Abstract
In Japan, where allograft bone transplantation is not widespread, prospects for artificial bones are very high. Therefore, artificial bones with various compositions, porous structures, and porosities have been developed and employed for clinical use. Both Affinos® and Regenos® (made of beta-tricalcium phosphate and hydroxyapatite, respectively) are artificial bones with a unique unidirectional porous structure, in which pores with a diameter suitable for tissue penetration (25–300 μm) are aligned in one direction. The unidirectional porous structure allows rapid penetration of blood deep into the materials by a capillary effect. In animal experiments, Affinos® showed well-balanced resorption and was replaced with the host’s own bone from an early stage after implantation and new bone formation and remodeling were observed in the cortical bone and medullary cavity. When implanted for clinical situation, resorption from an early stage and good replacement with the patient’s own bone were also observed. Regenos® has an internal osteon-like material and a vascular-like structure that is maintained within the pores even after long-term implantation, as noted in an animal experiment. When implanted for clinical situation, good osteoconductivity was observed from an early stage of implantation. In addition, the material was observed to be slowly absorbed over time in some cases. We have discussed the beneficial effects of combining teriparatide and platelet-rich plasma impregnation and the potential prospects of these artificial bones.
Highlights
Bone grafting is frequently performed in orthopedic surgery [1]
The types of grafted bones vary depending on the country, and in Japan, current trends indicate that autologous bones account for 56.4% of grafts, followed by artificial bones at 40%, and allogenic bones at 3.6% [2]; the latter are used in limited cases, such as filling massive bony defects in hip replacements [3]
In collaboration with Kuraray Co., Ltd (Tokyo, Japan), we developed A ffinos® and Regenos®, artificial bones made of β-TCP and HAp, respectively, that present a unique unidirectional porous structure (Figs. 1, 2)
Summary
Bone grafting is frequently performed in orthopedic surgery [1]. The types of grafted bones vary depending on the country, and in Japan, current trends indicate that autologous bones account for 56.4% of grafts, followed by artificial bones at 40%, and allogenic bones at 3.6% [2]; the latter are used in limited cases, such as filling massive bony defects in hip replacements [3]. After filling the site of a curetted chondroblastoma in the scapula with 20 g of granules, resorption was clearly seen to start from the margin of the artificial bone at 3 months after surgery, and the complete replacement by the patient’s own bone was observed at 2 years [10]. We had reported that in high tibial osteotomy for knee osteoarthritis, after we filled the osteotomy site with blocks and granules, adequate bony fusion due to good osteoconductivity and new bone formation were observed at the hinge joints at 6 months. In a report from another institution, when columnar blocks were implanted in the harvesting site of fibula in a pediatric patient, complete regeneration of the host bone with a tubular structure was observed 5 years after surgery [41]
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