➢ At any point in time, 3% to 4% of the 29.1 million diabetic patients in the United States (9.3% of the population) will have a foot ulcer.
➢ Diabetes-associated foot ulcers and infection lead to >70,000 lower-extremity amputations yearly in the United States.
➢ Between one-third and one-half of diabetic patients undergoing a major lower-extremity amputation will die within 2 years after the amputation.
➢ Multidisciplinary population health-management strategies have been developed to decrease the rate and magnitude of this important comorbidity in the diabetic population.
➢ The goal of the present review is to provide the reader with a framework for the development of a health-care-system strategy for addressing this complex patient population.
The United States Centers for Disease Control and Prevention has estimated that there are >29 million diabetic patients in the United States alone1. At any point in time, 3% to 4% of the 29.1 million diabetic patients in the United States (9.3% of the population) will have a foot ulcer. Diabetes-associated foot ulcers and infection lead to >70,000 lower-extremity amputations yearly in the United States. This dramatic increase over the past 20 years appears to be plateauing at >9% of the population1. The direct and indirect cost to the United States economy was over $245 billion in 20121. One of the most important resource-consuming comorbidities of diabetes is a foot ulcer and the subsequent infection that leads to lower-extremity amputation. This scenario leads to >70,000 lower-extremity amputations yearly in the United States1,2. Following transtibial amputation, the mortality rate at 2 years is 36%, a statistic that has not been improved on over the past 25 years1,3. Overall amputation rates have decreased over the past decade, primarily because of the changes in modern vascular surgery. Our vascular surgery colleagues appear to be making substantial inroads into decreasing amputation rates for patients with ischemic disease, whereas the amputation rate for ulcer or infection in the same population has demonstrated no change in the past decade (Fig. 1)4,5.
In the 21st century, the solution to this daunting problem is going to be more complex than simply developing a multidisciplinary clinic to address the multiple medical comorbidities in this complex patient population. The best-performing health systems will address this challenge by developing a health-care-system strategy of population management for groups of patients with resource-consuming medical conditions that cross multiple medical disciplines.
The clinical presentation of a diabetic patient who has a foot infection generally includes one or more open wounds and clinical signs of infection. A careful examination should be performed for patients without obvious open wounds as an infected ingrown toenail or skin cracks between the toes can serve as the portals of entry for bacteria that initiate infection. Erythema, warmth, and swelling in the absence of a wound or clinical signs of infection should alert the clinician to the possibility of Charcot foot arthropathy as an alternative diagnosis. Many patients undergo unnecessary and potentially harmful surgical biopsies and contamination of non-infected inflammatory bone when Charcot foot arthropathy is incorrectly diagnosed as infection.
Modifiable Risk Factors
The most efficient patient-safety methodology for avoiding complications following surgery is to operate on healthier patients. Our orthopaedic trauma colleagues have reported improved survival rates and patient outcomes following hip fracture since the development of systems that rapidly optimize patients prior to operative repair6,7. This experience has taught us the value of hospitalist co-management programs6-8. Moreover, this experience was expanded with the development of modern joint arthroplasty programs that also focus on disease-specific patient population management. Our arthroplasty colleagues have learned that outcomes are worse and complication rates are increased in patients with multiple medical comorbidities. Prior to urgent surgery (e.g., in the case of a hip fracture), many of these medical conditions can only be stabilized. The same medical comorbidities (e.g., an elevated hemoglobin A1c level, hypertension, or anemia) can be optimized prior to elective or semi-elective surgery. The comorbidities of untreated hypertension, morbid obesity, anemia, and poor glycemic control in diabetic patients (as defined by elevated hemoglobin A1c levels) are now considered to be modifiable risk factors. Rather than simply denying elective surgery to patients in these increased-risk groups, the modern health-care-system strategy is to develop associated interventional programs to decrease body mass index (BMI), to determine the cause of and treatment for anemia, to improve diabetic treatment, and to stabilize resting blood pressure. These associated programs act to decrease perioperative complications and to improve patient safety in the short term. The long-term benefit to the health-care system is an improvement in the overall health status of patients within the specific health-care system, which leads to a decrease in the consumption of health-care-system resources. The most proactive health-care systems will use interventions to identify and optimize health risk. When modifiable risk factors are improved, patient safety is improved. In financial terms, the best methodology to decrease health-care costs is to operate on healthier patients.
