Development of a Synthetic Spinal Dura for Surgical Training and Device Development

Introduction: Surgical training and device development is limited by the lack of physiologically relevant and low-cost synthetic (non-animal) models. We present a synthetic dura mater model designed to replicate the functional properties of biological dura mater for these applications.

Methods: A multi-part 3D computer-aided design (CAD) mold was created. The design featured an inner hollow shell and an outer semi-hollow shell. To ensure a consistent 1.1 mm spacing between the inner and outer shells, a central stabilizing shaft with click-lock mechanisms with .1 mm tolerance was incorporated into the outer shell. The CAD mold was then 3-D printed with either polylactic acid (PLA) or water-soluble polyvinyl alcohol (PVA) filament.

20A silicone rubber was used as molding material. After pouring degassed silicone into the outer shell, the inner shell was inserted and secured, and allowed to disperse evenly. Following the curing process, the PLA mold was physically removed while the PVA mold was immersed in water to dissolve the shells, resulting in silicone dura models with uniform thickness. The mock dura was then validated via tensile testing.

Results: More than 30 samples were created across three iterations of dura, and the mechanical properties of dura produced with the PVA mold were more comparable to physiological dura. Results of tensile testing of PVA dura approach literature stress/strain values for human dura (2 MPa). Notably, the 3-D printed (FDM) technique left a filamentous appearance to the molds, allowing the silicone to be both fused, but also carrying a pseudo-fibrous microarchitecture, revealed upon testing to failure.

Conclusion : The development of the modular CAD mold successfully facilitated the consistent production of uniform, physiologically comparable dura models. Further iteration is required to achieve comparable ultimate tensile strength. The use of water-dissolvable 3D printer filament preserved the mold's structural integrity, preventing tearing during silicone model removal and could be translated to other instances where simulation of tissues are needed.