Effects of Oxide Layer Composition and Radial Compression on Nickel Release in Nitinol Stents

Sullivan, Stacey J. L.; Dreher, Maureen L.; Zheng, Jiwen; Chen, Lynn; Madamba, Daniel; Miyashiro, Katie; Trépanier, Christine; Nagaraja, Srinidhi

doi:10.1007/s40830-015-0028-x

Cited by 50 publications

(56 citation statements)

References 23 publications

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“…Since corrosion damage was not observed in NaClO-soaked EP nitinol, it was expected that no differences in nickel ion release would be observed over the two-week test. Regardless of the NaClO soak, we found that BO nitinol released more nickel than EP nitinol which agrees with previous work on laser-cut nitinol stents (Ref 5). Because nitinol performance is dependent on processing, it is difficult to speculate how a chemically etched surface or a different electropolish would respond to an NaClO soak in terms of nickel release.…”

Section: Discussionsupporting

confidence: 92%

“…For our tests, we chose the BO and EP nitinol to attempt to bookend expected performance by having drastically different oxide thicknesses (11 nm for EP nitinol and 651 nm for BO nitinol). These oxide thicknesses are within the range of other studies on nitinol wires and stents (Ref 5, 16, 20, 21). Presumably other nitinol surface finishes would have similar or at least not worse performance after an NaClO soak.…”

Section: Discussionsupporting

confidence: 84%

“…Today nitinol is used in devices including transcatheter heart valves, vascular stents, endovascular grafts, endodontic files, inferior vena cava filters, atrial septal defect occluders, and bone staples (Ref 1–3). As experience with nitinol has increased over the years, so has the medical device community’s understanding of the importance of processing and microstructure on nitinol performance such as corrosion susceptibility, nickel release, and fatigue resistance (Ref 4, 5). During the nitinol manufacturing process, inclusions are formed as small quantities of oxygen and carbon are introduced into the material.…”

Section: Introductionmentioning

confidence: 99%

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Sodium Hypochlorite Treatment and Nitinol Performance for Medical Devices

Weaver

Gutierrez²,

Nagaraja

et al. 2017

J. of Materi Eng and Perform

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Processing of nitinol medical devices has evolved over the years as manufacturers have identified methods of reducing surface defects such as inclusions. One recent method proposes to soak nitinol medical devices in a 6% sodium hypochlorite (NaClO) solution as a means of identifying surface inclusions. Devices with surface inclusions could in theory then be removed from production because inclusions would interact with NaClO to form a visible black material on the nitinol surface. To understand the effects of an NaClO soak on performance, we compared as-received and NaClO-soaked nitinol wires with two different surface finishes (black oxide and electropolished). Pitting corrosion susceptibility was equivalent between the as-received and NaClO-soaked groups for both surface finishes. Nickel ion release increased in the NaClO-soaked group for black oxide nitinol, but was equivalent for electropolished nitinol. Fatigue testing revealed a lower fatigue life for NaClO-soaked black oxide nitinol at all alternating strains. With the exception of 0.83% alternating strain, NaClO-soaked and as-received electropolished nitinol had similar average fatigue life, but the NaClO-soaked group showed higher variability. NaClO-soaked electropolished nitinol had specimens with the lowest number of cycles to fracture for all alternating strains tested with the exception of the highest alternating strain 1.2%. The NaClO treatment identified only one specimen with surface inclusions and caused readily identifiable surface damage to the black oxide nitinol. Damage from the NaClO soak to electropolished nitinol surface also appears to have occurred and is likely the cause of the increased variability of the fatigue results. Overall, the NaClO soak appears to not lead to an improvement in nitinol performance and seems to be damaging to the nitinol surface in ways that may not be detectable with a simple visual inspection for black material on the nitinol surface.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionsupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Sodium Hypochlorite Treatment and Nitinol Performance for Medical Devices

