Patient adherence to consistent use of removeable offloading and immobilization devices is central to promote healing and prevent infection in diabetic foot ulcers, yet the tradeoff of removability easily compromises adherence. Choosing and customizing the right device is key.
By Barbara Boughton
A mainstay of treatment for diabetic wound care is the use of offloading and immobilization devices that allow patient mobility while reducing pressures on the foot that hamper wound healing. Total contact casts (TCCs) are the gold standard for healing diabetic wounds—particularly for large wounds that are difficult to heal—but TCCs are heavy and cumbersome and cannot be removed for sleep or showering.
Tall (to the knee) removable cast walker boots are more acceptable to patients, but because these devices are removed easily, patients do not always fully comply with their use, compromising wound healing. Research has demonstrated that diabetic patients wear their prescribed removeable cast walker for less than 30% to 60% of daily steps. 1,2
An advantage of a removable device is that wound inspection is accomplished more easily than with a TCC, and a patient who notes swelling or signs of infection after taking off a removable device can seek treatment. However, patients often do not appreciate the importance of such devices in ulcer healing, a view that may affect adherence.
Offloading removeable devices
The challenge for clinicians is to design devices that will improve patient adherence with the use of removeable devices without compromising efficacy. Although taller devices are generally more effective than ankle-height devices, taller devices tend to be heavier and may affect the wearer’s gait and balance.
Researchers in a 2012 study were among the first to assess the effect of strut height on the offloading capacity of a knee-high device, an ankle-high device, and an orthotic shoe offloader in 11 diabetic patients at moderate to high risk for ulceration. An athletic shoe was used as a control. Each study subject completed four 20-meter walking trials in each of the three devices and the control shoe. Both the knee-high and ankle-high devices performed significantly better than the shoes in offloading. Peak pressures were slightly greater in the ankle-high device than the knee-high device. Peak pressure at the hallux, for example, was 76kPa in the knee-high device compared with 90kPa in the ankle-high walker. 3
Yet the body’s center of mass range of motion during the patient’s first four steps in the ankle-high walker was lower than with the knee-high walker—signaling a potential lower risk for a fall. Those first four steps are a high-risk time for falls, according to Ryan Crews, MS, CCRP, lead author of the study and clinical research scientist and operations manager at the Center for Lower Extremity Ambulatory Research in Chicago. Because the ankle-high device was less cumbersome and caused fewer balance problems than the knee-high device, it may have the potential to improve adherence in patients wearing a removable cast walker, and thus improve wound healing, the researchers concluded. “Considering the ankle-high removable cast walker was a nearly equivalent offloader to the knee-high removable cast walker, while weighing less and potentially providing better stability, it may prove to provide better outcomes in treating diabetic foot ulcers,” they wrote. 3
“The slight reduction in offloading may be offset by improved adherence,” said Crews. The knee-high removable cast walker also resulted in a slower walking speed than was seen with the shorter walker. “Slower speed in walking has been linked to falls in previous research. These patients are physically deconditioned, so adding a big, heavy boot will just increase their challenges in walking,” Crews said.
In a 2016 study of 79 patients with diabetic foot ulcers, Crews and fellow researchers found that postural instability with removable cast walkers contributed to reduced off-loading adherence. 2 Factors that predicted improved adherence included larger and more severe baseline diabetic foot ulcers, more severe neuropathy, and greater foot pain. The researchers also found that better offloading adherence was linked to greater healing of ulcers over a six-week period.
An abstract presented by Crews at the 2017 American Diabetes Association annual scientific meeting also documented that removable cast walkers induced changes in spinal alignment, sagittal balance, pelvic tilt, and lordotic angles while walking compared with walking while wearing an athletic shoe. 4 Both knee-high and short walkers would be expected to have similar effects on spinal alignment, although the 2017 study evaluated only knee-high walkers, Crews said. A contralateral lift reduced the limb length discrepancy and subsequent balance and gait problems. “The removable cast walker induced changes in spinal alignment that could contribute to back pain and, subsequently, poor removable cast walker adherence. However, a contralateral lift may improve removable cast walker adherence by mitigating spinal alignment changes,” Crews said.
The next step for Crews is to study adherence and ulcer healing rates in diabetic patients wearing an ankle-high removable cast walker. Yet there’s no question that while TCCs and removable cast walkers have demonstrated similar capacities for offloading diabetic foot ulcers, research has demonstrated that patients who wear TCCs have better outcomes. The reason? TCCs must be cut off to be removed, whereas patients will often take off a removeable cast walker to sleep or when they’re at home. “As a result, they’re at increased risk for infection as well as nonhealing of the ulcer,” said Adam Isaac, DPM, a podiatric surgeon at Kaiser Permanente Mid-Atlantic States, Largo, MD. When patients don’t wear their offloading devices, they can also develop new wounds because of neuropathy, Dr. Isaac noted.
Both TCCs and removable cast walker boots have the potential to cause injury, owing to the postural imbalances they create, which can cause hip as well as back pain. “Although it’s rare, TCCs and controlled ankle motion boots can also cause additional pressure ulcers—some serious enough to require surgery,” said Dr. John Steinberg, DPM, professor in the department of plastic surgery at Georgetown University and president-elect of the American College of Foot and Ankle Surgeons.
