535233 research-article2014
POI0010.1177/0309364614535233Prosthetics and Orthotics InternationalJanisse and Janisse
INTERNATIONAL SOCIETY FOR PROSTHETICS AND ORTHOTICS
Literature Review
Pedorthic management of the diabetic foot Dennis Janisse1,2 and Erick Janisse3
Prosthetics and Orthotics International 2015, Vol. 39(1) 40–47 © The International Society for Prosthetics and Orthotics 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0309364614535233 poi.sagepub.com
Abstract Background: Conservative pedorthic management of the diabetic foot has been shown to be an effective method to prevent ulcers, amputations, and re-amputations. This article exhibits why and how pedorthics plays such an important role via modalities such as footwear, shoe modifications, custom foot orthoses, and partial foot prostheses. Objective: The objective of this article is to demonstrate how pedorthics has been shown to be an integral part of conservative diabetic foot care. The authors’ goal was to educate the reader about the different modalities that are available for use. Study design: This article is based largely on review of previously published research and scholarly articles, augmented by the more than 60 years of pedorthic and orthotic clinical experience of the authors. Methods: Approximately 60 journal articles and book chapters were reviewed by the authors. Articles were located via online resources such as PubMed as well as the authors’ own libraries. Results: It was repeatedly noted that pedorthic modalities such as shoes, foot orthoses, and shoe modifications may be utilized in the treatment and prevention of diabetic foot wounds and other complications. Conclusion: Pedorthic devices may be successfully integrated into a comprehensive treatment plan for patients with diabetes and foot ulcers. Clinical relevance This information is of special interest to those who treat patients with diabetes. The article demonstrates the efficacy of pedorthic intervention through the compilation and review of relevant previously published data. Keywords The diabetic foot, diabetes, lower limb orthotics, orthotics, skin stress, diabetes Date received: 25 February 2014; accepted: 16 April 2014
Background
The team approach
To be successful, a diabetic foot care program needs to focus its efforts on prevention.1–3 Two key elements of the preventive approach are education and proper footwear.4 Unfortunately, it is not uncommon for a patient to seek medical advice only after he has developed a problem like a diabetic foot ulcer. All too frequently, these patients have not been recently checked for peripheral neuropathy—some may never have been tested—and many are ignorant of diabetic neuropathy and its associated risks.5 It can be a real challenge to convince a person who has never had a foot ulcer or has not experienced foot discomfort to restrict their footwear choices to only those shoes that are considered by their health care provider to be appropriate. This task can be completed most easily when a diabetic foot care team is assembled and put into action.6–9
The physician and the patient form the foundation of the team, but there are several ancillary but indispensable members of a successful foot care team. Other practitioners who work with physicians to prevent foot ulcers and subsequent amputations are certified diabetic educators, wound care nurses, physical therapists, certified pedorthists, certified orthotists, and, seemingly inevitably, prosthetists. 1Department
of Physical Medicine and Rehabilitation, Medical College of Wisconsin, Milwaukee, WI, USA 2National Pedorthic Services, Inc., Milwaukee, WI, USA 3Orthotic and Prosthetic Design, Inc., St. Louis, MO, USA Corresponding author: Dennis Janisse, Medical College of Wisconsin, 7283 W Appleton Ave, Milwaukee, WI 53216, USA. Email: [email protected]
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The role of the certified pedorthist Pedorthics is the art and science concerned with the design, manufacture, fit, and modification of shoes and foot orthoses to alleviate foot problems caused by disease, overuse or injury.10 Pedorthists fabricate and fit foot orthoses, shoes, and shoe modifications according to a physician’s order. A pedorthist is schooled in foot anatomy, pathology and the construction of shoes and foot orthotic devices. Pedorthists are tested and certified by the American Board for Certification in Orthotics, Prosthetics and Pedorthics. Board-certified pedorthists are required to participate in continuing education programs and are bound by a strict code of ethics.10 The pedorthist plays a significant role in the prevention of ulcers and amputations by providing appropriate and properly footwear. This typically includes the construction of custom-made foot orthoses to fit inside the shoes and/or internal and external modifications to the shoes themselves. The pedorthist also plays the role of patient educator. Certified pedorthists are an invaluable resource for educating patients in shoe selection, including guidelines for proper fit, instructions for use, and appropriate materials and styles for an individual’s feet. As a member of the diabetic foot care team, the pedorthist also reinforces the treatment plan provided by the other team members.
Pedorthic objectives Total contact casting is considered to be the “gold standard treatment” for healing diabetic ulcers.11 Pedorthic and orthotic care is intended primarily as long-term management for maintaining healed ulcers and fractures and for preventing future ulcers and fractures, and in general, it is not considered the ideal treatment or healing option for open ulcers or acute Charcot fractures.6 Similarly, while there is little that shoes and foot orthoses can do to actually treat diabetic foot infections, they are powerful tools to be used for the prevention thereof. Ill-fitting shoes are a prevalent cause of skin trauma that precedes the diabetic foot ulcers that can potentially lead to partial foot amputation.12 Areas of excessive plantar pressure and shear—two mechanisms that combine to cause diabetic skin ulcerations—are issues that are alleviated with custom foot orthoses. Stated simply, the key to avoiding diabetic foot infections is to prevent the opening of a portal of entry for infection to occur. Amputations in patients with diabetes, while often preventable, are a too common reality; 15% of diabetics will develop a foot ulcer over the course of their lifetime, and foot ulcers are the precursor of 70%–90% of all diabetic amputations.13–19 Partial foot amputations are nearly twice as common in the United States as either transtibial or transfemoral amputations.20 Unfortunately, there is a high
re-amputation rate in patients who undergo a partial foot amputation.21,22 The role of the pedorthist should not be undervalued in the prevention of diabetic foot complications (amputations, revisions, and foot infections secondary to skin ulcerations) and in returning the patient a normal, active, and productive lifestyle after an amputation. The primary goals of the pedorthist and the prosthetist when working with partial foot amputees are to restore stability and function lost due to an amputation, facilitate energy-efficient gait, maintain support, and prevent any further complications.23
Shear and plantar pressure Excessive shear and high peak plantar pressures have been repeatedly implicated as causal agents in the formation of plantar foot ulcers in persons with diabetic neuropathy. Luckily, therapeutic footwear decreases weight-bearing pressure and shear forces applied to the skin of the foot.24 The plantar pressure gradient should be paid due attention, too.25 While much has been written about areas of high peak pressures as a predictor of foot ulcers, research has revealed that there is not a particularly high correlation between the two.26–29 Surely, reducing elevated pressure levels is important, but the need to reduce the duration of maximum pressure and shear stresses is perhaps more so.30 Foot ulcers often occur at locations where one has developed calluses.31 The callusing is not due solely to plantar pressures, but also from frictional shear forces.32,33 Tissue breakdown occurs more rapidly when shear is increased.34 In normal walking, shear stresses act twice as frequently as pressure characteristically. Since plantar shear is known to be a factor in the formation of pre-ulcerative calluses, it deserves consideration when discussing diabetic foot ulcers. Excessive levels of shear may also cause damage to underlying tissues.35 The damage done by repetitive friction load does not begin at the outermost layer of the skin; rather, the friction causes shear forces to act between the layers of skin.36 Diabetics with neuropathy experience increased plantar shear over a non-diabetic with no foot problems.35 Naylor37,38 demonstrated in the 1950s that a peak perpendicular load by itself is not necessarily harmful and established that the magnitude of repeated high peak pressures is of greater concern because of how they enable and relate to peak friction loads. Ensuring that the shoe size and shape are appropriate for the foot is perhaps the easiest way to reduce shear inside of a shoe. If the shoe fits and is secured snugly on the foot, the foot does not shift inside the shoe as much. Proper fit is critical as a loose shoe and a tight shoe both have the potential to increase shear, friction, and/or pressure on the foot.
