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Revision, without cement, of aseptically loose, cemented total hip prostheses. Quantitative comparison of the effects of four types of medullary treatment on bone ingrowth in a canine model.

A model that replicated the radiographic and histological features of aseptic loosening of the femoral component of a total hip replacement that had been done with cement was created in thirty-seven dogs. A deep wound infection developed in one dog, and that dog was excluded from the study. Revision was performed without cement in twenty-nine dogs, which were then followed for six months. The remaining seven dogs were used for histological study only. The components that were used for revision were made from Ti-6-Al-4-V, and a titanium fiber-metal porous surface had been applied to the anterior, posterior, and medial surfaces of the proximal part of the stem. The femora were revised either with no graft material applied to the osseous defect; with hydroxyapatite/beta-tricalcium phosphate placed in the defect; with application of an autologous cancellous bone graft as part of a one-stage revision; or with application of an autologous cancellous bone graft as the first part of a two-stage revision, with implantation of the component four months later. The use of an autologous bone graft led to greater and more consistent ingrowth of bone. The greatest amount of bone ingrowth was found in the group in which the procedure had been done in two stages (18 +/- 4.1 per cent), followed by the group in which the prosthesis and the graft had been inserted in a single stage (15 +/- 5.0 per cent), the group that had been treated with hydroxyapatite/beta-tricalcium phosphate (10 +/- 9.1 per cent), and the control group, in which no graft had been used (7 +/- 7.0 per cent). Notably, all of the components in the animals in which an autologous graft had been used were well fixed by bone ingrowth, while the component in two of the animals in the group in which no graft had been used in one animal in the hydroxyapatite/beta-tricalcium phosphate group had only fibrous-tissue ingrowth. In contrast to the findings with respect to bone ingrowth, there was more medullary bone adjacent to the lateral aspect of the implant in the groups in which hydroxyapatite/beta-tricalcium phosphate or no graft had been inserted than in the groups that had had an autologous graft.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

Photothermal sensitization of amelanotic melanoma cells by Ni(II)-octabutoxy-naphthalocyanine.

Incubation of B78H1 amelanotic melanoma cells with a potential photothermal sensitizer, namely, liposome-incorporated Ni(II)-octabutoxy-naphthalocyanine (NiNc), induces an appreciable cellular accumulation of the naphthalocyanine, which is dependent on both the NiNc concentration and the incubation time. No detectable decrease in cell survival occurs upon red-light irradiation (corresponding to the longest-wavelength absorption bands of NiNc) in a continuous-wave (c.w.) regime of the naphthalocyanine-loaded cells. On the other hand, 850 nm irradiation with a Q-switched Ti:sapphire laser operating in a pulsed mode (30 ns pulses, 10 Hz, 200 mJ/pulse) induces an efficient cell death. Thus, ca. 98% decrease in cell survival is obtained upon 5 min irradiation of cells that have been incubated for 48 h with 5.1 microM NiNc. The efficiency of the photoprocess is strongly influenced by the NiNc cell incubation time prior to irradiation. Photothermal sensitization with NiNc appears to open new perspectives for therapeutic applications, as suggested by preliminary in vivo studies with C57/BL6 mice bearing a subcutaneously implanted amelanotic melanoma.

Animals↗

Optimisation of the superplastic forming of a dental implant for bone augmentation using finite element simulations.

