Adaptive Mechanism for Designing a Personalized Cranial Implant and Its 3D Printing Using PEEK

Abstract

The rehabilitation of the skull's bones is a difficult process that poses a challenge to the surgical team. Due to the range of design methods and the availability of materials, the main concerns are the implant design and material selection. Mirror-image reconstruction is one of the widely used implant reconstruction techniques, but it is not a feasible option in asymmetrical regions. The ideal design approach and material should result in an implant outcome that is compact, easy to fit, resilient, and provides the perfect aesthetic and functional outcomes irrespective of the location. The design technique for the making of the personalized implant must be easy to use and independent of the defect's position on the skull. As a result, this article proposes a hybrid system that incorporates computer tomography acquisition, an adaptive design (or modeling) scheme, computational analysis, and accuracy assessment. The newly developed hybrid approach aims to obtain ideal cranial implants that are unique to each patient and defect. Polyetheretherketone (PEEK) is chosen to fabricate the implant because it is a viable alternative to titanium implants for personalized implants, and because it is simpler to use, lighter, and sturdy enough to shield the brain. The aesthetic result or the fitting accuracy is adequate, with a maximum deviation of 0.59 mm in the outside direction. The results of the biomechanical analysis demonstrate that the maximum Von Mises stress (8.15 MPa), Von Mises strain (0.002), and deformation (0.18 mm) are all extremely low, and the factor of safety is reasonably high, highlighting the implant's load resistance potential and safety under high loading. Moreover, the time it takes to develop an implant model for any cranial defect using the proposed modeling scheme is very fast, at around one hour. This study illustrates that the utilized 3D reconstruction method and PEEK material would minimize time-consuming alterations while also improving the implant's fit, stability, and strength.

Keywords: 3D printing; 3D reconstruction; PEEK; accuracy evaluation; customized implant; finite element analysis.

Figure 1

Deriving a cranial implant using a hybrid system.

Figure 2

Steps involved in the reconstruction of a tumor-resected implant template. (a) DICOM file. (b) 3D model. (c) Experimental Segmental tumor making. (d) Tumor resected template for implant design.

Figure 3

Modeling of the customized implant (a) asymmetrical skull defect; (b) identification of distorted region; (c) recognition of curves tangent to surface; (d) interpolation of curves; (e) surface generation; (f) surface acquired through curves; (g) splitting appropriate surface patch; (h) conversion of surface to part model; (i) implant placed on the skull.

Figure 4

(a) Cranial PEEK implant on the skull model; (b) mesh generation; (c) cross-sectional view of the screw, implant and bone; (d) exertion of forces at the three implant regions; (e) representation of the fixed supports and the nodal force.

Figure 5

INTAMSUITE software for the orientation and support generation of the PEEK 3D model.

Figure 6

(a) Intamsys 3D Printer used in the fabrication of the customized (b) PEEK cranial Implant; (c) Support structures bottom view; (d) removal of the supports using plyers; (e) the PEEK cranial implant after the supports’ removal.

Figure 7

(a) 3D printed skull model of the ABS material with supports, (b) ABS skull model after the removal of the supports, and (c) the rehearsal and fitting evaluation of the PEEK cranial implant on the ABS skull model.

Figure 8

Scenarios for redesigning the implant.

Figure 9

(a) Scanning system; (b) acquired point cloud data.

Figure 10

Procedure to estimate the fitting accuracy of the implant.

Figure 11

Computation of implant’s overall fitting accuracy. (a–c) Phase 1: Accuracy of the modeling approach; (a′,b′,b″,c′) Phase 2: Fabrication accuracy.

Figure 12

FEA results illustrating: (a–c) Von Mises stress at the point, (d–f) Von mises strain, (g–i) total deformation, and (j–l) the factor of safety at points X, Y and Z.

Figure 13

Deviation in the outward direction. (a) Healthy skull and the designed implant (virtual model); (b) designed implant (virtual model) and the fabricated implant.

Figure 14

Gap Analysis between the implant and the skull. (a) Defect length in the Y-direction; (a’) implant length in the Y-direction; (b) defect width in the X-direction; (b’) implant width in the X-direction.