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Another way to decrease friction and shear is to “lubricate” the surfaces moving against one another. This can be accomplished with the use of shear-reducing socks made from an acrylic blend fabric or other fiber that has a low coefficient of friction (COF). Traditional cotton socks have a relatively high COF, especially when damp. The use of double socks allows the shear to take place between the layers of socks as opposed to between the skin and sock or sock and insole.39 This “lubrication” can also be done using a low-friction interface on the interior of the shoe or on the surface of a foot orthosis or ankle–foot orthosis (AFO) under areas of high pressure or friction. A polytetrafluoroethylene material called ShearBan® is widely available to the orthotic, prosthetic, and pedorthic industry. The self-adhesive material can be adhered virtually anywhere inside of a shoe, brace, or prosthetic socket. It is also heat moldable. Discussion of the reduction of peak plantar pressures often focuses on the forefoot as diabetic ulcers occur most frequently in this area.25,26 It is also for that reason that so much research has been devoted to the reduction of forefoot pressures using shoes, rocker soles, and various types of foot orthoses.40–44 The spatial change in plantar pressure around the location of peak plantar pressure (peak pressure gradient) is another pressure variable that warrants attention. Mueller et al. suggest that it may be a strong indicator of pending skin breakdown. Their research showed that the peak pressure gradient was significantly higher in the forefoot than in the heel even when compared with the peak plantar pressure.25
Shoes Improper footwear is a common culprit in causing diabetic ulcers.12 Therapeutic footwear can help reduce a patient’s chances of developing foot ulcers.7,45 There are several objectives in providing footwear for patients with diabetes.46 It is important to understand these objectives before discussing the different types of shoes or shoe fitting. They are as follows: 1. 2. 3. 4. 5. 6. 7.
To protect the foot; To relieve areas of excess pressure; To reduce shock; To reduce shear; To accommodate deformities; To stabilize and support deformities; To accommodate foot orthoses and AFOs.
Shoe types Every diabetic footwear prescription should include indepth shoes. An in-depth shoe is an oxford-type or athletic shoe with an additional 1/4″–3/8″ of depth throughout the
shoe.46,47 These shoes offer even more space when the removable factory inlays are taken out. The additional volume afforded by an in-depth shoe makes it ideal for patients with diabetes as it can easily accept a foot orthoses or AFO without affecting the fit of the shoe and is also useful for accommodating deformities associated with the diabetic foot such as hammertoes or bony prominences resulting from Charcot arthropathy. Off-the-shelf shoes used for the diabetic foot are manufactured in multiple widths. When no off-the-shelf shoe is appropriate due to extreme deformities or variance in size from left foot to right, it may be necessary to modify the shoe. If the shoe cannot be modified to fit, the last alternative is a custommade shoe. Custom-made shoes are fabricated by creating a positive model from a mold of the patient’s foot. The shoe is then constructed around this model. Since they are made directly from molds of the feet, custom shoes offer the best possible accommodation and protection, but can be quite expensive and lack the cosmetic appeal of commercially available shoes.
Shoe selection Shoe selection is based on three things: the condition of the patient, the patient’s foot shape and type, and the patient’s daily activities. For a patient who has no history of ulcerations, shows no signs of peripheral neuropathy, and has a structurally normal foot, a properly fitting offthe-shelf shoe may be all that is necessary, whereas a patient with neuropathy and a history of ulcers, Charcot arthropathy, and/or amputations will need a more complex footwear prescription. The patient’s body type is also a crucial factor to consider when selecting shoes. The construction of the shoe should correspond to the patient’s body type. The key to both shoe selection and shoe fitting is choosing a shoe that fits the shape of the patient’s foot. Not only must the shoe be of the correct shape to fit the patient’s foot, but also it must be of the correct depth to properly accommodate additional devices such as foot orthoses. The shape and volume of a shoe are dependent on the last over which it was made. Lasts are made in innumerable shapes, but the manufacturer determines the particular last used for any given shoe. Therefore, a shoe in size 10B manufactured by company X could fit dramatically differently than a size 10B shoe produced by company Y.47,48 Lasts for therapeutic footwear are not only made in a variety of sizes but also widths and shapes. The depth of the shoe is important not only in the toe area but across the instep, too; the shoe should not put pressure across the dorsum of the foot. Shoes with laces or hook-and-loop closure systems tend to fit better than slipon shoes. Persons with neuropathy should avoid slip-on shoes as they are, by their very nature, too short and too tight.
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Shoe fitting Once a properly shaped shoe has been selected, the appropriate size is determined using a Brannock device. The Brannock measures overall foot length, arch length (heelto-ball), and width.48 A shoe of the proper length insures that the first metatarsophalangeal joint is seated comfortably in the widest part of the shoe. This is why arch length needs to be assessed. Both feet should be measured as most people have one foot longer than the other.49 If this difference is significant, a pair of mismated shoes may be in order. Measuring the foot by any means determines just that— the size of the foot. An individual’s foot measurement does not necessarily equal their shoe size. It is up to the pedorthist to know his inventory and have an intimate knowledge of how each different shoe fits and how each corresponds to the foot measurement. A properly fitted shoe should leave about 1/2″ between the end of the longest toe and the front of the shoe.47,48,50 The shoe should also allow for a small amount of movement of the heel since the foot stretches and the calcaneus shifts during gait. The upper should not be stretched taut across the ball of the foot; there should be appreciable slack in the material. As important as properly fitting shoes are in preventing and solving foot problems, a large percentage of the population continues to wear ill-fitting shoes.51 Foot orthoses, another important treatment modality for diabetic feet, are only as good as the shoes in which they are worn.52
Foot orthoses Foot orthoses are used in the prevention of foot ulcerations.53 Foot orthoses are available as custom-made devices or off-the-shelf devices. Both types can be made from a variety of materials differing in density, cushioning, shock absorption, support, and control. The use of a pre-fabricated device reduces the cost and time investment of both practitioner and patient, but sacrifices the fit, longevity, and adjustability of a custom device. Custom orthoses are necessary when the patient has any of the following: a foot deformity, a loss of protective sensation, and a history of ulcers and/or Charcot arthropathy and/or partial foot amputation. A custom foot orthosis can achieve total contact with the plantar surface of the patient’s foot, therefore employing the same total contact concept as the total contact cast.54 There are four main types of custom foot orthoses although not all are indicated for use in patients with diabetic neuropathy. They are the following: accommodative, semi-rigid, rigid, and the partial foot prosthesis. When evaluating a patient for foot orthoses, the practitioner needs to understand lower limb biomechanics and be
able to identify areas of high pressure; they also need to utilize the proper molding technique and be able to select the best material given the desired function of the orthosis.55 The primary function of a foot orthosis for a person with diabetes is to cushion and protect the foot. Additionally, the following component objectives should be realized:46,55 1. Provide shock absorption and shock attenuation; 2. Relieve areas of high plantar pressure by evenly redistributing weight-bearing pressures over the entire plantar surface; 3. Support, splint, and protect healed fracture sites by employing the total contact concept; 4. Reduce shear; 5. Control, stabilize, support, or correct flexible deformities; 6. Limit the motion of affected joints; 7. Accommodate fixed deformities.
