Shear-Reducing Insoles to Prevent Foot Ulceration in High-Risk Diabetic Patients

Transcription

1 NOVEMBER 2012 Shear-Reducing Insoles to Prevent Foot Ulceration in High-Risk Diabetic Patients C M E 1 AMA PRA Category 1 Credit TM ANCC 2.3 Contact Hours Lawrence A. Lavery, DPM, MPH & Professor & Department of Plastic Surgery & University of Texas Southwestern Medical Center & Dallas, Texas Javier LaFontaine, DPM, MS & Associate Professor & Department of Plastic Surgery & University of Texas Southwestern Medical Center & Dallas, Texas Kevin R. Higgins, DPM & Podiatrist & Private Practice & San Antonio, Texas Dan R. Lanctot, BS & Vice President-Engineering & Diabetica Solutions & San Antonio, Texas George Constantinides, BS & Diabetica Solutions & San Antonio, Texas This project was funded by National Institutes of Health NIDDK No. 1 R44 DK ; clinical trial number NCT Dr Lavery has disclosed that he was a recipient of grant/research funding from Smith & Nephew; is a recipient of grant/research funding from ConvaTec, Integra, and CoDa Therapeutics; is/ was a consultant/advisor to National Healing; was a consultant/advisor to GlaxoSmithKline and Osiris; is/was a member of the speaker s bureau for Advance Biohealing; was a member of the speaker s bureau for KCI; is a member of the speaker s bureau for Healthpoint Biotherapeutics; and is a stockholder in Diabetica Solutions. Dr LaFontaine, Dr Higgins, Mr Lanctot, and Mr Constantinides have disclosed that they have no financial relationships related to this article. The authors spouses/life partners (if any) have disclosed that they have no financial relationships with, or financial interests in, any commercial organizations pertaining to this educational activity. All staff and planners, including spouses/partners (if any), in any position to control the content of this CME activity have disclosed that they have no financial relationships with, or financial interests in, any commercial companies pertaining to this educational activity. Lippincott CME Institute has identified and resolved all conflicts of interest concerning this educational activity. To earn CME credit, you must read the CME article and complete the quiz and evaluation on the enclosed answer form, answering at least 13 of the 18 questions correctly. This continuing educational activity will expire for physicians on November 30, PURPOSE: To enhance the learner s competence with knowledge of the effectiveness of shear-reducing insoles for prevention of foot ulceration in patients with high-risk diabetes. TARGET AUDIENCE: This continuing education activity is intended for physicians and nurses with an interest in skin and wound care. OBJECTIVES: After participating in this educational activity, the participant should be better able to: 1. Demonstrate knowledge of foot ulceration risk, risk factors, incidence, and prevention. 2. Apply knowledge gained from reviewing this study and a literature review about the use of shear-reducing insoles to patient scenarios ADVANCES IN SKIN & WOUND CARE & NOVEMBER 2012

2 ABSTRACT OBJECTIVE: The objective of this study was to evaluate the effectiveness of a shear-reducing insole compared with a standard insole design to prevent foot ulceration in high-risk patients with diabetes. RESEARCH DESIGN AND METHODS: A total of 299 patients with diabetic neuropathy and loss of protective sensation, foot deformity, or history of foot ulceration were randomized into a standard therapy group (n = 150) or a shear-reducing insole group (n = 149). Patients were evaluated for 18 months. Standard therapy group consisted of therapeutic footwear, diabetic foot education, and regular foot evaluation by a podiatrist. The shear-reducing insole group included a novel insole designed to reduce both pressure and shear on the sole of the foot. Insoles were replaced every 4 months in both groups. The primary clinical outcome was foot ulceration. The authors used Cox proportional hazards regression to evaluate time to ulceration. RESULTS: There were 2 significant factors from the Cox regression model: insole treatment and history of a foot complication. The standard therapy group was about 3.5 times more likely to develop an ulcer compared with shear-reducing insole group (hazard ratio, 3.47; 95% confidence interval, ). CONCLUSIONS: These results suggest that a shear-reducing insole is more effective than traditional insoles to prevent foot ulcers in high-risk persons with diabetes. KEYWORDS: diabetic foot ulcers, shear-reducing insoles, high-risk persons with diabetes ADV SKIN WOUND CARE 2012;25:519-24; quiz There are only 2 randomized studies that evaluate ulcer prevention using therapeutic shoes and insoles in patients with diabetes. 