J. Marciniak

Diamond-like carbon coatings for biomedical applications

Abstract The results of experimental studies on amorphous diamond carbon layers obtained by a new method of r.f. dense plasma chemical vapour deposition onto orthopaedic pins and screws are presented. Research on this subject which has been carried out over many years allows us to draw optimistic conclusions concerning the biomedical applications of diamond-like carbon (DLC). In particular, preliminary medical research on a new DLC-steel substrate system developed in 1992, which has just been concluded, is extremely promising.

Corrosion resistance of Cr-Ni-Mo steel intended for urological stents

This work presents the influence of the surface treatment and plastic strain of Cr-Ni-Mo stainless steel, intended for implants applied in urogenital surgery, on the steels corrosion resistance. Tests were carried out in simulated urine at a temperature of 37 1C and pH = 66,4. In particular, pitting and crevice corrosion resistance tests were carried out. Furthermore, through the applied technique of stent implantation, the deformability of the passive layer was evaluated. The deformability tests of the passive layer were carried out with the use of a bend test followed by a corrosion test.

Influence of carbon coatings origin on the properties important for biomedical application

Abstract The purpose of the present study was to investigate the properties of a carbon layer depending of the origin of applied methods. Quasiamorphous carbon coatings prepared by ion beam methane decomposition by RF dense plasma and vacuum pulsed arc deposition were applied to stainless steel implants used in surgery. The studies of carbon films as coatings for implants in surgery were aimed on the investigations of biological resistance of implants, histopathological investigations using laboratory animals, tests of corrosion resistance, measurements of mechanical properties and a breakdown test in Tyrod solution. The comparison of the properties of the coating produced by these methods shows very good biotolerance and biocompatibility of all of the coatings. They are not corroded in physiological fluids. From the other side they have different properties, especially electrical and optical, and are not influenced on medical applications. The obtained results prove that the implants coated by all the methods mentioned are a very good material for medical use.

Biomechanical Analysis of Lumbar Spine Stabilization by Means of Transpedicular Stabilizer

The fundamental purpose of research was determination of biomechanical characteristic of lumbar spine–transpedicular stabilizer system made of stainless steel (Cr-Ni-Mo) and Ti6Al4V alloy. To define biomechanical characteristic of the system finite element method was applied. Geometric models of part spine L3-L4 and stabilizer, was discretised by means of SOLID 95 element. Appropriate boundary conditions imitating phenomena in real system with appropriate accuracy were established. The aim of biomechanical analysis was calculation of displacements and stresses in the vertebras and the stabilizer in a function of the applied loading: 700 N–1600 N. The results of the numerical analysis can be applied to determine a construction features of the stabilizer, and to select mechanical properties of metallic biomaterial. The defined displacements for vertebras L3-L4 show that the proposed type of stabilizer enables correct course of treatment.

The corrosion tests of amorphous carbon coatings deposited by r.f. dense plasma onto steel with different chromium contents

In the paper the results of experimental studies concerning characterization of amorphous carbon layers obtained by a new method of r.f. dense plasma CVD onto steel with different chromium contents are presented. Thin, amorphous carbon layers, deposited onto these substrates, are the subject of structural and physical investigations. This refers also to the system of carbon layer-steel substrate correlated with a microstructure of the layer, and to the determination of specifications resulting from the model for optimization of the synthesis and applicability of a new system as medical implants. Amorphous carbon coatings produced by the dense r.f. CH4 plasma method from steel AISI-316L used in medicine were investigated to determine their suitability as biomaterials.

Chemical, Corrosion and Topographical Analysis of Stainless Steel Implants after Different Implantation Periods

The aim of this work is to examine the corrosion properties, chemical composition, and material—implant interaction after different periods of implantation of plates used to correct funnel chest. The implants are made of 316L stainless steel. Examinations are carried out on three implants: new (nonimplanted) and two implanted for 29 and 35 months. The corrosion study reveals that in the potential range that could occur in the physiological condition the new bar has the lowest current density and the highest corrosion potential. This indicates that the new plate has the highest corrosion resistance and the corrosion resistance could be reduced during implantation by the instruments used during the operation. XPS analysis reveals changes in the surface chemistry. The longer the implantation time the more carbon and oxygen are observed and only trace of elements such as Cr, Mo are detected indicating that surface is covered by an organic layer. On some parts of the implants whitish tissue is observed: the thickness of which increased with the time of implantation. This tissue was identified as an organic layer; mainly attached to the surface on the areas close to where the implant was bent to attain anatomical fit and thus where the implant has higher surface roughness. The study indicates that the chest plates are impaired by the implantation procedure and contact with biological environment. The organic layer on the surface shows that the implant did not stay passive but some reactions at the tissue-implant interface occurred. These reactions should be seen as positive, as it indicates that the implants were accepted by the tissues. Nevertheless, if the implants react, they may continue to release chromium, nickel, and other harmful ions long term as indicated by lower corrosion resistance of the implants following implantation.

Electrochemical Impedance Spectroscopy and Corrosion Resistance of SiO2 Coated CpTi and Ti-6Al-7Nb Alloy

One of the ways to increase the hemocompatibility of surface of titanium and its alloys is to apply sol-gel method to form oxide films based on such elements as Ti or Si. However, the literature suggests existence of group of undefined phenomena associated with oxide layer formation on surfaces of metallic biomaterals in the presence of silicon. Therefore, the study involves development of conditions suitable for production of surface layers that have phisycal and chemical properties adequate for application in cardiovascular system. To assess the usefulness of proposed modifications, the Authors carried out electrochemical tests involving potentiodynamic and impedance measurements. The tests were performed in artificial serum in temperature T = 37±1°C in order to simulate real-life conditions. The obtained results show diverse properties of SiO2 layer that depend on process parameters of its formation.

