Original Research

Factors Associated With Lower-Extremity Amputation in Patients With Diabetic Foot Ulcers




This retrospective study was undertaken to evaluate factors associated with LEA in patients with diabetic foot ulcers. Patients with diabetes being treated at a wound care facility often require continuous surgical and metabolic intervention to promote optimal healing: drainage, surgical debridement, irrigation, culturing for infection, and monitoring of blood glucose levels. This treatment requires strict compliance with medical directions and, oftentimes, additional care, such as home-care nursing visits, to maintain a curative environment for the wound. Frequently, wounds on the lower extremity further complicate the healing process by reducing the patient’s mobility and daily life. Due to these factors, many patients progress to LEA. The link between diabetic ulcers and amputation has already been well described in previous studies, with studies showing that history of diabetic foot ulcer significantly predisposes an individual to LEA.4 However, few studies have further investigated demographic factors associated with risk for an amputation. Our study analyzed several categories of patient data taken from a baseline visit. We found that those with highly elevated HbA1c values were less likely to have an amputation than persons with relatively lower levels, a finding that is contrary to previous studies.

Our study’s findings suggest a higher risk for LEA with increased age. The amputation group was, on average, 7 years older than the other 2 groups. A recent study showed that risk for amputation is directly correlated to patient age, as is the mortality rate after undergoing LEA (2.3%; P < 0.05).5 Our study found that with each increase in age of 1 year, the odds of amputation increased by 6.5%. However, recent evidence on LEA risk and aging suggests that age is of less consequence than the duration of diabetes. One study found that the propensity to develop diabetic foot ulcers increases with the duration of diabetes.6 The same study found that prevalence of ulceration was correlated with age, but the relationship between age and LEA was less significant. A follow-up study for LEA could be done to examine the role of disease duration versus age in LEA.

A consensus among previous studies is that men have a higher risk for LEA.5,7 Men comprised the majority in all 3 groups in our study. In addition, the amputation group in our study had the lowest BMI. Higher BMI generally is associated with an increased risk for health complications. However, a past study conducted in Taiwan reported that obese patients with diabetes were less likely to undergo LEA than those within the normal range for BMI.8 Neither study suggests that obesity is a deterrent for LEA, but both studies may suggest that risk of amputation may approach a maximum frequency at a specific BMI range, and then decrease. This unconfirmed “cyclic” relationship should be evaluated further in a larger sample size.

Most patients in our analysis were Caucasian, followed by African American and South Asian. African Americans were the only racial group with an increased frequency in the amputation group. This finding is supported by a previous study that found that the rate of LEA among patients with diabetes in low-income, predominantly African-American neighborhoods was nearly double that in wealthier, predominantly Caucasian areas.9 A potential problem in the comparison between our data with previous studies is that the studies did not analyze patients with our inclusion criteria. All patients with diabetes in previous investigations were grouped by race, but were not necessarily required to have 1 or more ulcers. Multiple ulcers may predispose an individual to a greater risk for amputation.

Multinomial logistic regression did not suggest an association between initial size of a patient’s wound and the risk of amputation. However, the descriptive data suggests a trend. Patients who did not heal or require an amputation had the largest average wound area. This finding is not surprising in that our study followed individuals for only 3 months. Many wounds require a long course of treatment, especially in patients with diabetes, who may have poor vascularization. However, in comparison to the healed patients, the patients who required an amputation had a larger average wound area. A larger wound requires a plentiful vascular supply for the delivery of clotting factors and nutrients to the damaged area. As wound size increases, an individual’s body must transmit an increased quantity of these factors and nutrients for the regeneration of tissue. In addition, wounds that possess a larger surface area require more debridement and present a greater opportunity for infection. This may also foreshadow a longer, more costly course of treatment. Additionally, individuals coping with large ulcerations are burdened by more elaborate and complex wound dressings.

Elevated levels of HbA1c are associated with increased adverse effects of diabetes, including end-stage renal disease, neuropathy, and infection.10 In a previous study, the risk for amputation was 1.2 times higher in patients with elevated HbA1c.11 In contrast, our study suggested the odds of LEA versus not healing/not undergoing amputation decreased as HbA1c increased. As a patient’s HbA1c level increased by a value of 1, their odds for LEA decreased by 54.3%. This finding contradicts prior studies that have found a positive association between HbA1c and LEA risk, including a study where each percentage increase in HbA1c correlated with a 13% to 15% increased risk of LEA.12 The finding that patients who underwent amputation in our study had lower levels of HbA1c and blood glucose cannot be fully explained. The maximum HbA1c value in the amputated group was 7.9%. The average values for healed patients and those who underwent LEA were 8.75% and 6.77%, respectively.

Blood glucose levels were also found to be the lowest in the amputated group in our study (mean, 149.29 mg/dL vs 163.19 mg/dL in the healed group). Similar results were found in a Brazilian study, in which patients who did not require amputation had higher HbA1c levels. This study also found an association between blood glucose levels above 200 mg/dL and amputations.3 These findings provide interesting opportunities for repeat studies, preferably with a larger number of participants.

Our study is limited by the small sample size. The sample population had to be reduced, as many patients were lost to follow-up. Although this paring down of the sample size can introduce bias, we are confident that our study is representative of the demographic of patients treated in our facility. The loss of patients to follow-up in turn caused the window of analysis to be narrowed, as long-term outcome data were not available. A multisite study observing various population samples can better explore the relationship between HbA1c and risk of amputation.


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