Longitudinal in-shoe foot pressure relief achieved by specially designed footwear in high risk diabetic patients

DiabetesResearchand Clinical Practice31 (1996)109-114

Longitudinal in-shoe foot pressure relief achieved by specially designed footwear in high risk diabetic patients’ Valerie M. Donaghuea, Marc R. Sarnowa, John M. Giurini”, James S. Chrzana, Geoffrey M. Habershawa, Aristidis Vevesb,* aDepartment of Surgery, Division of Podiatry, Deaconess-Jo& Foot Center, One Deac0nes.y Road, Boston, MA 02215, USA bDepartment of Medicine, Harvard Medical School, Deaconess-Jo&n Foot Center, One Deaconess Road, Boston, MA 02215, USA

Received23 October 1995;revised2 January 1996;accepted12 February 1996

Abstract Specially designed Thor-Lo footwear has been shown to reduce the in-shoe foot pressures in diabetic patients at risk of foot ulceration when compared to their own footwear. Fifty at high risk patients 32 (64%) males, 17 (34%) type 1 diabetes) have been provided with this foot wear and have been followed up for 6 months. Mean age was 57.6 (range, 34-78) years, duration of diabetes 22.4 (range, 4-50) years, Neuropathy Symptom Score 3.36 + 2.96 (mean f S.D.), Neuropathy Disability Score 16.8 + 6.83, VF’T 43.4 + 11.8 Volts while 43 (86%) could not feel a 5.07 or smaller Semmes-Weinstein monofilament. Forty-two (84%) patients were re-examined at an interim visit 3 months after baseline, while 37 (74%) completed the study. In-shoe peak forces and pressureswere measured using the F-Scan system. No difference was found among the peak force among baseline (95.5 + 26 kg), interim (96.5 f 33) and final visit (97.7 f 25.2, P = NS). There was no difference in peak pressures at the baseline (3.98 f 1.42 kg.cm-2), second visit (4.13 + 2.30) and the final visit (4.25 f 1.51). Nine (18%) patients developed foot problems and one died during the study. We conclude that no changes in foot pressures were found over a period of 6 months of continuous usage of the specially designed footwear in a group of diabetic patients at risk of foot ulceration. Further prospective studies are required to evaluate the impact of specially designed footwear in reducing the rate of foot ulceration. Keywords: Footwear; Foot pressure; At risk foot

*Corresponding author. Tel.: + 1 617 6327075;fax: + 1 617 6327090. ’ Part of this work was presentedat the 31stAnnual Meeting of the EuropeanAssociationfor the Study of Diabetes, Stockholm, Sweden,12-16 September1995. Published as: Giurini, J.M., Sarnow, M.R., Donaghue,V.M., Rosenblum, B.I., Chrzan, J.S., Habershaw,G.M. and Veves,A. (1995) In-shoe foot pressurerelief achieved by specially designed footwearin high risk diabeticpatients.Diabetologia38 (Suppl 1): A273.

1. Introduction

Foot problems related to long-term complications of diabetes mellitus pose a significant burden to both the patient and the medical system [l]. Peripheral motor neuropathy leads to clawing of the toes and prominent metatarsal heads under

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V.M. Donaghue et al. 1 Diabetes Research and Clinical Practice 31 (1996) 109- 114

which high foot pressures develop [2]. In the presence of pain insensitivity, due to sensory neuropathy, these high pressures can lead to the development of foot ulceration [3,4]. Peripheral vascular disease and limited joint mobility are also main contributing factors [5,6]. Prevention rather than treatment is the key to success when dealing with neuropathic diabetic patients. Along with patient education, the reduction of abnormally high foot pressuresmay play a pivotal role in preventing foot ulceration in high risk patients [7]. Specially designed hosiery has been shown to provide substantial pressure relief in such patients and in combination with extradepth shoes can be an inexpensive and easy strategy [8,9]. However, the pressure relief achieved by this combination of specially designed shoes and socks has not been studied, mainly due to the lack of reliable methods for in-shoe foot pressure measurements, and until recently most studies have been limited to the evaluation of patients who were wearing socks only and were walking across a stationary foot plate [7,8,10]. The recent development of small, thin sensors that can be placed in the shoes has overcome this obstacle and has allowed the reliable measurement of both in and out of the shoe plantar foot pressures [11,12]. In this prospective study we have examined the effect of specially designed socks and extra-depth shoes on reducing the plantar foot pressures in diabetic patients at high risk for foot ulceration. The experimental footwear was compared at baseline to the patients own shoes and socks while during the next 6 months possible changes in the provided pressure relief were evaluated. 2. Research design and methods Fifty diabetic patients (32 males (64%), 17 (34%) with type I diabetes) at high risk for foot ulceration were recruited for the study. Mean age was 57.6 years (range, 34-78) and the mean duration of diabetes 22.4 years (range, 4-50). More clinical details about the group are given in Table 1. All patients were ambulatory, free from ulceration or major amputation upon enrolment and without severe visual impairment. They all had

