June 2010

Surgical site infection risk in patients with diabetes

Photo courtesy of David Armstrong, DPM

Surgical procedures are often unavoidable in patients with diabetes, and can even help reduce future risk of ulceration. But high postoperative infection rates in this patient population pose additional challenges to practitioners.

by Ryan L. McMillen, DPM, Nicholas J. Lowery, DPM, and Dane K. Wukich, MD

Diabetes mellitus (DM) is an increasing challenge for the medical community.  It is estimated that 23.6 million people are afflicted in the United States, accounting for  approximately 7.8% of the population.1 Nearly one third of persons with diabetes are unaware that they have DM. Often this disease is not diagnosed until patients present with complications of the disease. The incidence of DM has increased 30% over the past five years, and nearly 25% of the United States population over the age of 60 has DM.2 As the population continues to age, the prevalence will continue to rise. Alarmingly, DM is being diagnosed more frequently in younger patients.3 The rising prevalence of DM is a global problem, and it is estimated that there will be 366 million people with DM worldwide by the year 2030. The largest increases will occur in developing nations over that time span.4

Diabetes-related foot and ankle problems constitute a tremendous challenge for patients, caregivers, and the healthcare system, and the associated comorbidities should be considered a lifelong condition.  Foot disorders in patients with diabetes, such as ulcers, infection, peripheral arterial disease (PAD) and Charcot neuroarthopathy (CN), are associated with severe morbidity and premature mortality, and they are a leading cause of hospital admissions in patients with DM.1,2

A higher incidence of DM occurs in non-Hispanic blacks, Native Americans, and persons of Hispanic and Latin heritage.5 Diabetes is associated with numerous complications resulting in multisystem disease and is most prevalent in patients over age 65. Ethnic disparities have been reported that demonstrate Hispanic, Native American, and African American patients have a greater risk for diabetes-related amputations than age-matched Caucasian patients with diabetes mellitus.  Diabetes and ethnicity also appear to have a profound effect on amputations of the lower extremity worldwide.1 It is likely that the greatest rise in the prevalence of type 2 DM  over the next 20 years will be in the developing nations of Africa, Asia, and South America.1 Diet and exercise could prevent an estimated 50% of type 2 diabetes, which would result in a substantial impact on complications and medical costs.6

Pathophysiology

Peripheral nervous system involvement is one of the most common complications of DM, and 10% of patients have some form of neuropathy at the time of diagnosis. 7 Diabetic polyneuropathy, the most common form of neuropathy affecting the Western world, can result in sensory, motor, or autonomic dysfunction. The prevalence of diabetic neuropathy is approximately 30%, but has been reported to range anywhere from 14% to 60%, depending on the population studied and the criteria used to define the diagnosis.7 Patients often fail to seek medical attention in a timely manner due to their lack of protective sensation.  Autonomic dysfunction leads to dry skin and arteriovenous shunting in the microcirculation. The dry skin is susceptible to fissures, which are prone to skin breakdown and can be a direct source of bacterial entry into the foot.8

Foot and ankle surgery is common in the DM patient population. Surgeries in this patient group can be categorized into two separate categories, elective and preventive.  Elective surgeries should be approached with caution in patients with DM due to their increased rate of infection as well as decreased rate of healing the integument and osseous structures.9-11 Preventive surgery is indicated when the patient has a preulcerative lesion, bony prominence or non-infected ulceration. Surgery can be done prophylactically in these high risk patients, or in patients who have healed ulcers but are at risk of recurrence.

Most often, surgery is done to assist healing of diabetic foot ulcers. Hammertoe and clawtoe correction may be necessary to heal a forefoot ulcer or prevent ulceration, particularly if hammertoes or clawtoes cannot be accommodated in extra-depth shoes. Achilles tendon lengthening has been demonstrated to be effective in healing forefoot ulcers.11

Surgery is indicated in Charcot arthropathy when patients have recurring ulceration, pain associated with malalignment, joint instability or an offending exostosis that leads to potential or real skin complications. The inability to brace a non-plantigrade foot is also a surgical indication.12

Ankle fractures in patients with DM need to be treated with caution.  As the prevalence of diabetes mellitus has continued to increase, so too has the number of ankle fractures seen in this patient population.  Patients with DM who do not have neuropathy can be treated with standard techniques.  However, patients with DM and neuropathy should have double the fixation, double the office visits and should remain non-weightbearing for double the amount of time.13

Patients with DM often have macrovascular and microvascular disease and, consequently, peripheral pulses may be present despite local tissue hypoxia in the microcirculation of the foot.  Peripheral arterial disease is a contributing factor in approximately one third of diabetic foot ulcers (DFUs) and often is implicated in recurrent ulceration and infection.14 Prolonged exposure to hyperglycemia is now recognized as a major factor in the pathogenesis of atherosclerosis in diabetes, inducing a large number of alterations at the cellular level of vascular tissue that potentially accelerate the atherosclerotic process.14

This hypoxia results in decreased blood flow to the surgical site, which subsequently decreases a patient’s ability to mount an immune response and ward off infection.  Furthermore, when infection develops, the insensate foot or ankle keeps patients from recognizing the imminent problem. As such, there is often a delay in seeking medical attention.

