PMC

Yellow: positive control, green: models not statistically different from the positive control, blue: models trending towards a statistical difference when compared to the positive, red: models statistically different from the positive control.

(A) Cervical vertebrae placed in a tray following natural dissection by beetle digestion. (B) 3D printed models of cervical vertebrae and a box, made of Vero resin. (C) Silicon mold obtained following the addition of Mold Max 20 to the 3D printed box shown in B. (D) Dissected vertebrae were inserted into the silicon mold in C, and fixated in anatomical alignment with epoxy.

Model C made of nylon PA 12 using an EOS Formiga P100 printer and selective laser sintering printing technology. Note the characteristic hyperechoic appearance created by the strong reflection of the ultrasound beam by the model, simulating bone (*). The joint space is visible as a gap between the cranial (left) and caudal (right) articular processes (white arrow).

Both models are printed using the SLA printing technology and a surface resolution of 100 μm. The shell thickness of both models differs (2 mm vs. 5 mm). Note the similar cortical surface of bone (gold standard) and the 5 mm thick model, whereas multiple reflections are displayed beneath the surface of the 2 mm thick model.

The models are printed with a surface resolution of 100 μm and a shell thickness of 5 mm. (A) Model H: Onyx nylon with chopped carbon fiber, Markforged Onyx Two, fused deposition modeling. (B) Model I: polylactic acid, Ultimaker 3 Extended, fused deposition modeling. (C) Model D: gypsum, ProJet CJP 660 Pro, ColorJet Printing. (D) Model M: polylactic acid, Makerbot Replicator +, fused deposition modeling.

Yellow: positive control, green: models not statistically different from the positive control, blue: models trending towards a statistical difference when compared to the positive control, red: models statistically different from the positive control. Question 3 and 4 (graphs C and D respectively) did not reach a significant F value and post-hoc tests were therefore not performed; all models are displayed in grey. ^a Note that the model rank order based on the p values and medians differs for graph A since the Friedmans test from which the p values were calculated is based on the rank sums and not the medians. ^b The mean and median scores are respectively reported for normally and non-normally distributed data.