Comparative analysis of mechanical and drilling properties: Human skull vs. 3D-printed replicas for neurosurgical training

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Neurosurgery is one of the most difficult surgical disciplines, making neurosurgical simulation crucial for learners. 3D printing is increasingly used for this simulation due to its accessibility and cost-effectiveness compared to conventional methods. Previous studies have qualitatively evaluated the efficacy of 3D printing models for burr hole and craniotomy simulation using surgeon feedback. This study quantitatively evaluates the mechanical properties of human skulls and compares them with 3D-printed skulls to identify the necessary materials and technologies for accurate replication in neurosurgical training. Vickers hardness, compression, and drilling simulation tests were conducted on human cadaveric skulls and 3D-printed models manufactured using Fused Filament Fabrication (FFF), Stereolithography (SLA), and Material Jetting (MJ) technologies. Uniaxial force during a simulated burr hole procedure was measured as drilling progressed through the outer table (OT), diploë and inner table (IT) of the skull. The results showed that different 3D printing technologies and materials have qualities corresponding to each of the three layers of the human skull. For instance, the White Resin 40 model was the closest match to the OT of human skull, exhibiting the lowest mean difference of drilling modulus of 1.98. The OT of the human skull had a Vickers hardness of 38.6 ± 5 HV0.05. The closest 3D-printed models were SLA White at 16.6 ± 0.3 HV0.05 and Rigid 10K at 65.7 ± 3 HV0.05. In terms of mechanical properties, the human skull demonstrated a compression modulus that closely matched the SkullSTN 2, PC 60, PEEK 40, and PEEK 60, with differences of less than 0.1 GPa. These findings demonstrate the effectiveness of drilling simulation tests in evaluating various materials and infills to refine models before neurosurgeon evaluation, enabling the identification of an optimal 3D-printed training model for simulating burr hole procedures.