When it comes to diabetic foot ulcers, primary healing is only half the battle. Staggeringly high recurrence rates underscore the need to continue preventive measures long after the coast appears to be clear.
by Cary Groner
Clinicians seeking to preventing recurrence of diabetic foot ulcers in their patients have always faced significant challenges. Recent advances in risk assessment and ulcer management, combined with a dysfunctional reimbursement environment, may ironically make it easier to stop recurrence than to keep ulcers from developing in the first place. Even so, as research advances, clinicians must continually reevaluate the most efficacious approaches, because up to 60% of diabetic foot ulcers recur even with careful attention.
“Preventing ulcer recurrence may be the most important topic in diabetic foot disease,” said Peter Cavanagh, PhD, DSc, professor and vice chair for research in the department of orthopedics and sports medicine at the University of Washington Medical Center in Seattle. “Given the nature of reimbursement, our chances of preventing the first ulcer are limited; but once someone has had an ulcer, the warning flags go up and they meet the criteria under which intervention will be paid for.”
Diabetic foot ulcers represent a serious threat to life and limb regardless of whether they occur once or repeatedly. Up to a quarter of diabetes patients will develop a foot ulcer and more than half of ulcers become infected, requiring hospitalization and, in about 20% of cases, amputation.1 In fact, diabetes is associated with 80% of the nontraumatic amputations performed annually in the United States. Given that almost 24 million Americans now have diabetes, the scope of the problem is staggering.2
“Patients who have had one wound are at extremely high risk to develop another,” said David G. Armstrong, DPM, MD, PhD, professor of surgery and director of the Southern Arizona Limb Salvage Alliance (SALSA) at the University of Arizona College of Medicine in Tucson.
To evaluate patients’ risk of recurrence, Armstrong and his colleagues use foot assessment guidelines based on those from the American Diabetes Association (ADA). These include assessing patients for peripheral neuropathy, altered biomechanics, peripheral vascular disease, and a history of ulcers or amputation.3
“We will be having people at highest risk—especially those with a history of ulcer or amputation—back every couple of months,” he said. “One thing we look for is how they respond to repetitive stress, whether they show a propensity for developing calluses or pre-ulcerative lesions.”
Footwear and follow-up
Although a variety of approaches have been shown to help prevent ulcer recurrence, in some cases it remains unclear exactly how valuable they are. For example, two studies of total contact casting reported 50% and 60% recurrence rates, respectively.4,5 According to a study of patients treated in a comprehensive foot-care program, roughly 40% experienced ulcer recurrence, suggesting that follow-up may be at least as important as the initial healing provided by casting.6
Therapeutic footwear has long been considered a crucial aspect of ongoing care. For example, an Italian study of footwear designed for patients with diabetes found it effective in preventing reulceration: only 28% of those who wore the special shoes had their ulcers recur, versus 58% of those who wore their own shoes.7
But even that sacred cow has been challenged. Researchers at the VA Puget Sound Health Care System in Seattle published papers in the Journal of the American Medical Association in 2002, and Diabetes Care in 2004, concluding that therapeutic footwear may be of limited utility for preventing reulceration, except in patients with severe foot deformities.8,9
Reaction to the studies from the clinical community was swift and negative, however. Peter Cavanagh and several colleagues, including Armstrong, pointed out in a letter to the editors of JAMA that the studies suffered from several limitations, including that (a) almost half the subjects had protective sensation, and hence were not at risk for injury related to neuropathy or vascular disease; (b) the authors’ definition of an ulcer was overly conservative; (c) the authors provided no information about the biomechanical efficacy of the footwear, which appeared to be substandard and contained thin, prefabricated insoles; and (d) reexamining the data to consider only subjects who had lost protective sensation showed that even these relatively poor shoes provided benefit.10
“Shoes in and of themselves are not the answer,” added Jeffrey Robbins, DPM, national program director for podiatry at the VACO (Veterans Affairs Central Office) in Washington, DC, and chief of podiatry for the Louis Stokes VA in Cleveland. “It’s shoes along with proper fitting and surveillance that really do the trick.”
Follow-up, in other words, remains vital.
