Decision making regarding level of lower extremity amputation is sometimes challenging. Selecting an appropriate anatomic level for major amputation requires consideration of tradeoffs between postoperative function and risk of wound complications that may require additional operations, including debridement and/or conversion to above-knee amputation (AKA). We evaluated the utility of common, non-invasive diagnostic tests used in clinical practice to predict need for reoperations among patients undergoing primary, elective below knee-amputations (BKA) by vascular surgeons. Patients undergoing elective BKA over a five-year period were identified using CPT codes. Medical records were reviewed to characterize demographics, pre-amputation testing transcutaneous oxygen tension (TcPO), and ankle brachial index (ABI). Need for ipsilateral post-BKA reoperation (including BKA revision and/or conversion to AKA) regardless of indication was the primary outcome. Associations were evaluated using univariable and multivariable logistic regression models. Cut-points for TcPO values associated with amputation reoperation were evaluated using receiver operator characteristic (ROC) curves. We identified 175 BKAs, of which 46 (26.3%) required ipsilateral reoperation (18.9% BKA revisions and 14.3% conversion to AKA). Mean age was 63.3 ± 14.8 years. Most patients were male (65.1%) and white (72.0%). Mean pre-amputation calf TcPO was 40.0 ± 20.5 mmHg, and mean ABI was 0.64 ± 0.45. In univariable models, post-BKA reoperation was associated with calf TcPO [0.97 (0.94-0.99); P = 0.013] but not ABI [0.53 (0.19-1.46); P = 0.217]. Univariable associations with reoperation were also identified for age [0.97 (0.94-0.990); P = 0.003] and diabetes [0.43 (0.21-0.87); P = 0.019]. No associations with amputation revision were identified for gender, race, end stage renal disease, or preoperative antibiotics. Calf TcPO remained associated with post-BKA reoperation in a multivariable model [0.97 (0.94-0.99); P = 0.022] adjusted for age [0.98 (0.94-1.01); P = 0.222] and diabetes [0.98 (0.94-1.01); P = 0.559]. ROC analysis suggested a TcPO ≥ 38 mmHg as an appropriate cut-point for assessing risk for BKA revision (AUC 0.682; negative predictive value 0.91). Reoperation after BKA is common, and reoperation risk was associated with pre-amputation TcPO. For patients undergoing elective BKA, higher risk of reoperation should be discussed with patients with an ipsilateral TcPO < 38 mmHg.

中文翻译：

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经皮氧分压与踝臂指数作为膝下截肢术后再次手术预测因子的比较评估

关于下肢截肢程度的决策有时具有挑战性。为大截肢选择合适的解剖水平需要考虑术后功能和伤口并发症风险之间的权衡，伤口并发症可能需要额外的手术，包括清创和/或转换为膝上截肢（AKA）。我们评估了临床实践中常用的非侵入性诊断测试的效用，以预测血管外科医生接受初次选择性膝下截肢术 (BKA) 的患者是否需要再次手术。使用 CPT 代码识别在五年内接受选择性 BKA 的患者。审查医疗记录以描述人口统计特征、截肢前测试经皮氧分压 (TcPO) 和踝肱指数 (ABI)。无论适应症如何，主要结果是需要同侧 BKA 后再次手术（包括 BKA 翻修和/或转换为 AKA）。使用单变量和多变量逻辑回归模型评估关联性。使用受试者工作特征 (ROC) 曲线评估与截肢再手术相关的 TcPO 值的切点。我们确定了 175 个 BKA，其中 46 个（26.3%）需要同侧再次手术（18.9% 为 BKA 修正，14.3% 转换为 AKA）。平均年龄为 63.3 ± 14.8 岁。大多数患者是男性（65.1%）和白人（72.0%）。截肢前小腿平均 TcPO 为 40.0 ± 20.5 mmHg，平均 ABI 为 0.64 ± 0.45。在单变量模型中，BKA 再次手术后与小牛 TcPO 相关 [0.97 (0.94-0.99)；P = 0.013] 但不是 ABI [0.53 (0.19-1.46)；P = 0.217]。还确定了年龄与再次手术的单变量关联[0.97 (0.94-0.990)；P = 0.003] 和糖尿病 [0.43 (0.21-0.87)；P = 0.019]。没有发现性别、种族、终末期肾病或术前抗生素与截肢修复之间存在关联。在多变量模型中，小牛 TcPO 仍与 BKA 术后再次手术相关 [0.97 (0.94-0.99)；P = 0.022]根据年龄调整[0.98（0.94-1.01）；P = 0.222] 和糖尿病 [0.98 (0.94-1.01)；P = 0.559]。ROC 分析建议 TcPO ≥ 38 mmHg 作为评估 BKA 翻修风险的适当切点（AUC 0.682；阴性预测值 0.91）。BKA 后再次手术很常见，再手术风险与截肢前 TcPO 相关。对于接受择期 BKA 的患者，应与同侧 TcPO < 38 mmHg 的患者讨论再次手术的较高风险。