Objective: To determine patient characteristics and clinical factors associated with lower limb amputation in individuals with a diabetes-related foot wound.
Research Design and Methods: All individuals treated by the multidisciplinary diabetic foot unit at a tertiary referral centre, between January 2005 and June 2010, were prospectively recruited. All individuals had diabetes and a wound distal to the ankle. Demographic data, information regarding the foot complication and the presence of other diabetes-related complications were collected. Peripheral neuropathy (PN) was defined as the inability to detect a 10g monofilament at least at one pedal site. Peripheral arterial disease (PAD) was the absence of at least one pedal pulse. Presence and extent of infection was recorded. Univariate statistical analysis (Fisher's exact test was used to identify features associated with increased risk of minor (below ankle) and major (below or above knee) amputations.

Results: A total of 1245 individuals (70.8% male) were recruited, with 4.8% requiring major and 12.8% minor amputations. PAD was present in 60.3%, PN 73%, any infection 56.5% and osteomyelitis 19.4%. The presence of PAD and PN were each associated with increased risk of amputation (p=0.0001). PAD or any infection were equivalently associated with increased risk of amputation (p=0.001) but coexistence of both factors doubled the risk (p<0.0001). In the presence of osteomyelitis, PAD did not influence the risk of amputation. Previous ulcer increased minor but not major amputations. Age, sex, smoking status and retinopathy were not associated with increased risk of amputation.
Conclusion: Peripheral arterial disease and extent of infection appear to be the strongest risk factors leading to amputation in individuals with a diabetes-related foot lesion. The coexistence of the two factors amplifies the risk, except in the setting of PAD and osteomyelitis. Further analysis including multivariate analysis is required to further delineate the effects of other variables.