Accommodative foot orthoses An accommodative foot orthosis is designed primarily to cushion and protect the foot. It offers good shock absorption and padding. It may be designed to offload prominent areas. An accommodative orthosis is typically not one that will perform at a high level for a long period of time. Softer, less dense materials tend to wear out quickly, so this type of orthosis requires vigilant follow-up and needs to be repaired or replaced on a regular basis. Depending on the materials used, accommodative orthoses can be molded directly to the patient’s foot using either external heat and pressure, or the patient’s own body heat and weight to mold them. Accommodative orthoses can also be fabricated over a positive model of the patient’s foot. This model could be a plaster model made from a negative mold of the person’s foot or a computergenerated model based on a three-dimensional scan. Accommodative foot orthoses are made of soft, moldable materials. In general terms, moldable materials possess better pressure-distribution properties than the non-moldable materials, but are not as durable and compress more quickly.56
Semi-rigid foot orthoses Semi-rigid foot orthoses combine the cushion and protection of the accommodative orthoses with the support, control, and weight redistribution of the rigid orthoses. Semi-rigid orthoses also last longer than the accommodative orthoses. A semi-rigid orthoses for a patient with diabetes typically consists of a soft, cushioned protective top layer with a firmer, more supportive base material.
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Semi-rigid devices are used to alleviate areas of high pressure and prevent skin breakdown by redistributing and equilibrating plantar pressures. The soft materials in an accommodative orthoses accomplish this goal for only a very short period of time as soft materials compress rapidly under areas of high pressure, thereby quickly returning those areas to their previous state of elevated pressures. By using a firmer material to support the arch and cradle the heel, the soft materials in the top cover of a semi-rigid device do not compress as rapidly and the plantar pressures are more evenly distributed.55 In an insensate foot, the areas of highest pressure are typically under the heel and the ball of the foot.57 By using a total contact semirigid foot orthosis, the entire plantar surface of the foot shares in the weight-bearing process. The top layer or layers of a diabetic semi-rigid orthoses generally consist of thin layers of accommodative materials. Semi-rigid orthoses are typically made of combinations of two, three, four, or more different materials. A study of five commonly used foot orthosis materials by Brodsky et al.56 found that the soft polyethylene foams had better pressure-distribution characteristics when first applied, but that exposure to repeated pressures caused them to bottom out more rapidly than some of the more durable polymers. Other studies lend credence to this concept and also show that loss of thickness of the molded polyurethane foam is inversely related to its density.58,59 These studies suggest that in order to achieve the total contact objective as well as provide adequate shock absorption and support, a foot orthosis for use in treating the diabetic foot should be fabricated using of a combination of different materials. A triple-layer, molded orthoses has been suggested to provide the necessary combination of support and accommodation.55,60 The three layers would then be the following: 1. Soft, moldable polyethylene foam next to the foot; 2. A middle layer consisting of a urethane polymer that resists bottoming-out and offers good shock absorption; 3. A firm molded cork or dense ethylene vinyl acetate base for support and control. Orthoses made of material with good shock-absorbing qualities, like viscoelastic polymers, have been shown to significantly reduce the abnormally high plantar pressures of a diabetic foot.61
Rigid foot orthoses Rigid orthoses are contraindicated for persons with diabetes, especially if there is evidence of neuropathy or a history of ulcerations. They can be extremely difficult to fit.62 Rigid orthoses are not forgiving and do not mold or conform to prominences on the plantar surface of the foot and could actually cause injury.53
Rigid orthoses are often made of thermoplastics, acrylics, or carbon fiber composites. They are not easily adjustable. Rigid orthoses are durable and offer excellent support and control, but provide very little in the way of cushion, shock absorption, and protection.61
Partial foot prosthesis The main goal of amputation surgery for the surgeon is to salvage as much functional limb that will heal as possible; the goal for the pedorthist and prosthetist is to preserve and restore the patient’s functional level.23,63 The primary purpose of a partial foot prosthesis for a patient with diabetes is to protect the residual foot, with a secondary aim of restoring normal function and gait. Equal pressure distribution is especially important in the partial foot patient as peak plantar pressures rise exponentially as the amount of weight-bearing surface area decreases. The question of whether these tissues can handle the increased stress is why partial foot prostheses are often used in conjunction with an AFO—especially with a midfoot-level amputation—to transfer the stresses to more proximal normal tissue.64 The partial foot prosthesis is used primarily to help evenly redistribute plantar pressures in the foot, reduce areas of high peak pressure, and decrease shear. This is accomplished by fabricating a custom foot orthosis and adding an area of padding just distal to the end of the residual foot and then finishing it with a semi-rigid foam filler to maintain the foot’s position within the shoe. The loss of the hallux requires something to replace the lost lever arm for toe-off propulsion. This can be done through the use of either an extended shank in the sole of the shoe or by attaching a full-length carbon fiber footplate to the partial foot prosthesis. There is much literature on the use of silicone and/or acrylic resin partial foot prosthesis—especially for Lisfranc’s and Chopart’s amputations—such as a Chicago boot or a Lange prosthesis that slips over the residual foot, much like a sock or a shoe would.23,63–67 These types of devices provide cushion, stability, and reduction in shear forces. They can be difficult to don and doff but are cosmetically pleasing and some may even be worn without a shoe. However, discretion should be used when considering the use of these prostheses in the diabetic population as these devices tend to be hot, which could make the foot perspire, and do not permit any air circulation around the foot and may allow increased bacteria.23
Shoe modifications The sole of a shoe can be modified in a variety of ways for any number of reasons but are most commonly modified for one or more of the following reasons:
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Janisse and Janisse To replace lost motion; To restore lost function; To increase stability; To aid in forward propulsion or make ambulation more efficient; 5. To offload areas of high pressure; 6. To help the shoe better fit the foot; 7. To accommodate or enhance the function of an AFO.
1. 2. 3. 4.
Rocker soles The rocker sole is one of the most commonly prescribed shoe modifications. The primary function of a rocker sole is to rock the foot from heel strike to toe-off without requiring the shoe or foot to bend. Generally speaking, the biomechanical effects of rocker soles are restoring lost motion in the foot and ankle due to pain, deformity, stiffness, or surgical fusion, resulting in an overall improvement in gait, and offloading plantar pressure on some part of the foot.41 All types of rocker soles can offload the forefoot, which is beneficial and can help prevent ulcers as diabetics with neuropathy experience increased pressure under the forefoot.40,57 In fact, the rocker is considered the most effective way to offload the forefoot.68 There are two terms that need to be understood in order to discuss rocker soles: (1) the midstance or the section of the rocker sole that is in contact with the ground when standing erect and (2) the apex, or high point, of the rocker sole located at the distal end of the midstance.29 Proper placement of the apex is critical to the success of the modification; it should be placed just proximal to any area for which pressure relief is desired. For example, if the desire were to offload the ball of the foot, the apex would be placed directly behind the metatarsal heads. Many off-the-shelf walking shoes and running shoes are built with a mild rocker sole. This simple, generic rocker is often adequate for a foot that is not at risk. It provides some metatarsal head relief and gait assistance; however, for the patient who requires more relief or has deformity or neuropathy, a custom rocker sole is indicated.
