170 Towards Global Availability of Patient-Specific Cranial Implants: Creation and Validation of CranialRebuild Freeware Application

Abstract

INTRODUCTION: Financial restrictions limit attainment of hermetically-precise, patient-specific cranial implants (PSCIs) after decompressive hemicraniectomy (DHC) in developing countries. Several authors have reported use of image-segmentation, modeling software, and 3D printers to develop low-cost alternatives for PSCIs. However, technical expertise and time requirements have prevented widespread utilization of this technique. METHODS: A freeware algorithm titled CranialRebuild was constructed with the following capabilities: after upload of DICOM files, the normal side is analyzed in reference to the side of DHC, a Boolean subtraction algorithm is used to obtain a virtual image of the desired implant, a two-piece virtual (.STL) model of a negative of the implant is then generated. Following construction, CranialRebuild was evaluated in four cadaveric specimens. In each specimen, a standard DHC was performed. Post-DHC CT imaging were used to obtain a virtual model of the negative of the implant, which was then printed using low-cost polylactic acid (PLA). Methylmethacrylate cement was used to generate a PSCI from the PLA mold. The PSCIs were re-implanted into cadaveric specimens. Pictures were obtained, and cosmesis was subjectively evaluated using a 5-point Likert scale. RESULTS: Two of the four heads received a grade of 4/5, indicating optimal cosmesis could be obtained following minimal post-processing modification. Two of the heads were graded as 3/5, indicating optimal cosmesis could be obtained following moderate post-processing modification. CONCLUSIONS: The CranialRebuild freeware algorithm can be used to create low-cost, hermetically-precise PSCIs at a fraction of the price of third-party vendors. This technology is expected to greatly improve accessibility of customized cranial implants worldwide.