Study: Infection Dramatically Raises Risk Of Amputation, Hospitalization

By Brian McCurdy, Senior Editor

   It is no secret that foot infections can lead to a range of complications up to and including lower extremity amputation. However, a recent study has demonstrated a dramatically higher risk of both amputation and hospitalization in diabetes patients who develop foot infections as opposed to those without infection. The authors say this is the first prospective study to report the incidence of foot infections in a defined population as well as the risk factors for infection.    The study, published in a recent issue of Diabetes Care, found that patients with diabetes and a foot infection had a 154.5 times greater risk of amputation and are 55.7 times more at risk for hospitalization than those without infection.    The authors of the study tracked 1,666 patients with diabetes over two years and discovered that 151 patients (9.1 percent) developed 199 foot infections. Although most patients had infections that involved just the soft tissue, the study notes that approximately 20 percent of infected patients had osteomyelitis that was proven by bone cultures. In addition, the researchers discovered that foot wounds preceded all but one infection. Among the significant independent risk factors for foot infection were wounds that penetrated to bone, wounds present for over 30 days, recurrent wounds, wounds with a traumatic etiology and peripheral vascular disease.

How can DPMs prevent infection and accordingly lower the risk for amputation?

   Lawrence Lavery, DPM, a co-author of the study, emphasizes aggressive wound healing, noting that infection and amputation are not common unless the patient has a wound or portal through which bacteria can invade the foot. However, Dr. Lavery notes that many effective methods of facilitating wound healing, including total contact casts (TCCs) and instant TCCs, are “not attractive” to patients.     “Perhaps if they understood the risk of losing their leg, they would be more willing to undergo this type of therapy,” adds Dr. Lavery, an Associate Professor in the Department of Surgery at Texas A&M Health Science Center College of Medicine.    The best methods of preventing infection are those that help patients avoid foot wounds, says study co-author Benjamin Lipsky, MD. Citing a 2005 article he co-authored in the Journal of the American Medical Association, Dr. Lipsky says such methods include screening for loss of protective sensation, assessment of foot biomechanics and screening for peripheral vascular insufficiency. He notes that screening for these factors can help stratify patients into groups by their risk for developing an ulcer. Ensuring periodic foot examinations and debriding calluses can also prevent foot ulcers, according to Dr. Lipsky, a Professor of Medicine at the University of Washington School of Medicine.    In addition to educating patients on proper foot care, Dr. Lipsky says clinicians should encourage these patients to optimize their glycemic control, stop smoking, wear appropriate footwear and practice proper principles of foot hygiene.

Emphasizing Timely And Appropriate Antibiotic Usage

   If a patient does develop a wound, Dr. Lipsky says the clinician should quickly assess whether the patient has an infection. If so, the clinician should obtain proper culture specimens and choose an appropriate antibiotic regimen based on published guidelines.     “Quick and proper care of infections can usually prevent amputations, especially major ones,” asserts Dr. Lipsky.    Does prophylactic antibiotic therapy have a role for patients with diabetes at high risk for foot infection? Dr. Lavery notes DPMs have to balance the notion of preventing infection and avoiding the promotion of resistant organisms via the inappropriate overprescribing of antibiotics. Since there is little evidence of benefit from treating clinically uninfected wounds, he encourages judicious antibiotic selection.    Does the increasing prevalence of resistant organisms contribute to the fact that those with infections are at such a high risk for amputation? Dr. Lipsky believes the higher incidence of resistant organisms “has probably played some role” in the increasing incidence of lower extremity amputation, especially in the case of methicillin-resistant Staphylococcus aureus (MRSA). Although the study did not specifically examine that issue, Dr. Lavery says the results suggest there are more infections that are not effectively treated with first-line antibiotics. While infection has always been a major risk factor for amputation, Dr. Lavery does not believe researchers have quantified this as he and his colleagues did in this Diabetes Care study.

Calling Attention To Basic Principles Of Infection Control And Prevention

   However, both doctors also believe that clinicians should pay more attention to basic principles of managing and preventing infections. Dr. Lipsky says an important factor leading to unnecessary amputations is a failure to apply some of the basic principles of treating infection, including culture-based antimicrobial therapy, adequate surgical interventions, such as debridement and removal of necrotic soft tissue and bone, and revascularization when necessary.     “Some surgeons have insufficient faith in conservative therapy of foot infections and thus recommend amputation for infections that could be cured (or result in more minor foot infections) by assiduous attention to wound care, antimicrobial therapy and revascularization,” opines Dr. Lipsky, the Chairman of both the International Working Group for the Diabetic Foot and the Infectious Diseases Society of America diabetic foot infection committees.    Dr. Lavery says it may simply be a matter of DPMs and patients focusing on basic infection prevention such as washing their hands, noting this may still be the best method of preventing MRSA.

