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

Abstract

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.