Ultra-thin porous calcium phosphate coatings show extensive remodeling and high osseointegration after 24 weeks in a rabbit femoral condyle model.

Ultra-thin porous calcium phosphate (CaP) coatings may provide a transient osteoconductive interface while reducing the amount of coating material remaining on an implant. However, it remains unclear whether extensive remodeling of such coatings is compatible with high osseointegration in vivo. In this study, approximately 30-µm-thick porous high-velocity suspension flame-sprayed β-tricalcium phosphate (β-TCP) and GB14 (Ca2KNa(PO4)2) coatings, with and without copper-functionalized supraparticles, were evaluated in a rabbit femoral condyle model. The coatings were deposited onto TiAl6Nb7 implants and characterized with respect to morphology, thickness, porosity, and surface roughness. After 24 weeks in vivo, 19 evaluable implants were assessed by qualitative histology, quantitative histomorphometry, and sequential fluorochrome labeling. No histological signs of inflammatory tissue reactions were observed, and all coating variants showed direct bone apposition without interposed connective tissue. Bone-to-implant contact ranged from 76.5% ± 14.2% to 86.3% ± 4.6%, whereas residual coating coverage accounted for only 1.5% ± 1.8% to 6.4% ± 6.8% of the implant perimeter. Fluorochrome incorporation at 2, 4, 6, and 8 weeks indicated peri-implant bone formation at all investigated labeling time points. Paired analyses revealed no statistically significant Cu-associated differences in the investigated cellular, histomorphometric, or fluorochrome-labeling outcomes within either CaP system, either before or after false-discovery-rate correction. These findings demonstrate the coexistence of extensive coating remodeling and high osseointegration at 24 weeks across two ultra-thin porous CaP coating systems. The low residual coating coverage together with direct bone apposition supports the concept of ultra-thin bioresorbable CaP coatings as transient osteoconductive interfaces for orthopedic implants.