OBJECTIVES: The phenomenon of superplasticity has made it possible to form complex shapes that require extremely high degrees of ductility in titanium alloy with minimal internal stresses. Combined with the use of an investment casting material as the die material, which makes possible the forming of re-entrant angles, it is possible to produce membranes for ridge augmentation. The aim is to characterise the metal alloy sheet and simulate the superplastic forming process in three dimensions to produce process parameters, namely gas pressure as a function of time, to accurately adapt the titanium sheet to the bone surface. METHOD: The surface of the die was digitised using a 3D laser scanning system (UBM-Keyence LC2450). Ti-6Al-4V sheet of 140 mm diameter was modelled using a grid of triangular membrane elements. This mesh was automatically refined during the simulations. Finite element simulation was carried out using the Superflag software program (University of Wales Swansea) Three different options for gas pressure control were adopted, namely, target flow stress, target strain rate and target energy dissipation. The pressure cycles produced from the simulation were used to form titanium alloy sheet at 900 degrees C using argon gas. The deformed regions of the formed sheet were then examined to determine the regions of contact with the die and to characterise surface damage. RESULTS: Comparison of the simulations with experiment showed that there was good agreement between simulated and experimental thickness distributions in most parts of the sheet that were examined. Interrupted tests showed that in the intermediate positions of the forming sheet the simulations were slightly ahead of the experiment. The target stress option was found to produce the best degree of adaptation and the sheet formed using this cycle showed good surface quality, whereas in highly deformed regions using the other target options, the sheet was found to have formed microcracks. The use of a solid lubricant on the surface of the forming sheet was not found to have a significant influence on the adaptation of the titanium alloy sheet except in areas of high deformation where the sheet perforated. SIGNIFICANCE: The finite element membrane formulation is well adapted to the superplastic forming of a ridge augmentation membrane prosthesis. The simulation accurately describes the evolution of the shape of the prosthesis and its thickness distribution with time, which allows the manufacturer to select an appropriate initial thickness of titanium alloy sheet prior to attempting to form the component. The investment dies are found to have sufficient strength to withstand the forming operation if a suitable orientation of the titanium sheet with respect to the die is adopted. A metal surface of good quality can be produced in the formed prosthesis using the appropriate gas control option.

Alloys↗

Hydration and preferential molecular adsorption on titanium in vitro.

Surface sensitive spectroscopies, Auger electron and X-ray photoelectron (XPS), were used to determine changes in titanium oxide composition, oxide stoichiometry, and adsorbed surface species as a function of exposure to human serum in a balanced electrolyte (serum/SIE) and 8.0 mM ethylenediaminetetraacetic acid in a balanced electrolyte (EDTA/SIE) at 37 degrees C. Before immersion, the oxide was near ideal TiO2, covered by two types of hydroxyl groups: acidic OH(s) with oxygens doubly coordinated to titanium, and basic Ti-OH groups singly coordinated. After extended exposure to both solutions, up to 5000 h (ca. 208 d), the surface concentration of OH groups increased and non-elemental P appeared. The P LVV Auger transition and P 2p spectra indicated the peak positions were similar to reference phosphate compounds. The adsorbed phosphate species were presumed to be either Ti-H2PO4 or Ti-HPO4-. The XPS data suggested that a lipoprotein and/or glycolipid film was adsorbed to the specimens exposed to serum/SIE. Analysis of the preferential lipoprotein/glycolipid adsorption using electrostatic bonding concepts contributed to the refinement of the hierarchical model for the Ti-tissue interface. The salient features are that Ti metal is not in direct contact with the biological milieu, rather there is a gradual transition from the bulk metal, near-stoichiometric oxide, Ca and P substituted hydrated oxide, adsorbed lipoproteins and glycolipids, proteoglycans, collagen filaments and bundles to cells.

Adsorption↗

Subclavian artery resection and reconstruction for thoracic inlet cancers.

PURPOSE: We previously described an original transcervical approach to resect primary or secondary malignant diseases that invade the thoracic inlet (TI). The purpose of this study was to evaluate the technical aspects and long-term results of the resection and revascularization of the subclavian artery (SA). METHODS: Between 1986 and 1998, 34 patients (mean age, 49 years) underwent en bloc resection of TI cancer that had invaded the SA. The surgical approach was an L-shaped transclavicular cervicotomy in 33 patients. In 14 of these patients, this approach was associated with a posterolateral thoracotomy (n = 10) or a posterior midline approach (n = 4). In one patient, the procedure was achieved with a single posterolateral thoracotomy approach. An end-to-end anastomosis was performed in 16 patients. In one patient, a subclavian-left common carotid artery transposition was performed. In one other patient, an end-to-end anastomosis was performed between the proximal innominate artery and the SA. The right carotid artery was transposed into the SA in an end-to-side fashion. In 16 patients, prosthetic revascularization with a polytetrafluoroethylene graft was performed. Thirty-three patients underwent postoperative radiation therapy. RESULTS: There were no cases of perioperative death, neurologic sequelae, graft infections or occlusions, or limb ischemia. There were two delayed asymptomatic polytetrafluoroethylene graft occlusions at 12 and 31 months. The 5-year patency rate was 85%. During this study, 20 patients died: 18 died of tumor recurrence (5 local and systemic and 13 systemic), one of respiratory failure, and one of an unknown cause at 74 months. The overall 5-year survival rate was 36%, and the 5-year disease-free survival rate was 18%. CONCLUSION: Tumor arterial invasion per se should not be a contraindication to TI cancer resection. This study shows that cancers that invade the SA can be resected through an L-shaped transclavicular cervicotomy, with good results with a concomitant revascularization of the SA.