Extended shank The extended shank is made of either spring steel or carbon graphite composite and is inserted between the layers of the sole, extending from the heel to the toe of the shoe. Extended shanks are commonly used in conjunction with a rocker sole and make the rocker sole more effective. The shank keeps the shoe from bending and reduces forces through the midfoot and forefoot. It strengthens the entire sole and shoe and maintains the continuity of the rocker sole.9
Re-last Re-lasting a shoe may be indicated for a severe rigid pes planus deformity or a midfoot that has widened due to Charcot arthropathy. The soles of many off-the-shelf shoes can be reconstructed or reconfigured to accommodate severe deformities.69 Re-lasting is a viable alternative to custom shoes for many patients. This process involves customizing an off-the-shelf shoe, by widening it through the midfoot or forefoot, to fit a foot that would not otherwise be able to use an off-the-shelf shoe. This is done by removing the outsole and making a cut through the sole, midsole, and innersole and widening the shoe according to a pattern of the foot. A new outsole is applied, and to the casual observer, the shoe looks “normal.”
Conclusion The team approach, patient education, and pedorthic and orthotic modalities have all been shown to be valuable tools in the care of the diabetic foot. The team approach is probably as, if not more, beneficial to the successful treatment of the diabetic foot than nearly any other problem the physician encounters. The understanding of pedorthic principles and how to include and utilize the appropriate clinicians on the team can simplify the patient care process while decreasing life-altering complications such as ulcerations and amputations. Author contribution All authors contributed equally in the preparation of this manuscript.
Conflict of interest None declared.
Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
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6. Coleman WC. Footwear for injury prevention: correlation with risk category. In: Levin ME, O’Neal LW and Bowker JH (eds) The diabetic foot. 5th ed. St. Louis, MO: MosbyYear Book, 1993, pp. 493–505. 7. Edmonds ME, Blundell MP, Morris ME, et al. Improved survival of the diabetic foot: the role of a specialized foot clinic. QJM 1986; 60: 763–771. 8. Hobgood E. Conservative therapy of foot abnormalities, infections and vascular insufficiency. In: Davidson JK (ed.) Clinical diabetes mellitus. New York: Thieme Medical Publishers, 1986, pp. 599–610. 9. Janisse DJ. The role of the pedorthist in the prevention and management of diabetic foot ulcers. Ostomy Wound Manage 1994; 8: 54–65. 10. PFA. Pedorthic reference guide. Columbia, MD: PFA, 1996. 11. Brodsky JW, Crenshaw SJ, Kirksey C and Pollo FE. Eliminating the Risk of Foot Ulcerations. Diabetic Foot Solutions. Mar/Apr 2001; 3(2). Available at: http://www. orthopedictechreview.com/issues/marapr01/pg33.htm. 12. 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(19): 2552–2558. 13. Mancini L and Ruotolo V. The diabetic foot: epidemiology. Rays 1997; 22(4): 511–523. 14. Harvey D. New, improved Kerraboot: a tool for leg ulcer healing. Br J Community Nurs 2006; 11(6): S26, S28–S30. 15. Reiber GE, Vileikyte L, Boyko EJ, et al. Causal pathways for incident lower-extremity ulcers in patients with diabetes from two settings. Diabetes Care 1999; 22: 157–162. 16. Sedory Holzer SE, Camerota A, Martens L, et al. Costs and durations of care for lower-extremity ulcers in patients with diabetes. Clin Ther 1998; 20: 169–181. 17. Ollendorf DA, Kotsanos JG, Wishner WJ, et al. Potential economic benefits of lower-extremity amputation prevention strategies in diabetes. Diabetes Care 1998; 21: 1240– 1245. 18. Apelquist J, Bakker K, Van Houtum WH, et al. International consensus on the diabetic foot. Amsterdam: International Working Group on the Diabetic Foot, 1999. 19. Slater R, Ramot Y and Rapoport M. Diabetic foot ulcers: principles of assessment and treatment. Isr Med Assoc J 2001; 3: 59–62. 20. Owings M and Kozak L. Ambulatory and inpatient procedures in the United States, 1996. Vital Health Stat 13 1998; 139: 1–119. 21. Izumi Y, Satterfield K, Lee S, et al. Risk of reamputation in diabetic patients stratified by limb and level of amputation: a 10-year review. Diabetes Care 2006; 29(3): 566–570. 22. Borkosky SL and Roukis TS. Incidence of re-amputation following partial first ray amputation associated with diabetes mellitus and peripheral sensory neuropathy: a systemic review. Diabet Foot Ankle. Epub ahead of print 20 January 2012. DOI: 10.3402/dfa.v3i0.12169. 23. Philbin TM, Leyes M, Sferra JJ, et al. Orthotic and prosthetic devices in partial foot amputations. Foot Ankle Clin 2001; 6(2): 215–228. 24. Pinzur MS and Dart HC. Pedorthic management of the diabetic foot. Foot Ankle Clin 2001; 6(2): 205–214.
25. Mueller MJ, Zou D and Lott DJ. “Pressure Gradient” as an indicator of plantar skin injury. Diabetes Care 2005; 28(12): 2908–2912. 26. Yavuz M, Erdemir A, Botek G, et al. Peak plantar pressure and shear locations. Diabetes Care 2007; 30(10): 2643– 2645. 27. Armstrong DG, Peters EJ, Athanasiou KA, et al. Is there a critical level of plantar foot pressure to identify patients at risk for neurotrophic foot ulceration? J Foot Ankle Surg 1998; 37: 303–307. 28. Lavery LA, Armstrong DG, Wunderlich RP, et al. Predictive value of foot pressure assessment as part of a populationbased diabetes disease management program. Diabetes Care 2003; 26: 1069–1073. 29. Veves A, Murray HJ, Young MJ, et al. The risk of foot ulceration in diabetic patients with high foot pressure: a prospective study. Diabetologia 1992; 35: 660–663. 30. Dahmen R, Haspels R, Koomen B, et al. Therapeutic footwear for the neuropathic foot: an algorithm. Diabetes Care 2001; 24(4): 705–709. 31. Murray HJ, Young MJ, Hollis S, et al. The association between callus formation, high pressures and neuropathy in diabetic foot population. Diabet Med 1996; 13: 979–982. 32. Goldblum RW and Piper WN. Artificial lichenation produced by a scratching machine. J Invest Dermatol 1954; 22(5): 405–415. 33. MacKenzie IC. The effects of frictional stimulation on mouse ear epidermis. J Invest Dermatol 1974; 63(2): 194–198. 34. Goldstein B and Sanders J. Skin response to repetitive mechanical stress: a new experimental model in pig. Arch Phys Med Rehabil 1998; 79(3): 265–272. 35. Yavuz M, Tajaddini A, Botek G, et al. Temporal characteristics of plantar shear distribution: relevance to diabetic patients. J Biomech 2008; 41: 556–559. 36. Sulzberger MB, Cortese TA, Fishman L, et al. Studies on blisters produced by friction. J Invest Dermatol 1966; 47: 456–465. 37. Naylor PFD. The skin surface and friction. Br J Dermatol 1955; 67: 239–248. 38. Naylor PFD. Experimental friction blisters. Br J Dermatol 1955; 67: 327–342. 39. Carlson JM. The friction factor. Orthokin Rev 2001; 1(7): 1–3. 40. Janisse DJ, Brown D, Wertsch JJ, et al. Effects of rocker soles on plantar pressures and lower extremity biomechanics. Arch Phys Med Rehabil 2004; 85: 81–86. 41. Nawoczenski DA, Birke JA and Coleman WC. Effect of rocker sole design on plantar forefoot pressures. J Am Podiatr Med Assoc 1988; 78: 455–460. 42. Lavery LA, Vela SA, Fieischli JG, et al. Reducing plantar pressure in the neuropathic foot: a comparison of footwear. Diabetes Care 1997; 20(11): 1706–1710. 43. Tsung BYS, Zhang M, Mak AFT, et al. Effectiveness of insoles on plantar pressure redistribution. J Rehabil Res Dev 2004; 41(6A): 767–774. 44. Hastings MK, Mueller MJ and Pilgram TK. Effect of metatarsal pad placement on plantar pressure in people with
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45. 46. 47. 48. 49. 50.