Surgical site infections

Many basic guidelines have been published to help to eliminate potential causes of surgical site infections. A surgical site infection is defined as an infection that develops within 30 days after an operation, or within one year if an implant was placed, and the infection appears to be related to the surgery.9 The Surgical Care Improvement Project is a national quality partnership of organizations in the United States focused on improving surgical care by substantially reducing surgical complications. Initiated in 2003 by the Centers for Medicare and Medicaid Services and the Centers for Disease Control and Prevention, the Surgical Care Improvement Project partnership is coordinated by a steering committee of 10 national organizations, including the Agency for Healthcare Research and Quality, the American College of Surgeons, the American Hospital Association, the American Society of Anesthesiologists, the Association of Perioperative Registered Nurses, the Centers for Disease Control and Prevention, the Centers for Medicare and Medicaid Services, the Department of Veterans Affairs, the Institute for Healthcare Improvement, and the Joint Commission on Accreditation of Healthcare Organizations.

The Surgical Care Improvement Project states that several preexisting factors, including diabetes, obesity, tobacco use, malnutrition, and the use of immunosuppressive medications, increase a surgical patient’s risk for postoperative infection.15,16 The Surgical Care Improvement Project recommendations for modifiable risk factors that help to prevent surgical site infections include controlling hypothermia, monitoring elevated blood glucose levels, use of electric clippers to remove hair from the surgical site, and administering preoperative, procedure-specific antibiotics within an appropriate time frame.15 Recognizing the factors that may play an increased role in the patient with diabetes mellitus can help to mitigate postoperative infection through education, controlling hyperglycemia, administering appropriate antibiotics, and ensuring the patient has adequate nutritional status.

Literature review

Surgical site infections have become an increasing concern for surgeons.  Infection rates have been reported between 1% and 5% historically.  In a large case series of 3836 general surgery patients, including abdominal and vascular surgery, the overall infection rate was 4.7%.17 The reported SSI rate for clean orthopaedic procedures has ranged from 0.5% to 6%.18 Very little research has been performed to quantify the potential risk of postoperative infection in foot and ankle surgery. In 1983, Miller19 reported an infection rate of 2.2% among 1841 patients undergoing so-called “clean” foot and ankle operations. The study did not mention whether any patients were diagnosed with diabetes mellitus, nor did it describe any other comorbid conditions attributed to the surgical patients.

Armstrong et al 20 found that diabetic patients with loss of protective sensation, but no open wound, who underwent forefoot surgery had a postoperative infection rate of 6.7%. This was one of the first studies that provided evidence that the presence of peripheral neuropathy can predispose diabetic patients to postoperative infection. Costigan et al21 evaluated 84 patients with DM who underwent operative management of ankle fractures. Patients with diabetes mellitus and peripheral neuropathy developed a postoperative complication 91% of the time,  and 10 of the 12 complications were postoperative infections.

Infection and ankle fracture

A recent study of complication rates following open reduction and internal fixation of ankle fractures found an overall rate of wound infection of 1.44% in a large series of 57,183 patients.9 Patients were divided into three groups for analysis: a control group of patients without DM, patients with uncomplicated DM, and patients with complicated DM.  Uncomplicated DM was defined as carrying a diagnosis of DM, but not having associated comorbidities of the disease including peripheral neuropathy, retinopathy, and nephropathy. The overall infection rate in study was 1.4%.  Uncomplicated patients with DM had a postoperative infection rate of 3.55%. Complicated diabetes was defined as having associated co-morbidities of DM (including peripheral neuropathy, retinopathy, and nephropathy). In this group, the risk of infection was 7.71%. The presence of complicated diabetes and peripheral vascular disease were particularly strong predictors of short-term complications, including pulmonary embolism, infection, mortality and amputation.

The surgical site infection (SSI) data for ankle fractures seem to mirror that of all foot and ankle cases.  In a retrospective review of 1000 consecutive foot and ankle procedures, the reported overall infection rate was 4.8% (see Figure 1).10 Patients with peripheral neuropathy were at a four-times greater risk for the development of a postoperative infection than patients without peripheral neuropathy. The presence of neuropathy proved to be the strongest predictor for infection in this cohort. The association of neuropathy and postoperative infection was not restricted to diabetic patients, as six (16%) of the 37 patients with nondiabetic neuropathy in this study also developed a postoperative infection.  The infection rate was 2.8% in the control group (patients without DM) and 13.2% in the diabetic study group.  Patients with complicated diabetes had a tenfold greater risk of infection compared to nondiabetic patients, and  a sixfold greater risk of  infection compared to patients with uncomplicated diabetes (see Table 1). This study demonstrated that a history of diabetes mellitus significantly increases the risk for severe infection requiring hospitalization and/or surgical intervention. The unadjusted relative risk of acquiring a severe infection was five times greater for diabetic patients than for nondiabetic patients. Interestingly, these data mirror the findings in the ankle fracture study, which found complicated diabetes to be a significant predictor of postoperative wound infection in foot and ankle surgery.  These two studies add credence to the long held belief that patients with diabetes mellitus are more prone to infection. 9,10

Conclusion

Surgical site infections continue constitute a challenge for surgeons and protocols are now in place that help to reduce the rate of post operative infection.  Complications of DM, specifically peripheral neuropathy, have been shown to increase the risk of developing a post operative infection.  Recognition of neuropathy and PAD preoperatively is paramount in stratifying which patients with DM are at increased risk for SSI.

