The resorption of bone‐implanted corals varies with porosity but also with the host reaction

Abstract

Three different exoskeletons of coral species Porites asteroides (P), Montastrea annularis (M), and Dichocoenia stokesi (D) were implanted for 2-20 weeks in rabbits. At 2, 4, 8, or 20 weeks, the exoskeletons presented variations in their resorptions depending on the species. To understand the variations in the decreasing speed of the implants despite their similar chemical composition, a study of the surface and architecture of the coral was carried out using scanning electronic microscopy, porosity was evaluated, and growth and differentiation of osteogenic cells cultured in vitro were observed for more than 1 month. At the cellular level, the surface of the implants was identical. Three-dimensional structures of the implants were variable, but the porosity values [P = 42.7%, M = 40.7%, and D = 17.4%] could not completely account for the differences in the resorbing process of the species. Standard histologic studies performed at 2, 4, 8, and 20 weeks after implantation produced the same pattern with P or M, showing aspects of rapid resorption; however, with D there were images resembling those of a foreign-body reaction. It seems that when resorption is not quick enough, a foreign body reaction develops which further slows down the process. This work focuses on the importance of porosity when using coral as bone substitute.

Is there a role of coral bone substitutes in bone repair?

“…Other coral genera have been previously investigated but with very limited use. 14,15,16 Among them, Dichocoenia stokes were found to trigger a foreign-body reaction when implanted in rabbits. 14 These corals were also found to have slow resorption rates.…”

Clinical applications of bone graft substitutes in spine surgery: consideration of mineralized and demineralized preparations and growth factor supplementation

“…The coral species Porites astreoides was chosen because of its theoretically ideal pore size for the ingrowth of bone. On electron microscopic examination, the average pore size of Porites astreoides was found to be 153.95±25.36 µm [61,62].…”

“…Resorption of the mineral component of the matrix may be variable. The resorption of implanted hydroxyapatite is dependent upon pore size, crystalline structure, and local host reaction [61]. Overall, mineralized bone matrices have the advantage of offering immediate structural support and, in unstable osseous defects, stabilization may contribute importantly to the creation of a microenvironment that promotes osteoneogenesis [3,86].…”

Preparation, physical–chemical characterisation and cytocompatibility of calcium carbonate cements

“…Many surgeons use bone hetero-or autografts or implants of natural origin (coral for example) [1][2][3][4][5][6]. However, supply difficulty, biological variability and viral or bacterial contamination risks are major drawbacks [6][7].…”

“…Considering that the biological resorption of bone substitute materials is generally related to the solubility of their constituting phase(s), brushite cements or associations of CaP with more resorption is crucial to obtain good clinical results and parameters such as implant porosity, size and association with growth factor, bone specific protein and/or cells can be involved to adapt implant biodegradability [3,5,[34][35][36][37][38][39]. The mechanical properties of coral-based graft substitute remain poor and implant rejection can occur probably due to the presence of organic matter residue [7,40].…”