5,6 However, the results are contradictory. A recent systematic review by Patton et al 7 demonstrated that insoles may prevent diabetic foot ulceration, but most of the evidence is poor and inconclusive. Their group found and included only 5 studies with high levels of evidence. One study showed a significant benefit, and 1 study showed no difference when therapeutic shoes were used compared with self-selected shoes. The current state of the art in insole design primarily addresses vertical forces with the aim of reducing foot pressures There are no insole designs available that specifically reduce both abnormal pressure and shear. Both empiric evidence and a growing body of basic science work support the important role of friction and shear in ulcer development in the neuropathic foot The authors hypothesized that an insole that could reduce shear, as well as pressure, would reduce the incidence of foot ulcers better than traditional insoles. In previous work, the authors evaluated a shear-reducing insole (SRI) design in healthy patients without diabetes or sensory neuropathy. This study demonstrated a 2.5-fold reduction in shear forces and an equivalent reduction in pressure compared with traditional insole designs and material combinations with in-shoe pressure studies. 15 The aim of this study was to evaluate the effectiveness of a novel SRI to prevent foot ulcerations in high-risk persons with diabetes. After reading this article, clinicians will be better able to determine if an SRI would help prevent ulcers in their high-risk patients with diabetes. EXPERIMENT DESIGN AND METHODS This was a single (physician) blinded randomized trial. Two hundred ninety-nine patients at high risk for diabetic foot ulceration INTRODUCTION Foot ulceration in persons with diabetes is the most frequent precursor to amputation. In the United States, there are approximately 120,000 nontraumatic lower-extremity amputations performed each year. 1 The incidence of amputation ranges from 70 to 150 per 10,000 person-years. It has been estimated that 5% to 15% of persons with diabetes will have a lower-extremity amputation in their lifetime. 2,3 In the United States, 45% to 83% of all lower-extremity amputations involve persons with diabetes. 2,3 Overall, patients with diabetes are 15 to 46 times more likely to have an amputation than patients without diabetes. 4 Several studies have demonstrated a significant decrease in ulceration, reulceration, and amputation when therapeutic footwear, education, and regular diabetic foot care are provided. However, even at specialty diabetic foot centers, 19% to 40% of high-risk patients still had reulceration within a year of healing. 2,3 Figure 1. COMPARING INSOLES ADVANCES IN SKIN & WOUND CARE & VOL. 25 NO

3 were randomized from 3 clinics in south Texas into 2 treatment groups (Figure 1). Approval for the study was obtained from the local hospital institutional review board. Informed consent was obtained prior to evaluation and enrollment in the study. Patients were assigned to receive either a standard insole or an SRI. The standard therapy group (STG) consisted of foot and lower-extremity evaluation by a physician every 10 to 12 weeks, an education program that focused on foot complications and self-care practices, and therapeutic shoes and insoles. The education segment of training was provided by a video that addressed the etiology of diabetic foot ulcers, risk factors, self-care practices, and early warning signs of diabetic foot disease. If study patients identified an area of concern on their feet, they were instructed to contact the study nurse. All patients were provided with the same brand of therapeutic shoes, with one specific model for men and another for women. The insoles were replaced every 4 months, and shoes once a year. These time parameters were based on current guidelines of the Medicare Diabetic Therapeutic Shoe Bill. Patients in the SRI group received the same therapy as patients in the STG with one exception: SRI patients used an insole design to reduce shear instead of the standard insole. A multilaminar design was used for both experimental and control groups. Insoles were constructed with a 35-durometer ethyl vinyl acetate (EVA), upper pad (3 mm thick), a 45-durometer EVA lower pad (3mmthick),anda20-durometer,closed-cell,cross-linkedpolyethylene foam top cover (1.5 mm). The only difference between the