To evaluate the in vivo performance of "duplex" hydroxylapatite top coat/TiO(2) bond coat systems, cylindrical Ti6Al4V rods of 130 mm in length and 11-13 mm in diameter were coated by atmospheric plasma spray (APS) technique with both a standard hydroxylapatite (HAp) layer and a HAp+TiO(2) bond coat "duplex" layer. In this pilot study coated and uncoated rods serving as controls were implanted into the femur of sheep so that their distal ends were freely suspended in the medulla of the femur. After an observation time of six months it was found that bone apposition and bone ingrowth were considerably increased in the presence of a osteoconductive coating. In particular, in vivo spalling and delamination frequently observed with HAp coatings was virtually absent in duplex coatings owing to the strong adhesion of the bond coat to the HAp top coat that anchored the latter solidly to the metallic surface of the implant. Some tentative mechanisms leading to this improved coating adhesion will be discussed.
The shear strength of the cement-metal interface using rods with different surface treatments and a clinical standardized cementing technique was studied. Under "dry" conditions, a low interface shear strength can be obtained with polished and smooth CoCrMo surfaces (peak-to-valley height Rt: 1 microm, average 0.2 MPa; 5 microm, 0.38 MPa). Grit-blasted and polymethylmethacrylate (PMMA)-precoated surfaces achieved higher values (PMMA precoat: average 5.16 MPa; CoCrMo peak-to-valley height Rt: 20 microm, average 8.61 MPa: 60 microm, average 7.8 MPa). After immersion in physiological saline solution for 60 days, the PMMA-precoated rods kept their initial stability whereas all the other test rods had lost their stability completely. A microscopic analysis of cross-sections revealed gap formations at the cement-metal interface to varying degrees (1-16 microm). PMMA-precoated rods rarely showed any gap formation at all. The above-mentioned gap formation was seen independently of the porosity at the cement-metal interface and corresponds to the clinical and postmortem observed debonding of the interface.
The osseointegration of long‐term implants is often incomplete such that gaps remain between the implant surface and the surrounding hard tissue. This study examines the effect of soluble recombinant human bone morphogenic protein 2 (rhBMP‐2) on gap healing and osseous integration. The effect of a single, intraoperative application of soluble rhBMP‐2 on the formation of new bone around titanium implants was studied. A total of 8 titanium‐alloy cylinders (Ti‐6Al‐4V) with a plasma spray coating (TPS; 400 μm thickness) were implanted into femoral condyles of mature sheep: rhBMP‐2 solution (1 μg) was pipetted into the 1 mm wide cleft around 4 implants; 4 further implants served as rhBMP‐2‐free controls. Two of these controls exhibited an additional calciumphosphate‐coating. The cleft around the implants served as testing zone to study the formation of new bone by microradiographical and histological analyses. The follow‐up periods were 4 and 9 weeks, respectively. A significant amount of new bone contacting the implants' surface was detected where rhBMP‐2‐solution had been used: In 50% a circumferential osseoinduction occurred within 4 weeks and a nearly complete osseointegration was observed after 9 weeks. In all cases bone formation was exaggerated and filled the spongiosa with compact bone. Time matched TPS‐controls and controls with calciumphosphate coating showed no notable formation of new bone. The results suggest that a single administration of soluble rhBMP‐2 into a bone cavity can augment bone formation and also osseointegration of titanium implants. Further investigations based on these findings are necessary to develop long‐term implants (e. g. joint replacements) with rhBMP‐2‐biocoating for humans.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.