Predictors of Postoperative Complications in Patients Undergoing Below Knee Amputation

Abstract

To identify risk factors for development of wound complications in patients undergoing a below knee amputation (BKA). Retrospective chart review was performed of patients who underwent BKA between January 1, 2014, and December 31, 2016. Data on patient demographics, preoperative comorbidities, limb salvage attempts (LSA) before amputation, and outcomes after BKA were collected for each limb analyzed. LSAs were defined as endovascular revascularization, open surgical revascularization, wound debridement requiring intravenous sedation or general anesthesia, and amputation at or below the level of transmetatarsal amputation. Postoperative wound complications were defined as residual limb wound infection or nonhealing wound. Primary outcome was the need for procedural reintervention on the ipsilateral limb within 12 months of the initial amputation (washout, debridement, or revision to higher level). There were 155 BKAs identified in 129 patients. Mean age at amputation was 63.7 ± 11.7 years. Of BKAs, 72.3% were performed on male patients. Mean follow-up was 836 days after index amputation. Patients with a history of deep venous thrombosis (DVT) in either lower extremity before amputation had a higher risk of developing post-BKA wound complications (26.7% vs 12.7%; P = .034). Of patients who did not have a preoperative popliteal pulse, 60.0% developed wound complications within 12 months, compared to 24.2% of those with a popliteal pulse (P = .004). Additionally, of patients without a popliteal pulse, 31.3% eventually needed revision to above the knee amputation, compared to 9.7% of those with a popliteal pulse (P = .013). If a patient experienced a complication after any LSA (postoperative DVT, Clostridium difficile, community-acquired infection, need for postoperative transfusion, acute cardiopulmonary event, or need for unplanned surgical reintervention within 24 hours), their risk for developing wound complications after BKA more than doubled (45.6% vs 22.0%; P = .003). Patients admitted more than 17 cumulative days after LSAs were more likely to experience a BKA complication (38.1% vs 22.0%; P = .030). Patients who underwent two or more prior revascularizations experienced a higher rate of BKA complications (36.7% vs 21.0%; P = .032). Risk factors for wound complications after BKA include prior DVT, absence of a popliteal pulse, complications with prior LSA, longer total admissions for LSA, and multiple revascularizations before amputation. Absence of a popliteal pulse increases the risk of eventual need for above the knee amputation by over three-fold. This research suggests that a complete pulse examination and greater scrutiny regarding the usefulness of multiple LSAs may decrease rates of wound complications after BKA.