Diabetic Educator (www.diabeteseducator.org)
The responsibilities of the modern diabetic educator have progressed from simple patient education on diet, glycemic control, and lifestyle. Enlightened health-care systems use the patient relationship and trust to empower the diabetic educator to serve as a patient navigator/case manager. Patients with modifiable risk factors can enroll in specific programs to decrease their potential for developing complications associated with specific risk factors. The diabetic educator and the physician champion work closely with a certified pedorthist, whose knowledge and skill of health maintenance and therapeutic footwear (shoes, orthoses, and shoe modifications) can establish an important relationship in the prevention and treatment of diabetic ulcers. Proactive foot-specific patient education and therapeutic footwear are more effective than intervention following the development of a foot wound or infection. Screening and preliminary patient education by the diabetic educator is far more efficient than asking the already overburdened primary-care physician to screen for yet another of the litany of health risks attributed to diabetes9. This already-developed relationship allows the diabetic educator to serve as an educated case manager who can guide the patient through the treatment process when foot morbidity develops10-12.
Patient education is a critical component in a preventive-strategy program. Patients must be taught how to perform daily self-examinations. Examining the plantar surface of the foot can be challenging when the patient is limited by diabetes-related impaired vision and/or morbid obesity and joint stiffness that can limit access to the feet. Magnifying glasses and lighted mirrors mounted on a telescoping handle can be used as a creative solution for patients with retinal disease. When available and capable, a spouse or caregiver can act as a surrogate. Instruction in appropriate footwear and stockings has been effective for low-risk patients, and referral to a certified pedorthist for therapeutic footwear has been effective for low to moderate-risk patients12-15.
The diabetic educator becomes a key team player in managing psychosocial issues that are unique to this patient population. There is a common misconception among physicians and nurses that diabetic patients are noncompliant or in denial; in fact, these patients have cognitive and judgment deficits, secondary to central peripheral neuropathy, that cause them to make poor health-care decisions. In order to educate these patients, both the diabetic educator and the treatment team need to constantly reinforce lifestyle adjustments to promote good health and avoid morbidity10,11,14,15.
A foot ulcer or foot infection is most likely to develop in diabetic patients who have had a previous foot ulcer or infection, a partial or whole-foot amputation, or peripheral neuropathy or vascular disease. Patients in whom a foot ulcer or infection has already developed should be managed in a structured longitudinal program to prevent recurrence. The key risk factor to be identified in a patient without a previously identified foot ulcer or infection is peripheral neuropathy as evidenced by insensitivity to testing with a Semmes-Weinstein 5.07 (10-g) monofilament (Fig. 2). The identification of peripheral neuropathy and osseous deformity are important as preventive strategies can be initiated for affected patients9,12,13,16,17. Such is not the case for patients with silent vascular disease (i.e., those with a diminished or absent pulse) as the vascular surgeon does not consider intervention until the patient has a nonhealing wound or ischemic pain at rest.
Many grading systems have been developed to categorize risk. Most are cumbersome and not predictive. Understanding the spectrum of the potential risk for a patient to develop a foot ulcer can allow the physician to advise on the preventive strategies that should be implemented for an individual patient. At the low-risk end of the spectrum is the diabetic patient with no structural deformity, protective sensation (as measured with the Semmes-Weinstein 5.07 [10-g] monofilament), and normal palpable pedal pulses. At the high-risk end of the spectrum is the patient with structural deformity (hallux valgus, hammer toe, or Charcot-associated deformity), peripheral neuropathy (insensitivity to the monofilament), and absent pedal pulses.
Grading of Foot Ulcers
The Wagner-Meggitt grading system for the classification of diabetic foot ulcers is a validated tool that can be used to categorize risk status and to determine treatment strategy (Fig. 3)18-22. Patients with Wagner-Meggitt Grade-0 involvement either have a history of a foot ulcer or infection or are at increased risk for the development of a foot ulcer or infection. These patients are managed longitudinally with patient education (as described in the section on the diabetic educator) and therapeutic footwear (as described in the section on the certified pedorthist).
Patients with Wagner-Meggitt Grade-1 or 2 involvement have a superficial foot ulcer that is treated simply with local debridement in the outpatient clinic, empiric oral first-generation antibiotic therapy, and either a commercially available offloading device or total-contact cast. Once the ulcer has healed, these patients are managed longitudinally with ongoing patient education, periodic monitoring, and therapeutic footwear12,14,16,17.
