Abstract 128: Potential Virulence of MRSA and Enterococcus in Patients Undergoing Free Tissue Transfer for Chronic, Non-healing Lower Extremity Wounds

Abstract

PURPOSE: Chronic wounds in the lower extremity (LE) often fail to heal, necessitating free tissue transfer (FTT) for limb salvage. Patients in whom microsurgical LE reconstruction is indicated are often highly comorbid and prone to infection. In LE free flap studies, Hashimoto et al.1 and Corten et al.2 reported common wound colonization with Staphylococcus and Enterococcus, findings similar to those within patients of our tertiary-care center. While larger studies have investigated the microsurgical significance of Staphylococcus, few, if any, have investigated Enterococcus. The purpose of this study was to investigate the potential virulence of bacterial colonization on microsurgical limb-salvage outcomes. METHODS: Between April 2011 and May 2018, 140 LE FTT procedures were performed by the corresponding author for reconstruction of chronic wounds. The average patient age was 54.2yrs, the average BMI 29, and 50.3% of patients had diabetes. An average of 2.65 wound-bed debridements were performed per patient prior to FTT. Deep, intra-operative qualitative tissue cultures were obtained. Average follow-up after FTT was 17 months. Using multivariate analysis we studied the implications of wound colonization with Methicillin-resistant Staphylococcus aureus (MRSA) or Enterococcus on microsurgical success and limb-status after closure was attempted via FTT. RESULTS: Overall microsurgical success and limb-salvage rates were 91.4% (128/140) and 85% (119/140), respectively. Flaps contaminated with Enterococcus at the time of surgery were at increased risk for failure (OR6.21, p=0.05). In addition, risk for flap infection was greater in patients with wounds contaminated with Enterococcus during preoperative debridement (OR4.3; 95%CI, 1.518–11.997; p=0.006). Major amputation risk was increased in patients with wounds previously contaminated with MRSA (OR9.08; 95%CI, 2.721–30.320; p=0.0003), patients with positive Enterococcus cultures at the time of surgery (OR6.4; 95%CI, 1.21–34.43; p=0.03), and patients who developed flap infection with Enterococcus (OR19.7; 95%CI, 1.9–199.5; p=0.01). CONCLUSION: FTT can salvage the limb that has otherwise failed all other attempts at wound closure, obviating the need for major amputation. However, the medical demographics of this patient population and technical complexity of FTT make microsurgical outcomes vulnerable to many factors. Thus, part of restoring limb function in these patients is optimizing patient condition by mitigating perioperative risk factors. The negative impact of colonization of chronic wounds with bacteria, including MRSA, has been described. However, studies placing primary focus on individual pathogens in this population are lacking. Our results indicate potential adverse outcomes associated with noninfectious MRSA and Enterococcus colonization of chronic leg wounds. With this information, microsurgeons could stratify patients by infectious etiology for risk of adverse events, potentially allowing for earlier, mitigating treatment in the preoperative course. CITATIONS 1. Hashimoto I, Abe Y, Morimoto A, Kashiwagi K, Goishi K, Nakanishi H. Limb salvage and vascular augmentation by microsurgical free flap transfer for treatment of neuropathic diabetic foot ulcers. J Med Investig. 2014. doi:10.2152/jmi.61.325 2. Corten K, Struelens B, Evans B, Graham E, Bourne RB, MacDonald SJ. Gastrocnemius flap reconstruction of soft-tissue defects following infected total knee replacement. Bone Jt J. 2013. doi:10.1302/0301-620X.95B9