Interconnected porous hydroxyapatite ceramics for bone tissue engineering

Abstract

Several porous calcium hydroxyapatite (HA) ceramics have been used clinically as bone substitutes, but most of them possessed few interpore connections, resulting in pathological fracture probably due to poor bone formation within the substitute. We recently developed a fully interconnected porous HA ceramic (IP-CHA) by adopting the 'foam-gel' technique. The IP-CHA had a three-dimensional structure with spherical pores of uniform size (average 150 mm, porosity 75%), which were interconnected by window-like holes (average diameter 40 mm), and also demonstrated adequate compression strength (10-12 MPa). In animal experiments, the IP-CHA showed superior osteoconduction, with the majority of pores filled with newly formed bone. The interconnected porous structure facilitates bone tissue engineering by allowing the introduction of mesenchymal cells, osteotropic agents such as bone morphogenetic protein or vasculature into the pores. Clinically, we have applied the IP-CHA to treat various bony defects in orthopaedic surgery, and radiographic examinations demonstrated that grafted IP-CHA gained radiopacity more quickly than the synthetic HA in clinical use previously. We review the accumulated data on bone tissue engineering using the novel scaffold and on clinical application in the orthopaedic field.

Medical Application of Calcium Orthophosphate Bioceramics

“…In 1997, Tsurga and coworkers implied that the optimal pore size of bioceramics that supported ectopic bone formation was 300 -400 μm [454]. Thus, there is no need to create calcium orthophosphate bioceramics with very big pores; however, the pores must be interconnected [95,384,397,398]. Interconnectivity governs a depth of cells or tissue penetration into the porous bioceramics, as well as it allows development of blood vessels required for new bone nourishing and wastes removal [455,456].…”

“…Namely, porous HA bioceramics can be colonized by bone tissues [381,[386][387][388][389][390][391][392][393][394][395][396]. Therefore, interconnecting macroporosity (pore size > 100 μm) [111,374,381,397,398], which is defined by its capacity to be colonized by cells, is intentionally introduced in solid bioceramics (Fig. 6).…”

Rietveld Refinement of the Crystal Structure of Hydroxyapatite Using X-ray Powder Diffraction

“…Another important characteristic of HAp is its biodegradability. Previous studies [7][8][9][10][11][12] have shown that hydroxyapatite tends not to trigger a response from the immune system, embedding itself successfully in the surrounding tissue and degrading over time as the host tissue begins to regenerate.…”

Application of interconnected porous hydroxyapatite ceramic block for onlay block bone grafting in implant treatment: A case report (Review)

“…Interconnected porous hydroxyapatite ceramic (IP-CHA) materials with high porosity have been developed and used successfully in the field of orthopedics medicine (10). An IP-CHA block, which consists of a porous sintered body composed of hydroxyapatite ceramics with a unique pore structure, is able to undergo extensive incorporation into host bone more rapidly than conventional porous calcium hydroxyapatite ceramic (10,11).…”

“…An IP-CHA block, which consists of a porous sintered body composed of hydroxyapatite ceramics with a unique pore structure, is able to undergo extensive incorporation into host bone more rapidly than conventional porous calcium hydroxyapatite ceramic (10,11). We speculated that problems associated with autogenous block bone grafting could be avoided if an IP-CHA block of the same size as an autogenous block bone were to be used for onlay grafting.…”