The depression paradox
Psychosocial factors such as cognitive function and depression have long been suspected of contributing to ulcer recurrence. In 2008, for example, Italian researchers reported in the Journal of the American Podiatric Medical Association that in 80 type 2 diabetes patients studied, the 60% who suffered recurrent ulcers had higher levels of depressive symptoms than others, among other factors.11
But even such time-honored risk factors are drawing new scrutiny in the age of evidence-based medicine. A recent study from Germany, reported in Diabetes Care, concluded that cognitive function was not an important determinant of foot reulceration.12 And a large 2010 U.S. study of 333 patients with neuropathy reported, oddly enough, that depression was associated with an increased risk of first foot ulcers but not of recurrent ones.13
“It’s an interesting paradox, because you’d think that if the first ulcer were associated with depressive symptoms, the second would be even more so,” said Cavanagh, one of the coauthors. “Whether there is a cause-and-effect relationship between psychosocial factors and outcome, or whether the psychological factors follow the outcome, is not something our study design could untangle.”
Responsibility for preventing recurrent ulcers falls on patients and providers equally, according to Mark Hinkes, DPM, chief of the podiatry section and chair of the amputation prevention program at the VA in Nashville, TN.
“Patient responsibility is key to preventing a second ulcer,” he said. “If the patient doesn’t manage his blood sugar; stop smoking; understand nutrition, diet, and exercise; and if he doesn’t practice proper foot care, it’s a losing situation.”
Practitioners have significant responsibilities as well, of course.
“You have to evaluate circulation,” Hinkes continued. “You have to know whether they are neuropathic. You have to assess them from a multidisciplinary view including shoes, because these people have special needs.”
Ulcers are likely to recur unless their etiology is understood, Hinkes emphasized.
“You have to find out why it happened the first time,” he said. “Is it a bone problem? A shoe problem? Just because you put someone in a diabetic shoe, the issue is not over. If I have a person with an ulcer under their big toe, I will make them an orthosis that will offload that spot. Nineteen percent of all foot ulcers happen under the first metatarsal. You have to understand the biomechanics of the foot, because people who don’t would not understand the concept of a plantar-flexed and hypermobile first ray.”
Hinkes considers proper footwear a crucial part of the healing equation and believes patients should see specialists when appropriate.
“I am absolutely in favor of diabetic patients being evaluated by a pedorthist,” he said.
The role of pedorthics
Dennis Janisse, CPed, reiterates Hinkes’s emphasis on patient responsibility.
“You can usually tell fairly quickly if you’re dealing with someone who is going to take responsibility for themselves,” said Janisse, who is assistant professor of physical medicine and rehabilitation at the Medical College of Wisconsin, and president and CEO of National Pedorthic Services Inc., headquartered in Milwaukee. “If they don’t, it dramatically increases the risk of reulceration.”
Not surprisingly for a pedorthist, Janisse considers proper footwear and well-designed orthoses essential to preventing ulcer recurrence. In a 2004 paper he coauthored, for example, researchers found that rocker soles successfully redistributed forefoot pressures in 40 patients, suggesting the soles’ potential for offloading problem areas.14
Janisse also thinks collaborative professional relationships are vital.
“It’s important to work with a physician who understands the importance of using pedorthics for conservative management of the diabetic foot,” he said. “The doctors we work with will tell you that our amputation rate is much lower than the national average.”
Janisse is concerned that some wound-care clinics don’t offer adequate follow-up.
“If the wound is on the leg and it closes, then fine, you can forget about it,” he said. “But if it’s on the foot, they may get it healed, but they have no idea what to do after that to prevent further ulceration. We have to do appropriate patient education.”
Surgery, too, is gaining an increasingly accepted role in preventing ulcer recurrence, according to Mark Hinkes.
“In high-risk patients who have adequate circulation, prophylactic surgery can be the correct thing to do,” he said. “If you have a hammer toe and it’s rubbing against your shoe, it is unlikely to get better. If your labs are good and you’re healthy enough, you might want to consider having it fixed before you get an infection.”
Dane Wukich, MD, chief of the division of foot and ankle surgery and associate professor of orthopedic surgery at the University of Pittsburgh School of Medicine, concurred.
“Recurrence is definitely related to deformity,” Wukich said. “If you have a forefoot ulcer and you don’t correct hammer toes, the ulcer is very likely to recur.”
Hinkes added that in his experience, physicians often overlook the possibility of local nerve entrapment in the feet and ankles because they are so conditioned to expect neuropathy in diabetes patients. In such cases, some recent research supports the efficacy of surgery.
For example, this year a study in JAPMA found that in 65 patients with previous neuropathic ulcers, surgical decompression of the peroneal and posterior tibial nerve branches was followed by a low annual incidence of ulcer recurrence—just 4% at a mean follow-up of 2.5 years (range 1–13 years). 15 The author noted that “unrecognized nerve entrapment may frequently coexist with diabetic sensorimotor peripheral neuropathy in patients with diabetic foot ulcers.”
