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At least 37 records · Page 2Linked to original sources
PubMed1992

Ni-Ti memory alloy clamp plate for fracture of short tubular bone.

The clamp shape implant has a special memorial function. It consists of one main rod and 3 or 4 pairs of curved short arms located at both sides of the rod. Each pair of arms rolls into a circle, which can embrace 2/3 of the circumference of the fractured bone shaft, thus fixing fragmental bones at multiple points more securely without any limitation to the motion of adjacent joints. Therefore, clamp implant is especially useful for comminuted fracture of the short tubular bone, which is difficult to fix by other methods.

Adolescent↗
PubMedDate not supplied

A new thermal shape memory Ti-Ni alloy stent covered with silicone.

An attempt was made to develop an airway stent for nonsurgical transluminal implantation using a bronchofiberscope. The stent is composed of a single wire with a diameter of 0.5 mm. The wire is made of thermal shape memory titanium nickel alloy, with a transition temperature of 25-30 degrees C. To avoid direct contact between the metal and the tissue, the wire is covered with a 300 microns thick coating of silicone. The stent is horseshoe shaped in cross-section. It is 15 mm in outer transverse diameter and 40 mm long. Ten stents were implanted in 10 dogs whose tracheal cartilages had been previously broken. The stents were first cooled in ice water to reduce their diameter and then inserted into the target site. The wire was warmed to body temperature and recovered its initial shape within 10 sec. The dogs were killed for examination between 1 week and 6 months after implantation. All the stents were located at the implantation sites and were patent. Tissue reactions, such as ulceration and granulation formation, were less severe than in those with previously implanted non-silicone covered stents. Microscopic observation showed that the wires became gradually covered with epithelium within 2 months. This transluminal technique for preserving airway patency shows promise for clinical application.

Alloys↗
PubMed1977

New prospects for a prolonged functional life-span of artificial hip joints by using the material combination polyethylene/aluminium oxide ceramin/metal.

Investigations over the years have shown that the mirror-finished Al2O3 ceramic is a much more suitable frictional counterpart to ultrahigh molecular weight (UHMW) polyethylene than metal. Despite the extremely gread hardness difference between polyethylene and Al2O3 ceramic, a considerable lower wear rate is obtained for the polyethylene socked with this new low-friction material combination. The unexpectedly favorable tribological behavior of this ceramic material in contact with polyethylene may be attributed to the following factors: better values for corrosion resistance characteristics, wettability with liquids, surfact gloss, hardness, and scratch resistance of the ceramic material in comparison with those of the hitherto used metallic implant materials (AISI-316L steel or cast Co-Cr-Mo alloy). It appears that, by using this new combination of materials for the socket and the ball, it will be possible to prolong the service life of artificial hip joints considerably without having effecy any fundamental changes in the present design and implantation principle retaining the hitherto used anchorage shaft made of wrought Co-Ni-Cr-Mo-Ti alloy Protasul-10 of extremely high corrosion fatigue strength.

Alloys↗
PubMed1978

Evaluation of couple/crevice corrosion by prosthetic alloys under in vivo conditions.

Alloys of cast Co-Cr-Mo, wrought Co-Cr-W, wrought, Co-Ni-Cr-Mo(MP35N), Ti-60% Al-4% V, and graphite were incorporated in specimens which simulated both a couple and a crevice corrosion condition. These specimens were implanted in a dog for 30 months. Post-sacrifice examination showed no substantial evidence of corrosion activity on the surfaces of the metals except for a tarnish film on the titanium alloy specimens. The presence of the tarnish film is taken as more evidence of corrosion activity and this correlated with a thicker average fibrous membrane, cellular activity in and near the fibrous membrane, and some increased vascularity. These must be regarded as preliminary observations.

Alloys↗
PubMed1979

Successful replacement of the aortic valve, mitral valve and ascending aorta with re-implantation of the coronary arteries.