Adult↗

Cell/surface interactions on laser micro-textured titanium-coated silicon surfaces.

This paper examines the effects of nano-scale titanium coatings, and micro-groove/micro-grid patterns on cell/surface interactions on silicon surfaces. The nature of the cellular attachment and adhesion to the coated/uncoated micro-textured surfaces was elucidated by the visualization of the cells and relevant cytoskeletal & focal adhesion proteins through scanning electron microscopy and immunofluorescence staining. Increased cell spreading and proliferation rates are observed on surfaces with 50 nm thick Ti coatings. The micro-groove geometries have been shown to promote contact guidance, which leads to reduced scar tissue formation. In contrast, smooth surfaces result in random cell orientations and the increased possibility of scar tissue formation. Immunofluorescence cell staining experiments also reveal that the actin stress fibers are aligned along the groove dimensions, with discrete focal adhesions occurring along the ridges, within the grooves and at the ends of the cell extensions. The implications of the observed cell/surface interactions are discussed for possible applications of silicon in implantable biomedical systems.

Actins↗

Laser induced hierarchical calcium phosphate structures.

The surface properties of biomedical implant materials control the dynamic interactions at tissue-implant interfaces. At such interfaces, if the nanoscale features influence protein interactions, those of the microscale and mesoscale aid cell orientation and provide tissue integration, respectively. It seems imperative that the synthetic materials expected to replace natural hard tissues are engineered to mimic the complexity of their hierarchical assembly. However, the current surface engineering approaches are single scaled. It is demonstrated that using laser surface engineering a controlled multiscale surface can be synthesized for bioactive functions. A systematic organization of bioactive calcium phosphate coating with multiphase composition on Ti-alloy substrate ranging from nano- to mesoscale has been achieved by effectively controlling the thermo physical interactions during laser processing. The morphology of the coating consisted of a periodic arrangement of Ti-rich and Ca-P-deficient star-like phases uniformly distributed inside a Ca-P-rich self-assembled cellular structure with the presence of CaO, alpha-tricalcium phosphate, CaTiO(3), TiO(2) and Ti phase in the coating matrix. The cellular structures ranged in diameter from 2.5 microm to 10 microm as an assembly of cuboid shaped particles of dimensions of approximately 200 nm x 1 microm. The multiscale texture also included nanoscale particles that are the precursors for many of these phases. The rapid cooling associated with the laser processing resulted in formation, organization and controlling dimensions of the Ca-P-rich glassy phase into a micron scale cellular morphology and submicron scale clusters of CaTiO(3) phase inside the cellular structures. The self-assembly of the coating into multiscale structure was influenced by chemical and physical interactions among the multiphases that evolved during laser processing.

Biocompatible Materials↗

Biologic response to hydroxylapatite-coated titanium hips. A preliminary study in dogs.

Hydroxylapatite (HA)-coated and uncoated Ti-6A1-4V alloy femoral endoprostheses were evaluated in adult dogs. The femoral stems had proximal anterior, posterior, and medial pockets of either a commercially pure titanium porous coating or a grooved macrotexture. They also had a medial collar, with an inferior surface pocket of either the porous coating or the grooved macrotexture. HA-coated and uncoated specimens of each type were evaluated. The devices were placed as unilateral hemiarthroplasties in 12 dogs and remained in function for up to 52 weeks. Histologic sections from the uncoated grooved implants showed no direct bone-implant apposition in the proximal regions after up to 10 weeks; the HA-coated grooved implants demonstrated extensive direct bone-coating apposition after 5 weeks. Sections from uncoated porous implants evaluated after 10 weeks demonstrated approximately equivalent in-growth to those sections from the HA-coated devices after 6 weeks. All HA-coated implants demonstrated consistent bone-implant apposition with no fibrous tissue interposition. The HA-coated surfaces were associated with increased bone deposition and proliferation at early implantation periods. In no histologic section examined was there any evidence of deterioration of the HA coating, nor was any separation of the coating from the substrate material observed.

