Renal Function as a Predictor of Reamputation After Initial Transmetatarsal Amputation in the Perioperative Period

Abstract

Category: Midfoot/Forefoot Introduction/Purpose: With increasing rates of patients being newly diagnosed with diabetes mellitus, foot complications are becoming more common, which often lead to amputation. Compared to major lower extremity amputations, transmetatarsal amputations (TMA) are associated with lower cost, better function, and more aesthetically satisfactory results for patients. Renal failure has been shown to be a significant predictor of morbidity and mortality in lower extremity amputations at various levels. However, previous reports examining the effect of renal function on reamputation rates after TMA have been mixed. As a result, the purpose of this study was to evaluate renal dysfunction as a risk factor for reamputation after initial TMA during the 30-day perioperative period in a large population database. Methods: Patients under 90 years of age who underwent a TMA between 2012 and 2015 were retrospectively identified in the prospectively collected American College of Surgeons-National Surgical Quality Improvement Program® (ACS-NSQIP®) database using the Current Procedure Terminology (CPT) code 28805. Failure of the initial TMA was defined as reamputation in the 30-day perioperative period through corresponding CPT codes. From these criteria, a total of 1,775 patients were identified. More than 150 unique patient factors were included in the study, but glycated hemoglobin (HbA1C) was not reported by the ACS-NSQIP® database. Diabetes status was categorized into four groups: “Insulin” dependent, “Non-Insulin” dependent, or “None.” Filtration rate was estimated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation, and patients were categorized into stages of chronic kidney disease (CKD). Results: Over the 30-day perioperative period, the rate of reamputation after TMA was 6.5%. No statistical differences in age, gender, race, body-mass index, or level of pre-operative functional status were found between groups. Reamputation rates after TMA was significantly correlated with higher white blood cell counts (p<.00001), greater serum creatinine (p=.021), higher blood urea nitrogen (p=.021), type of glycemic control (p=.002), stage of CKD (p=.003), dialysis (p=.001), and pre-operative blood transfusion (p=.042). Stage IV-V CKD was associated with 75% increased odds of reamputation (OR=1.75, 95% CI=1.12-2.73), and higher stage of CKD was associated with greater reamputation rates (p=.003) where stage II CKD had the lowest reamputation rate (3.6%) and stage V with the highest reamputation rate (10.9%). A similar trend was seen with 30-day mortality (p<.00001). Conclusion: In the current study, CKD was significantly correlated with reamputation rates after TMA as well as 30-day mortality. In contrast to a previous report, dialysis was also associated with TMA failure and need for reamputation. Our findings corroborate previous findings correlating dialysis-dependent renal failure and mortality. Whether patients in certain stages of CKD would achieve better outcomes with higher-level amputation rather than a TMA should be investigated in future studies.