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Brian P. Scharfstein, C. Ped (C)
Foothealth Centre
Winnipeg, MB Introduction
Diabetes is a multi-system condition leading to multiple end organ complications. Peripheral neuropathy is the key factor leading to the lower extremity complications of diabetes. These lower extremity complications include loss of protective sensation which leads to ulcerations, Charcot changes and there may also be associated neuropathic pain.
The simplest technique for detecting the presence of loss of protective sensation is the ten gram monofilament.1,2 The Carville approach utilizes the ten gram monofilament in conjunction with previous ulceration and morphologic abnormalities to establish risks for foot complications such as ulcerations in persons with diabetes.2 The Carville approach stratifies individuals into 4 categories 0 through 3 based upon the presence of a condition that leads to insensitivity the absence of plantar ulcer and preserved sensation are category 0; while those individuals with a history of plantar ulcer and lack of sensation would be in the highest risk category for complications, risk category 3.2
Since the neurologic and morphologic changes from diabetes in the foot are fixed and cannot be reversed, it is therefore contingent upon the care providers to offer the person with diabetes the best possible protection and support for their feet. While custom molded insoles are part of the solution, the type and fit of the footwear is of paramount importance.3 It is important to note, however, that studies have demonstrated that a large majority of persons with diabetes with appropriate footwear seldom wear it. Reasons given by those persons, are that the footwear does not fit perfectly, is unsightly, and it is difficult for ambulation.4
The health care provider must be familiar with the various aspects of footwear so as to best guide their patient. The basic concepts of the footwear management of the person with diabetes, with or without a lower extremity complication, include the basic anatomy of the footwear, the type and features thereof, as well as the principle of obtaining appropriately fitted footwear.
What Does the Footwear Do?
The footwear serves as a container designed to cover the foot, providing protection from external forces and debris. The footwear must also provide support to allow the foot to function adequately in both dynamic and static conditions. If a custom molded orthotic is to be used, the footwear must be compatible with the orthotic so that both can function optimally. Figure 1 demonstrates the anatomy of typical footwear. The heel counter stabilizes the foot in the footwear. The top line should always be located below the malleoli. The flex point corresponds to the location of the metatarsal heads. The toebox should be of sufficient depth to accommodate the toes. This is particularly important in individuals with claw or hammertoes for whom a shoe with a deeper toe box is necessary. The upper must comply with the morphology of the foot. The outsole should be flexible and non-slip. The heel height (difference between rear foot and forefoot) should not exceed 2.5 cm. The lining should be smooth and free of seams which may create unanticipated pressure points within the shoe.
Figure 1: Anatomy of the Shoe
What Types of Footwear Exist?
Using the Carville Approach as a guide for footwear choices, it is important to note that for individuals without foot ulcers and preserved protective sensation (risk category 0) conventional footwear is appropriate. For those individuals who have lost protective sensation but lack plantar ulcerations and foot deformity (risk category 1) soft orthotics and appropriately fitted footwear is the therapeutic modality necessary to prevent foot problems. In those who lack protective sensation and plantar ulcers but who have foot deformities, and in those who lack protective sensation and who have a history of plantar ulcers (risk category 3) prescription footwear and custom molded orthotics are necessary.1 It is important to note that for those individuals with underlying neuropathy without other foot problems, the use of an inexpensive running shoe could be viewed as the minimally acceptable choice for footwear.3 For those individuals who require more sophisticated or "prescription" footwear, the morphology of the foot and risk category will determine whether an individual will require therapeutic/orthopaedic, or custom made/molded or customized footwear. There are different categories of footwear that a person with diabetes may require depending upon the presence and magnitude of neuropathy and whether there are morphologic abnormalities. The major categories include therapeutic/orthopaedic, custom made/molded and customized. The requirements for each of these types of footwear is as follows:
- Therapeutic/orthopaedic footwear: This type of footwear is mass manufactured and must have all of the following features; a minimum depth of at least 3/16 of an inch with a full removable insole, available in at least 4 widths, have a high, broad toe shape that accommodates forefoot shape and deformities, have an adjustable closure (laces, VelcroTM) to stabilize the foot, a broad sole to provide sufficient tortional stability along the medial and longitudinal arch area, a sole designed to allow for normal propulsion, heel stability via a firm, heel counter, easily modifiable upper and sole material, upper made of leather or other materials which breath, are moldable and durable, have a smooth protective lining, possess a shock absorbent midsole with sufficient thickness for protection and has a heel height which does not exceed 2.5 cm. The therapeutic/orthopaedic footwear can accept a custom molded orthotic.
