Assessing the Utility of Toe Arm Index and Toe Pressure in Predicting Wound Healing in Patients Undergoing Vascular Intervention

Background: Objective measures of perfusion such as an ankle-brachial index (ABI) and toe pressure remain important in prognosticating wound healing. However, the use of ABI is limited in patients with incompressible vessels and toe pressure may not be comparable across patients. While a toe arm index (TAI) may be of value in this setting, its role as clinical indicator of perfusion for healing in patients with lower-extremity wounds has not been well established.

Methods: A retrospective review was performed of all vascular patients with lower-extremity wounds that underwent peripheral vascular intervention between 2014-2019. Data regarding patient demographics, comorbidities, TAI, ABI, toe pressures, and the wound, ischemia, and foot infection (WIfI) score were collected. Associations between patient variables and wound healing at various time points were evaluated.

Results: A total of 173 patients (67.7 ± 10.9 years; 71.1% male) were identified with lower-extremity wounds. Most patients underwent endovascular intervention (77.5%). Patients were followed for a median of 416 (IQR 129-900) days. Mean postoperative TAI was 0.35 ± 0.19 and mean WIfI score was 2.60 ± 1.17. Nine percent (15) of patients healed within 1 month, 44.8% (69) healed within 6 months, and 65.5% (97) healed within 1 year of revascularization without need for major amputation. Those that healed within 1 year without any major amputation did not differ from those that did not heal based on age, gender, race, comorbidities, periprocedural medications, or procedures performed. However, patients that healed without major amputation had a higher postoperative TAI (0.38 vs. 0.30, P = 0.02), higher toe pressure (53 vs. 40 mm Hg, P = 0.004), and lower WIfI score (2.26 vs. 3.12, P < 0.001). Patients that healed with 1 year without requiring any amputation had similar associations with postoperative TAI, toe pressure, and WIfI. Additionally, they were more likely to be White (P = 0.019) and have an open surgical procedure (P < 0.001) and less likely to have chronic kidney disease (P = 0.001) or diabetes (P = 0.008). A Youden index was calculated and identified a TAI value of 0.30 that optimized sensitivity and specificity for wound healing. The area under the curve for TAI as a predictor of wound healing was 0.62.

Conclusions: Higher postoperative TAI is associated with higher odds of wound healing without need for major amputation. Toe arm index is therefore a useful tool to identify patients with adequate arterial perfusion to heal lower-extremity wounds. However, the area under the curve is poor for TAI when used as a sole predictor of wound healing potential suggesting that TAI should be one of multiple factors to considered when prognosticating wound healing potential.