A mechanical model based on watermelons for the study of dynamic cranial remolding orthoses

Deformational plagiocephaly is a head deformity in newborns that can be treated in some cases with cranial remodeling orthoses that constrain head growth to reshape it. To mitigate complications arising from the treatment with these orthoses, and for the exploration of novel functionally graded lattice structures, a biological model that mimics some aspects of human head growth could provide a development and testing platform for these lattices. In this work, we propose a novel biological model of infant heads in which watermelons are used for the study of cranial remodeling orthoses during head growth and the correction of deformities. First, we reshaped ten watermelons with infant head shapes with deformities via custom molds, which were generated from MRI scans of infants with head deformities. The shaped watermelons were subsequently compared with the original head scans to assess the accuracy of the process via standard clinical measurements. Finally, the growth of four of these watermelon shapes was monitored after the molds were left for several days. The watermelon head shapes registered an average shape difference from the original models of 1.6 millimeters, with a standard deviation of 1.88 millimeters. After leaving the molds, the shapes continued growing, maintaining the ability to be reshaped by external physical constraints. By mimicking two key mechanical aspects of head growth in newborns - growth and deformability - this preliminary approach to a biological phantom offers a promising platform for studying the mechanical behavior of novel lattice structures in the development of cranial remodeling orthoses.