W. Kajzer

The study of physicochemical properties of stabilizing plates removed from the body after treatment of pectus excavatum.

This paper presents the results of a physicochemical surface study and clinical observation of a new generation of plates for the treatment of pectus excavatum. Analysis of the data allowed us to investigate the effect of implant design and condition of their surface on the results of treatment of pectus excavatum. In the study, we performed an analysis of clinical data, obtained after a suitable period of treatment with the use of implants, as well as a study of physicochemical properties of stabilizing plates after their removal from the body. Surface roughness, the surface wettability and corrosion resistance were measured, and the results were compared with clinical observations. When removing the plates we found only slight inflammatory-periosteal reactions around the wire fixing transverse stabilizing plates to the ribs and locking the base plate correcting the distortion. The corrective plates did not shift or rotate during the entire treatment period, giving an optimal, oval and natural shape of the chest. The obtained values of the parameters investigated indicate that the reduction in resistance to pitting corrosion occurred in the areas where laser marking was made to identify the plate. The remaining plates, in spite of mechanical damage of the surface, were characterized by good corrosion resistance, a fact which is confirmed by the results of clinical evaluation.

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.

Comparison of numerical and experimental analysis of plates used in treatment of anterior surface deformity of chest

The work discusses the results of numerical and experimental research of the plates for treatment of deformations of the frontal wall of chest. The conducted analyses included determination of: within numerical research, the state of displacement, strain and reduced stresses as well as reactions and moments of forces in supports, while within experimental research, the values of displacements at characteristic points of the system.

Metatarsal Osteotomy Using Double-Threaded Screws - Biomechanical Analysis

The fundamental purpose of this research was to determine the biomechanical characteristics of the first metatarsal bone - double-threaded screws system made of stainless steel (Cr-Ni-Mo) and an assessment of its stability. To define the biomechanical characteristics of the system, the finite element method and experimental method were applied. Geometric models of metatarsal bone and double-threaded screws, were discretized by means of SOLID 95 element. Appropriate boundary conditions imitating phenomena in the real system with appropriate accuracy were established. The aim of biomechanical analysis was calculation of displacements and stresses in the bone and the stabilizers in a function of the applied loading. The experimental method was carried out to calculate displacements of the analyzed system. The obtained results can be applied to determine the construction features of the stabilizer and to select mechanical properties of metallic biomaterial (selection of degree of strain hardening).

Evaluation of physicochemical properties of surface modified Ti6Al4V and Ti6Al7Nb alloys used for orthopedic implants.

The paper presents the results of selected functional properties of TiO2 layers deposited by ALD method on the surface of Ti6Al4V and Ti6Al7Nb alloys intended for implants in bone surgery. TiO2 layer was applied at the constant temperature of the ALD process at T=200°C at a variable number of cycles, which resulted in a different layer thickness. Different process cycles of 500, 1250, and 2500 were analyzed. The application of experimental methods (AFM, SEM, wettability, potentiodynamic test, EIS, scratch test, nanohardness and layer thickness) enabled to select the optimal number of cycles, and thus the thickness of the TiO2 layer of the most favorable functional properties. The obtained results clearly showed that regardless of the type of titanium substrate, the TiO2 layer applied in a 2500cycle ALD process has the best physicochemical and electrochemical properties. These properties have major impact on biocompatibility, and therefore the quality of the final product. The information obtained can be useful for manufacturers of medical devices involved in the production of implants used in reconstructive surgery of skeletal system.

Corrosion Resistance of Hip Endoprosthesis Cups in the Initial State and after Implantation

The aim of the paper was to compare physicochemical features of hip joint cups coated with hydroxyapatite in the initial state and after period of 36 months of implantation. The cups we produced from stainless steel Cr-Ni-Mo with increased content of azote dedicated to implants which chemical composition is compatible with recommended ISO 5832-9 standards. On the basis of obtained results it can be stated that hydroxyapatite resorption did not affect equally the entire surface of the cup. It was also stated that tested biomaterial of the cup was well wetted (hydrophilic). For all the tested samples prepared from cups in the initial state and cups after the implantation the presence of transpassivation potential Etr was stated, which proves not only good corrosion resistance but also biocompatibility of analyzed cups.

