PMC

FIG. 3. Gross appearance of the lesion showing a fragile cortical shell and spongy, soft tissue.

Structural characteristics of bone. Bone is comprised of a dense cortical shell that surrounds a spongy trabecular bone network. The periosteal diameter combined with the endosteal diameter determines cortical thickness. The size of bone along with cortical thickness and porosity significantly contribute to bone strength. The inner trabecular compartment contains a network of plates and rods that also contribute to bone strength

Scanning electron microscope images of thin sections from selected eggshells showing microstructures of the shell units. A–C: Radial section of Ellipsoolithus khedaensis egshells belonging most likely to abelisaurid theropods. A: Distinct two layered structure showing a basal mammillary zone and an upper spongy zone. B: Same as A, closer view. C: Distinct calcite spherulite structure of the mammillae. D–F: Radial sections Tubospherulithic Megaloolithus rahioliensis eggshells belonging most likely to titanosaurid sauropods. D. Discrete shell units showing spherulite structure of basal mammillae and radiating calcite crystals. E–F: calcite crystal radiating from the mammillae and fanning to the top of the shell units.

(A) L3 vertebrae with PLA shell removed demonstrating the spongy PVA matrix (white arrow). Pedicle screws are seen within the matrix. (B) Laminar screws placed in the C2 experimental model without model failure. (C & D) Fluoroscopic images obtained post instrumentation. The PVA infill matrix can be seen under X-ray (black arrow).
PLA, polylactic acid; PVA, polyvinyl alcohol