Investigating mechanical properties for developing a human infant cranial bone surrogate in pediatric craniofacial surgery

Beyond the surgeon's feedback on bone behavior in the operating room, there is a paucity of data present in the literature on the mechanical properties of pediatric calvarial bone. The present study tested the calvarial bone of four species (Adult Humans, Dog, Pig, and Monkey) to find the mechanical properties. Three types of tests were performed; flexural, compression, and torsion to mimic how bone is handled during the surgery and the results were further compared with the existing published data for human pediatric calvarium. Test results indicated a significant difference between the modulus (p = 0.006 for flexural, 0.0002 for compression, and 0.0075 for shear) and strength (p = 0.0005 for flexural, 0.0051 for compression, and p < 0.0001 for shear) amongst the tested groups. Compared with published data, the flexural properties of the 12-day-old pig were found to be closest to that of an 11-month-old human infant (E = 0.783 GPa). In contrast, the adult human was found to have a flexural modulus 3.9 times that of the pig, and specimen thickness of adult humans had a strong positive correlation (r = 0.77, p = 0.0237) with its flexural modulus, strengthening the disparity between infant and adult human skull bone material properties. Based on these results, neonatal piglet calvarium was selected as a model for 1-year-old human infants commonly presented for total cranial vault reconstruction. These results will help to inform the development and use of new technologies and techniques for bone graft manipulation in the laboratory and the operating room.