groups was that the SRI also includes elastic binders and 2 thin nonstick sheets. The nonstick sheets were placed between the upper and lower pads of the insole, and the binders held the insole together. Shear and pressure-reduction characteristics of the SRI have previously been published. Inclusion criteria included diagnosis of diabetes by American Diabetes Association criteria, ability to provide informed consent, 18 to 80 years of age, history of a foot ulceration, or presence of sensory neuropathy with loss of protective sensation and foot deformity. Patients were excluded if there was an open ulcer or open amputation site, Charcot arthropathy, unable or unwilling to use an over-the-counter shoe, severe peripheral vascular disease (ankle brachial index <0.70), transmetatarsal foot amputation or higher, active foot infection, dementia, impaired cognitive function, history of drug or alcohol abuse within 1 year of the study, or other conditions based on the investigator s clinical judgment. Neuropathy with loss of protective sensation was defined as vibratory perception threshold testing greater than 25 V or any site missed with the 10-g Semmes Weinstein monofilament. The authors used the techniques described by Young et al 16 and Mayfield and Sugarman. 17 Range of motion of the ankle, subtalar, and first metatarsophalangeal joint was assessed using standard landmarks and procedures. 18 Hallux rigidus was defined as first metatarsophalangeal joint dorsiflexion of 50 degrees or less, and equinus as 10 degrees of dorsiflexion or less. Toe and metatarsophalangeal joint deformities were defined as rigid, nonreducible deformities. The International Working Group on the Diabetic Foot s Risk Classification (IWGDF) was used. 19,20 Enrollment included patients with a history of a foot ulcer (IWGDF group 3) and with neuropathy and structural foot deformity of limited joint motion (IWGDF group 2). The primary clinical outcome was foot ulceration, which was defined as full-thickness loss of epidermis and dermis or involvement of deeper structures. At the conclusion of the study, patients were asked to complete a questionnaire about their compliance with wearing prescribed shoes and insoles (Table 1). Sample Size Estimation and Statistical Analysis Sample size was calculated based on the proportion of patients expected to develop foot complications in the 18-month study period. For this study, the statistical model used to examine the 2 treatments was a binomial model in which the proportion of patients who developed foot ulceration in the 2 treatment groups was examined. The outcome is a dichotomous variable (0 or 1), representing whether the patient had an ulceration. If 35% of the STG would have a foot ulcer during the study period, a sample size of 120 patients per group was required to detect a 25% difference between groups with an! of.05 and a power of 80%. Expectations are that 20% of the patients would not be able to complete the study and subsequently drop out. Therefore, we estimated to enroll 150 patients in each treatment arm to get 120 patients to fully complete the study. Statistical Analysis The data were evaluated with the last observation carried forward intent-to-treat approach. The Fisher exact test was used to compare incident ulcers during the study in patients who used SRI and standard insoles. To determine odds ratio and confidence intervals, the authors used the method described by Woolf as referenced by Schlesselman. 21 The Cox proportional hazard model was used to conduct a survival analysis based on the time to ulceration comparing the SRI with a standard insole. Several variables were included in the Cox regression analysis (risk group, treatment group, vibration perception threshold, ankle joint range, metatarsophalangeal joint range of motion, ABI, foot deformity, and race, type of diabetes, age). RESULTS No significant differences in patient characteristics (Table 1) were found. The SRI patients had fewer foot ulcers than did patients who received standard prevention therapy; however, this trend ADVANCES IN SKIN & WOUND CARE & NOVEMBER 2012