- Custom made/molded footwear: This footwear is created for the specific patient by a qualified shoemaker. The process entails taking a negative cast from which a cast is then created. From this positive, the shoemaker then creates footwear that resembles "off the shelf" footwear, known as custom made, or, alternatively, a foot cover which serves all the same purposes but does not have the appearance of conventional footwear. The latter is referred to as a custom molded shoe.
- Customized Footwear: Therapeutic/orthopaedic footwear can be customized to accommodate morphologic variation and biomechanical deficiencies in the lower extremities of persons with diabetes. The modifications can include rocker soles to allow for alterations in gait pattern, and to off load areas of maximum impact; balloon patches to increase the surface area over specific areas and thus accommodate for morphologic abnormalities such as bunions or any other extoses. Buttresses and sole flares are utilized to stabilize the sub-talar joint, increasing stability to the lower extremity.
What Type of Footwear Is Inappropriate?
For persons with diabetes, the following features of footwear would be inappropriate as they do not provide adequate support and protection, thus, putting the foot at risk of trauma: backless, open toe or slip on shoes (without laces), soft soles that would allow inversion or eversion and that would flex at points other than the location of the metatarsal heads.
One of the most common myths encountered when individuals purchase footwear is that it should be of a specific pre-determined size. Because there are variations amongst manufacturers, it is important that when purchasing footwear both feet be measured in the weight bearing and non-weight bearing state to ensure that the correct foot size and shape are measured to ensure the best match between the foot and footwear. A common problem witnessed by shoe fitters is that persons with diabetes may independently obtain footwear which is of an inappropriate size as they may be unable to appreciate whether it is too tight or too loose. Footwear that is too tight may lead to areas of ischemic necrosis, while shoes that are too loose may lead to shearing and ultimately blisters which may ulcerate. Properly fitted footwear is one of the key elements for the successful foot management of the person with diabetes.
Where to Obtain Footwear?
Although there are many vendors of footwear, it is ideal to refer the person with diabetes to a skilled shoefitter who is knowledgeable about neuropathy. Typically, specialty shoe stores employing pedorthists or trained shoefitters can provide this service. It is important that the vendor have an adequate footwear inventory as delays in obtaining appropriate footwear may have significant and disastrous implications. The vendor must also be knowledgeable about the interaction between custom molded orthotics and the footwear which is being provided.
How Should Footwear be Prescribed?
When providing a prescription to a person with diabetes, it is critical to specify the condition for which the footwear is being requested. It should be specified whether the person with diabetes suffers from neuropathy, has had an amputation of a digit, or has an ongoing or healed plantar ulceration. The category of footwear must also be specified, specifically, does the person with diabetes require therapeutic/orthopaedic custom made/molded, customized or merely conventional yet appropriately fitted footwear. It may also be prudent to specify in the prescription that modifications can be made at the discretion of the provider.
Summary
Footwear for persons with diabetes serves an important purpose, specifically, protection and support allowing for individuals to perform their activities of daily living. Ideally the selected footwear should be fitted by an experienced provider and include the full range of appropriately fitted conventional footwear with or without modifications to custom made/molded based upon the Carville criteria.
Acknowledgments
The author wishes to thank Ms. Carolyn Schlippert for the secretarial skills necessary for completing this overview.
References
- Birke J.A., Sims D.S.: Plantar Sensory Threshold in the Ulcerative Foot, Leper Rev 57:261-267, 1986.
- G.W. Long, Hansen's Disease Centre, Rehabilitation Branch: Foot Screening: Care of the Foot in Diabetes…The Careville Approach, The Carville Project, LA. United States Government.
- Perry J.E., Ulbrecht J.S., Derr J.A., Kavanagh P.R.: The Use of Running Shoes to Reduce Plantar Pressure in Patients Who Have Diabetes, J Bone Joint Surg Am, 77 (12): 1819-1828, 1995.
- Chantelau E., Haage P.: An Audit of Cushioned Diabetic Footwear: Relation to Patient Compliance. Diabet Med 11: 114-116, 1994.
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