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diabetes mellitus and peripheral neuropathy. Foot Ankle Int 2007; 28(1): 84–88. Sanders LJ. Diabetes mellitus: prevention of amputation. J Am Podiatr Med Assoc 1994; 84(7): 322–328. Janisse DJ. Prescription insoles and footwear. Clin Podiatr Med Surg 1995; 1: 41–61. Janisse DJ. Art and science of fitting shoes. Foot Ankle Int 1992; 5: 257–262. Rossi WA and Tennant R. Professional shoe fitting. New York: National Shoe Retailers Association, 1984. Rossi WA. The high incidence of mismated feet in the population. Foot Ankle 1983; 4(2): 105–112. Janisse DJ. Shoes and shoe modifications. In: Hsu J, Michael JW, Fisk JR (eds) Atlas of orthoses and assistive devices. 4th ed. St. Louis, MO: Mosby, 2008; 223–235. Frey C, Thompson F, Smith J, et al. American Orthopaedic Foot and Ankle Society women’s shoe survey. Foot Ankle 1993; 14(2): 78–81. Michaud TC. Orthotic Dispensing, Shoe Gear, and Clinical Problem Solving. In: Foot orthoses and other forms of conservative foot care. Michaud TC (ed.) Newton, MA: Michaud Chiropractic Center, 1997, pp. 223–235. Chantelau E and Haage P. An audit of cushioned diabetic footwear: relation to patient compliance. Diabet Med 1994; 11: 114–116. Sinacore DR and Mueller MJ. Total contact casting in the treatment of neuropathic ulcers. In: Levin ME, O’Neal LW and Bowker JH (eds) The diabetic foot. 5th ed. St. Louis, MO: Mosby-Year Book, 1993, pp. 283–304. Janisse DJ. A scientific approach to insole design for the diabetic foot. Foot 1993; 3: 105–108. Brodsky JW, Kourosh S, Stills M, et al. Objective evaluation of insert material for diabetic and athletic footwear. Foot Ankle 1988; 9: 111–116. Caselli A, Pham H, Giurini JM, et al. The forefoot-to-rearfoot plantar pressure ratio is increased in severe diabetic neuropathy and can predict ulceration. Diabetes Care 2002; 25: 1066–1071. Kuncir EJ, Wirta RW and Golbranson FL. Load-bearing characteristics of polyethylene foam: an examination of
structural and compression properties. J Rehabil Res Dev 1990; 27: 229–238. 59. Leber C and Evanski PM. A comparison of shoe insole materials in plantar pressure relief. Prosthet Orthot Int 1986; 10: 135–138. 60. Janisse DJ. Pedorthic care of the diabetic foot. In: Levin ME, O’Neal LW and Bowker JH (eds) The diabetic foot. 5th ed. St. Louis: Mosby-Year Book, 1993, pp. 549–576. 61. Boulton AJ, Franks CI, Betts RP, et al. Reduction of abnormal foot pressure in diabetic neuropathy using a new polymer insole material. Diabetes Care 1984; 7: 42–46. 62. Michael JW. Lower limb orthoses. In: Hsu J, Michael JW, Fisk JR (eds) Atlas of orthoses and assistive devices. 4th ed. St. Louis, MO: Mosby, 2008; 343–356. 63. Rheinstein J, Yanke J and Marzano R. Developing an effective prescription for a lower extremity prosthesis. Foot Ankle Clin N Am 1999; 4(1): 113–139. 64. Condie DN and Stills ML. Chapter 16. Partial-foot amputations: prosthetic and orthotic management. In: Bowker JH and Michael JW (eds) Atlas of limb prosthetics: surgical, prosthetic and rehabilitation principles. 2nd ed. Rosemont, IL: American Academy of Orthopaedic Surgeons, 1992. 65. Lange LR. The Lange silicone partial foot prosthesis. J Prosthet Orthot 1992; 4(1): 56–61. 66. Burger H, Erzar D, Maver T, et al. Biomechanics of walking with silicone prosthesis after midtarsal (Chopart) disarticulation. Clin Biomech 2009; 24(6): 510–516. 67. Dillon MP and Barker TM. Comparison of gait of persons with partial foot amputation wearing prosthesis to matched control group: observational study. J Rehabil Res Dev 2008; 45(9): 1317–1334. 68. Praet SF and Louwerens JK. The influence of shoe design on plantar pressures in neuropathic feet. Diabetes Care 2003; 26: 441–445. 69. Marzano R. Fabricating shoe modifications and foot orthoses. In: Janisse DJ (ed.) Introduction to pedorthics. Columbia, MD: PFA, 1998, pp. 221–234.
