Background: The posterior flap is a conventional technique for closing a below-knee amputation (BKA) that uses the gastrocnemius and soleus muscle and relies on the popliteal and posterior compartment arteries. If the prior mentioned arterial blood supply is compromised, this flap likely relies on collateral flow. The purpose of this study is to identify and differentiate any significant associations between preoperative popliteal and tibial arterial flow and BKA outcomes and patient-reported function.
Methods: A retrospective review identified patients from a single tertiary wound care center who received BKAs and angiogram between 2010 and 2017 by a single surgeon. BKA complications, wound healing, and amputee ambulatory status at latest follow-up were all stratified for differences according to baseline tibial vessel run-off (VRO) status, popliteal artery patency, and popliteal angioplasty outcome. Chi-square, Fisher's exact, and Wilcoxon rank sum tests were used with significance defined as p ≤ 0.05.
Results: BKAs were performed on 313 patients, of which, 167 underwent preoperative angiography. Thirty-two were excluded due to lack of adequate follow-up leaving a total of 135 patients in the studied population. Diabetes was present in 87%, and 36% had end-stage renal disease. By the study's conclusion, 92% of BKAs had fully healed, with median time-to-healing of 79 days (range 19-1314 days). 60% of patients were ambulatory at 9.5 months. Higher VRO was associated with higher healing rates and lower complications and time-to-healing. The conversion rate of BKA to above-knee amputation (AKA) was 4%. Preoperative popliteal patency was associated with higher postoperative ambulation rates when compared to patients without popliteal flow preoperatively (patent: 71/109, 65%; occluded: 10/26, 40%; p = 0.02) and independently increased the likelihood of postoperative ambulation.
Conclusions: The posterior flap design for BKA works even in the setting of popliteal occlusion. Complication rates are higher in patients with more compromised blood flow, which may ultimately lead to AKA. Given poor ambulation rates in patients who undergo AKA, the results of this study should encourage surgeons to consider a more functional BKA, even in instances when the popliteal artery is occluded.
Keywords: Below-knee amputation; activities of daily living; ambulation; vascular studies; vessel run-off.