Alloys↗

A comparison of stainless steel and CP titanium rods for the anterior instrumentation of scoliosis.

Use of 4.0 mm and 5.0 mm steel rods have resulted in proximal screw pullout. Titanium rods, which encompass a reduced yield point, may increase the effective stiffness of the construct when used with segmental anchors. Seven human thoracic spines were loaded in axial compression, axial torsion, flexion, extension, and lateral bending. Testing was performed on intact, discectomy and simulated bony fusion specimens. Specimens were randomly instrumented with 4.0 mm and 5.0 mm steel, and 4.5 mm CP Ti rods. In compression and torsion, the intact spine demonstrated increased stiffness with respect to all instrumentation employed in a discectomy condition. No significant differences between the intact and the instrumentation systems were detected for torsion or compression under simulation of fusion. Under flexural loading, no significant differences were detected between the intact specimen and the instrumentation systems. When used in conjunction with segmental force anchors, the use of CPTi rods which posses reduced yield points can provide sufficient rigidity as compared to stainless steel rods of comparable diameter. Implants of reduced yield point will permit permanent deformation with low force. Screw pullout may result when high yield materials are employed in conjunction with anchors.

Bone Plates↗

Factors affecting surgical alloy/bone cement interface adhesion.

Interfaces were formed between acrylic bone cement and three commonly used surgical alloys (316L SS, Co-Cr-Mo, and Ti-6A1-4V), in an attempt to further define cementation parameters of acrylic bone cement for use in orthopaedic surgery. Metal/cement interfaces were made at three distinct times during the setting cycle of the cement and were cured for 1 hr, 1 day, and 1 week. The metals were prepared with roughly polished or finely polished prepassivated surfaces. Tensile bond strengths and residual cement on metal coverage data indicated that, for each metal system, interfaces created prior to and at the onset of the dough stage formed superior interfaces for implantation compared to those formed late in the dough stage. Furthermore, electropolishing plus prepassivation offered a more efficient bonding surface than mechanical polishing.

Adhesiveness↗

Behaviour of nitinol in osteoblast-like ROS-17 cell cultures.

Nickel titanium shape memory metal alloy Nitinol (NiTi) has been used in dental wares and in gastrointestinal surgery. Nitinol is a promising implant material in orthopedics, but its biocompatibility, especially in long-term implantation is not confirmed yet. We studied Nitinol's effect on a cell culture model. Comparisons to stainless steel, pure titanium and pure nickel were performed. The effects of Nitinol on cell death rate, the apoptosis rate and the formation of local contacts were studied on rat osteosarcoma cell line ROS-17 in 48-h cultures. The cell death rate was assessed with combined calcein-ethidium-homodimer labelling. The amount of dead cells 1000 cells were as follows: four in the NiTi, 21 in the Stst, 4.8 in the Ti and 51 in the Ni group. In the NiTi and Ti groups, the number of dead cells was significantly lower (p < or = 0.01) than in Ni group. The rate of apoptosis was detected with TUNEL-assay. The assay results were: 1.93 apoptotic cells 1000 cells in the NiTi, 1.1 in the Stst, 2.98 in the Ti and 0.62 in the Ni group. A comparison of these two results shows that 48% of the dead cells were apoptotic in the NiTi, 56.6 in the Stst, 62% in the Ti and only 1.8% in the Ni group. The focal contacts were stained with a paxillin antibody and counted. There were marked differences in the number of focal contacts per unit area compared to NiTi (774 focal contacts): 335 in Stst (p < or = 0.01), 462 in Ti (p < or = 0.01) and 261 in Ni (p < or = 0.005). Our results show that NiTi is well tolerated by the osteoblastic type ROS-17 cells.

Alloys↗

Development of plasma-sprayed bioceramic coatings with bond coats based on titania and zirconia.