A 63-year-old man was operated upon with replacement of the aortic valve, mitral valve and ascending aorta with re-implantation of the coronary arteries. A composite graft with a 27 mm Björk-Shiley tilting disc prosthesis was inserted with 3 continuous Prolene sutures in the aortic position. The coronary arteries were thereafter re-implanted in holes made in the graft. A 31 mm Björk-Shiley valve was sutured in the mitral position with about 20 isolated mattress sutures of Ti-Cron. Selective myocardial hypothermia was instituted with Ringer's solution of 4 degrees C. The total perfusion time was 185 min compared with 240 and 275 min in two previously reported, similar cases. We consider that the use of cardioplegia, a composite graft and continuous sutures makes it possible to reduce the operation time in these complex cases. Our patient is in good condition 9 months postoperatively.

Aortic Aneurysm↗
PubMedDate not supplied

The influence of chronic cerebellar stimulation on respiratory muscle coordination in a patient with cerebral palsy.

The effect of chronic cerebellar stimulation on respiratory muscle coordination has been evaluated using a relatively simple and objective target breathing test on one patient. Seven normal subjects were used as controls. Magnetometer recordings were used to determine whether abdominal and rib cage expansion were in phase. Subjects were asked to match their breathing frequency to a metronome signal. Their ability to control respiratory timing voluntarily was assessed in terms of the coefficient of variation (CV) of inspiratory time (Ti) and of expiratory time (Te). The CV's of Ti and Te were much greater in the patient in the absence of cerebrellar stimulation than they were in normal subjects. Both at 3 weeks and 6 months after implantation of the stimulator, a significant improvement in the performance of the patient was demonstrable with the stimulator on, although normal values were never achieved. This demonstrable influence of chronic cerebellar stimulation on respiratory muscle coordination has important implications for both the avoidance of respiratory complications and the potential improvement of speech in patients with cerebral palsy.

Adolescent↗
PubMed1992

Formation of focal contacts by osteoblasts cultured on orthopedic biomaterials.

The nature of the contact sites formed during the adhesion of osteoblasts to orthopedic implant materials was investigated by fluorescence microscopy. More specifically, the cytoskeletal organization of and the focal contact formation by neonatal rat calvarial osteoblasts attaching to and spreading on 316L stainless steel, Ti-6Al-4V, Co-Cr-Mo, Synamel (hydroxyapatite), alumina, and borosilicate glass were examined. Focal contacts are regions where the plasma membrane approaches the substrate to within 10-15 nm and where bundles of cytoskeletal microfilaments terminate. Fluorescent-labeling of F-actin-containing microfilaments demonstrated a typical sequence of events as rounded, suspended osteoblasts spread onto the substrates. Immunofluorescent-labeling of the protein vinculin, which is found at the cytoplasmic face of focal contacts, initially showed the formation of streak-like focal patches. On the biomaterials, the vinculin staining subsequently extended up and along, but ventral to, the microfilament bundles. The fibrillar patterns observed at later times may evidence the formation of extracellular matrix contacts.

Actin Cytoskeleton↗
PubMedDate not supplied

Potential applications of certain nickel-titanium (nitinol) alloys.

The mechanical behavior ("shape memory") associated with martensitic solid-state transformation in nearly equiatomic Ni-Ti alloy (55-Nitinol) has been studied. Potential dental and medical applications for 55-Nitinol (55% Ni, 1.5% Co, balance Ti, by weight) and for 60-Nitinol (60% Ni, by weight) have been suggested.

Dental Alloys↗
PubMed1992

Exit-site/tunnel infection and catheter outcome in peritoneal dialysis patients.