Total Ankle Arthroplasty: Do The Risks Decrease With Experience?

By Brian McCurdy, Senior Editor    While the total ankle arthroplasty has been associated with a challenging learning curve, a recent retrospective study notes that perioperative complications may decrease as a surgeon gains more experience performing the procedure.    The Journal of Foot and Ankle Surgery (JFAS) study examined one surgeon’s experience with 50 total ankle arthroplasties. Among those patients, 26 percent of the cases had concomitant bony realignment procedures, 20 percent had a history of major hindfoot corrective procedures, 19 patients had intraoperative malleolar fractures, 12 exhibited some degree of malalignment, six patients had syndesmotic nonunion, and eight ankles required early component revision, according to the study. In addition, researchers note that nine patients had minor wound complications that resolved with local wound care and one patient had a major wound complication requiring flap coverage.    As the study notes, all the complications, except for wound complications, decreased with the surgeon’s increased experience. John Grady, DPM, who has performed 104 total ankle joint replacements, agrees there is a learning curve with the procedure. He suggests that complications decrease after a surgeon has performed about 10 to 20 procedures.    Dr. Grady says he has experienced six major complications with significant morbidity. Two of his patients had infections, one of which resulted in a below-knee amputation. Two had unresolved pain that necessitated arthrodesis and two had embolic or vascular problems, one of which necessitated a below-knee amputation, according to Dr. Grady, who has a private practice in Oak Lawn, Ill.    Among Dr. Grady’s other complications were 22 fractured malleoli, most of which happened in the OR and were repaired intraoperatively. Of those, he says he had three nonunions, two of which were asymptomatic, and one patient who continued with unresolved pain. He also experienced three dehiscences, one with a superficial infection that resolved.    The JFAS authors, in reviewing the procedures, also say that performing major realignment procedures concurrent with implant arthroplasty is not associated with a higher incidence of complications. Dr. Grady, in reviewing his procedures, notes that performing major realignment at the same time “definitely increased (his) complications.”

Can A New Anticonvulsant Help Treat Neuropathy?

By Brian McCurdy, Senior Editor    A recent study, presented at a meeting of the American Pain Society, tests the efficacy of using lacosamide to treat diabetic neuropathic pain in rats.    As part of a phase III clinical trial, researchers induced diabetic neuropathic pain in rats via injections of 55 mg/kg of streptozotocin. Between 10 to 21 days after injection, lacosamide had a maximal treatment response of 73 percent for thermal allodynia, 93 percent for mechanical allodynia and 47 percent for mechanical hyperalgesia, according to the study.    Researchers note lacosamide had greater treatment responses than amitriptyline, levetiracetam, pregabalin, lamotrigine and venlafaxine with the exception of amitriptyline’s effects on thermal allodynia. Lacosamide also had strong antinociceptive activity on all parameters assessed in the study and “seemed to be the compound with the broadest efficacy in inhibiting pain behavior,” according to the study.    Although he is not familiar with lacosamide, Jeffrey Page, DPM, says anticonvulsants have a well-established track record in managing painful neuropathy. While it is reasonable to conclude that lacosamide might have similar efficacy, adverse effects will be a concern in human trials, says Dr. Page, the Director of the Arizona Podiatric Medicine Program at Midwestern University.    If the data on safety and the low incidence of side effects are accurate, Matthew Rampetsreiter, DPM, believes lacosamide may be effective in treating neuropathy. For diabetic neuropathic patients, he uses pregabalin (Lyrica, Pfizer), gabapentin (Neurontin, Pfizer), Foltx (PamLab), Metanx (PamLab) and Folgard (Upsher Smith). Although he finds pregabalin effective, some patients develop gastrointestinal upset from it and it is expensive, says Dr. Rampetsreiter, who practices in Minnesota.    When treating symptomatic diabetic neuropathy, Dr. Page first strives for optimal glucose management if possible. He also prescribes treatments for immediate pain relief, saying he uses antidepressants and anticonvulsants as first line agents. Dr. Page then attempts to modify the inexorable progression of the disease process by using nutriceuticals. He adds that while the evidence is still limited, nutriceuticals containing potent antioxidants can help mitigate the long-term effects of oxidative stress, an integral part of the disease process.

In Brief

   Advanced BioHealing, Inc. has acquired the advanced wound care products Dermagraft® and TransCyte® from Smith & Nephew, saying both are approved for marketing in the United States and other countries.    Advanced BioHealing says it will immediately begin returning its manufacturing facility to operation and expects it to be fully functional by early next year.    Dermagraft is indicated for treating full-thickness diabetic foot ulcers. The company notes the product is a cryopreserved human fibroblast-derived dermal substitute. TransCyte is indicated as a temporary wound covering for surgically excised full-thickness and deep partial-thickness, thermal burn wounds. TransCyte is a human fibroblast-derived temporary skin substitute.

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