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POI0010.1177/0309364614535233Prosthetics and Orthotics InternationalJanisse and Janisse
INTERNATIONAL SOCIETY FOR PROSTHETICS AND ORTHOTICS
Literature Review
Pedorthic management of the diabetic foot Dennis Janisse1,2 and Erick Janisse3
Prosthetics and Orthotics International 2015, Vol. 39(1) 40–47 © The International Society for Prosthetics and Orthotics 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0309364614535233 poi.sagepub.com
Abstract Background: Conservative pedorthic management of the diabetic foot has been shown to be an effective method to prevent ulcers, amputations, and re-amputations. This article exhibits why and how pedorthics plays such an important role via modalities such as footwear, shoe modifications, custom foot orthoses, and partial foot prostheses. Objective: The objective of this article is to demonstrate how pedorthics has been shown to be an integral part of conservative diabetic foot care. The authors’ goal was to educate the reader about the different modalities that are available for use. Study design: This article is based largely on review of previously published research and scholarly articles, augmented by the more than 60 years of pedorthic and orthotic clinical experience of the authors. Methods: Approximately 60 journal articles and book chapters were reviewed by the authors. Articles were located via online resources such as PubMed as well as the authors’ own libraries. Results: It was repeatedly noted that pedorthic modalities such as shoes, foot orthoses, and shoe modifications may be utilized in the treatment and prevention of diabetic foot wounds and other complications. Conclusion: Pedorthic devices may be successfully integrated into a comprehensive treatment plan for patients with diabetes and foot ulcers. Clinical relevance This information is of special interest to those who treat patients with diabetes. The article demonstrates the efficacy of pedorthic intervention through the compilation and review of relevant previously published data. Keywords The diabetic foot, diabetes, lower limb orthotics, orthotics, skin stress, diabetes Date received: 25 February 2014; accepted: 16 April 2014
Background
The team approach
To be successful, a diabetic foot care program needs to focus its efforts on prevention.1–3 Two key elements of the preventive approach are education and proper footwear.4 Unfortunately, it is not uncommon for a patient to seek medical advice only after he has developed a problem like a diabetic foot ulcer. All too frequently, these patients have not been recently checked for peripheral neuropathy—some may never have been tested—and many are ignorant of diabetic neuropathy and its associated risks.5 It can be a real challenge to convince a person who has never had a foot ulcer or has not experienced foot discomfort to restrict their footwear choices to only those shoes that are considered by their health care provider to be appropriate. This task can be completed most easily when a diabetic foot care team is assembled and put into action.6–9
The physician and the patient form the foundation of the team, but there are several ancillary but indispensable members of a successful foot care team. Other practitioners who work with physicians to prevent foot ulcers and subsequent amputations are certified diabetic educators, wound care nurses, physical therapists, certified pedorthists, certified orthotists, and, seemingly inevitably, prosthetists. 1Department
of Physical Medicine and Rehabilitation, Medical College of Wisconsin, Milwaukee, WI, USA 2National Pedorthic Services, Inc., Milwaukee, WI, USA 3Orthotic and Prosthetic Design, Inc., St. Louis, MO, USA Corresponding author: Dennis Janisse, Medical College of Wisconsin, 7283 W Appleton Ave, Milwaukee, WI 53216, USA. Email: [email protected]
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The role of the certified pedorthist Pedorthics is the art and science concerned with the design, manufacture, fit, and modification of shoes and foot orthoses to alleviate foot problems caused by disease, overuse or injury.10 Pedorthists fabricate and fit foot orthoses, shoes, and shoe modifications according to a physician’s order. A pedorthist is schooled in foot anatomy, pathology and the construction of shoes and foot orthotic devices. Pedorthists are tested and certified by the American Board for Certification in Orthotics, Prosthetics and Pedorthics. Board-certified pedorthists are required to participate in continuing education programs and are bound by a strict code of ethics.10 The pedorthist plays a significant role in the prevention of ulcers and amputations by providing appropriate and properly footwear. This typically includes the construction of custom-made foot orthoses to fit inside the shoes and/or internal and external modifications to the shoes themselves. The pedorthist also plays the role of patient educator. Certified pedorthists are an invaluable resource for educating patients in shoe selection, including guidelines for proper fit, instructions for use, and appropriate materials and styles for an individual’s feet. As a member of the diabetic foot care team, the pedorthist also reinforces the treatment plan provided by the other team members.
Pedorthic objectives Total contact casting is considered to be the “gold standard treatment” for healing diabetic ulcers.11 Pedorthic and orthotic care is intended primarily as long-term management for maintaining healed ulcers and fractures and for preventing future ulcers and fractures, and in general, it is not considered the ideal treatment or healing option for open ulcers or acute Charcot fractures.6 Similarly, while there is little that shoes and foot orthoses can do to actually treat diabetic foot infections, they are powerful tools to be used for the prevention thereof. Ill-fitting shoes are a prevalent cause of skin trauma that precedes the diabetic foot ulcers that can potentially lead to partial foot amputation.12 Areas of excessive plantar pressure and shear—two mechanisms that combine to cause diabetic skin ulcerations—are issues that are alleviated with custom foot orthoses. Stated simply, the key to avoiding diabetic foot infections is to prevent the opening of a portal of entry for infection to occur. Amputations in patients with diabetes, while often preventable, are a too common reality; 15% of diabetics will develop a foot ulcer over the course of their lifetime, and foot ulcers are the precursor of 70%–90% of all diabetic amputations.13–19 Partial foot amputations are nearly twice as common in the United States as either transtibial or transfemoral amputations.20 Unfortunately, there is a high
re-amputation rate in patients who undergo a partial foot amputation.21,22 The role of the pedorthist should not be undervalued in the prevention of diabetic foot complications (amputations, revisions, and foot infections secondary to skin ulcerations) and in returning the patient a normal, active, and productive lifestyle after an amputation. The primary goals of the pedorthist and the prosthetist when working with partial foot amputees are to restore stability and function lost due to an amputation, facilitate energy-efficient gait, maintain support, and prevent any further complications.23
Shear and plantar pressure Excessive shear and high peak plantar pressures have been repeatedly implicated as causal agents in the formation of plantar foot ulcers in persons with diabetic neuropathy. Luckily, therapeutic footwear decreases weight-bearing pressure and shear forces applied to the skin of the foot.24 The plantar pressure gradient should be paid due attention, too.25 While much has been written about areas of high peak pressures as a predictor of foot ulcers, research has revealed that there is not a particularly high correlation between the two.26–29 Surely, reducing elevated pressure levels is important, but the need to reduce the duration of maximum pressure and shear stresses is perhaps more so.30 Foot ulcers often occur at locations where one has developed calluses.31 The callusing is not due solely to plantar pressures, but also from frictional shear forces.32,33 Tissue breakdown occurs more rapidly when shear is increased.34 In normal walking, shear stresses act twice as frequently as pressure characteristically. Since plantar shear is known to be a factor in the formation of pre-ulcerative calluses, it deserves consideration when discussing diabetic foot ulcers. Excessive levels of shear may also cause damage to underlying tissues.35 The damage done by repetitive friction load does not begin at the outermost layer of the skin; rather, the friction causes shear forces to act between the layers of skin.36 Diabetics with neuropathy experience increased plantar shear over a non-diabetic with no foot problems.35 Naylor37,38 demonstrated in the 1950s that a peak perpendicular load by itself is not necessarily harmful and established that the magnitude of repeated high peak pressures is of greater concern because of how they enable and relate to peak friction loads. Ensuring that the shoe size and shape are appropriate for the foot is perhaps the easiest way to reduce shear inside of a shoe. If the shoe fits and is secured snugly on the foot, the foot does not shift inside the shoe as much. Proper fit is critical as a loose shoe and a tight shoe both have the potential to increase shear, friction, and/or pressure on the foot.
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Another way to decrease friction and shear is to “lubricate” the surfaces moving against one another. This can be accomplished with the use of shear-reducing socks made from an acrylic blend fabric or other fiber that has a low coefficient of friction (COF). Traditional cotton socks have a relatively high COF, especially when damp. The use of double socks allows the shear to take place between the layers of socks as opposed to between the skin and sock or sock and insole.39 This “lubrication” can also be done using a low-friction interface on the interior of the shoe or on the surface of a foot orthosis or ankle–foot orthosis (AFO) under areas of high pressure or friction. A polytetrafluoroethylene material called ShearBan® is widely available to the orthotic, prosthetic, and pedorthic industry. The self-adhesive material can be adhered virtually anywhere inside of a shoe, brace, or prosthetic socket. It is also heat moldable. Discussion of the reduction of peak plantar pressures often focuses on the forefoot as diabetic ulcers occur most frequently in this area.25,26 It is also for that reason that so much research has been devoted to the reduction of forefoot pressures using shoes, rocker soles, and various types of foot orthoses.40–44 The spatial change in plantar pressure around the location of peak plantar pressure (peak pressure gradient) is another pressure variable that warrants attention. Mueller et al. suggest that it may be a strong indicator of pending skin breakdown. Their research showed that the peak pressure gradient was significantly higher in the forefoot than in the heel even when compared with the peak plantar pressure.25
Shoes Improper footwear is a common culprit in causing diabetic ulcers.12 Therapeutic footwear can help reduce a patient’s chances of developing foot ulcers.7,45 There are several objectives in providing footwear for patients with diabetes.46 It is important to understand these objectives before discussing the different types of shoes or shoe fitting. They are as follows: 1. 2. 3. 4. 5. 6. 7.