received education about foot care from their podiatrist and this was assessedusing a questionnaire. Briefly, patients were asked: (1) If they had been told that diabetes can affect the feet, (2) Had they received information concerning foot care, (3) If they took care of their own feet such as cutting nails, and (4) About satisfaction with their level of knowledge. Many patients were wearing appropriate extra-depth shoes with or without moulded insoles before their enrolment in the study. All patients were provided with three pairs of Thor-Lo experimental hosiery (Thor-Lo, Statesville, NC) designed with extra density padding at the heel, forefoot and covering the tops of the toes, and two pairs of commercially available extra depth shoes (SAS, (San Antonio, TX) extra depth shoes and New Balance (Boston, MA) extra depth shoes or extra width running shoes). The new footwear was fitted by a pedorthotist who supervised its proper use while the patients were in the study. At the same time all patients watched an informational video regarding foot care. The patients were reexamined at 3 and 6 months and were asked to complete a satisfaction questionnaire that has been previously described [9]. Briefly, they were asked to report the frequency and duration they wear the footwear, any problems associated with it, to compare it with their previous footwear and if they would like to continue wearing it in the future. Table 1 Clinical details of study population Characteristic

Value

Age (years, meamrange)) Sex M/F Weight, kg (mean & SD.) Type of diabetes l/2 Duration of diabetes (years, mean (range)) Nephropathy, no. of patients Retinopathy, no. of patients Peripheral vascular disease, no. of patients Neuropathy symptom score, (mean k SD.) VPT (Volts), (mean _+ SD.) Semmes-Weinsteinmonofilaments, no. of patients unable to feel a 5.07 or smaller filament

57.6 (34-78) 32/18 84.2 k 18.9 17133 22.4 (4-50) 9 (18%) 31 (62%) 12 (24%) 3.36 + 2.96 43.4 _+ 11.8 43 (86%)

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The peripheral neuropathic status was assessed at baseline employing clinical symptoms, signs and quantitative sensory testing. More specifically, a modified Neuropathy Symptom Score (NSS) was used in which patients were asked for the presence, of the following symptoms in the feet or legs: (1) muscular cramps, (2) numbness, (3) abnormally hot or cold sensation, (4) tingling or prickling sensation, (5) sharp, shooting pain, (6) burning pain, and/or (7) irritation caused by bedclothes. These symptoms were scored with one point if present and two points for nocturnal exacerbation [12]. The evaluation of clinical signs was quantified using the Neuropathy Disability Score (NDS) which represented the sum of the motor and sensory scores. For the evaluation of the motor score the knee and ankle reflexes for both legs were tested and scored with 0 points if normal, 1 point if they were elicited by reinforcement and with 2 points if they were absent. The sensory score was evaluated by testing the sensations of pain, light touch, vibration and cold perception. Each modality was scored according to the anatomical location it was first felt as follows: if felt at the tip of the toe it was scored as 0 points, at the base of the toe with 1 point, at the midfoot level with 2 points, ankle with 3 points, midleg with 4 points and at the knee level with 5 points. The average of both feet was calculated and the sum of all four modalities represented the sensory score. The NDS was the sum of the sensory and motor score. The Vibration Perception Threshold was measured at the great toe of both feet using a Biothesiometer (Biomedical Instrument, Newbury, OH). A mean of three readings was used to determine the value for each foot. A value greater than 25 V was considered to be indicative of high risk of ulceration [ 133. The Cutaneous Perception Threshold was assessed using a set of eight Semmes-Weinstein monofilaments (Gillis W. Long, Hansen’s Disease Center, Carville, LA) [ 141.Inability to feel a pressure of 10 g applied by a 5.07 monofilament was suggestive of an at risk patient. The peripheral vascular status, history of previous foot ulceration, renal and visual complications were also assessedand recorded. Periph-

