[Quantitative volumetric analysis of the lower extremity: validation against established tape measurement and water displacement]

BACKGROUND: Tape measures continue to be used for the diagnosis and evaluation of lipoedema and lymphoedema in the clinical routine. Extremity volumes are calculated based on standardised circumferential measurements. Other volume measurements such as water displacement are not applied on a regular basis. This study aimed to evaluate a 3D scanner as an alternative and reproducible tool to objectively measure the volumes of the lower extremity. PATIENTS, MATERIALS AND METHOD: We used a commercially available 3D scanner, the Artec Eva®, to perform 3D scans of the lower extremities on 20 subjects and calculated the volume using the appropriate software. In addition, limb volume was determined with standardised methods using the circumferential method (cone method and disc method) and the water displacement technique. The results and the time taken to perform the three measurement methods were documented and statistically evaluated. RESULTS: There were no significant deviations between the results from 3D volumetry and water displacement (p > 0.05). The cone method significantly overestimated the volume measured by water displacement and 3D volumetry. The disc method revealed no statistically significant differences, but clinically relevant differences with a high variance in the 95 % confidence interval. All methods demonstrated high positive correlations with each other. Water displacement was the most timeconsuming method. CONCLUSION: Our findings obtained from the examination of 40 lower extremities show that 3D scans and software-based volumetric calculations can achieve objective and reproducible measurements in a relatively short time. The deviation from the gold-standard method of water displacement is small. Compared with the cone and disc method, however, we observed clinically relevant deviations with a high variance. We therefore recommend the 3D scan procedure for the objective documentation of conservative and surgical treatments for lipoedema or lymphoedema and have incorporated it into our clinical routine.