Weaver

Gutierrez²,

Nagaraja

et al. 2017

J. of Materi Eng and Perform

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“…35 However, a recent study showed that oxide layers created by some surface treatment methods might not be as stable as previously thought. 123 In particular, a strong positive correlation between oxide layer thickness (from various methods of surface treatment) and nickel ion release was found. Furthermore, it was shown that severe mechanical deformations that Nitinol devices normally experience during deployment and function can further increase the release of nickel from the Nitinol alloy as oxide layers lack the superelastic mechanical properties and develop cracks under large strains.…”

Section: Nitinol Alloysmentioning

confidence: 95%

Nitinol Stents in the Femoropopliteal Artery: A Mechanical Perspective on Material, Design, and Performance

et al. 2018

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Endovascular stenting has matured into a commonly used treatment for peripheral arterial disease (PAD) due to its minimally invasive nature and associated reductions in short-termmorbidity and mortality. The mechanical properties of the superelastic Nitinol alloy have played a major role in the explosion of peripheral artery stenting, with modern stents demonstrating reasonable resilience and durability. Yet in the superficial femoral and popliteal arteries, even the newest generation Nitinol stents continue to demonstrate clinical outcomes that leave significant room for improvement. Restenosis and progression of native arterial disease often lead to recurrence of symptoms and reinterventions that increase morbidity and health care expenditures. One of the main factors thought to be associated with stent failure in the femoropopliteal artery (FPA) is the unique and highly dynamic mechanical environment of the lower limb. Clinical and experimental data demonstrate that the FPA undergoes significant deformations with limb flexion. It is hypothesized that the inability of many existing stent designs to conform to these deformations likely plays a role in reconstruction failure, as repetitive movements of the leg and thigh combine with mechanical mismatch between the artery and the stent and result in mechanical damage to both the artery and the stent. In this review we will identify challenges and provide a mechanical perspective of FPA stenting, and then discuss current research directions with promise to provide a better understanding of Nitinol, specific features of stent design, and improved characterization of the biomechanical environment of the FPA to facilitate development of better stents for patients with PAD.

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“…This is critical for retrieval studies whose goals are to analyze corrosion or fretting of implants such as in metal‐on‐metal orthopaedic implants or cardiovascular endovascular devices . Maintaining explant integrity is particularly important for Nitinol devices whose corrosion resistance is highly dependent on the oxide layer composition and chemistry …”

Section: Introductionmentioning

confidence: 99%

Effects of tissue digestion solutions on surface properties of nitinol stents

et al. 2017

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Analysis of explanted medical implants can provide a wealth of knowledge about device safety and performance. However, the quality of information may be compromised if the methods used to clean tissue from the device disturb the retrieved condition. Common solutions used to digest tissue may adversely affect the surface of the device and its severity can be material and processing dependent. In this study, two groups of stents made from the same material (Nitinol) were shape set in a salt pot (SP) or further processed by mechanical polishing (MP) and then immersed in one of three tissue digestion solutions (TDS): nitric acid (HNO 3 ), sodium hydroxide (NaOH), or papain enzyme (papain). Nickel (Ni) ion concentrations were measured for each stent-TDS combination and post-immersion stent surface constituents, morphology and oxide depths were compared to baseline samples. Exposure to the HNO 3 TDS resulted in relatively high Ni ion release and surface damage for both stent types. Papain TDS induced a greater Ni ion release than NaOH TDS, however, both were significantly lower than HNO 3 . The NaOH TDS increased the oxide layer thickness on MP stents. In contrast, all other stent immersions resulted in thinner oxide layers. For the Nitinol finishes used in this study, HNO 3 is not recommended while papain and NaOH solutions may be appropriate depending on the post-retrieval analysis performed. This study elucidates the importance of preliminary testing for TDS selection and how the surface finish can affect the sensitivity of a material to a TDS.

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Effects of Oxide Layer Composition and Radial Compression on Nickel Release in Nitinol Stents

Cited by 50 publications

References 23 publications

Sodium Hypochlorite Treatment and Nitinol Performance for Medical Devices

Sodium Hypochlorite Treatment and Nitinol Performance for Medical Devices

Nitinol Stents in the Femoropopliteal Artery: A Mechanical Perspective on Material, Design, and Performance

Effects of tissue digestion solutions on surface properties of nitinol stents

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