Bond coats for plasma-sprayed hydroxyapatite (HAp) coatings on Ti-6A1-4V hip endoprotheses are being developed for improved in vivo performance. Bond coat powders consisting of (i) CaO-stabilized zirconia, (ii) a eutectic composition of titania and non-stabilized zirconia, and (iii) titania were applied by atmospheric plasma spraying (APS) to Ti-6A1-4V-coupons and 100 microm-thick Ti-6A1-4V foils. Subsequently, a thick layer of HAp was sprayed onto the thin bond coats. Peel tests on Ti-6A1-4V foil/bond coat/HAp top coat assemblies revealed that titania and titania/ zirconia bond coats increased the peel adhesion strength in a statistically significant way from 22 N m(-1) (HAp without a bond coat) to >42 and 32 N m(-1), respectively. Microstructural investigations by SEM on cross-sections of coatings leached in simulated body fluid for up to 28 days led to the conclusion that the chemically very stable bond coats act as an improved chemical barrier against in vivo release of metal ions from the implant, as well as an improved adhesive bond by development of very thin well-adhering reaction layers, presumbly composed of perovskite, calcium dititanate, and/or calcium zirconate.

Alloys↗

Biocompatibility of chemical-vapour-deposited diamond.

The biocompatibility of chemical-vapour-deposited (CVD) diamond surfaces has been assessed. Our results indicate that CVD diamond is as biocompatible as titanium (Ti) and 316 stainless steel (SS). First, the amount of adsorbed and 'denatured' fibrinogen on CVD diamond was very close to that of Ti and SS. Second, both in vitro and in vivo there appears to be less cellular adhesion and activation on the surface of CVD diamond surfaces compared to Ti and SS. This evident biocompatibility, coupled with the corrosion resistance and notable mechanical integrity of CVD diamond, suggests that diamond-coated surfaces may be highly desirable in a number of biomedical applications.

Absorption↗

Effects of Ti ions and particles on neutrophil function and morphology.

We compared the cytotoxicity of soluble and particulate titanium (Ti), vanadium (V) and nickel (Ni) by biochemical functional analysis and by microscopic morphology with micro-area elemental analysis in vitro using human neutrophils as probes and in vivo in animals. The biochemical analyses of LDH, superoxide anion, TNF-alpha and scanning electron microscopy (SEM) showed that Ni in solution destroys the cell membrane of neutrophils, whereas Ti and V in solution stimulate neutrophils and increase the quantity of released superoxide anions. Fine Ti particles (1-3 microm), which smaller than neutrophils (about 5 microm), were phagocytized by the cells and the results were similar in vivo. These results showed that the cytotoxic effect of Ti particles is size dependent, and that they must be smaller than that of cells. The present study demonstrated that the biochemical functional tests are useful for evaluating the biocompatibility of materials.

Animals↗

Vagally mediated volume-dependent modulation of inspiratory duration in the neonatal lamb.

Inspiratory mechanical loads elicit a reflex volume-timing response in human infants and experimental animals. In adult animals, this reflex has been shown to be mediated by vagal afferents. It was hypothesized that the volume-related regulation of inspiratory duration would also be vagally mediated in the newborn. Single-breath graded inspiratory loads were presented to 4-day-old anesthetized neonatal lambs breathing through a facemask, after tracheostomy, and after bilateral cervical vagotomy. Inspired volume decreased and inspiratory duration (TI) increased with increasing load magnitude. The increase in TI was greater with facemask loads than with loads presented after tracheostomy for equivalent changes in inspired volume. The volume-related prolongation of TI after tracheostomy was abolished after cervical bilateral vagotomy. The results demonstrate that the volume-timing reflex in neonatal lambs after tracheostomy is mediated by vagal afferents. However, in the intact lamb, there is also a significant contribution to this reflex by upper airway afferents.

Airway Resistance↗

Substratum roughness alters the growth, area, and focal adhesions of epithelial cells, and their proximity to titanium surfaces.