To protect the foot; To relieve areas of excess pressure; To reduce shock; To reduce shear; To accommodate deformities; To stabilize and support deformities; To accommodate foot orthoses and AFOs.
Shoe types Every diabetic footwear prescription should include indepth shoes. An in-depth shoe is an oxford-type or athletic shoe with an additional 1/4″–3/8″ of depth throughout the
shoe.46,47 These shoes offer even more space when the removable factory inlays are taken out. The additional volume afforded by an in-depth shoe makes it ideal for patients with diabetes as it can easily accept a foot orthoses or AFO without affecting the fit of the shoe and is also useful for accommodating deformities associated with the diabetic foot such as hammertoes or bony prominences resulting from Charcot arthropathy. Off-the-shelf shoes used for the diabetic foot are manufactured in multiple widths. When no off-the-shelf shoe is appropriate due to extreme deformities or variance in size from left foot to right, it may be necessary to modify the shoe. If the shoe cannot be modified to fit, the last alternative is a custommade shoe. Custom-made shoes are fabricated by creating a positive model from a mold of the patient’s foot. The shoe is then constructed around this model. Since they are made directly from molds of the feet, custom shoes offer the best possible accommodation and protection, but can be quite expensive and lack the cosmetic appeal of commercially available shoes.
Shoe selection Shoe selection is based on three things: the condition of the patient, the patient’s foot shape and type, and the patient’s daily activities. For a patient who has no history of ulcerations, shows no signs of peripheral neuropathy, and has a structurally normal foot, a properly fitting offthe-shelf shoe may be all that is necessary, whereas a patient with neuropathy and a history of ulcers, Charcot arthropathy, and/or amputations will need a more complex footwear prescription. The patient’s body type is also a crucial factor to consider when selecting shoes. The construction of the shoe should correspond to the patient’s body type. The key to both shoe selection and shoe fitting is choosing a shoe that fits the shape of the patient’s foot. Not only must the shoe be of the correct shape to fit the patient’s foot, but also it must be of the correct depth to properly accommodate additional devices such as foot orthoses. The shape and volume of a shoe are dependent on the last over which it was made. Lasts are made in innumerable shapes, but the manufacturer determines the particular last used for any given shoe. Therefore, a shoe in size 10B manufactured by company X could fit dramatically differently than a size 10B shoe produced by company Y.47,48 Lasts for therapeutic footwear are not only made in a variety of sizes but also widths and shapes. The depth of the shoe is important not only in the toe area but across the instep, too; the shoe should not put pressure across the dorsum of the foot. Shoes with laces or hook-and-loop closure systems tend to fit better than slipon shoes. Persons with neuropathy should avoid slip-on shoes as they are, by their very nature, too short and too tight.
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Shoe fitting Once a properly shaped shoe has been selected, the appropriate size is determined using a Brannock device. The Brannock measures overall foot length, arch length (heelto-ball), and width.48 A shoe of the proper length insures that the first metatarsophalangeal joint is seated comfortably in the widest part of the shoe. This is why arch length needs to be assessed. Both feet should be measured as most people have one foot longer than the other.49 If this difference is significant, a pair of mismated shoes may be in order. Measuring the foot by any means determines just that— the size of the foot. An individual’s foot measurement does not necessarily equal their shoe size. It is up to the pedorthist to know his inventory and have an intimate knowledge of how each different shoe fits and how each corresponds to the foot measurement. A properly fitted shoe should leave about 1/2″ between the end of the longest toe and the front of the shoe.47,48,50 The shoe should also allow for a small amount of movement of the heel since the foot stretches and the calcaneus shifts during gait. The upper should not be stretched taut across the ball of the foot; there should be appreciable slack in the material. As important as properly fitting shoes are in preventing and solving foot problems, a large percentage of the population continues to wear ill-fitting shoes.51 Foot orthoses, another important treatment modality for diabetic feet, are only as good as the shoes in which they are worn.52
Foot orthoses Foot orthoses are used in the prevention of foot ulcerations.53 Foot orthoses are available as custom-made devices or off-the-shelf devices. Both types can be made from a variety of materials differing in density, cushioning, shock absorption, support, and control. The use of a pre-fabricated device reduces the cost and time investment of both practitioner and patient, but sacrifices the fit, longevity, and adjustability of a custom device. Custom orthoses are necessary when the patient has any of the following: a foot deformity, a loss of protective sensation, and a history of ulcers and/or Charcot arthropathy and/or partial foot amputation. A custom foot orthosis can achieve total contact with the plantar surface of the patient’s foot, therefore employing the same total contact concept as the total contact cast.54 There are four main types of custom foot orthoses although not all are indicated for use in patients with diabetic neuropathy. They are the following: accommodative, semi-rigid, rigid, and the partial foot prosthesis. When evaluating a patient for foot orthoses, the practitioner needs to understand lower limb biomechanics and be
able to identify areas of high pressure; they also need to utilize the proper molding technique and be able to select the best material given the desired function of the orthosis.55 The primary function of a foot orthosis for a person with diabetes is to cushion and protect the foot. Additionally, the following component objectives should be realized:46,55 1. Provide shock absorption and shock attenuation; 2. Relieve areas of high plantar pressure by evenly redistributing weight-bearing pressures over the entire plantar surface; 3. Support, splint, and protect healed fracture sites by employing the total contact concept; 4. Reduce shear; 5. Control, stabilize, support, or correct flexible deformities; 6. Limit the motion of affected joints; 7. Accommodate fixed deformities.
Accommodative foot orthoses An accommodative foot orthosis is designed primarily to cushion and protect the foot. It offers good shock absorption and padding. It may be designed to offload prominent areas. An accommodative orthosis is typically not one that will perform at a high level for a long period of time. Softer, less dense materials tend to wear out quickly, so this type of orthosis requires vigilant follow-up and needs to be repaired or replaced on a regular basis. Depending on the materials used, accommodative orthoses can be molded directly to the patient’s foot using either external heat and pressure, or the patient’s own body heat and weight to mold them. Accommodative orthoses can also be fabricated over a positive model of the patient’s foot. This model could be a plaster model made from a negative mold of the person’s foot or a computergenerated model based on a three-dimensional scan. Accommodative foot orthoses are made of soft, moldable materials. In general terms, moldable materials possess better pressure-distribution properties than the non-moldable materials, but are not as durable and compress more quickly.56
Semi-rigid foot orthoses Semi-rigid foot orthoses combine the cushion and protection of the accommodative orthoses with the support, control, and weight redistribution of the rigid orthoses. Semi-rigid orthoses also last longer than the accommodative orthoses. A semi-rigid orthoses for a patient with diabetes typically consists of a soft, cushioned protective top layer with a firmer, more supportive base material.
