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Analysis of friction and wear processes in an innovative spine stabilization system. Part 2. A study and model of the wear of a metal rod-polymer cord friction joint

Brończyk Anna

Acta of Bioengineering and Biomechanics

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2022

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Vol. 24, no. 2

23--35

EN

The purpose of this study was to model and describe the processes and phenomena occurring during the sliding interaction between biometal rods (titanium alloys Ti6Al4V and Ti6Al7Nb, austenitic steel AISI 316L, alloy CoCrMo) and PE-UHMW cords, used in spine stabilization systems to treat early-onset idiopathic scoliosis. Methods: The wear of friction joints in two lubricating solutions (acidic sodium lactate and distilled water) at stabilized temperature T = 38 C was studied. The wear of the polymeric cords was investigated through analyses of the chemical composition of the surface of the cords and microscopic examinations of the changes occurring on this surface. In addition, microscopic examinations and EDS analyses of the wear products filtered out from the lubricating medium were carried out. Results: Metallic particles were found to be present in both lubricating solutions at each stage of the friction process. The largest amount of metallic particles was recorded after 5000 motion cycles. Conclusions: The presence of metallic wear products is an evidence of the wear of the harder metal rod due to its friction against the PE-UHMW cord. This means that the use of guided-growth implants poses a risk of inflammations in the peri-implant tissues.

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Analysis of friction and wear processes in an innovative spine stabilization system. Part 1. A study of static and kinetic friction of a metal rod-polymer cord friction joint

Brończyk Anna

Acta of Bioengineering and Biomechanics

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2022

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Vol. 24, no. 1

118--130

EN

This analysis is the first part of research that aims to develop a model of the tribological wear of PE-UHMW cord – biometal rod combination. This type of sliding joint is applied in spine stabilization systems that enable the treatment of early-onset idiopathic scoliosis. Methods: The friction tests included force measurements, followed by the determination of static and kinetic friction coefficients as a function of the number of the performed movement cycles, and static friction coefficient with regards to the string tension force FN in the range of 50–300 N. Additionally, the surface roughness and microscopic observations of the metal rods were made. The friction measurements were carried out at a stabilized temperature T = 38 °C in the presence of distilled water and acidic sodium lactate. Results: The measurements confirmed the impact of both the number of completed movement cycles and the value of the force loaded on the cord on the static friction coefficient. Similar values of kinetic friction force occur for the pairs with the titanium alloys rods, as well as for the pairs with the steel and CoCr rod. The type of lubricant affected the obtained measurement results unevenly: (Ti6Al4V and Ti6Al7Nb – slight impact, steel 316L and CoCrMo – large impact). During microscopic observations, numerous wear products, were visible, including harder than the base material large conglomerates. Conclusions: Susceptibility of polymer fibres results in its increased resistance to wear, but it can be also combined with an increase in wear of the surface of the metal rod.

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Investigation of the adhesion properties of calcium-phosphate coating to titanium substrate with regards to the parameters of high-frequency magnetron sputtering

Kenzhegulov Aidar K., Mamaeva Axaule A., Panichkin Alexander V., Prosolov Konstantin A., Brończyk Anna, Capanidis Dymitry

Acta of Bioengineering and Biomechanics

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2020

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Vol. 22, no. 2

111--120

EN

The main goal of the work was to find the interconnection between the high-frequency magnetron sputtering parameters and the adhesion properties of CaP coatings formed on the surface of titanium substrate. Methods: Calcium-phosphate coatings, similar in composition to hydroxyapatite, were generated by high-frequency magnetron sputtering on titanium substrate at different values of high-frequency specific power over times of one and two hours. Afterwards, the generated coatings were studied using the method of X-ray phase analysis, and sclerometric tests (scratch test) were carried out. The adhesion strength of the deposited coatings was tested for different coating thicknesses from 0.45 to 1.1 x 10–3 mm. Results: According to the results of sclerometry, it was found that with an increase in the high-frequency specific power of plasma to 3.15 W/cm2 , the adhesion strength of the calcium-phosphate coating also increases. For all the coatings, the critical loads at which the coating completely exfoliated from the substrate were determined. Conclusions: According to the research results, the most optimal conditions for obtaining high-adhesive calcium-phosphate coatings were determined.