Epithelial (E) cells were cultured on smooth tissue culture plastic (TCP), TCP-Ti, polished Ti (P), and rough grit-blasted Ti (B), acid-etched Ti (AE), and grit-blasted and acid-etchedTi (SLA) surfaces and their growth, area, adhesion, and membrane-Ti proximity assessed. Rough surfaces decreased the growth of E cells compared to smooth surfaces in cultures up to 28 days. In general rough surfaces decreased the spreading of E cells as assessed by their area with the most pronounced affect for the SLA surface. On the other hand, the strength of E cells adhesion as inferred by immunofluorescence staining of vinculin in focal adhesions indicated that E cells formed more and larger focal adhesions on the smooth P surface compared to the rougher AE surface. As this finding indicates a stronger adhesion to smooth surfaces, it is likely that E cells on rough surfaces are more susceptible to mechanical removal. An immunogold labeling method was developed to visualize focal adhesions using back-scattered electron imaging with a scanning electron microscope (SEM). On rough surfaces focal adhesions were primarily localized on to the ridges rather than the valleys and the cells tended to bridge over the valleys. Transmission electron microscopy (TEM) measurements of membrane proximity to the Ti surface indicated that average distance of cell to the Ti increased as the Ti surface roughness increased. Therefore, the size and shape of surface features are important determinants of epithelial adhesive behavior and epithelial coverage of rough surfaces would be difficult to attain if such surfaces become exposed.

Cell Adhesion↗

Effect of titanium carbide coating on the osseointegration response in vitro and in vivo.

Titanium has limitations in its clinical performance in dental and orthopaedic applications. This study describes a coating process using pulsed laser deposition (PLD) technology to produce surfaces of titanium carbide (TiC) on titanium substrates and evaluates the biological response both in vitro and in vivo. X-ray photoelectron spectroscopy (XPS) analysis revealed the presence of 18.6-21.5% TiC in the surface layer, accompanied by oxides of titanium 78.5-81.4% in the following concentrations: 11.1-13.0% Ti(2)O(3), 50.8-55.8% TiO(2), 14.5-14.7% TiO. Expression of genes central to osteoblast differentiation (alkaline phosphatase, A2 pro-collagen type 1, osteocalcin, BMP-4, TGFbeta and Cbfa-1) were up-regulated in all cell lines (primary human osteoblasts, hFOB1.19 and ROS.MER#14) grown on TiC compared with uncoated titanium when measured by semiquantitative PCR and real time-PCR, whilst genes involved in modulation of osteoclastogenesis and osteoclast activity (IL-6 and M-CSF) were unchanged. Bone density was shown to be greater around TiC-coated implants after 2 and 4 weeks in sheep and both 4 and 8 weeks in rabbits compared to uncoated titanium. Rapid bone deposition was demonstrated after only 2 weeks in the rabbit model when visualized with intravital staining. It is concluded that coating with TiC will, in comparison to uncoated titanium, improve implant hardness, biocompatibility through surface stability and osseointegration through improved bone growth.

Animals↗

Fibrin-mediated endothelial cell adhesion to vascular biomaterials resists shear stress due to flow.

In vitro endothelial cell (EC) seeding onto biomaterials for blood-contacting applications can improve the blood compatibility of materials. Adhesive proteins adsorbed from serum that is supplemented with the culture medium intercede the initial cell adhesion and subsequent spreading on material surface during culture. Nevertheless, physical and chemical properties of vascular biomaterial surface fluctuate widely between materials resulting in dissimilarity in protein adsorption characteristics. Thus, a variation is expected in cell adhesion, growth and the ability of cell to resist shear stress when tissue engineering on to vascular biomaterials is attempted. This study was carried out with an objective to determine the significance of a matrix coating on cell adhesion and shear stress resistance when cells are cultured on materials such as polytetrafluoroethylene (PTFE, Teflon) and polyethyleneterephthalate (Dacron), ultra high molecular weight polyethylene (UHMWPE) and titanium (Ti), that are used for prosthetic devices. The study illustrates the distinction of EC attachment and proliferation between uncoated and matrix-coated surfaces. The cell attachment and proliferation on uncoated UHMWPE and titanium surfaces were not significantly different from matrix-coated surfaces. However, shear stress resistance of the cells grown on composite coated surfaces appeared superior compared to the cells grown on uncoated surface. On uncoated vascular graft materials, the cell adhesion was not supported by serum alone and proliferation was scanty as compared to matrix-coated surface. Therefore, coating of implant devices with a composite of adhesive proteins and growth factors can improve EC attachment and resistance of the cells to the forces of flow.

Journal Article↗