Patients with Wagner-Meggitt Grade-3 involvement have a deep infection with a combination of soft-tissue abscess and osteomyelitis. These patients generally are managed as inpatients as they require surgical debridement and treatment for osteomyelitis. In addition to surgical excision of the infected tissue and subsequent wound care, these patients require acute medical treatment of diabetes and the associated confounding medical comorbidities of cardiovascular disease and renal failure. The combination of a hospitalist co-management acutely and a longitudinal health-care-system strategy following the acute episode is crucial for individual patient outcomes, resource consumption, and resource allocation23.
Patients with Wagner-Meggitt Grade-4 and 5 involvement have irreversible tissue damage with associated gangrene. These patients require partial or whole-foot amputation in the short term23-26. They consume substantial health-care resources during the acute episode of treatment, rehabilitation in a rehabilitation unit or skilled nursing facility, and ongoing prosthetic management1,3,23,26.
Health-Care-System Strategy for Outpatient Care
In addition to the toll that a diabetic foot ulcer takes on the individual patient, most mature health-care systems will appreciate both the clinical and financial liability associated with a diabetic foot ulcer. As previously discussed, these patients consume a great deal of health-care-system resources. Once identified, the most mature health-care systems will use this diagnosis as a trigger for aggressive proactive intervention.
Forward-thinking health-care systems will assign a dual responsibility for the diabetic educator. Constant reinforcement during ongoing patient education and monitoring are essential to identify problems early and to initiate intervention before problems escalate. Low-risk patients require ongoing patient education and advice on appropriate footwear. High-risk patients require multi-specialty management. Optimization of diabetic medical management and a methodology for addressing morbid obesity are crucial. The vascular surgeon rarely plays a role at this phase of care, generally not having interventional tools until the patient develops a nonhealing wound or ischemic pain at rest9,12,14.
Health-Care-System Strategy for Inpatient Treatment
Wagner-Meggitt Grade-3 involvement implies the presence of a deep abscess and osteomyelitis. The diagnosis is made with the probe-to-bone test (Fig. 4). Every diabetic foot ulcer should undergo the probe-to-bone test to determine if the applicator stick (i.e., probe) pierces the wound. The probe-to-bone test, when positive, vitally ensures the presence of a deep abscess and osteomyelitis. A negative test does not guarantee the absence of either an abscess or osteomyelitis. When a Wagner-Meggitt Grade-3 lesion is confirmed, the patient requires hospitalization, surgical debridement, and parenteral antibiotic therapy17,23.
Clinically defined responsibilities become crucial at this stage as this group of patients consumes substantial health-care-system resources. Effective health-care systems use the initial inpatient encounter to initiate the optimization of diabetic, cardiac, and renal failure management acutely during hospitalization and longitudinally following conclusion of the initial intervention. Most patients can be acutely medically optimized prior to the initiation of surgical debridement. The surgeon should then initiate a plan that considers resolution of the acute infection, ongoing wound management, and options for optimal long-term functional outcome. This is the point when vascular surgery consultation is appropriate if patients have less-than-normal palpable pedal pulses. Depending on the environment, this is the time to interact with wound-care and/or reconstructive plastic-surgery consultants. Aggressive treatment of wounds at this point in the disease process can avoid a prolonged period of non-weight-bearing, disability, and wound management. A structured plan of transition to the outpatient environment must be initiated at this time, which will include longitudinal case management for diabetes, cardiac, and renal medical comorbidities.
Orthopaedic trauma surgeons have demonstrated the value of hospitalist co-management in the care of elderly patients with hip fractures and associated comorbidities6,7. Diabetic patients who are admitted for the treatment of a foot infection require similar multidisciplinary management to avoid the acute medical complications that lead to increased length of hospital stay and resource consumption. Co-management, as opposed to medical consultation, is crucial to optimize the inpatient phase of care. The infectious-disease specialist is essential for choosing parenteral antibiotic therapy and managing the dosing of those drugs during the treatment period to avoid drug-associated organ-system comorbidity6-8.
The “captain of the ship” in the management of patients who have diabetic foot infections is going to vary depending on the culture of the institution. It might be an orthopaedic surgeon, a vascular surgeon, or a podiatrist. On occasion, an internist or endocrinologist may take the lead.