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era1 vascular disease was diagnosed in the presence of claudication with absent foot pulses and/or history of previous vascular by-pass operation in the lower extremities. Dynamic (walking) peak foot pressures and forces were measured at baseline and at each subsequent visit using the F-Scan program (TekScan, Boston, MA) [11,12]. Briefly, this system uses an insole consisting of 960 sensor units which can be placed in the shoe or taped to the foot and is calibrated using the subjects body weight. For this study, during the baseline visit the foot pressures were measured with the patients wearing their old shoes and socks, the provided new footwear, the old socks alone and the new socks alone. For the second and third visit the foot pressures of the new footwear alone were measured. A pair of new sensors was used for the baseline measurements while a second pair was used for the foot pressure measurements at second and third visit. The sensors were changed because early data had shown that reliable measurements could be obtained for the first 25 steps, almost the number of steps measured during the first visit. Statistical analysis was conducted using Minitab statistical software (Minitab Inc., State College, PA). Non-parametric methods using the Wilcoxon rank pair test were employed for the comparison of the different measurements either during the same visit or during different visits. The study was approved by the Institutional Review Board at New England Deaconess Hospital and written informed consent was obtained. 3. Results

All participating patients were at risk of foot ulceration as defined by their history or clinical examination. A history of previous foot ulceration was present in 41 (82%) patients The Vibration Perception Threshold was greater than 25 V in 48 (96%) patients while 43 (86%) could not feel a Semmes-Weinstein monofilament of 5.07 or smaller. Peripheral vascular diseasewas present in 12 (24%) patients of whom seven (14%) had a history of previous vascular operation. All patients had received information about foot care,

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Table 2 Details of baseline measurements Measurement

Provided new footwear

Patients’ own footwear

Baseline, with patients wearing socks only Baseline, with patients wearing both shoes and socks Interim visit at 3 months, with patients wearing both shoes and socks Final visit at 6 months, with patients wearing both shoes and socks

6.15 3.98 4.13 4.24

6.56 f 2.70* 4.46 k 1.64**

_+ 2.78* & 1.42** + 2.30 k 1.51

Data are mean + SD., pressures measured in kg.cm-’ *P < 0.01. **p
were knowledgeable about the ways diabetes can affect their feet, had regular follow up visit with their podiatrists and were satisfied with the level of their knowledge. Forty-two (84%) patients were seen during the interim visit at 3 months while 37 (74%) completed the study. From the remaining 13 (26%) patients, one (2%) died during the study for reasons not related to it, one (2”/) moved to another state, two (4%) did not return for their appointments and refused to give any reasons, four (8%, three women) withdrew because they did not like the shoes while five (10%) developed a foot ulcer which prohibited the use of the foot wear and had to be withdrawn from the study. Four (8%) more patients developed foot problems of mild severity during the study and were able to complete it. Peripheral vascular disease (claudication) was present in one patient who ulcerated during the study. There were no differences in the demographics of those subjects who finished the study compared to those that did not. The shoes and socks were worn for a mean of 11 h per day for 6 days per week (range, 5-7 days). All patients who completed the study were satisfied with the new shoes and socks. Twentyfour subjects rated the new footwear as much better than the previous footwear, 12 rated them as better and one as the same. Desire to continue to wear the new socks and shoes all or most of the time was expressedby all 37 subjects who finished the study. The results of the baseline measurements between the patients’ old footwear and the newly provided one are shown in Table 2. No difference

was found among the peak force among baseline (95.5 f 26 kg), interim (96.5 f 33) and final visit (97.7 + 25.2, P = NS). Significant pressure relief was provided by the new footwear when it was compared to their own. Similar results were also noticed when they wore the experimental or their old socks, without any shoes. When the performance of the provided footwear was evaluated no significant differences were found among baseline, interim and final visits. No significant differences were also found among the foot pressures measured with the provided footwear at the last two visits and the foot pressures of the first visit while the patients were wearing their own footwear. 4. Discussion In the present study we have evaluated the performance of the combination of specially designed socks and commercially available extra depth shoes in high risk diabetic patients. Our results show a significant pressure relief achieved by the provided footwear when compared to the patients’ own shoes and socks and that there were no significant changes in the foot pressure measurements when the patients wore these continuously for the next 3 or 6 months. However, no differences were also found between the pressure measurements with the patients’ old footwear at baseline and the measurements with the experimental footwear after 3 or 6 months of extensive use. This is probably due to the fact that the great majority of the patients were wearing similar shoes before they entered the study, usually with commercially available thick padded socks.