4 Table 1. PATIENT DEMOGRAPHICS AND CHARACTERISTICS EXPRESSED IN MEAN (SD) OR N (%) Table 1. PATIENT DEMOGRAPHICS AND CHARACTERISTICS EXPRESSED IN MEAN (SD) OR N (%), CONTINUED Shear-Reducing Insole (n = 149) Standard Insole (n = 150) Shear-Reducing Insole (n = 149) Standard Insole (n = 150) Age, y 69.4 (10.04) 71.5 (7.9) Gender, (% male) 102 (68.5%) 100 (66.7%) Duration of diabetes, y 13.0 (8.7) 12.0 (4.9) Amputation history n = 18 n = 13 Hallux 5 (3.4%) 8 (5.3%) 2nd toe 0 1 (6.6%) 3rd toe 3 (2.0%) 1 (6.6%) 4th toe 2 (1.4%) 0 5th toe 8 (5.4%) 3 (1.9%) Ulcer history 40 (27.5%) 38 (25.3%) Hallux 23 (15.5%) 25 (16.5%) Toes 13 (8.7%) 8 (5.3%) Submetatarsal 12 (8.1%) 18 (11.9%) Right ankle brachial index 0.97 (0.11) 0.98 (0.13) Left ankle brachial index 0.95 (0.11) 0.99 (0.12) Sensory neuropathy 100% 100% Right Semmes Weinstein monofilament (sites missed out of 10) 5.7 (2.7) 5.1 (2.5) Left Semmes Weinstein monofilament (sites missed out of 10) Right vibration perception threshold, V 6.3 (2.8) 4.4 (2.2) 28.2 (17.3) 30.0 (16.1) Left vibration perception 29.6 (14.8) 28.0 ( 14.0) threshold, V Right ankle equinus 68 (43.6%) 84 (56.4%) Left ankle equinus 98 (65.3%) 80 (53.7%) Ist Metatarsophalangeal joint dorsiflexion, right foot 52.4 (14.4) 47.2 (19.1) Ist metatarsophalangeal joint dorsiflexion, left foot 54.5 (13.9) 54.2 (12.2) Hallux rigidus, right 75 (51.0%) 87 (58.4%) Hallux rigidus, left 75 (51.0%) 87 (58.4%) Hallux valgus/hammertoe/ 51 (34.0%) 48 (32.2%) tailor s bunion right Footwear compliance Hours per day shoes and insoles were used 4 h/d 23 (15.5%) 16 (10.6%) 4 8 h/d 77 (52.0%) 83 (55.0%) 8 12 h/d 38 (25.7%) 46 (30.5%) h/d 10 (6.8%) 6 (3.9%) was not statistically significant (Fisher exact P =.08). Three ulcers developed in the SRI group, and 10 ulcers in the STG. A trend of fewer amputations in the SRI group was noticed; however, the analysis was not statistically significant. Patients in the STG were about 3.5 times more likely to develop an ulcer during the study period compared with patients treated in the SRI (odds ratio, 3.47; 95% confidence interval, ). No significant difference was self-reported in frequency of shoe and insole usage in SRI and STG (Table 1). DISCUSSION There are only 2 other randomized clinical trials the authors identified that have evaluated ulcer prevention with therapeutic shoes and traditional custom-molded insoles. Uccioli et al 6 demonstrated a significant reduction in the incidence of foot ulcers in persons with a history of diabetic foot ulcers that were treated with custom shoes and insoles compared with a second group that used self-selected shoes. In the therapeutic shoe and insole group, 28% of patients developed ulcers compared with 58% of patients who used their own shoes. On the other hand, Reiber et al 5 did not demonstrate any difference in outcomes among patients treated with therapeutic shoes and insoles and selfselected shoes. Reiber et al 5 evaluated a cohort of 400 persons with diabetes who were randomized to self-selected shoes, and 2 treatment groups who were provided therapeutic shoes and either a custom-made cork insole or a prefabricated polyurethane insole. Over a 2-year period, there was no difference in foot ulcers in patients who used self-selected shoes (17%), cork insoles (15%), and prefabricated insoles (14%). The yearly ulcer incidence was probably low in this study because the authors enrolled a population with a low risk for ulceration. Only 58% of the study population had sensory neuropathy, 32% had foot deformity, and 1% had peripheral vascular disease. The results of the authors study suggest a trend toward fewer foot ulcers, but the results did not meet the requirement for statistical significance. The main shortcoming of the study was that it was underpowered. In this study, the authors group evaluated patients ADVANCES IN SKIN & WOUND CARE & VOL. 25 NO

5 who are characteristically prescribed therapeutic shoes and insoles to prevent foot ulceration. The study population fit the highest-risk groups described in the IWGDF, patients with neuropathy, a foot deformity, and a history of a foot ulcer. The study demonstrated fewer ulcers than expected in this study. This was due to, at least in part, a large proportion of the study population having a lower risk of ulceration than the authors anticipated. At the time, the study did not have incidence data available for diabetic foot risk groups. 24,25 In this study, a minority of study patients had a history of previous foot ulceration (25.3% and 27.5%; Table 1), and a majority of patients in both treatment arms were in IWGDF risk group 2 (neuropathy and foot deformity). 24 In patients with sensory neuropathy and structural foot deformity, the incidence of ulceration is only about 3% to 6% a year. In contrast, among patients with a history of a foot ulcer, the incidence of ulceration is 19% to 40% per year. 6,26,27 And, without preventive care, the incidence of ulceration increases to 50% to 83% per year. 6,26 The etiology of ulcerations in persons with diabetes is commonly associated with the presence of peripheral neuropathy and repetitive trauma due to normal walking activities to areas of the foot exposed to moderate or high pressure and shear forces. 