Ryan L. McMillen, DPM, is a current resident and future foot and ankle fellow and Nicholas J. Lowery, DPM, is the current foot and ankle fellow in the department of orthopaedic surgery at the University of Pittsburgh Medical Center. Dane K. Wukich, MD, is the medical director of the UPMC Comprehensive Foot and Ankle Center, and chief of the division of orthopaedic foot and ankle surgery in the department of orthopaedic surgery.

References:

  1. Boulton AJ, Vileikyte L, Ragnarson-Tennvall G, Apelqvist J. The global burden of diabetic foot disease. Lancet 2005;366(9498):1719-1724.
  2. Gazis A, Pound N, Macfarlane R, et al. Mortality in patients with diabetic neuropathic osteoarthropathy (Charcot foot). Diabet Med 2004;21(11):1243-1246.
  3. Lipsky BA, Berendt AR, Deery HG, et al. Diagnosis and treatment of diabetic foot infections. Plast Reconstr Surg 2006;117(7 suppl):212S-238S.
  4. Apelqvist J. The foot in perspective. Diabetes Metab Res Rev 2008;24(Suppl 1):S110-S115.
  5. Centers for Disease Control and Prevention. National diabetes fact sheet: general information and national estimates on diabetes in the United States, 2007. Available at:  http://www.cdc.gov/diabetes/pubs/pdf/ndfs_2007.pdf. Accessed May 11, 2010.
  6. Herman WH. Diabetes epidemiology: guiding clinical and public health practice. The Kelly West Award lecture, 2006. Diabetes Care 2007;30(7):1912-1919.
  7. Rathur HM, Boulton AJ. Recent advances in the diagnosis and management of diabetic neuropathy. J Bone Joint Surg Br 2005;87(12):1605-1610.
  8. Bristow I. Non-ulcerative skin pathologies of the diabetic foot. Diabetes Metab Res Rev 2008;24(Suppl 1):S84-S89.
  9. SooHoo NF, Krenek L, Eagan MJ, et al. Complication rates following open reduction and internal fixation of ankle fractures. J Bone Joint Surg Am 2009;91(5):1042-1049.
  10. Wukich DK, Lowery NJ, McMillen RL, Frykberg RG.  Post operative rates in foot and ankle surgery:  A comparison of patients with and without diabetes mellitus.  J Bone Joint Surg Am 2010;92(2):287-295.
  11. Armstrong DG, Stacpoole-Shea S, Nguyen H, Harkless LB. Lengthening of the Achilles tendon in diabetic patients who are at high risk for ulceration of the foot. J Bone Joint Surg Am 1999;81(4):535-538.
  12. Bevan WP, Tomlinson MP. Radiographic measures as a predictor of ulcer formation in diabetic charcot midfoot. Foot Ankle Int 2008;29(6):568-573.
  13. Wukich DK, Kline AJ. The management of ankle fractures in patients with diabetes. J Bone Joint Surg Am 2008;90(7):1570-1578.
  14. Boulton AJ, Armstrong DG, Albert SF, et al. Comprehensive foot examination and risk assessment: a report of the task force of the foot care interest group of the American Diabetes Association, with endorsement by the American Association of Clinical Endocrinologists. Diabetes Care 2008;31(8):1679-1685.
  15. Mangram AJ, Horan TC, Pearson ML, et al. Guideline for prevention of surgical site infection 1999, Hospital Infection Control Practices Advisory Committee. Infect Control Hosp Epidemiol 1999;20(4):250-280.
  16. Brendle TA. Surgical Care Improvement Project and the perioperative nurse’s role. AORN J 2007;86(1):94-101.
  17. Weber WP, Marti WR, Zwahlen M, et al. The timing of surgical antimicrobial prophylaxis. Ann Surg 2008;247(6):918-926.
  18. Zgonis T, Jolly GP, Garbalosa JC. The efficacy of prophylactic intravenous antibiotics  in elective foot and ankle surgery. J Foot Ankle Surg 2004;43(2):97-103.
  19. Miller WA. Postoperative wound infection in foot and ankle surgery. Foot Ankle 1983;4(2):102-104.
  20. Armstrong DG, Lavery LA, Frykberg RG, et al. Validation of a diabetic foot surgery classification. Int Wound J 2006;3(3):240-246.
  21. Costigan W, Thordarson DB, Debnath UK. Operative management of ankle fractures in patients with diabetes mellitus.  Foot ankle Int 2007;28(1):32-37.
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