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Semi-rigid devices are used to alleviate areas of high pressure and prevent skin breakdown by redistributing and equilibrating plantar pressures. The soft materials in an accommodative orthoses accomplish this goal for only a very short period of time as soft materials compress rapidly under areas of high pressure, thereby quickly returning those areas to their previous state of elevated pressures. By using a firmer material to support the arch and cradle the heel, the soft materials in the top cover of a semi-rigid device do not compress as rapidly and the plantar pressures are more evenly distributed.55 In an insensate foot, the areas of highest pressure are typically under the heel and the ball of the foot.57 By using a total contact semirigid foot orthosis, the entire plantar surface of the foot shares in the weight-bearing process. The top layer or layers of a diabetic semi-rigid orthoses generally consist of thin layers of accommodative materials. Semi-rigid orthoses are typically made of combinations of two, three, four, or more different materials. A study of five commonly used foot orthosis materials by Brodsky et al.56 found that the soft polyethylene foams had better pressure-distribution characteristics when first applied, but that exposure to repeated pressures caused them to bottom out more rapidly than some of the more durable polymers. Other studies lend credence to this concept and also show that loss of thickness of the molded polyurethane foam is inversely related to its density.58,59 These studies suggest that in order to achieve the total contact objective as well as provide adequate shock absorption and support, a foot orthosis for use in treating the diabetic foot should be fabricated using of a combination of different materials. A triple-layer, molded orthoses has been suggested to provide the necessary combination of support and accommodation.55,60 The three layers would then be the following: 1. Soft, moldable polyethylene foam next to the foot; 2. A middle layer consisting of a urethane polymer that resists bottoming-out and offers good shock absorption; 3. A firm molded cork or dense ethylene vinyl acetate base for support and control. Orthoses made of material with good shock-absorbing qualities, like viscoelastic polymers, have been shown to significantly reduce the abnormally high plantar pressures of a diabetic foot.61
Rigid foot orthoses Rigid orthoses are contraindicated for persons with diabetes, especially if there is evidence of neuropathy or a history of ulcerations. They can be extremely difficult to fit.62 Rigid orthoses are not forgiving and do not mold or conform to prominences on the plantar surface of the foot and could actually cause injury.53
Rigid orthoses are often made of thermoplastics, acrylics, or carbon fiber composites. They are not easily adjustable. Rigid orthoses are durable and offer excellent support and control, but provide very little in the way of cushion, shock absorption, and protection.61
Partial foot prosthesis The main goal of amputation surgery for the surgeon is to salvage as much functional limb that will heal as possible; the goal for the pedorthist and prosthetist is to preserve and restore the patient’s functional level.23,63 The primary purpose of a partial foot prosthesis for a patient with diabetes is to protect the residual foot, with a secondary aim of restoring normal function and gait. Equal pressure distribution is especially important in the partial foot patient as peak plantar pressures rise exponentially as the amount of weight-bearing surface area decreases. The question of whether these tissues can handle the increased stress is why partial foot prostheses are often used in conjunction with an AFO—especially with a midfoot-level amputation—to transfer the stresses to more proximal normal tissue.64 The partial foot prosthesis is used primarily to help evenly redistribute plantar pressures in the foot, reduce areas of high peak pressure, and decrease shear. This is accomplished by fabricating a custom foot orthosis and adding an area of padding just distal to the end of the residual foot and then finishing it with a semi-rigid foam filler to maintain the foot’s position within the shoe. The loss of the hallux requires something to replace the lost lever arm for toe-off propulsion. This can be done through the use of either an extended shank in the sole of the shoe or by attaching a full-length carbon fiber footplate to the partial foot prosthesis. There is much literature on the use of silicone and/or acrylic resin partial foot prosthesis—especially for Lisfranc’s and Chopart’s amputations—such as a Chicago boot or a Lange prosthesis that slips over the residual foot, much like a sock or a shoe would.23,63–67 These types of devices provide cushion, stability, and reduction in shear forces. They can be difficult to don and doff but are cosmetically pleasing and some may even be worn without a shoe. However, discretion should be used when considering the use of these prostheses in the diabetic population as these devices tend to be hot, which could make the foot perspire, and do not permit any air circulation around the foot and may allow increased bacteria.23
Shoe modifications The sole of a shoe can be modified in a variety of ways for any number of reasons but are most commonly modified for one or more of the following reasons:
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Janisse and Janisse To replace lost motion; To restore lost function; To increase stability; To aid in forward propulsion or make ambulation more efficient; 5. To offload areas of high pressure; 6. To help the shoe better fit the foot; 7. To accommodate or enhance the function of an AFO.
1. 2. 3. 4.
Rocker soles The rocker sole is one of the most commonly prescribed shoe modifications. The primary function of a rocker sole is to rock the foot from heel strike to toe-off without requiring the shoe or foot to bend. Generally speaking, the biomechanical effects of rocker soles are restoring lost motion in the foot and ankle due to pain, deformity, stiffness, or surgical fusion, resulting in an overall improvement in gait, and offloading plantar pressure on some part of the foot.41 All types of rocker soles can offload the forefoot, which is beneficial and can help prevent ulcers as diabetics with neuropathy experience increased pressure under the forefoot.40,57 In fact, the rocker is considered the most effective way to offload the forefoot.68 There are two terms that need to be understood in order to discuss rocker soles: (1) the midstance or the section of the rocker sole that is in contact with the ground when standing erect and (2) the apex, or high point, of the rocker sole located at the distal end of the midstance.29 Proper placement of the apex is critical to the success of the modification; it should be placed just proximal to any area for which pressure relief is desired. For example, if the desire were to offload the ball of the foot, the apex would be placed directly behind the metatarsal heads. Many off-the-shelf walking shoes and running shoes are built with a mild rocker sole. This simple, generic rocker is often adequate for a foot that is not at risk. It provides some metatarsal head relief and gait assistance; however, for the patient who requires more relief or has deformity or neuropathy, a custom rocker sole is indicated.
Extended shank The extended shank is made of either spring steel or carbon graphite composite and is inserted between the layers of the sole, extending from the heel to the toe of the shoe. Extended shanks are commonly used in conjunction with a rocker sole and make the rocker sole more effective. The shank keeps the shoe from bending and reduces forces through the midfoot and forefoot. It strengthens the entire sole and shoe and maintains the continuity of the rocker sole.9
Re-last Re-lasting a shoe may be indicated for a severe rigid pes planus deformity or a midfoot that has widened due to Charcot arthropathy. The soles of many off-the-shelf shoes can be reconstructed or reconfigured to accommodate severe deformities.69 Re-lasting is a viable alternative to custom shoes for many patients. This process involves customizing an off-the-shelf shoe, by widening it through the midfoot or forefoot, to fit a foot that would not otherwise be able to use an off-the-shelf shoe. This is done by removing the outsole and making a cut through the sole, midsole, and innersole and widening the shoe according to a pattern of the foot. A new outsole is applied, and to the casual observer, the shoe looks “normal.”
Conclusion The team approach, patient education, and pedorthic and orthotic modalities have all been shown to be valuable tools in the care of the diabetic foot. The team approach is probably as, if not more, beneficial to the successful treatment of the diabetic foot than nearly any other problem the physician encounters. The understanding of pedorthic principles and how to include and utilize the appropriate clinicians on the team can simplify the patient care process while decreasing life-altering complications such as ulcerations and amputations. Author contribution All authors contributed equally in the preparation of this manuscript.
Conflict of interest None declared.
Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
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