To assess safety and performance of a bone substitute (GreenboneTM) obtained by biomorphic transformation of natural wood into 3D biomimetic substituted calcium phosphate (hydroxyapatite and b-tricalciumphosphate) scaffold for segmental bone reconstruction in sheep model
The study evaluated bone implant in 24 sheep randomized to three groups, Greenbone scaffold I, Greenbone scaffold II, and allograft, followed up to 6 months. Bony defects were created in the metatarsus and the scaffold was inserted. Safety assessment considered any AE, macroscopic presentation and treatment-related abnormalities (popliteal lymph nodes histopathology). Performance (cumulative score for callus formation, new bone and implant resorption) was assessed by X-ray or CT and by ex vivo analyses after implant retrieval including microCT, macroscopic, and histological and histomorphometric assessments. Further bone biopsies were conducted for assessing mechanical, osteogenic, osteoclastic and angiogenic characteristics of newly formed bone
Observations confirmed osteoinductive properties for Greenbone scaffolds. Medullary bone formation was observed for the Greenbone groups only, already at month 3. Both interfaces of the scaffolds were covered by newly formed bone, without interposition of fibrous connective tissue in the most internal part of the scaffolds, with the new osteonic systems and newly formed blood vessels; many osteocytes and osteoblasts lining the edges of the calcified structures and outbreaks of osteoclastic resorption on the scaffolds. Presence of bone callous containing micro vessels and osteoblasts was seen in most of the samples. Cortical volume and thickness were similar among groups. Both GB I (p=0.0092) and GBII (p=0.014) scaffolds presented higher OS/BS values vs AG-allograft, with highest OSTh and Ob/BS for GBI-doped with ions compared to GBII HA only non doped and AG. Implant resorption started after the first month.
The present study has confirmed Greenbone's characteristics in terms of biocompatibility, mechanical properties and bioresorbability to provide a safe and highly performing bone substitute for segmental bone reconstruction