Biomechanical Behaviour of Double Threaded Screw in Tibia Fixation

The aim of the work was assessment of stability of tibia fixation realized with the use of double threaded screw. Biomechanical analysis of the tibia – double threaded screw system was carried our for the implant made of two biomaterials used in bone surgery – Cr-Ni-Mo stainless steel and Ti-6Al-4V alloy. Finite element method was applied to calculate displacements, strains and stresses. The obtained results allowed to work out biomechanical characteristics of the analyzed system. These characteristics can be a basis for selection of degree of strain hardening of the applied metallic biomaterial and optimization of the screw’s geometry.

Total hip arthroplasty using cementless avantage cup in patients with risk of hip prosthesis instability.

BACKGROUND The aim of the study was to assess total hip arthroplasty procedures using the cementless Avantage cup in women with additional risk factors for postoperative hip instability. MATERIAL AND METHODS A total of 280 cementless Avantage and Avantage Reload cups were implanted in 260 women aged between 29 and 79 years (60.9 years on average) in the years 2004-2010. In 217 women, there was at least one additional risk factor for prosthesis dislocation. The survival of the cup was assessed by using the necessity of cup replacement as an endpoint of the study. The statistical analyses used the Fisher test to assess the difference in the necessity of revision surgery between the Avantage and Avantage Reload cups, and the Kaplan Meier method was used to evaluate the effective functioning time of the prosthesis. Additionally, tests were conducted on the surface layer of 2 not used and 4 removed cups. RESULTS 239 patients (259 arthroplasties) were subjected to the final examination. The follow-up period ranged from 2.7 to 9.7 years, 7.0 years on average. None of the patients demonstrated postoperative prosthesis instability. Aseptic loosening was observed in 19 cups in 18 women (7.3%). Intra-prosthetic dislocation occurred 4 times, and in two cases it was combined with loosening of the cup. Revision surgery was required more often in patients with the Avantage cup (9.5%, 17 out of 179) in comparison to the Avantage Reload (2.5%, 2 out of 80). However, the observed differences did not reach the level of statistical significance. The cumulative survival rate of the Avantage cup was 0.94 at 5 years and 0.86 at 8 years. CONCLUSIONS 1. Avantage cups reduce the risk of postoperative hip instability. 2. Patients with cementless Avantage cups should be closely monitored for signs of aseptic loosening.

Structure Modification of Surface Layers of Ti6Al4V ELI Implants

In the work, the influence of electrochemical modifications of Ti6Al 4V ELI on the in vitro corrosion resistance was studied. The specimens with carbon lay er produced with the use of IBAD method on the passivated specimens were also examined. The char acteristics of the grinded, the electropolished, the electropolished and electrochemically passiva ted and with the passivecarbon layer specimens were evaluated by the potentiodynamic tests in Tyrode’s solution. A flexibility of the passive layer was examined in potentiodynamic tests of the bended specimens. Results show that electropolishing and anodic oxidation in the examined s olutions increased the in vitro corrosion resistance of the alloy. The corrosion potential of t he polished and passivated specimens is much higher then the grinded samples. The increase of pa sive current density was not observed for the polished and passivated specimens. The passive layer wa s uniform that was proved by the AFM investigation. The tests proved high corrosion resistance of the passivated specimens that were bended (up to 90 °) to evaluate the flexibility of passive layer. The passive-car bon layer ensures corrosion resistance, which is not as high as for passivated samples. Introduction Titanium and its alloys are corrosion resistant biomaterials tha t are characterized by a wide passive range [1, 2, 3]. The breakdown potentials are higher then membrane potential s of ssue in a living body (0,2-0,45V)[4]. It should be assumed that the loss of passivity in the el ectrochemical fluids and tissue system is rather impossible. However, a passive layer can be mechanically or chemically damaged. Metallic surface is then uncovered and corrosion processes ar e initi ted. Currently the scientific research is focused on surface layer modification te chniques in order to increase the corrosion resistance of implants. It should be said that implants underg o plastic deformation. For this reason prepared layers should be characterized by the plastic deforma tion ability. The aim of the work was to work out conditions of producing passive-carbon layers on Ti6Al4V ELI alloy surface and the evaluation of the corrosion resistance. Materials and methods Ti6Al4V ELI was used in the research. Chemical composition and mecha nical properties met the ASTM standard [5]. Surface preparation involved: grinding, electrochemic al polishing, anodic oxidation and carbon layer creation with the use of double beam method I on Beam Assisted Deposition (IBAD) [6]. Electrochemical polishing was carried out i n the bath composed of: sulfuric acid (20÷70% vol.) + hydrofluoric acid (20 ÷50% vol.) + ethylene glycol (10 ÷20% mass) + acetanilide (20% mass). Anodic oxidation was carried out in the soluti on of CrO3 – 100÷200g/litre. The specimens were passivated at different potentials. The corrosi on resistance of layers was evaluated by potentiodynamic method in the Tyrode’s solution (36,6 ±1°C and pH=6,9÷7,5). NonKey Engineering Materials Online: 2003-12-15 ISSN: 1662-9795, Vols. 254-256, pp 387-390 doi:10.4028/www.scientific.net/KEM.254-256.387