Bioelectrical impedance: a new method for measuring post-traumatic swelling.

Objectives: The aim of this pilot study was to investigate whether measurement of the bioelectrical impedance of the lower limb could be used to measure the swelling resulting from acute ankle fracture. Methods: The impedance of each ankle was measured in 14 patients with isolated acute ankle fracture. The degree of ankle swelling was also directly assessed by measurement of the ankle circumference and diameter and by the water displacement method. A control group of 17 healthy subjects with uninjured ankles was similarly assessed. Results: The impedance of the ankle was significantly reduced in patients with ankle fracture, and there was a strong inverse relationship between the degree of this reduction and the amount of swelling as directly measured. The relationship was stronger using the impedance method than the circumference and diameter methods. Conclusions: We conclude that bioelectrical impedance can be used to measure ankle swelling in the presence of injury and could potentially be used both to monitor swelling clinically and as a research tool in studies of swelling management. More research is required to further define the potential role for this technique.