An analysis of risk factors associated with failure of below knee amputations

Below knee amputation (BKA) is often required in patients with critical limb ischemia. When such a procedure fails, an above knee revision (AKA) is required. This can cause further complications in this group of patients, who already have a high incidence of medical co-morbidities.

Case records of 47 patients (51 procedures performed) with BKA for peripheral vascular diseases during a 4-year period were reviewed. Clinical factors were analyzed using bi- and multi-variate analysis against the procedure outcome. Degree of social deprivation was evaluated with DEPCAT score in relation to amputation failure. Each arterial segment of the pre-operative arteriograms was scored based on a 3-point scoring system (0=normal, 1=stenosis, and 2=cclusion). With the assignment of an arbitrary weight for each segment, a total arterial score (TAS) was derived for each patient.

Eighteen percent of BKA (n=9) failed. Absence of popliteal pulse (failure vs. success: 100% vs. 63%, P=0.04), calf rest pain (67% vs. 20%, P=0.01), combination of calf rest pain and feet tissue loss (CRPFTL; 67% vs. 3%, P=0.00), postoperative stump trauma (44% vs. 10%, P=0.03), and wound infection (WI; 89% vs. 26%, P=0.00) were factors associated with the failure of a BKA in bivariate analysis. Using multiple logistic regression, WI (OR=14) and CRPFTL (OR=47) were found to be independent predictors for the outcome of BKA. No statistical significance was found between the DEPCAT score and the failure rate. TAS was significantly higher in the failure group (median=17 vs. 9; P=0.00).

This study suggests that CRPFTL and postoperative WI are predictor variables for the failure of a BKA. In addition, there is the potential role of arteriogram scoring in predicting the outcome of a BKA.