Take A Load Off: Offloading Tips And Pearls In Wound Care
Diabetic foot ulcerations (DFUs) affect approximately 26 million people worldwide, with a staggering 2.5 times increased risk of death at five years.1-3 While many etiologies and conditions contribute to a wound, offloading is crucial to solving the wound healing puzzle.
In some literature, offloading is the most important aspect of DFU treatment in patients with neuropathy.4-6 The thought behind offloading is relief of mechanical and abnormal stresses that the foot experiences from a loss of protective sensation. This combination results in tissue damage, thought to lead to many DFUs.1,4,7 Specifically, mechanical stress is due to increased plantar pressure and shearing forces during the gait cycle, causing repetitive microtrauma. While we cannot relieve the neuropathic sensory loss, podiatrists and other specialists have developed several ways to relieve mechanical stress placed on the foot.
Understanding The Available Categories And Applications Of Offloading
Since 1999, the International Working Group on the Diabetic Foot (IWGDF) has published evidence-based guidelines on preventing and managing diabetic foot disease. In 2019, they published guidelines specifically for offloading DFUs. Their first recommendation for a patient with diabetes and a neuropathic forefoot or midfoot ulceration is using a non-removable, knee-high offloading device with an appropriate foot-to-device interface.8 These devices include total contact casts (TCCs) and non-removable walkers. When comparing these two devices, one study found greater reduction in plantar pressure in a non-removable knee-high walker device (92 percent forefoot, 77 percent midfoot) than the TCC (84 percent forefoot, 63 percent midfoot).5
An appropriate foot-to-device interface should evenly distribute peak pressures across the plantar aspect of the foot and away from the ulceration site. Several studies found that non-removable devices significantly improved healing outcomes for neuropathic diabetic foot ulcers compared to removable devices. Specifically, a scientific review found that while ulcer healing improved with total contact casting, irremovable cast walkers, and removable cast walkers, removable cast walkers had lower healing rates than the other two options. In interviews, patients perceived better healing with total contact casts over removable walkers but felt the removable walkers were more convenient. Researchers also noted that access to offloading devices would save the health care system $17 million to $20 million per year.9
Unfortunately, although primarily based on expert opinions, there are some contraindications to non-removable offloading devices, including: ischemia; heavily exudating ulcers; infection; and patient intolerance. Clinical assessments can identify infection and heavily exudating wounds, and the use of the ankle-brachial index can screen for ischemia. Although the recommended cutoff for application of a TCC is an ABI of 0.70, one systematic review found that an ankle-brachial index of 0.55 or greater was considered acceptable for total contact cast application.10
If a patient does not qualify for or tolerate a non-removable offloading device, a removable knee-high device with an appropriate foot-to-device interface is the second-line recommended choice of treatment.8 Some scholars argue this device is effective because of reduced walking done in these devices.8 The removable offloading device should distribute the peak pressures in a very similar fashion to non-removable devices. Literature shows that removable offloading devices are more effective at healing ulcerations than surgical debridements or dressings alone.11 Furthermore, a removable offloading device combined with an Achilles tendon lengthening procedure was more successful than a non-removable cast alone for DFUs.9 Although some literature found that a knee-high device is more effective than an ankle-high device,4,7 recent studies contradict these findings.12-14
Patients should rarely take off these devices, ideally wearing the device constantly. Therefore, selection of a removable offloading device for each patient must consider their specific individual needs. Patient adherence, device design, and maintenance of a good foot-to-device interface are key components. Contraindications for knee-high removable devices are similar to those for total contact casts. However, patients with mild-to-moderate infection or ischemia can be placed in a removable offloading device.8
For the patient who cannot or should not wear a knee-high removable offloading device, the third-line choice is an ankle-high offloading device.10 Regardless of method, the podiatric physician should educate patients on the crucial role of these devices. Ideally, one can entertain a shoe-based offloading device to provide some plantar pressure relief. In this case, a the use of a felted foam dressing in a properly fitted depth shoe can be a lower, fourth-line alternative to knee- or ankle-high devices.8 Clinicians may want to employ adjunct interventions, such as Achilles tendon lengthening, to reduce forefoot pressure, along with metatarsal head resections, arthroplasties, and other surgical interventions if conservative offloading fails.8
For non-plantar or heel DFUs, there are specific offloading considerations. In non-plantar ulcerations, one should tailor offloading devices to the type and location of the wound.8 In heel ulcerations, some studies found no significant increased healing with a TCC compared to therapeutic footwear.15 Another study found significantly increased rearfoot pressures in TCC when in conjunction with an Achilles lengthening procedure compared to TCC alone.16 Finally, another study found a 10 percent increase in rearfoot pressure from baseline in removable knee-high walkers.17 However, the literature is mixed as to the effects of total contact casts compared to removable knee-high walkers. Unfortunately, no known studies tested efficacy of heel pressure relief in specific heel offloading shoes.8
