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Evaluating measurement accuracy of a structured light scanner versus goniometry for the assessment of angulation
Allen E. Siapno, BS, Brendan C. Yi, BA, Aswani Bolagani, MPH, Doug Daniels, MLIS, Renea Sturm, MD.
University of California Los Angeles, Los Angeles, CA, USA.

BACKGROUND: A specific aspect of the hypospadias phenotype that may contribute to long-term outcomes is the presence of penile curvature and the adequacy of its surgical correction. The current gold standard to assess this angle is intraoperative goniometry of an erect penis. The aim of this study is to evaluate the measurement accuracy and reliability of a structured light scanner versus goniometry for angle assessment in a laboratory setting.
METHODS: Blocks with specified angles (10 to 45 degrees; 1" width, 2" height) were printed using a Zortrax M200 3-dimensional (3D) printer (0.2% accuracy). Each block was then scanned in the Lux lab with an Artec Space Spider to create a complete digital model in Artec Studio 13. These models were imported into the software Autodesk Inventor in which the mean of six automated angle measurements through the central plane was obtained for each model. Following completion of standardized education, blinded participants measured each block angle using a Baseline digit goniometer.
RESULTS: Four 3D printed blocks were evaluated. 5 models per block were scanned; 10 participants completed goniometry. Mean angle measurements and standard error for each angle is noted in the attached table. Test-retest reliability using the scanner was excellent (ICC 0.99); inter-rater reliability of goniometry was moderate (ICC 0.78). There was no significant difference between naive and expert participants in assessment of goniometric angle (p=0.7).
CONCLUSIONS: This study demonstrated excellent reliability of an off-the-shelf, readily used, handheld technology developed for the International Space Station when applied to measurement of angulation in small blocks. In particular, we have demonstrated high-fidelity model creation of angles that have historically been most challenging to measure using either goniometry or eyeball analysis in a 3D printed penile model (Villanueva SPU 2019). Structured light scanning may provide reliable, reproducible phenotypic analysis of congenital genitourinary conditions for future intraoperative and database development applications.

Table: Overall Angle Measurements
Block AngleGoniometerDevice
3D Printedn=10 subjectsn=5 models/block
DegreesMeanSEMMeanSEM
1013.93.19.750.01
1517.91.7214.710.03
3027.81.4229.950.02
4542.31.5244.820.01

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