28,29 Foot deformities, limited joint mobility, partial-foot amputations, and other structural deformities often predispose persons with diabetes with peripheral neuropathy to abnormal weight bearing, areas of concentrated pressure, and abnormal shear forces that significantly increase their risk of ulceration The SRI used in this study has demonstrated a significant reduction in shear in laboratory studies with a similar reduction of pressure compared with standard insole designs in healthy adults. 15 Shear is probably a strong component in many patients who develop wounds in the presence of relatively moderate vertical forces. However, at this time, in vivo testing of shear in the gait laboratory or clinic setting is not readily available; thus, very little has been published regarding the contribution of shear to the development of foot ulcers in the neuropathic foot. CONCLUSIONS The authors results may not reflect outcomes observed in the general medical community because foot ulcer prevention is often overlooked. Only a small percentage of patients who are eligible for therapeutic shoes and insoles receive them. 33 Patients in this trial received a higher level of preventative care than is generally provided in the general medical community. As part of the study, insoles were replaced every 4 months, and shoes were replaced once a year, per Medicare guidelines. In addition, patients had structured foot care and foot-specific education. These practices are used in many clinic practice guidelines as standards of care, but they are not often implemented in community practices. 34,35 In addition, patients could have had better results simply because they were participating in a clinical study that allowed more personal contact and attention to their feet. 36,37 The results of this study suggest that an insole that reduces shear at the foot-insole interface can significantly reduce the risk of foot ulcerations in high-risk patients with diabetic neuropathy, deformity, and a history of foot ulcer than traditional insoles. The SRI used in this study worked well with conventional therapeutic shoes. They did not require any modifications, and they were tolerated as well as traditional shoe and insole combinations. More work is needed to understand effective therapies and risk factors for foot ulcers, such as factors that influence compliance and durability of insoles over time.& PRACTICE PEARLS & Foot ulceration in persons with diabetes is the most frequent precursor to amputation. & A recent systematic review demonstrated that insoles may prevent diabetic foot ulceration, but most of the evidence is poor and inconclusive. & Only a small percentage of patients who are eligible for therapeutic shoes and insoles receive them. & Empiric evidence and a growing body of basic science work support the important role of friction and shear in ulcer development in the neuropathic foot. & Shear-reducing insole patients had fewer foot ulcers than did patients who received standard prevention therapy; however, this trend was not statistically significant. REFERENCES 1. American Diabetes Association. Foot care in patients with diabetes mellitus. Diabetic Care 1997;20(Suppl 1):S Lavery LA, Ashry HR, van Houtum W, Pugh JA, Harkless LB, Basu S. Variation in the incidence and proportion of diabetes-related amputations in minorities. Diabetes Care 1996;19: Lavery LA, van Houtum WH, Ashry HR, Armstrong DG, Pugh JA. Diabetes-related lower-extremity amputations disproportionately affect Blacks and Mexican Americans. South Med J 1999;92: Reiber GE, Boyko EJ, Smith DG. Lower extremity foot ulcers and amputations in diabetes. In: Harris MI, Cowie C, Stern MP, eds. Diabetes in America. 2nd ed. NIH Publication 95, 1995: Reiber GE, Smith DG, Wallace C, et al. Effect of therapeutic footwear on foot reulceration in patients with diabetes: a randomized controlled trial. JAMA 2002;287: Uccioli L, Faglia E, Monticone G, et al. Manufactured shoes in the prevention of diabetic foot ulcers. Diabetes Care 1995;18: Patton J, Bruce G, Jones R, Stenhouse E. Effectiveness of insoles used for the prevention of ulceration in the neuropathic diabetic foot: a systematic review. J Diabetes Complications 2011;25: Lavery LA, Vela SA, Fleischli JG, Armstrong DG, Lavery DC. Reducing plantar pressure in the neuropathic foot. A comparison of footwear. Diabetes Care 1997;20: Mueller MJ, Strube MJ, Allen BT. Therapeutic footwear can reduce plantar pressures in patients with diabetes and transmetatarsal amputation. Diabetes Care 1997;20: Reiber GE, Smith DG, Boone DA, et al. Design and pilot testing of the DVA/Seattle Footwear System for diabetic patients with foot insensitivity. J Rehabil Res Dev 1997; 34(1): Laing P, Deogan H, Cogley D, Crerand S, Hammond P, Klenerman L. The development of the low profile Liverpool shear transducer. Clin Phys Physiol Meas 1992;13: ADVANCES IN SKIN & WOUND CARE & NOVEMBER 2012