A Closer Look At U.S. Trends In Offloading
As evidenced by the previous discussion, the TCC and now the non-removable walker, also called an instant total contact cast (iTCC), are gold standards for offloading the diabetic foot. The cast walker, both removable and non-removable, continues to gain popularity as the offloading modality of choice. While approximately six percent of clinicians in the U.S. embrace the TCC, as many as 15 percent use the cast walker.18-20 However, shoes remain the most commonly employed offloading device used to manage DFUs, despite definitive studies supporting use of non-removable knee-high devices.19-21
In a study conducted by Wu and colleagues that interviewed 895 clinicians, they discovered that the most commonly used offloading device in the U.S. was the depth shoe (41.2 percent), followed by the removable cast walker (15.2 percent), non-weight bearing strategies (12.3 percent), and lastly, TCCs (1.7 percent).19 If it were not for the reimbursement associated with TCC, we believe its numbers would even be lower, despite excellent data in existence supporting its use. Cast walkers suffer the opposite problem. Despite excellent data supporting their use as offloading devices for DFUs, we find many insurance providers refuse to cover a cast walker for a diagnosis of an ulcer alone and force clinicians to use an “orthopedic” diagnosis to cover the device. Most guidelines recommend that patients use one of the many ambulatory aides available, but patients notoriously avoid using canes, crutches, and walkers, seemingly abandoning them at an even higher rate than removable offloading devices.19
What You Should Know About Shoe-Based Offloading Methods
Shoe-based offloading systems include commercial diabetic “healing” shoes, surgical shoes, wedge shoes, half shoes, and, unfortunately, depth shoes or standard therapeutic footwear. Despite evidence presented by the IWGDF that contradicts the use of conventional or standard therapeutic footwear for DFU treatment, they remain the most commonly employed devices.8 The IWGDF goes so far as to state that there is no evidence to support their use in comparison to other offloading devices, but they remain in use for many reasons.8 Patients frequently insist on a shoe-based system so they can work or drive. Many patients with ulcers are older, and balance issues take center stage. One may best accommodate fluctuating edema with a shoe with a lacing system, and vasculitic legs with lymphedema are often painful and may not tolerate the TCC or even a knee-high walker.
Patients with plantar ulcers may have significant financial constraints, and costs involved in acquiring a cast walker, commercial offloading system, or commercially available offloading insoles are prohibitive. Others have not come to grips with the dangers of plantar neuropathy and don’t want to give up the freedom of movement of a shoe-based device when they feel no pain and don’t fear the consequences of an infection developing in a painless foot.
One can enhance shoe-based offloading by using various foot-to-device interfaces. Among the choices are total contact molded insoles, pixelated insoles, custom padding, commercial offloading insoles, or custom-molded biomechanically balanced orthotics.21,22 One of the more commonly used shoe-based systems is the modified Carville healing sandal, where a total contact, molded multilayer insole made from a cast of the foot or direct molded from thermoldable material goes in a surgical shoe, preferably one with a rocker sole.21,22
Clinicians should only consider conventional or standard therapeutic footwear when wounds have healed and matured or when other offloading devices are contraindicated or unavailable. The patient is the primary decision-maker in shoe use, which clinicians must overcome with education and persistence.8 Eventually, all patients must return to some form of regular-use footwear. It is important to avoid transitioning to standard footwear too quickly to avoid ulcer recurrence.1,8 Instead, it is preferrable to first employ one or more of the transitional shoe-based devices with a total contact or adjusted, pixelated, foot-to-device interface for offloading the area of the previous ulcer. Options for this are the wedge shoe, commercial diabetic healing shoes, or a rocker bottom surgical shoe with a molded or pixelated offloading insole.1,23 Custom-molded shoes are not proven to be better at offloading the foot than properly fitted and molded depth footwear. They are however, a great deal more expensive. Because of this, we find custom-molded shoes are best used only for foot shapes that cannot be accommodated by the many commercial lasts on the market today. They should also be restricted to a patient’s final footwear and never be used as a wound healing device.8
Transitional shoe-based devices help to restrict the patient from full-weight bearing activity, slowing or altering their normal gait. In our experience, an additional benefit is promotion of skin thickening and maturation while maintaining an acceptable protection level. One should only consider transitioning to the patient’s final footwear should after at least three continuous weeks of wound closure. As soon as patients return to final footwear, they have the temptation to resume full, normal weight bearing activity, walking speed and stride length. The patient may also resume normal activity more rapidly than advisable.24 Close monitoring for ulcer recurrence should be part of this transitionary period. We recommend a two-, four-, six-, eight-week visit schedule, culminating in a return to the pre-ulcer, two to three month return schedule. At no point should a previously ulcerated patient be dismissed with a “come back when you need us” instruction.