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Despite the proper footwear and the education the patients had received by their doctor foot problems were not completely avoided. Whether this was related to poor patient compliance, although strongly suspected in some cases, cannot be answered by the design of the study. The fact that four subjects (three women) refused to wear the provided footwear because of cosmetic reasons further emphasizes this point. Behavior modification does not depend only on patient education and when it is not achieved the rest of the employed strategies alone cannot fully protect the patients from the development of foot ulceration [15]. A more intensive intervention, including frequent reinforcement with visits to the nurse educator or by postcard reminders, has been shown to reduce the risk for foot ulceration and should probably be employed as an adjunctive to other therapeutic interventions [ 161. Another contributing factor for this observed foot ulceration rate may be that all participating patients were at extremely high risk, as best shown by the fact that a history of previous foot ulceration was present in 41 (82%) of them. Previous studies have shown that in such patients the risk for re-ulceration is considerably high and that the majority of the foot ulcers are of neuro-ischaemic origin [6,17- 191. Support to these arguments can be also drawn from results which show a similar rate of foot ulceration in another prospective study which provided proper foot wear in at risk patients and followed them for a period of 12 months [20]. Therefore, under these circumstances it would be unrealistic to expect that the provided footwear could completely prevent all foot problems and further prospective randomized studies are required to examine the rate of reduction of foot problems in such high risk diabetic populations. The present study is the first to employ inshoe foot pressure measurements in order to evaluate specially designed footwear in diabetic patients. The F-Scan system which was used in the present study employs thin sensors which can be placed in the patients shoes without occupying considerable space which could lead to artificially high pressures and has been shown to

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be a reliable method of measuring in-shoe foot pressures [ 11,12,21]. However, when the patients walk without their shoes the results depend on the quality of the surface the patients walk on, and each lab should obtain its own limits of normality. This of course would not be expected to influence the results of this longitudinal study where patients served as their own controls. We have previously shown that the usually worn shoes, either by healthy subjects or by high risk diabetic patients, significantly reduce the foot pressures compared to the ones measured when they walk without their shoes [l 11. This pressure distributing ability of the shoes was confirmed by the results of the present study where both the patients’ own shoes and the provided extra-depth ones achieved a significant pressure relief. The use of modern technology as the one employed in this will, hopefully, be helpful in designing special shoes and insoles which will redistribute and reduce the high foot pressures from areas which are prone to ulceration. Previous studies in diabetic patients have shown that when the experimental hosiery was worn without shoes it was able to reduce the abnormally high pressures by 20-30% when measured by the optical pedobarograph [8,22]. In this study we have failed to achieve this degree of pressure reduction either with the patients wearing their socks alone or wearing both shoes and socks. One possible explanation may be that the foot pressures in this study were measured with the patients walking without their shoes over a thick carpet in contrast to the hard surface of the glass plate of the pedobarograph. In summary, in the present study we have employed in-shoe foot pressure measurements to examine the effect of specially designed footwear in diabetic patients at risk of foot ulceration. Our results show that the tested footwear provided an initial significant pressure relief and that no changes were found after a period of 6 months of continuous usage but foot problems were not fully avoided. Further prospective studies are required to evaluate the impact of specially designed footwear in reducing the rate of foot ulceration.

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Acknowledgements

We would like to thank Thor-Lo Foot Systems for providing the footwear and the services of a pedorthotist to the participating patients. The same company also provides a research grant for the conduction of this study.

[lo] Veves, A. and Boulton, A.J.M. (1993) The optical pedobarograph. Clin. Podiatric Med. Surg. 10, 463-470. [ll] Sarnow, M.R., Veves, A., Giurini, J., Rosenblum, B.I., Chrzan, J.S. and Habershaw, G.M. (1994) In-shoe pressure measurements in diabetic patients with at-risk feet and in healthy subjects. Diabetes Care 17, 1002- 1006. [12] Veves, A., Samow, M.R., Giurini, J.M. et al (1995) Differences in joint mobility and foot pressures between black and white diabetic patients. Diabetic Med. 12, 585-589.

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[17] Thomson, F.J., Veves, A., Ashe, H. et al. (1991) A team approach to diabetic foot care - the Manchester experience. Foot 1, 75-82. [18] Most, R.S. and Sinnock, P. (1983) The epidemiology of lower extremity amputations in diabetic individuals. Diabetes Care 6, 87-91. [19] Pecoraro, R.E., Reiber, G.E. and Burgess, E.M. (1990) Pathways to diabetic limb amputation. Basis for prevention. Diabetes Care 13, 513-521. [20] Uccioli, L., Faglia, F., Monticone, G. et al. (1995) Manufactured shoes in the prevention of diabetic foot ulcers. Diabetes Care 18, 1376-1378. [21] Pitei, D.L., Edmonds, M.E.E., Lord, M. and Watkins, P.J. (1993) FSCAN: a new method of in-shoe dynamic measurement of foot pressures [abstract]. Diabetic Med. 7 (Suppl. 2), s39. [22] Veves, A., Masson, E.A., Fernando, D.J.S. and Boulton, A.J.M. (1989) The use of experimental hosiery to reduce plantar foot pressures in diabetic neuropathy. Diabetes Care 9, 653-655.