The Role of Consultants
The Medicare Therapeutic Foot Bill of 19939 allows every Medicare patient who meets documented medical criteria to receive 1 pair of therapeutic footwear and 3 pairs of prefabricated or custom foot orthoses per calendar year. Appropriate shoe modifications such as rocker soles may be substituted for a pair of orthoses. Each health-care system will use different applications of total-contact casting techniques, custom orthoses, and commercially available products to assist in the care of these patients27. In enlightened health-care systems, the certified pedorthist is enlisted as a member of the health-care team as opposed to functioning as an outside consultant. On-site availability eliminates transportation barriers and allows the certified pedorthist team member to reinforce patient education during fitting. When considering the spectrum of disease, low-risk patients require ongoing patient education and footwear counseling.
Moderate to high-risk patients will require commercially available therapeutic shoes and prefabricated to custom-fabricated accommodative foot orthoses. Hybrid custom orthoses not only can accommodate deformities but also can stabilize destructive motion and offload areas of high pressure9,12,14,16. Severe foot deformities may require the fabrication of custom shoes or boots with protective inserts and rocker soles. Having a certified orthotist as a member of the team allows coordinated fitting of an ankle-foot orthosis when stability of the foot-and-ankle complex is necessary to reduce the ground-reaction force applied to a diabetic foot ulcer. These accommodative therapeutic devices become more complex with the severity of risk, making immediate access even more beneficial. If amputation becomes the treatment of choice, the certified prosthetist can be available prior to surgery to educate the patient on the postoperative prosthetic treatment and long-term care plan27,28.
Vascular surgery consultation is warranted for patients with a nonhealing diabetic foot ulcer and a nonpalpable pedal pulse. In the absence of a palpable pedal pulse, the vascular laboratory can perform several noninvasive studies to determine if vascular intervention is required. Arterial duplex ultrasonography can be very useful for localizing occlusion or severe stenosis, whereas ankle brachial indices can quantify the physiological impact of the stenosis. Unfortunately, diabetic patients often have severely calcified arterial disease, limiting the utility of arterial duplex ultrasonography and providing a falsely elevated ankle-brachial index. In these instances, toe pressures can be utilized. Ramsey et al. found that a toe pressure of >30 mm Hg was predictive of wound-healing in patients with toe ulcers or undergoing toe amputation29. Normal and abnormal toe-pressure tracings are depicted in Figures 5-A and 5-B.
The majority of patients with nonpalpable pedal pulses and borderline toe pressures will undergo angiography. Arterial calcifications tend to limit the utility of computed tomographic angiography, especially in tibial vessels. Should the patient have severe renal insufficiency, angiography can still be performed with use of CO2 as a contrast agent instead of iodinated contrast medium. Using CO2 as the contrast agent provides limited visualization of the tibial vessels; however, interventions can still be successfully performed without the use of iodinated contrast medium.
A final point is that a majority of the interventions to improve perfusion to the foot can be performed with percutaneous endovascular techniques involving local sedation. Patients with severe comorbidities can tolerate the procedure quite well, and, if the procedure is successful, can avoid more proximal amputation. Referral to a vascular surgeon should not be limited by the fear that a patient cannot tolerate an open operation under a general anesthetic. As stated earlier, modern endovascular techniques are likely responsible for the decreased rate of amputations for ischemic disease over the past decade4.
Numerous imaging tests are available to evaluate both the soft tissues and the osseous structures of the at-risk and the infected diabetic foot. However, it is not diagnostically beneficial or fiscally sound to apply all modalities to each case. As part of the multidisciplinary health-care team, the musculoskeletal radiologist can contribute valuable information regarding the anticipated diagnostic utility of the various modalities and also can provide meaningful interpretation of the tests once they have been completed.
For example, the local radiologist will have intimate knowledge of ongoing availability of imaging resources peculiar to the home institution such as equipment upgrades (e.g., the acquisition of a 3T magnetic resonance imaging (MRI) unit in addition to a preexisting 1.5T unit) or mechanisms to acquire same-day imaging. Similarly, a close relationship between the radiologist and the clinical team will enable the imaging department to appropriately weight recommendations to hospital administrators for financial support for equipment for ongoing and future programs. Another important role of the musculoskeletal radiologist is to ensure patient safety during the various imaging tests as technology continues to evolve and new information is continually added to the literature. A dramatic example of alteration in the imaging paradigm was the discovery of the relationship between renal insufficiency and the administration of certain gadolinium-based imaging agents during MRI as combined risk factors for the development of nephrogenic systemic fibrosis. Furthermore, a working familiarity between the radiologist and the foot-care specialist allows effective communication by the radiologist of emergent or unexpected findings as well as enhanced interpretation of imaging findings by the radiologist as the radiologist is familiar with the needs and expectations of the clinicians involved17,21.