How Can One Modify Peak Pressures With Specific Materials And Treatment Plans?
Studies demonstrate high peak plantar pressures in the diabetic foot. A proper choice of shoe design and orthotic materials can reduce pressure on areas of ulceration, thereby reducing repetitive insult to the area.25 Materials such as Plastazote®, ethylene vinyl acetate (EVA), or styrene butadiene rubber (SBR) can be heat-molded to a plaster mold or scan, instantly molded to the patient’s foot, or dynamically-molded to the foot over time with weight bearing. Each method produces a total contact innersole helping redistribute forces away from high-pressure areas and towards areas of lower pressure.26,27 Heat-molding or padding is always preferable to dynamic-molding that uses the foot itself to create the mold, posing a risk of ulceration during the process.
Paton and colleagues studied 119 patients, comparing offloading and kinematic data of custom-made EVA insoles manufactured from a foam box cast versus prefabricated EVA insoles.28 The custom-made insoles were more expensive and no better in reducing peak pressures, so they recommended prescribing the more cost-effective prefabricated insoles for patients with diabetes and neuropathy.28 In another study performed by D’Amico and team of CAD-CAM orthoses made from a foam box mold versus standard diabetic insoles, CAD-CAM orthoses achieved better offloading than the traditional shape-only based approach, which uses dynamic molding of a flat multi-density insole.29 Regardless of insole material, an intimate contact or total contact insole acts to redistribute pressure from high-pressure areas to the entire plantar surface reducing chance of injury to the skin.
Eligible patients with diabetes may obtain diabetic shoes through the Medicare Therapeutic Shoe Bill and by most insurances and supplemental plans. Prescription of therapeutic shoes should take place early during the ulcer healing process, so they are ready when discontinuing transitional devices.30 If patients wore depth shoes when they developed their wound, they should not return to the exact same shoes and insoles after healing. Poor planning creates an unnecessary “danger zone” for early ulcer recurrence. Many patients receive therapeutic footwear with a minimally manipulated OTC multilayer insoles to comply with the requirement for molding the device to the patient’s foot. My experience with diabetic shoe providers is that they often do not produce a truly total contact innersole. We recommend always examining the shoes and insoles and modifying or molding the insoles to create the total contact surface you desire.
What Are The Felted Foam And Football Techniques?
Felted foam techniques have been used for many years as both a primary offloading technique and as a way to augment other forms of offloading. Just as padding is a method for improving the offloading capacity of in insole, felt padding the dressing can be an effective way to improve the offloading capacity of a dressing. The original technique applied pads directly to the skin using rubber cement as a protective interface between adhesive felt or foam and the skin. Anatomically designed felt pieces applied to the foot specifically offloaded areas of ulceration, followed by one’s dressing of choice. Clinicians then placed the foot in an offloading device, usually a surgical shoe or a cast walker.31 We modified this technique to avoid taping the felt to the skin and instead place the offloading padding outside the initial contact and secondary dressing layers.
A more elaborate version of this system is the Rader football dressing, which uses adhesive foam and a thick, multilayer, non-removable padded dressing secured by self-adherent wraps.32 In addition to improving dressing offloading, the bandage remains in place between clinic visits, providing a level of non-removable offloading to a removable shoe-or walker system.
Both the felted foam and the Rader Football dressings have similar studies showing impressive healing rates in the hands of the researchers. The IWGDF concludes that although the quality of evidence is low, many practitioners utilize felted foam to reduce pressure to assist with healing. Clinicians may also incorporate felted foam into non-removable and removable knee-high devices for additional offloading.22 Armstrong demonstrated that when patients are free to remove a device, on average, they only wear it 28 percent of the time, and even the most adherent patients only wear the device for a maximum of 60 percent of their daily activity.33 Using a modification of the felted foam technique may greatly enhance effectiveness of a removable walker.
