Assessment of the Efficiency of Measuring Foot and Ankle Edema with a 3D Portable Scanner

Background: To prospectively evaluate the reliability of a portable optical scanner compared to the water displacement technique for volumetric measurements of the foot and ankle and to compare the acquisition time associated with these two methods. Methods: Foot volume was measured in 29 healthy volunteers (58 feet, 24 females and 5 males) by a 3D scanner (UPOD-S 3D Laser Full-Foot Scanner®) and by water displacement volumetry. Measurements were performed on both feet, up to a height of 10 cm above the ground. The acquisition time for each method was evaluated. The Kolmogorov-Smirnov test, Lin's Concordance Correlation Coefficient, and a Student's t-test were performed. Results: Mean foot volume was 869.7 +/- 165.1 cm³ (3D scanner) versus 867.9 +/- 155.4 cm³ (water-displacement volumetry) (p < 10^-5). The concordance of measurements was 0.93, indicative of a high correlation between the two techniques. Volumes were 47.8 cm³ lower when using the 3D scanner versus water volumetry. After statistically correcting this underestimation, the concordance was improved (0.98, residual bias = -0.03 +/- 35.1 cm³). The mean examination time was 4.2 +/- 1.7 min (3D optical scanner) versus 11.1 +/- 2.9 min (water volumeter) (p < 10^-4). Conclusions: Ankle/foot volumetric measurements performed using this portable 3D scanner are reliable and fast and can be used in clinical practice and research.