Inter-Rater Reliability and Criterion Validity of a 3D Scanner to Produce Customized Short Leg Brace and Insole Orthoses

Background: The production of personalized short leg brace (SLB) and insole orthoses using three- dimensional (3D) printing offers efficiency and addresses limitations of traditional methods involving plaster molds. To fabricate 3D printing orthoses, a 3D scanner capable of acquiring personalized models of individual lower limb segments is necessary. Thus, investigating the reliability and validity of clinical application of a 3D scanner is a foundational step in customized orthoses production. Purpose: To verify the reliability and validity of lower leg and foot measurement data related to the SLB fitting process obtained through 3D lower limb scanning equipment. Study design: A cross-sectional and repeated-measures study design Methods: This study involved 40 adult participants. Inter-rater reliability of a novel 3D scanner was assessed through measurements performed by two different raters within a 3-day interval. Criterion validity of the 3D scanner was verified through comparison with physical measurements. Intraclass correlation coefficient (ICC) were used to investigate inter-rater reliability and criterion validity for measurement variables of the 3D scanner equipment. Results: The inter-rater reliability for the 3D scanner showed excellent correlation with ICC 0.90 or higher for most measurement variables. For the validity of the 3D scanner, ICC values of rater A ranged from 0.84 to 0.96 (p<0.01) and those of rater B ranged from 0.91 to 0.99 (p<0.01). The average ICC value was 0.86 for navicular height, medial malleolus height, and lateral malleolus height variables. However, most ICC values showed very good and reliable correlation. Conclusions: The inter-measurement reliability of each measurement variable through test-retest of the 3D scanner equipment showed a high level of good correlation. There was a high level of correlation for most measurement variables between caliper measurements directly performed by the rater and 3D scanner measurements. Therefore, production and clinical application of 3D printing-based personalized SLB and insole orthoses could correct, manage, and treat various musculoskeletal diseases of the lower extremities through clinical use of 3D scanner equipment.