FEM Analisys of the Expandable Intramedullar Nail

The paper presents results of numerical analysis of new form of expandable intramedullary nail (patent no. P382247) used in stabilization of proximal femur in adults. The obtained results can be used to optimize geometry of implants as well as mechanical properties of metallic biomaterial they are to be made of.

Corrosion resistance of PLGA-coated biomaterials

The aim of the study was to determine the influence of PLGA bioresorbable polymer coating on corrosion resistance of metal biomaterial. Polymer coating deposited by immersion method was applied. Corrosion resistance of metal biomaterials (stainless steel, Ti6Al4V, Ti6Al7Nb) coated with PLGA polymer, after 90 days exposure to Ringers solution was tested. The amount of metal ions released to the solution was also investigated (inductively coupled plasma-atomic emission spectrometry (ICP-AES) method). The surface of the samples was observed using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Degradation of PLGA was monitored with the use of the 1H NMR spectroscopy and GPC (Gel Permeation Chromatography). The studies were carried out for non-sterilized (NS) and sterilized (S) samples. Application of the polymer coating causes a reduction of release of metal ions to the solution. Depending on metal substrate different course of destruction of polymer layer was observed. After 90 days of incubation in Ringers solution polymer layer was highly degraded, however, the composition of copolymer (ratio of the comonomeric units in the chain) remained unchanged during the whole process, which suggests even degradation. The polymer layer reduced degradation kinetics of the metal substrate. Moreover, degradation process did not change surface morphology of metal substrate and did not disturb its integrity. The results obtained indicate that the applied polymer layer improves corrosion resistance of the alloys being investigated. Thus, the developed implants with bioresorbable coatings could be advantageous for medical applications.

Influence of Ultrasound Bone Union Stimulation on Corrosion Resistance of Titanium Alloys

The influence of bone union activation realized with the use of the low-intensity pulsed ultrasound (LIPUS) on degradation of titanium alloys was presented in the work. Ti6Al4V ELI and Ti6Al7Nb alloy samples of modified surface layer were used in the study. The preliminary surface treatments were: grinding, vibration machining, mechanical polishing, sandblasting and electrochemical polishing. The final procedures of the surface modification were anodization and steam sterilization. The scope of the work included the study of pitting corrosion resistance and concentration of metal ions released to the Ringer’s solution. The study was performed for the undeformed and deformed samples subjected to the influence of ultrasound. The reference samples were the samples kept in the solution and not having the impact of ultrasound. On the basis of the study it was found that the conditions for bone union stimulation by low intensity pulsed ultrasound do not initiate pitting corrosion of the titanium alloy samples, although they increase the mass of ions released from the surface to the solution.

Biomechanical analysis of the femur- Dynamic Condylar Screw (DCS) system

Purpose: The aim of this study was a biomechanical evaluation of the (Dynamic Condylar Screw DCS) system after epicondyle fractures and a comparison of obtained results of the two alternative biomaterials for the stabilizer. Design/methodology/approach: Models of stabilizer and femur were designed, the discretization was conducted and boundary conditions were set. Numerical analysis with the use of the finite element method was performed in the ANSYS Workbench 15 Software. Two models of system: M-316 LVM (stabilizer with properties CrNiMo steel femur) and M-Ti64 (stabilizers with properties Ti6Al4V alloys – femur) were subjected to numerical analysis. As a reference point the state of displacement, strain and von Misses stresses by in helfy femur (M-HF) were determined. Findings: For all of the analysed models, the values of assumed mechanical properties of cortical bone and cancellous bone were not exceeded. Simultaneously, it is possible to use alternative biomaterials, CrNiMo steel or Ti6Al4V alloy for DCS system. Research limitations/implications: In order to perform more detailed characteristics of analysed DCS implant, in future research it is expected to carry out macro and microscopic observations for implants removed from the body and their electrochemical evaluation. Practical implications: The analysis allows the determination of potentially dangerous areas, affected to damage due to overloading. Furthermore, the analysis identifies the areas of initiation and development of crevice, pitting and fatigue corrosion. Originality/value: The presented work allows the selection of alternative metallic biomaterials for the manufacturing of the evaluated DCS system and indicates its potentially dangerous area. This work might be interesting for engineers and doctors dealing with the construction of a new forms of implants used in orthopedics.