1525. Risk Factors for Below the Knee Amputation in Diabetic Foot Osteomyelitis
Session: Poster Abstract Session: Clinical Infectious Diseases: Diabetic Foot Infections
Saturday, October 10, 2015
Room: Poster Hall
  • Risk Factors for Below the Knee Amputation-version 2.pdf (164.3 kB)
  • Background: Diabetic foot osteomyelitis (DFO) is present in up to 20% of diabetic foot ulcers and is a leading cause of below knee amputation (BKA). Despite high prevalence, optimal treatment of DFO remains undefined. The purpose of this study is to evaluate risk factors for BKA after DFO.  

    Methods: This is a retrospective cohort of patients discharged from Denver Health Medical Center between 2/1/2012 and 12/31/2014. Patients who underwent minor amputation for diagnosis of DFO and were referred to the musculoskeletal infections service were eligible for inclusion. Patients were excluded for being lost to follow up at 6 months. The primary outcome was BKA in the 6 months following minor amputation. Variables of interest included demographic information, tobacco use, severity of DFO, type of amputation, antibiotic treatment duration, histopathologic evaluation, wound healing, and unplanned surgery for contiguous spread of infection. Descriptive statistics were used to calculate frequencies. The chi-squared test was used to determine relationships between BKA and variables.

    Results: 168 patients were eligible for inclusion in this study. 13 patients were lost to follow up and 2 patients died of other causes. 11 patients (7%) had BKA.  Failure to heal surgical incision in 3 months and surgery for contiguous spread of infection in 6 months was associated with BKA in 6 months ( P<.0001 for both). Age, homelessness, tobacco use, severity of infection, bacteremia, hemoglobin A1C, and histopathological margins were not associated with progression to BKA. The median duration of antibiotics was 42 days for those whose histopathologic bone resection margin was positive for residual osteomyelitis (IQR 32-47), and 16 days for those with no osteomyelitis at the bone resection margin (IQR 8-29). Longer duration of antibiotics did not protect against BKA in either those with a positive or negative histopathologic margin.

    Conclusion: Our study suggests patients who fail to heal their amputation sites in 3 months or require repeat surgical debridement in 6 months are at increased risk for BKA. Additional studies are warranted to evaluate if aggressive wound care can facilitate healing and prevent progression to BKA or if failure to heal is a marker of another unmeasured variable.

    Whitney Hernandez, NP, Infectious Disease, Denver Health Medical Center, Denver, CO, Heather Young, MD, Infectious Diseases, Denver Health Medical Center, Denver, CO, Bryan Knepper, MPH, MSc, CIC, Patient Safety and Quality, Denver Health Medical Center, Denver, CO, Susan Heard, BS, Rocky Mountain Poison and Drug Center, Denver, CO, Michael Wilson, MD, FIDSA, Pathology & Laboratory Services, Denver Health Medical Center, Denver, CO and Chrystal Berg, DPM, Denver Health Medical Center, Denver, CO


    W. Hernandez, None

    H. Young, None

    B. Knepper, None

    S. Heard, None

    M. Wilson, None

    C. Berg, None

    Findings in the abstracts are embargoed until 12:01 a.m. PDT, Wednesday Oct. 7th with the exception of research findings presented at the IDWeek press conferences.