STUDY OBJECTIVE: To study exit-site/tunnel infections and catheter outcomes in peritoneal dialysis patients. DESIGN: The study was designed to investigate exit-site (ESI)/tunnel infections (TI) and catheter losses in all chronic PD catheters inserted in ESRD patients from 9/88 to 9/91. SETTING: Tertiary-referral university hospital. PATIENTS AND METHODS: Seventy-three patients (40 males, 33 females) underwent 78 double-cuff coiled swan-neck catheter implantations surgically. The curettage of exit site was performed weekly for tunnel infection refractory to medical management. The subcutaneous cuff was excised in persistent ESI/TI. RESULTS: Fifty-nine episodes of ESI/TI in 34 patients were observed over 946 patient-months. Thirty-nine patients experienced no ESI/TI, 27 patients had one and seven had two or more episodes of ESI/TI. Four patients had five episodes of peritonitis associated with ESI/TI. Eight recurrent episodes of ESI/TI with S. aureus in 8 patients were treated successfully with Rifampin. Seven subcutaneous cuffs were excised successfully in 7 patients with tunnel infection, five with S. aureus and two with Pseudomonas aeruginosa. No catheter was removed due to ESI/TI or ESI/TI associated peritonitis. CONCLUSIONS: Aggressive exit site care including repeated curettage, excision of the subcutaneous cuff and appropriate antibiotics reduced significantly catheter losses related to ESI/TI.

Bacterial Infections↗
PubMedDate not supplied

The resorption rate of atheroma lipids in situ and implanted subcutaneously.

Resorption rates have been investigated in the rabbit for atheroma-lipids and cholesterol injected subcutaneously, atheroma lipids in situ in the mildly atheromatous aorta and lipid in the degenerating peripheral nerve. Atheroma lipids injected subcutaneously resorb relatively rapidly, subcutaneous cholesterol and lipid in Wallerian degeneration are intermediate in this respect, whereas only the group with an initially low blood cholesterol (small than approximately equal to 100 mg/100 ml) showed even a suggestion of lipid resorption from their mild or trivial atheromatous lesions. Ti is not clear whether or not atheroma resorbed at all in the groups with initial blood cholesteroles above 100 mg//00 ml. The relative inertia of the arthromatous lesion is mainly attributed to the relative absence of reticuloendothelial phagocytes in it.

Animals↗
PubMed1992

Comparison of the electrochemical properties of various orthopedic porous metals.

The electrochemical properties of various porous metal coatings used in reconstructive orthopedic prosthetics were examined. Potentiodynamic corrosion testing was used to evaluate the behavior of the following porous metals; CSTi on Cast CoCr, CSTi on Ti-6Al-4V, CoCr beads on Cast CoCr, CoCr beads on Ti-6Al-4V, CP Ti beads on Cast CoCr, and CP Ti beads on Ti-6Al-4V. Analysis of the resultant corrosion scans showed that these materials behave similarly to one another. No corrosion-related anomalies were noted.

Corrosion↗
PubMed1992

Role of ceramic implants. Design and clinical success with total hip prosthetic ceramic-to-ceramic bearings.

Ceramic implants have become of great interest because of the increased awareness that wear debris from metal-polyethylene components of total hip prostheses can cause osteolysis around implants. Polyethylene wear rates with the Charnley total hip prosthesis were found to be from 0.1 to 0.2 mm/year in the elderly, which corresponded to 30 to 80 mm3 of polyethylene debris being released to the joint tissues. This in turn can be related to 40 million to 40 billion particles being released into the joint every year. This polyethylene particulate is heavily implicated in the osteolytic destruction of periarticular tissues. The ceramic ball, ceramic cup combination of total hip prostheses may have promise of wear rates that could be thousands of times smaller than polyethylene alone. Such alumina ceramic prosthetic concepts were introduced in Europe from 1970 to 1973. Under Food and Drug Administration regulations at that time, the only U.S. introductions allowed circa 1980 were the Autophor and Xenophor types of ceramic prostheses. However, this particular prosthetic design was not successful in the United States because of pain, neck-socket impingement, ceramic fracture, and component loosening. This did not therefore appear to be a successful compromise in the hands of U.S. surgeons. Ceramic innovations from Europe now include cemented ceramic cups of "matching" tolerances with the femoral ball, and press-fit Ti-alloy acetabular shells with modular ceramic inserts. In addition, alumina and zirconia ceramic balls are now in routine clinical use in Europe. The objectives of this Symposium are to highlight these ceramic ball, ceramic cup innovations with their long-term clinical results from Europe. Then one can evaluate which of these innovations in material and design selections offers the best possible alternatives in the 1990s.

