Treating fractures involving complex bone defects remains a major challenge in regenerative medicine. Additive manufacturing enables the fabrication of patient-specific implants, while surface anodization may enhance osseointegration by improving cell adhesion at the bone–implant interface. This study evaluated the feasibility of porous Ti-6Al-4V implants produced by additive manufacturing and surface-modified by anodization for repairing critical-sized femoral defects. Eighty rats were assigned to four groups: control (no graft), non-anodized Ti-6Al-4V implants, nanoporous implants, and nanotubular implants. After six weeks, bone regeneration and mechanical performance were assessed. Newly formed bone volume was significantly higher in the implanted groups compared to control (24.62 ± 3.11%), reaching 47.25 ± 3.92% (non-anodized), 58.20 ± 5.39% (nanoporous), and 40.72 ± 2.22% (nanotubular). Bone strength was also greater in implanted groups (150.27 ± 2.94 N, 151.98 ± 10.37 N, and 156.59 ± 4.95 N, respectively) compared to control (128.16 ± 2.17 N), with no significant differences among treated groups. No signs of implant rejection or inflammation were observed, indicating good biocompatibility. Anodized surfaces demonstrated enhanced osteogenic performance, particularly in the nanoporous group. These findings indicate that anodized porous Ti-6Al-4V implants produced by additive manufacturing combine biological compatibility with mechanical stability, supporting their potential application in bone reconstruction therapies.

Background: Additive manufacturing has emerged as a promising technology for the fabrication of patient-specific metallic implants with complex architectures for craniofacial reconstruction. Among metallic biomaterials, cobalt–chromium–molybdenum (Co–28Cr–6Mo) alloys exhibit excellent mechanical strength and corrosion resistance. Plasma anodization has been proposed as a surface engineering strategy to enhance the biological performance of metallic implants; how-ever, its ability to improve osseointegration and bone regeneration remains uncertain. This study investigated the biological response of plasma-anodized additively manufactured Co–28Cr–6Mo implants in a rat critical-size calvarial defect model. Methods: Forty-eight male Wistar rats were randomly assigned to eight experimental groups (n = 6 per group) receiving untreated Co–28Cr–6Mo implants, plasma-anodized Co–28Cr–6Mo implants, titanium-coated plas-ma-anodized Co–28Cr–6Mo implants, or empty defects (control). Animals were euthanized after 6 or 12 weeks. Biological performance was assessed by macroscopic and radiographic examina-tions, histological analyses (Stevens Blue and Von Kossa staining), and quantitative histomor-phometric evaluation of newly formed bone area. Results: All implant surfaces demonstrated excellent in vivo biocompatibility, with no evidence of chronic inflammation, implant rejection, corrosion, or postoperative complications throughout the experimental period. Histological analyses consistently revealed limited bone formation confined to the margins of the defects and the persistence of fibrous connective tissue between the implant surface and the host bone. Quan-titative histomorphometry showed a slight increase in newly formed bone after 12 weeks com-pared with 6 weeks; however, no statistically significant differences were observed among the Control, Co–28Cr–6Mo, Co–28Cr–6Mo PIII, and Co–28Cr–6Mo/Ti PIII groups (p > 0.05). Conclu-sions: Plasma anodization preserved the excellent biocompatibility of additively manufactured Co–28Cr–6Mo implants but did not significantly improve osseointegration or bone regeneration in a rat critical-size calvarial defect model. These findings indicate that plasma anodization alone is insufficient to enhance the regenerative performance of Co–Cr–Mo implants and suggest that additional bioactive surface functionalization strategies may be necessary to promote bone re-pair in critical-size craniofacial defects.