脊椎固定術における患者特異的格子ケージの設計と有限要素解析

Interbody cages used in spinal fusion require improved mechanical compatibility with surrounding bone to prevent collapse, stress shielding, and poor osseointegration. This study proposes a patient-specific cage design with graded stiffness distributions analogous to the Young modulus at the cervical spinal bone interface, aiming to enhance physiological load sharing and bone formation.

A synthetic database of spinal bone Young modulus values was used, incorporating anatomical regions (cervical, thoracic, lumbar) and patient-specific factors (age, bone density, health status). A parametric generative design approach allowed dynamic modification of lattice unit cell geometry to achieve target stiffness values (200-3000 MPa) while preserving structural integrity.

Finite element endplate analysis demonstrated a 30%-50% reduction in stress shielding compared with conventional solid or homogeneous mesh lattices. Additively manufactured prototypes showed tunable stiffness-porosity trade-offs, achieving yield strength ≥150 MPa while supporting osseointegration.

This study demonstrates improved load distribution and reduced risk of cage collapse compared with cadaveric spine data. Integrating computational design, biomechanical compatibility, and additive manufacturing may facilitate the development of patient-specific spinal implants with superior mechanical and biological performance.