Comparative in vivo evaluation of porous and dense duplex titanium and hydroxyapatite coating with high roughnesses in different implantation environments.

Ti (PG60) and Ti plus HA (HPG60) dense coatings with ultrahigh roughness (Ra: 74 +/- 8 microm and 53 +/- 18 microm, respectively) were compared to high Ti (Ti60) and Ti plus HA (HT60) high roughened porous coatings (Ra: 40 +/- 7 microm and 36 +/- 3 microm, respectively). Surfaces were implanted in cortical and trabecular bone of young adult (YOUNG), aged (AGED) and estrogen-deficient sheep (OVX) and analyzed by means of histology, histomorphometry and push-out tests 3 months after implantation. A significantly lower value in affinity index (AI) of PG60 when compared to TI60 (p < 0.01) was observed in cortical bone. In trabecular bone, lower values in AI were found in TI60 and PG60 when compared to their HA-coated surfaces (p < 0.0005). Bone ingrowth (BI) of TI60 and PG60 was significantly lower than that of the HA-coated surfaces in trabecular bone (p < 0.05). Significantly lower values in BI in OVX sheep in comparison to YOUNG sheep in both cortical and trabecular bone were observed (p < 0.05). Data showed that high roughness and Ti and HA-coated surfaces are suitable for aged and osteoporotic patients. HA coatings represent the most successful strategy in trabecular bone.

Sandblasted titanium osteointegration in young, aged and ovariectomized sheep.

To evaluate how aging and estrogen deficiency influence the success rate of Sandblasted Titanium (Ti/SA) implants, the osteointegration of Ti/SA rods was studied in the cortical and trabecular bone of 5 young, 5 aged and 5 ovariectomized (OVX) sheep. The characterization of the host bone by transiliac biopsies of the iliac crest showed a progressive rarefaction of trabecular bone in aged and OVX animals when compared to young ones. A significant reduction, both in cortical and trabecular bone, of the osteointegration rate of Ti/SA rods in the presence of estrogen deficiency compared to young animals was observed, while only a minor reduction was observed in aged animals. These results were confirmed by the pushout test in cortical bone. Bone quality affected the biological response of bone to Ti/SA implants in both trabecular and cortical bone; consequently, strategies to maximize the bone osteogenic properties of osteoporotic patients should be adopted.

Soft tissue response to a new austenitic stainless steel with a negligible nickel content.

This study evaluates the soft tissue response to a new austenitic stainless steel with a low nickel content (P558) in comparison with a conventional stainless steel (SSt)and a titanium alloy (Ti6Al4V). Previous findings showed its in vitro biocompatibility by culturing P558 with healthy and osteoporotic osteoblasts and its in vivo effectiveness as bone implant material. Regarding its use as a material in osteosynthesis,P558 biocompatibility when implanted in soft tissues, as subcutis and muscle, was assessed. Disks and rods of these metals were implanted in rat subcutis and in rabbit muscle, respectively. Four and twelve weeks post surgery implants with surrounding tissue were retrieved for histologic and histomorphometric analysis: fibrous capsule thickness and new vessel formation were measured. Around all implanted materials, light microscopy highlighted a reactive and fibrous capsule formation coupled with ongoing neoangiogenesis both in rats and in rabbits. Histomorphometric measurements revealed a stronger inflammatory response,in terms of capsule thickness,surrounding SSt implants (9.8% Ni content) both in rat subcutis and in rabbit muscle independently of shape and site of implantation. A progressive decrease in capsule thickness around P558 (<0.02% Ni content) and Ti6Al4V, respectively, was seen. Regarding new vessel density, the data showed a different response dependent on the site of implantation. However,in the light of the previous and present studies, P558 is a good material, instead of titanium alloys, in orthopedic research.

A new austenitic stainless steel with a negligible amount of nickel: an in vitro study in view of its clinical application in osteoporotic bone.

A biomaterial named P558 is a new austenitic stainless steel (SS) with a negligible amount of Ni (<0.20%). In previous in vitro and in vivo studies it was compared with conventional SS and Ti6Al4V and shown to be a promising material in orthopedics. Because osteoporosis is a type of pathology very often encountered in implanted patients and can be studied with in vitro models, the purpose of the present study was to evaluate P558 in vitro through comparison of normal (nOB) with osteopenic (oOB) bone-derived primary rat osteoblasts. Osteoblasts were cultured directly on P558 and polystyrene as controls for 72 h. Osteoblast proliferation, adhesion, and activity (ALP, OC, TGF-beta1, and IL-6) were evaluated at 24 and 72 h. Results demonstrated that the growth of nOB and oOB cultured on P558 was not affected negatively when compared to control. Cells on P558 did not show any alteration in terms of adhesion, proliferation, and metabolic marker production in nOB and oOB cultures, and a significant increase in ALP, OC, and TGF-beta1 production was observed. SEM images revealed no alteration in cell morphology. The current findings demonstrate that P558 promotes osteoblast proliferation, activation, and differentiation not only in normal bone, but also in osteopenic bone-derived osteoblasts.