In the clinic
Dr. Steinberg prefers TCCs for his patients with diabetic foot ulcers. TCCs improve adherence, said Dr Steinberg, adding, “although some patients absolutely refuse to have a TCC. If we run into strong patient resistance, we will try a removable cast. But if the wound doesn’t heal, we’ll then suggest a TCC again, and at that point, the patient usually agrees,” he added. Dr. Steinberg also noted that the type of deformity in the diabetic foot also has a role in the type of device chosen. For example, significant bony deformity calls for a TCC more than does a tissue deformity.
Dr. Isaac usually recommends a TCC for his diabetic patients with hard-to-heal ulcers, particularly if the ulcer is large or if the patient has a significant deformity, such as Charcot foot. At the very least, patients with large ulcers and foot deformities should wear a tall removable cast walker boot, he noted.
Although many clinicians favor TCCs, they are used less often than removable cast walkers because of the expertise needed to apply the TCC and patient resistance.4,5 Many practices have moved toward wrapping removable cast walkers in cast tape or other material after they are applied—essentially making them irremovable. The application of a removable cast walker in this manner does not require the specialized expertise demanded of a TCC, and the device is not easily removed by the patient—theoretically improving adherence and healing, said Dr. David Armstrong, founder and director of the Southwestern Limb Salvage Alliance, and professor of clinical surgery at the Keck School of Medicine at the University of Southern California.
The orthotist and pedorthist also have greater flexibility in customizing a removable device, such as by adding straps for adherence and adjusting for gait, said Eric Burns, CO, regional director of Hanger Clinics in Arizona.
Short walkers vs tall
Shorter removable cast walkers are more popular with patients than are taller devices. “Many of my patients with diabetic ulcers do prefer a short device set about the ankle level. These devices are easier to take on and off and less cumbersome than higher devices that come to the knee,” Dr. Isaac said. Short devices can be particularly useful in offloading small diabetic ulcers in patients without major foot deformities, he noted. “I usually prefer to sacrifice a little offloading capacity with a shorter device— if it will improve patient [adherence],” he added.
In his practice, Burns has found that although a shorter removable device will have less of an effect on balance and gait than a taller removable device, not all patients can use a shorter device. “A taller device would be a better choice for patients who need to heal from more serious wounds or have more serious deformities,” he said.
Emphasis on patient education for adherence
An ideal offloading device for a diabetic foot ulcer is one that maintains correct foot mechanics, enables the patient to have variable range of motion, and offloads pressure points, according to Robert Tillges, CPO, owner of Tillges Certified Orthotics and Prosthetics in Minneapolis, MN. Removable devices are generally more comfortable and promote better hygiene and wound care. “Still, you must have [an adherent] patient for these devices to be effective,” said Tillges.
Due to the high rate of patient nonadherence with removable offloading devices, patient education is vital, Dr. Steinberg agreed. Steinberg makes sure to explain to his diabetic patients with pressure ulcers the risks and benefits of wearing a removable offloading device. “If a patient truly understands the risks and benefits, he is more likely to be [adherent],” he said. To enhance adherence, Dr. Steinberg will even share with patients scientific papers detailing the efficacy of offloading devices for healing diabetic ulcers.
“Simply reminding people is not enough,” Crews said. “Patients get a false sense of safety in their own home, which leads to nonadherence in the home.”
A thorough foot assessment and complete medical history are crucial before deciding on the type of device and before designing a device for each patient, according to Tillges. Evaluating the patient for acute, chronic, or recurring problems is important. An older adult with osteoarthritis who is already at risk for falls, for example, may benefit from a lighter device that provides better balance. “The device also has to be designed to reduce enough shear and pressure, while also ensuring good biomechanical alignment,” Tillges said.
“Whichever device is used, we want to make sure we’re doing everything we can to get diabetic patients with wounds up and moving safely so they can heal. Safe mobility can have a dramatic effect on wound outcomes,” Burns added.
- Armstrong DG, Lavery LA, Kimbriel HR, et al. Activity patterns of patients with diabetic foot ulceration: Patients with active ulceration may not adhere to a standard pressure off-loading regimen. Diabetes Care. 2003;26:2595.
- Crews RT, Shen BJ, Campbell L, et al. Role and determinants of adherence to offloading in diabetic ulcer healing. A prospective investigation. Diabetes Care. 2016;39:1371.
- Crews RT, Sayeed F, Najafi B. Impact of strut height on offloading capacity of removable cast walkers. Clin Biomech. 2012;27;7:725.
- Crews RT, Girgis C, Domijancic R, et al. Influence of offloading induced limb length discrepancies upon spinal alignment. Presented at the 2017 American Diabetes Association Annual Meeting; June 22-26, 2018; Orlando, FL. Abstract 104-OR.
- Wu SC, Jensen JL, Weber AK, et al. Use of pressure offloading devices in diabetic foot ulcers: Do we practice what we preach? Diabetes Care. 2008;31:2118.
- Crews RT, King AL, Yalla SV, et al. Recent advances and future opportunities to address challenges in offloading diabetic feet: A mini review [published online ahead of print January 16, 2018]. Gerontology. 2018:doi: 10.1159/000486392.