Apatite Nuclei Treatment of Three-Dimensional Printed Porous Carbon-Reinforced Polyetheretherketone: A Case Study of Rat Femoral Segmental Defect.

Polyetheretherketone (PEEK) is a promising orthopedic implant material with an elastic modulus similar to that of human bone, offering potential advantages over titanium implants. However, PEEK is inherently biologically inert and hydrophobic, limiting its bone-bonding capacity. This study investigated the efficacy of apatite nuclei (AN) treatment in enhancing the bioactivity of 3D-printed porous carbon-reinforced PEEK (CR-PEEK) implants. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy analysis confirmed uniform AN treatment penetration throughout the porous structure, with a calcium peak detected both on the surfaces and in the interior regions. Forty-eight male Sprague-Dawley rats, divided into four groups, received segmental femoral defect implants based on structure (porous vs. dense) and AN treatment (with vs. without); the AN treatment effects were evaluated within each structural type. At 8 weeks, Micro computed tomography analysis demonstrated a significant enhancement in bone formation in AN-treated groups for both porous (p = 0.003) and dense (p = 0.004) implants. Histological evaluation revealed that AN treatment promoted bone ingrowth from 4.50% to 25.10% in porous implants (p = 0.006) and improved bone-implant contact from 2.94% to 9.33% in dense implants (p = 0.008). These findings demonstrate that AN treatment enhances osseointegration in CR-PEEK implants regardless of implant structure, and confirm for the first time that AN treatment effectively penetrates complex 3D porous geometries. The combination of 3D-printed porous architecture and AN treatment offers a technically feasible strategy for developing bioactive CR-PEEK implants, with the increased surface area of porous structures potentially augmenting the effects of AN treatment.