The surgeon is responsible for making the diagnosis of infection of the diabetic foot. The infectious-disease consultant is best utilized to choose appropriate antibiotic therapy, to guide the duration of therapy, and to monitor associated antibiotic-induced organ-system morbidity during the postoperative period.
The initial choice of antibiotic therapy is based on a number of factors, including the severity of the infection, prior culture data when available, and risk factors for certain organisms. Key decision points include the likelihood of methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas, and anaerobic infection. In cases of severe infection, it is often appropriate to promptly obtain culture specimens and to initiate therapy with broad-spectrum antibiotics and then adjust the antibiotics on the basis of the results of properly performed cultures. Diabetic foot infections are often polymicrobial. Consultation with an infectious-disease specialist may be helpful to assist in deciding which organisms should be targeted as pathogens and which are more likely to represent colonization. For example, the need to target enterococci, coagulase-negative staphylococci, and corynebacteria often will need to be considered as these organisms may or may not be pathogenic24,30.
The infectious-disease specialist will consider whether parenteral antibiotics are required and when oral antibiotic therapy will suffice. Initial selection and dosing will depend on the extent and location of the infection. Knowledge regarding antibiotic bone penetration in cases of osteomyelitis will help to define the drug of choice as well as the dose. A higher dose may be indicated to achieve improved bone penetration. Dosing will be adjusted for renal and hepatic function, and close monitoring of laboratory studies by a physician or doctor of pharmacy is useful for achieving the required dose adjustments and drug-level monitoring.
An infectious-disease consultant will follow patients who are receiving parenteral antibiotics as outpatients through an outpatient parenteral antimicrobial therapy (OPAT) program. This program will include monitoring of drug levels when indicated and monitoring of other pertinent laboratory results, including complete blood-cell count, creatinine, liver function tests, and inflammatory markers. On review of these results, changes in dose or drug selection will be determined.
Too often, irreversible renal failure occurs after the injudicious use of parenteral cephalosporin therapy for infections of lesser toes. There is strong evidence to justify oral first-generation cephalosporin antibiotic therapy in cases of Wagner-Meggitt Grade-1 and 2 wounds associated with cellulitis17. If patients do not respond in a timely fashion, surgically obtained culture specimens (as opposed to swabbing) are necessary to direct therapy. Empiric therapy in cases of Wagner-Meggitt Grade-3 or greater infections should consist of parenteral cephalosporin pending the results of cultures of surgically obtained specimens. In addition to tissue culture, microscopic examination is valuable to assist the infectious-disease specialist in advising therapy17,30.
Finally, the infectious-disease specialist may be utilized to assist in difficult cases when a patient has multiple drug allergies or adverse drug reactions and can help with recommendations regarding second-line and less-commonly-used antibiotics. After appropriate antibiotics are selected, the infectious-disease specialist often will participate in shared decision-making regarding the duration of therapy, in close consultation with the orthopaedic surgeon or podiatrist, and the final duration often will depend on clinical observation of healing.
Depending on the health-care-system model, the plastic-surgery and wound-care consultants are valuable consultants as one plans surgical reconstruction and transition to longitudinal care following the initial treatment of a foot infection.
Each health-care system will develop different algorithms for managing patients who have wounds. This will require different inputs from the wound-care specialist, plastic surgeon, and reconstructive orthopaedic surgeon. Developing relationships and clinical-care algorithms will lead to improved patient-care outcomes.
Development of a diabetic foot ulcer or foot infection is likely to have a severely negative impact on health-related quality of life. Such patients are 8 times more likely to undergo a lower-extremity amputation and have a substantial risk of mortality at 2 years following development of the abnormality1-5. The first step in attempting to decrease the negative impact on quality of life and resource consumption has been the development of multidisciplinary teams. The next step is the development of a consistent strategy to be used throughout the individual hospital or local health-care system.
Investigation performed at the Loyola University Health System, Maywood, Illinois
Disclosure: No external funds were received in support of this study. The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article.
- Copyright © 2016 by The Journal of Bone and Joint Surgery, Incorporated