Differential effects of different forms of hydroxyapatite and hydroxyapatite/tricalcium phosphate particulates on human monocyte/macrophages in vitro

Size dependent induction of proinflammatory cytokines and cytotoxicity of particulate beta-tricalciumphosphate in vitro

“…Based on these and our data we hypothesize that an absence or inefficacy of phagocytosis due to particle size and shape might potentiate subsequent inflammatory responses. In this context, it has already been shown that HA particles of a needle-like and sharp-edged shape cause the strongest induction of cytokine expression and production in vitro [15,17]. In addition, the importance of a phagocytosable size and shape has already been demonstrated regarding the effects of hydroxyapatite in vivo: whereas smaller particles are phagocytosed rapidly, larger particles remain extracellularly and lead to a maintained foreign body reaction, formation of granulomas and encapsulation indicating inflammatory responses [36].…”

“…Biological responses of biomaterial particles do not only depend on the chemical composition [20], but also on size, morphology and structure of the particles. Indeed, particulate HA induces proinflammatory cytokines predominantly in a needle-like form [15] and also after drying at low temperatures resulting in non-sintered particles with sharp edges and of irregular shape [17].…”

The presence of different growth factors does not influence bone response to hydroxyapatite: preliminary results

“…So, it has been reported that the presence of BMP-2 greatly increased bone ingrowth, whereas that of TGF-β1 reduced bone formation compared with untreated controls [28,82]; BMP mixed with activin (a 25-kDa homodimeric protein purified from demineralized bovine bone extract) enhanced bone formation, whereas BMP alone showed poor activity, and a combination of BMP and TGF-β induced bone formation with an abundance of cartilage [83]; the degree of osteogenesis promoted by PDGF was similar to that of controls [38], and the numbers of mineralization nodules increased in vitro when multiple, brief treatments with PDGF were adopted, whereas they decreased when PDGF was given continuously [84]. In reality, the effects induced by pHA implants soaked in growth factors depend on a number of variables: sintering temperatures of pHA [85] and its geometry [86], width and geometry of its pores [21, 87,88], surface properties [89][90][91] and above all the surface reactivity of pHA [92], the size of its granules or particles [93], local tissue strain [94] and underlying diseases [95]. It has also been suggested that, depending on the roughness or smoothness of its pore surface, HA may or may not have osteoinductive properties [23].…”

Abrasive waterjet peening: A new method of surface preparation for metal orthopedic implants

“…Excessively rough implant surfaces may generate cement debris (in cemented arthroplasty), or foster the development of metal particles (in either cemented or cementless fixation). The generation and/or migration of particles from porous coated rough surfaces have been found to contribute to biological complications [29][30][31] and third-body wear of the articulating surfaces. 32,33 Either of these complications may lead to premature joint replacement failure.…”