According to Wukich, other problems such as tightness of the Achilles tendon can increase the risk of ulcer recurrence. Limited ankle dorsiflexion means that loading during gait is less likely to be absorbed by the heel and more likely to be redistributed distally.
“That increases forefoot and midfoot pressures, so you want to address that with a good stretching program and sometimes a surgical release,” he said.
A 2003 study in the Journal of Bone and Joint Surgery (JBJS) supports this approach. Researchers at Washington University in St. Louis randomized 64 subjects into two groups, to be treated with a total-contact cast alone or combined with percutaneous Achilles tendon lengthening. In the first seven months of follow-up, 59% of patients in the cast-only group had reulceration, versus just 15% of those who also received the surgery. The difference was smaller but still significant at two years.16
“Achilles lengthening can reduce plantar pressures by about 28%,” said David Armstrong, who sometimes performs the procedure and was principal author of a 1999 JBJS study on which the Washington University study was based.17
Armstrong explained that diabetes patients are prone to a non-enzymatic glycation of their soft tissues that can, in turn, lead to tightening of the periarticular structures around the joints.
“You can end up with a functional shortening of the Achilles tendon, which contributes to an equinus deformity and increased forefoot pressures,” he said. “Couple that with neuropathy, and you increase the risk of skin breakdown.”
Of course, offloading ulcerated areas has always been among the primary strategies to prevent ulcer recurrence, but even this field is changing rapidly.
According to Armstrong, protecting the foot should ideally involve evaluating not only vertical stress but shear stress.
“Shear stress explains why you might see a callus in an area that isn’t the site of peak plantar pressure,” he said. “We now have so many different types of insoles, materials, and shoe-gear permutations that we can do something about those problems once we’ve identified them.”
Armstrong and his colleagues have determined that one key factor associated with reulceration is wound location—and that wounds underneath the hallux are more likely to recur.18
“We think that’s because of the combined vertical and shear stresses there, because rarely is that the highest [vertical] pressure point on the foot,” he said.
Skin temperature provides crucial information about hot spots, as well.
“You can use it as a surrogate marker for inflammation,” Armstrong said. “People can dose their activities by checking skin temperatures just as they dose their insulin by checking their blood glucose, and newer thermometers are coming out that fit into the shoes and measure the bottom of the foot very well.”
Two 2007 randomized controlled trials, in Diabetes Care and the American Journal of Medicine, confirmed that subjects who didn’t use temperature measurements were more than four times as likely to develop foot ulcers than those who did.19,20 The Diabetes Care study was specifically designed to assess ulcer recurrence; the AJM study included patients who were considered high risk either because of a history of ulceration or because of diabetic neuropathy.
It’s also increasingly important to evaluate plantar pressure using dynamic measures, both to guide orthotic fabrication and to evaluate interventions (both orthotic and surgical) after they have occurred, Armstrong said (see “Pressure treatment: Dynamic data guide orthotic therapy.”)
‘Toe & flow’
Armstrong and his colleagues have observed that comorbid vascular disease may increase the risk of reulceration by as much as tenfold.18 This has led to a professional alliance between podiatrists and vascular surgeons at UA, now known within the university medical center as “toe & flow.”
According to Joseph Mills, MD, professor and chief of vascular and endovascular surgery at UA (and Armstrong’s “SALSA partner”) about a third of diabetes patients have abnormal blood flow, but physicians often fail to assess vascular status in those with foot ulcers.
“If you look hard enough, you’ll find that most of these patients have peripheral arterial disease, which can progress rapidly,” Mills said. “So even if they’ve had blood flow assessed before, if the ulcer recurs we always think of two things: is there still infection? And is the blood flow adequate?”
Armstrong said that although many medical centers boast of such a team approach, few actually practice it; rather, they simply refer patients back and forth between specialists, often in different buildings and on different days.
“We’re on the same hallway and on the same service,” Mills noted. “We both see almost every diabetes patient that comes through the door with a foot ulcer.”
Staying on your feet
Because so many strategies for preventing ulcer recurrence are relatively new, it may be some time before outcomes studies help determine their efficacy. Regardless, clinicians’ dedication to developing innovative approaches to risk evaluation and patient care suggest that the recurrent ulcers so often associated with subsequent amputation may be preventable.
That’s good news for everyone involved, particularly patients who’d like to keep their feet.
Cary Groner is a freelance writer based in the San Francisco Bay area.
1. Southern Arizona Limb Salvage Alliance patient information. Available at: http://diabetic-foot.net/CLEAR/Patients.html. Accessed August 31, 2010.
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