Conceptual design of growth-adaptive calcium phosphate cement implants for large paediatric cranial defects

This study presents the development of a modular, growth-adaptive skull implant composed of calcium phosphate cement (CPC) intended for the reconstruction of large cranial defects in paediatric patients. The primary objective was to establish a systematic design and manufacturing workflow enabling patient-specific, resorbable implant solutions that accommodate dynamic skull growth while maintaining initial structural stability and supporting biological integration. A six-phase methodology was implemented, including CT-based geometry acquisition, image segmentation, CAD-based implant modelling, and additive manufacturing using material extrusion. The implant design was subdivided into ten interlocking segments employing an S-shaped segmentation strategy and S-shaped cutting profiles to optimise inter-segment interaction, geometric stability, and guided mobility. A compact radial stabilisation and guidance structure was integrated to support geometrically critical regions while preserving overall porosity. Fixation was achieved using absorbable sutures in combination with form-fitting plug connections. The workflow was applied to a bilateral frontal cranial defect with an approximate area of 160 cm². The implant model was successfully designed and manufactured, demonstrating high geometric fidelity, effective modularity, and good manufacturability within the defined process chain. The segmentation strategy enabled controlled inter-segment mobility while maintaining overall implant coherence. No biomechanical simulations or biological evaluations were performed at this stage, as the focus was deliberately placed on validating the functional design and manufacturing process. The presented approach demonstrates the technical feasibility of a modular, growth-adaptive CPC-based cranial implant and establishes a validated design and manufacturing framework. This work provides a fundamental basis for future biomechanical, biological, and clinical investigations aimed at advancing growth-adaptive implants for paediatric cranial reconstruction.