Although patients are the ultimate decision-makers as to what they will tolerate for an offloading device, clinicians have limitations that also matter. Technician skillset, resource availability, economic factors, and severity of foot deformity also play a role.8,19,21,22 One must also consider patient circumstances, such as occupational demands or restrictions that may not support the use of a particular device.8,21,22 Patient adherence to wear times and activity are essential for the success of any offloading device.
Better Understanding Rocker Soles And Patient-Specific Considerations
The primary feature of many shoe-based systems is a rigid rocker sole to prevent midfoot collapse, alter gait timing, and reduce weight transfer to the forefoot during push-off. In order to further restrict weight transfer to the forefoot, added restriction of ankle motion to the system can keep the knee from moving out over the forefoot during gait. Devices in this category include the molded ankle-foot orthosis (MAFO) and the ankle-foot orthosis (AFO) that restricts ankle motion. These include over-the-counter ankle braces or custom-made Arizona™ or Richie™ braces. Proper ambulation for any patients that need one of these devices requires a rocker sole, but prescriptions often omit this feature.26,27
Rocker soles are essential for comfortable ambulation with any device that restricts ankle motion. If the tibia cannot move forward over the midfoot during the end of the mid-stage period of the gait cycle, the patient compensates by hyperextending the knee, rising up on the forefoot early, or abducting the foot and rolling over the medial side of the foot. All of these contribute to increased forefoot loading and shear with rotation of the forefoot on the ground. Rocker soles move the apex of the metatarsal rocker, normally provided by the metatarsophalangeal joints, to a position behind the heads themselves.34 This reduces shear and movement in the shoe and transfers weight stress to the metatarsal necks and midfoot, depending on the position of the rocker.34
Patient-specific factors to consider when determining the best offloading plan include: body mass index (BMI); edema; foot biomechanics; stability in gait; and prior history regarding adherence to offloading devices. BMI is a significant factor in offloading device selection, and both ends of the spectrum may lead to increased foot pressures and ulceration.34 Increased BMI leads to greater total forces on the weight-bearing foot, which increases risk of developing DFUs.34 Conversely, patients with a low BMI and little plantar padding are also at increased risk for plantar ulceration. Both extremes require offloading with total contact insoles for pressure redistribution to heal and prevent foot re-ulceration.34 Patient education should focus on wise footwear choices to minimize plantar pressures and healthy eating and regular exercise to maintain optimal body weight. One cannot overstress daily blood glucose monitoring and control of blood sugar, as elevated glucose levels lead to glycosylation of connective tissues and an increased risk of developing complications such as neuropathy, decreased joint flexibility, ulcerations, delayed wound healing, ischemia, and infection.35
Stability in gait is critical, as many patients require assistive devices to ambulate with offloading devices. Many devices can create a significant limb length discrepancy, raising the hip on the affected side. Transfer of weight to the “good leg” is often just an opportunity to develop bilateral problems, so one must always address the opposite foot with any offloading strategy. Before prescribing an offloading device, it is critical to observe the patient’s gait and ability to use assistive devices. Referral to physical therapy for gait training may be indicated. Patient safety is paramount, as is minimization of fall risk.
After applying the offloading device, the clinician should analyze the patient’s gait, make any necessary adjustments, and confirm the proper use of assistive devices.26,27
Patient trust in your advice and acceptance can contribute to adherence to instructions for wear time. Encourage patients to monitor foot hygiene, follow up weekly for cast changes and wound care, and adhere to disease management strategies developed by their medical team.35,36 It is critical for these patients to have continuous access to care, as rapid response to problems is key to avoiding complications from offloading devices.26,27 Access to you or a hotline that answers their calls and provides an immediate response is essential to prevent complications during the healing process.
In Summary
Selection of appropriate offloading devices is critical to the success of any DFU healing program. Understanding the need for offloading is straightforward, implementation is complicated by several factors. There is no single, universally appropriate offloading device for all patients. Many factors come into play, including, but not limited to: the character of the ulceration; the condition of the patient; the commitment of the patient to adhere to the plan laid out for them; nutrition; access to resources; social support; and more.
Dr. McGuire is an Associate Professor in the Department of Medicine and Director of the Leonard Abrams Center at the Temple University School of Podiatric Medicine in Philadelphia.
Dr. Ansert is a third-year podiatric resident at St. Vincent Hospital in Worcester, Mass.
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