination of skin hardness by this instrument has been proven to be accurate and reproducible, both in normal and pathological conditions.4,5 The purpose of this study was to measure skin hardness in diabetic neuropathic feet, in order to check if neuropathy-associated modifications of skin elasticity may be found before the occurrence of ulcerations. METHODS We studied a selected group of outpatients attending our diabetic clinic, chosen among those who were attending a routine periodic control scheduled between June and December 1996. Patients were selected according to the following inclusion criteria: diagnosis of type I or type II diabetes mellitus from more than 5 years, age range between 18 and 60 years, presence of peripheral polyneuropathy as ascertained by the bilateral absence of Achilles tendon reflexes, Michigan Neuropathy Screening Instrument [MNSI, normal range