Alloys↗
PubMed1992

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↗
PubMed1976

The adhesion of thin carbon films to metallic substrates.

As part of the development of carbon-coated prosthetic devices, the adhesion of thin carbon films to metallic substrates has been studied. The bond strength of carbon films about 5000 A thick on Ti-6A1-4V and stainless steel was measured in a pull test and found to be greater than 4700 psi. Auger electron spectroscopy showed a reactive film/substrate interface. The ultimate bond strength was found to be dependent on the substrate and the deposition parameters.

Adhesiveness↗
PubMed1992

Adsorption of glycosaminoglycans to commercially pure titanium.

Aqueous solutions of the glycosaminoglycans (GAG), chondroitin-4-sulphate (C4S), chondroitin-6-sulphate (C6S), heparan sulphate (HS) and hyaluronan (HY) were reacted with 5 g samples of both native and calcium-treated titanium powder (99.5% pure) for 0-48 h in 10 ml volume at 37 degrees C. Residual GAG was detected in the supernatant following recovery of the TiO2-GAG complex by centrifugation (5000 g for 1 min) as hexuronic acid using the carbazole tetraborate method of Bitter and Muir. No adsorption on to native TiO2 was evident. In contrast, prior treatment of TiO2 with calcium produced a significant adsorption of C4S to a maximum of 60 micrograms of GAG per gram Ti. Only trace amounts of C6S, HS and hyaluronan interacted in the same way. Further evidence of interaction was obtained following the liberation of bound GAG from the TiO2-Ca-GAG complex with EDTA and identification using cellulose acetate electrophoresis. These findings suggest that calcium ions are required for adsorption of GAG to TiO2 which is mediated through the anionic determinants of the GAG surface and that the special configuration of C4S, the predominant chondroitin sulphate isomer found in alveolar bone, is important in the adsorption process. The implication of these findings in relation to the interaction between bone and titanium implants is discussed.

Adsorption↗
PubMed1992

Bone tissue growth enhancement by calcium phosphate coatings on porous titanium alloys: the effect of shielding metal dissolution product.

The possible mechanism of minimization of prosthesis-derived bone growth inhibitors by shielding of the metal and the reduction, if not elimination, of the associated metal dissolution was investigated. Titanium, aluminium and vanadium release rates were determined in vitro for Ti alloy specimens both with and without a calcium phosphate coating. Ti orderly oriented wire mesh (OOWM) porous coatings on Ti-6Al-4V substrates were used as the metal specimens. Half of the specimens were coated with a 75 microns calcium phosphate ceramic (CPC coating). Seven reference (OOWM) and seven coated (OOWM-CPC) specimens were immersed and placed along with seven control solutions for various periods in an incubator maintained at 37 degrees C and 5% CO2 - air atmosphere. Whereas the reference solutions showed a Ti release increasing as a function of time, the solutions that had the CPC-coated specimens contained no measurable amounts of titanium. The Al in solution around the CPC-coated specimens was significantly greater than the concentration around non-coated specimens. The Al, however, did not increase significantly with time, at least up to 4 wk immersion. The ceramic coating had a small beneficial effect on V concentration. In the absence of a significant adverse effect of Ti on local bone tissue formation, we focus on the Al data of our study. The possible adverse effect of this element is well documented. The calcium phosphate coating produced a significant increase of biological fixation, yet at the same time a greater Al release into solution, calling into question the significance of CPC coating in shielding adverse metal passive dissolution to explain enhanced bone growth [corrected].

Alloys↗