6 12. Lord M, Hosein R, Williams RB. Method for in-shoe shear stress measurement. J Biomed Eng 1992;14: Yavuz M, Tajaddini A, Botek G, Davis BL. Temporal characteristics of plantar shear distribution: relevance to diabetic patients. J Biomech 2008;41: Zou D, Mueller MJ, Lott DJ. Effect of peak pressure and pressure gradient on subsurface shear stresses in the neuropathic foot. J Biomech 2007;40: Lavery LA, Lanctot DR, Constantinides G, Zamorano RG, Athanasiou KA, Agrawal CM. Wear and biomechanical characteristics of a novel shear-reducing insole with implications for high-risk persons with diabetes. Diabetes Technol Ther 2005;7: Young MJ, Breddy JL, Veves A, Boulton AJ. The prediction of diabetic neuropathic foot ulceration using vibration perception thresholds. A prospective study. Diabetes Care 1994;17: Mayfield JA, Sugarman JR. The use of the Semmes-Weinstein monofilament and other threshold tests for preventing foot ulceration and amputation in persons with diabetes. J Fam Pract 2000;49(11 Suppl):S Lavery LA, Lavery DC, Quebedeax-Farnham TL. Increased foot pressures after great toe amputation in diabetes. Diabetes Care 1995;18: Schaper NC, Apelqvist J, Bakker K. The international consensus and practical guidelines on the management and prevention of the diabetic foot. Curr Diab Rep 2003;3(6): Newrick P. International consensus on the diabetic foot. BMJ 2000;321(7261):642A. 21. Schlesselman J. Case Control Studies: Design, Conduct, Analysis. New York: Oxford University Press; Mayfield JA, Reiber GE, Nelson RG, Greene T. A foot risk classification system to predict diabetic amputation in Pima Indians. Diabetes Care 1996;19: Peters EJ, Armstrong DG, Lavery LA. Risk factors for recurrent diabetic foot ulcers: site matters. Diabetes Care 2007;30: Peters EJ, Lavery LA; International Working Group on the Diabetic Foot. Effectiveness of the diabetic foot risk classification system of the International Working Group on the Diabetic Foot. Diabetes Care 2001;24: Lavery LA, Peters EJ, Williams JR, Murdoch DP, Hudson A, Lavery DC; International Working Group on the Diabetic Foot. Reevaluating the way we classify the diabetic foot: restructuring the diabetic foot risk classification system of the International Working Group on the Diabetic Foot. Diabetes Care 2008;31: Edmonds ME, Blundell MP, Morris ME, Thomas EM, Cotton LT, Watkins PJ. Improved survival of the diabetic foot: the role of a specialized foot clinic. Q J Med 1986;60: Mueller MJ, Sinacore DR, Hastings MK, Strube MJ, Johnson JE. Effect of Achilles tendon lengthening on neuropathic plantar ulcers. A randomized clinical trial. J Bone Joint Surg Am 2003;85-A(8): Brand PW. Management of the insensitive limb. Phys Ther 1979;59(1): Brand PW. The Diabetic Foot. New York: Medical Examination Publishing; Armstrong DG, Lavery LA. Plantar pressures are higher in diabetic patients following partial foot amputation. Ostomy Wound Manage 1998;44(3):30-32, 34, 36 passim. 31. Armstrong DG, Lavery LA. Diabetic foot ulcers: prevention, diagnosis and classification. Am Fam Physician 1998;57: , Lavery LA, Armstrong DG, Vela SA, Quebedeaux TL, Fleischli JG. Practical criteria for screening patients at high risk for diabetic foot ulceration. Arch Intern Med 1998;158: Sugarman JR, Reiber GE, Baumgardner G, Prela CM, Lowery J. Use of the therapeutic footwear benefit among diabetic Medicare beneficiaries in three states, Diabetes Care 1998;21: Frykberg RG, Armstrong DG, Giurini J, et al. Diabetic foot disorders: a clinical practice guideline. American College of Foot and Ankle Surgeons. J Foot Ankle Surg 2000; 39(5 Suppl):S Mayfield JA, Reiber GE, Sanders LJ, Janisse D, Pogach LM. Preventive foot care in diabetes. Diabetes Care 2004;27(Suppl 1):S Grufferman S. Complexity and the Hawthorne effect in community trials. Epidemiology 1999;10: Lied TR, Kazandjian VA. A Hawthorne strategy: implications for performance measurement and improvement. 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