Validity and Reliability of Craniofacial Anthropometric Measurement of 3D Digital Photogrammetric Images

Abstract

Background: Direct anthropometry performed during a patient examination is the standard technique for quantifying craniofacial dysmorphology, as well as for surgical planning and outcome assessment. Several new technologies have been designed to computerize anthropometric measurements, including three-dimensional (3D) digital photogrammetry. These digital systems have the advantage of acquiring patient craniofacial surface images quickly and noninvasively. Before morphometry using digital photogrammetry can be applied in clinical and research practice, it must be assessed against direct anthropometry. Objective: To evaluate the validity and reliability of facial anthropometric linear distances imaged by 3D digital photogrammetry with respect to direct anthropometry. Design, Setting, Participants, Measures: Standard craniofacial distances were directly measured twice on 20 normal adult volunteers. Craniofacial surfaces were also imaged using the 3dMDface digital photogrammetry system, and distances were digitally measured twice for each subject. Validity measures of accuracy and bias (for direct versus digital measurements) and reproducibility measures of precision and test-retest reliability (for repeated sets of digital measurements) were computed. Results: Seventeen of the 18 direct measurements correlated highly with digital values (mean r = 0.88). The correlation for one measurement (upper prolabial width) was not statistically significant. The overall precision of all 17 digital measurements was less than 1 mm, and the reliability was high (mean r = 0.91). Conclusions: Craniofacial anthropometry using the 3dMDface System is valid and reliable. Digital measurements of upper prolabial width may require direct marking, prior to imaging, to improve landmark identification.