Prognostic value of toe pressure measurements in patients with diabetic foot ulcers and medial arterial calcification

Objectives: Diabetic foot ulcers (DFU) are one of the most serious chronic diabetes related complications. Since medial arterial calcification (MAC) can be present in patients with a DFU, toe pressure (TP) measurements are advised to grade potential ischemia. However, the value of TP to predict clinical outcomes in this group of patients is poorly understood. Therefore, the primary aim of this study was to investigate the relationship between TP values and ulcer healing in patients with DFU and concomitant MAC.

Methods: A single-centre retrospective cohort study was conducted. Patients were included if they were 18 years or older, presented with a DFU, had a TP measurement and concomitant MAC in the same limb. MAC was defined as an ABI above 1.30, or incompressible arteries during ABI measurement. Multi-state models were fitted to analyse the outcomes of interest (ulcer healing, revascularisation, amputation and mortality).

Results: In total, 148 patients were included. During the 180 days follow-up, the cumulative incidence of a healed ulcer was 34% (95% Confidence Interval [CI] 27 - 42%), whereas 32% (95% CI 26 - 41%) of patients had a persisting open wound. An approximately positive linear correlation was observed between TP values and the probability of ulcer healing, regardless of whether patients had undergone a revascularisation procedure. However, the absolute healing rate was low, and no clear distinction could be made for intermediate TP values (between 30 and 80 mmHg).

Conclusions: Lower TP values are correlated with non-healing of a DFU in patients with MAC, but clear absolute differences in healing are only seen between very low (below 30 mmHg) and high (above 80 mmHg) measurements. For intermediate TP values, the predictive strength of ulcer healing is weak. This should be of particular importance when grading ischemia in this subgroup of patients in wound classification systems.