transfer and unipedal balance in the elderly. Arch Phys Med Rehabil Nov 1996;77:1152, 1156.
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28 Footwear for People with Diabetes Peter R. Cavanagh and Jan S. Ulbrecht
INTRODUCTION One afternoon, almost 20 years ago, during a visit to our laboratory, the late Dr Paul Brand , who was still engaged in an active clinical practice of hand and foot surgery , was musing about his potential activities after retirement.
Only partly in jest, he declared that he thought he might become a shoemaker, because he had the impression that more diabetic patients had congrat- ulated him on the shoes he had prescribed for them than on the foot surgery he had performed.
Dr Brand actually ‘retired’ to an active lecture schedule, but the anecdote reflects the impor- tance that this eminent scholar and teacher of neuropathic foot pathology placed on therapeutic footwear.
Despite his own pioneering experimental work more than 40 years ago,1,2 the state of the art in footwear prescription for patients with diabetes is still rudimentary.
Studies have shown that different practitioners faced with the same patient devise very different solutions, which can differ greatly in their efficacy.3 (Some of the prescribed interventions even increased pressure at a region of interest, something that would certainly be categorised as a negative out- come.) The authors of the above study have urged the development of ‘unambiguous guidelines that enable improved education and consequently less variation between therapists’.3 Unfortunately, such guidelines have been slow to emerge from the research laboratories.
As we shall discuss, there have been important technical developments , notably, good in-shoe pressure measurement techniques and computer-aided design, computer-aided manufacture (CAD-CAM) systems to make insoles.
Scientists have embraced these tools to show that technology can produce improved products or at least evaluate the effectiveness of footwear prescriptions.
However, these tools have been slow to flow to the practitioner.
Trends in footwear prescription have also been influenced by cost constraints , such as those in the United Kingdom that require at least 75% of items dispensed to be ‘off-the-shelf’, or the Medicare guidelines in the United States that reimburse for one pair of custom-made shoes plus two pairs of insoles (or one pair of extra-depth shoes and three pairs of insoles) per calendar year to qualified patients.
In this chapter, we shall examine the evidence that guides the prescription of therapeutic footwear, discuss the mechanisms whereby therapeutic footwear is believed to exert its effect and make recommendations for best practice in the absence of clear, evidence-based guidelines.
The physician seeing a patient for diabetes-related medical issues should understand which
The Foot in Diabetes, 4th Edition. Edited by Andrew J.M. Boulton, Peter R. Cavanagh and Gerry Rayman. C 2006 John Wiley & Sons, Ltd. ISBN: 0-470-01504-7
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WHAT DOES THE LITERATURE SAY? 337
patients will need footwear, what can safely be dispensed to a given patient and what conditions require a referral to a local provider of therapeutic footwear.
WHAT DOES THE LITERATURE SAY? Three subsets of the literature are relevant to therapeutic footwear for people with diabetes: retrospective studies, in which the role of footwear in injury is inferred from charts or self- report; clinical trials and controlled studies, in which patients have been prescribed footwear, and the outcomes, usually ulcer prevention, have been examined; and biomechanical studies, in which different interventions have been tried, and some component of the foot, shoe interface has been measured. All of these approaches are potentially instructive, and all have shed some light on the role of therapeutic footwear in people with diabetes.
Retrospective Studies Footwear is widely believed to cause many foot injuries, ulcers and even amputations in persons with diabetes.
Various authors have retrospectively identified ‘narrow shoes’,4 ‘pressure from footwear’,5 ‘inadequate footwear’,6 ‘trauma from footwear’7 and footwear in general8 as being responsible for between 21 and 89% of ulcers.
The ‘pivotal event’ in a series of 80 consecutive patients with amputations was reported to be ‘shoe related’ in 42% of cases.9 To prevent injury from simple mis-sizing, it is essential for diabetic patients that shoe length and width be carefully determined by measurement, since a neuropathic patient will not be able to give adequate feedback regarding shoe fit.
One study showed that in 66% of cases, the foot width of neuropathic patients was much broader than that of conventional shoes.10 This suggests that shoes with additional width and/or depth should often be prescribed.
Clinical Trials and Controlled Studies Very few randomised controlled studies have tested the effectiveness of therapeutic footwear in preventing foot ulceration or re-ulceration.11,12 One study, which showed no effect in a large number of patients,13 was probably influenced by study design issues, including the fact that a break in the skin that lasted less than 30 days was not defined as an ulcer.14 Those studies that have shown a benefit to wearing prescription footwear are generally smaller and less well con- trolled.
Three studies in which a control group of patients used their own footwear after healing an ulcer have shown, not surprisingly, that a therapeutic intervention reduces the risk of re- ulceration.15−17 The reductions observed were substantial (28% vs 50% at 12 months,16 15% vs 60% at 12 months,15 and 4% vs 33% at 9 months17 for therapeutic vs own shoes, respectively).
A significant problem in designing a study of therapeutic shoes is determining, preferably a priori, whether or not the footwear prescription used is effective for every patient in the trial , that is, does it reduce plantar pressure at the regions of interest (see below).
The doctor who recommends prescription footwear also faces this problem, as will be discussed further below.
Biomechanical Studies Studies in this category do not use a clinical outcome to judge the effectiveness of shoes. Most frequently, they use the measurement of pressure exerted between the bottom surface of the
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338 FOOTWEAR FOR PEOPLE WITH DIABETES
(a) (b)
Figure 28.1 Peak plantar pressure during walking, measured in the same subject, (a) under the foot during barefoot walking and (b) inside a shoe which provides pressure relief at areas of elevated pressure under the metatarsal heads and hallux. Both data sets are to approximately the same scale. Peak pressure in barefoot walking > 1 MPa
foot as it meets the insole of the shoe (plantar pressure) usually during walking, as shown in Figure 28.1.18 Early studies were done with individual pressure sensors,2 but these tended to cause a concentration of pressure at the site being measured.
Today, there are a variety of products that comprise a matrix of flat sensors embedded in a thin insole, and the patient walks for 20, 30 steps while data are captured on a computer.
It is also now possible to monitor for longer periods of up to 8 h.
Although the results from sensors made by different manufacturers are not comparable (because of different surface areas and other issues), comparative studies are possible with a given insole: e.g., is shoe condition A better than shoe condition B?
Using this methodology, strategies for the reduction of plantar pressure have been tested.
It can reasonably be assumed that if plantar pressure at a site of importance (such as a prominent metatarsal head (MTH)) is reduced in a given condition, and the prescription shoe is worn consistently by the patient (see below), then the clinical outcome may be improved.
A variety of interventions, including custom insoles,19 metatarsal pads,20,21 metatarsal bars22 and rigid or semi-rigid shoes23 (see below), have been studied.24 The results have led to insight into the placement and design of the various interventions.
Making the sole of the shoe rigid and contoured (rather like a Dutch clog, see below), together with the provision of an appropriate insole, has been shown to be the most successful intervention, reducing plantar pressures by up to 50%.23,25
HOW DOES THERAPEUTIC FOOTWEAR WORK? The designer of therapeutic footwear attempts to do a number of things, depending on the needs of the diabetic patient. Some of the most frequently used strategies are (1) providing room to accommodate deformity (most often prominent dorsal surfaces of toes and medial and lateral prominences); (2) providing adequate depth to allow thick insoles, thick socks and special features of the insoles , such as metatarsal pad and bars and arch supports , without putting pressure on the dorsum of the foot; (3) reducing load at critical areas of focal pressure, such as MTHs, the tips of clawed toes or midfoot prominences secondary to Charcot fractures;