Disruptive technologies are rare phenomena. However, when they do come about, they have the potential to change the course of entire industries. Such is the case with the new three-dimensional (3D) printing technology from Carbon3D Inc. (Redwood City, California, USA), dubbed Continuous Liquid Interface Production (CLIP). With its innovative approach to additive manufacturing, CLIP has the potential to usurp and revolutionize 3D printing, with reverberations into several fields, including neurologic surgery 1).
A technique using an industrial rapid prototyping process by three-dimensional (3D) printing was developed, from which accurate spatial models of the nasal cavity, paranasal sinuses (sphenoid sinus in particular), and intrasellar/pituitary pathology were produced, according to the parameters of an individual patient. Image-guided surgical (IGS) techniques on two different platforms were used during endoscopic transsphenoidal surgery to test and validate the anatomical accuracy of the sinus models by comparing the models with radiological images of the patient on IGS. RESULTS: It was possible to register, validate, and navigate accurately on these models using commonly available navigation stations, matching accurately the anatomy of the model to the IGS images 2)
Neurosurgeons regularly plan their surgery using magnetic resonance imaging (MRI) images, which may show a clear distinction between the area to be resected and the surrounding healthy brain tissue depending on the nature of the pathology. However, this distinction is often unclear with the naked eye during the surgical intervention, and it may be difficult to infer depth and an accurate volumetric interpretation from a series of MRI image slices.
MRI data are used to create affordable patient-specific 3-dimensional (3D) scale models of the brain which clearly indicate the location and extent of a tumour relative to brain surface features and important adjacent structures.
This is achieved using custom software and rapid prototyping. In addition, functionally eloquent areas identified using functional MRI are integrated into the 3D models.
Preliminary in vivo results are presented for 2 patients. The accuracy of the technique was estimated both theoretically and by printing a geometrical phantom, with mean dimensional errors of less than 0.5 mm observed.
This may provide a practical and cost-effective tool which can be used for training, and during neurosurgical planning and intervention 3).
The advent of multimaterial 3D printers allows the creation of neurosurgical models of a more realistic nature, mimicking real tissues. Warren et al. used the latest generation of 3D printer to create a model, with an inbuilt pathological entity, of varying consistency and density. Using this model the authors were able to take trainees through the basic steps, from navigation and planning of skin flap to performing initial steps in a craniotomy and simple tumor excision. As the technology advances, models of this nature may be able to supplement the training of neurosurgeons in a simulated operating theater environment, thus improving the training experience 4).
Aoun RJ, Hamade YJ, Zammar SG, Patel NP, Bendok BR. Futuristic Three-Dimensional Printing and Personalized Neurosurgery. World Neurosurg. 2015 Oct;84(4):870-1. doi: 10.1016/j.wneu.2015.08.010. Epub 2015 Aug 20. PubMed PMID: 26299265 5).
Large format (ie, >25 cm) cranioplasty is a challenging procedure not only from a cosmesis standpoint, but also in terms of ensuring that the patient's brain will be well-protected from direct trauma. Until recently, when a patient's own cranial flap was unavailable, these goals were unattainable. Recent advances in implant computer-aided design and 3-dimensional (3-D) printing are leveraging other advances in regenerative medicine. It is now possible to 3-D-print patient-specific implants from a variety of polymer, ceramic, or metal components. A skull template may be used to design the external shape of an implant that will become well integrated in the skull, while also providing beneficial distribution of mechanical force in the event of trauma. Furthermore, an internal pore geometry can be utilized to facilitate the seeding of banked allograft cells. Implants may be cultured in a bioreactor along with recombinant growth factors to produce implants coated with bone progenitor cells and extracellular matrix that appear to the body as a graft, albeit a tissue-engineered graft. The growth factors would be left behind in the bioreactor and the graft would resorb as new host bone invades the space and is remodeled into strong bone. As described in a review, such advancements will lead to optimal replacement of cranial defects that are both patient-specific and regenerative 6).