There is a public health need to understand the effects of surface layer thickness and composition on corrosion in nickel-containing medical devices. To address this knowledge gap, five groups of Nitinol stents were manufactured by various processing methods that altered the titanium oxide layer. The following surfaces were created: [3500 nm thick mixed thermal oxide (OT), *420 nm thick mixed thermal oxide (SP), *130 nm thick mixed thermal oxide (AF), *4 nm thick native oxide (MP), and an *4 nm thick passivated oxide (EP). Radially compressed and not compressed devices were evaluated for nickel (Ni) ion release in a 60-day immersion test. The results indicated that OT stents released the most Ni, followed by stents in the SP and AF groups. For OT and SP stents, which exhibited the thickest oxide layers, radial compression significantly increased Ni release when compared to non-compressed stents. This result was not observed in AF, MP, SP stents indicating that the increased Ni release may be explained by cracking of the thicker oxide layers during crimping. Strong correlations were observed between oxide layer thickness and cumulative Ni release. These findings elucidate the importance of oxide layer thickness and composition on uniform corrosion of laser-cut Nitinol stents.

Nitinol is a commonly used material in cardiovascular medical devices. However, relationships between nitinol surface finishing, in-vivo metal ion release, and adverse biological responses have yet to be established. We addressed this knowledge gap by implanting single and overlapped nitinol stents with different surface finishes to assess systemic impact on minipigs (i.e. serum and urine nickel levels, liver and kidney function, immune and blood count) over the 6 month implantation period. In addition, nickel levels and histopathology in stented arteries were analyzed on explant to determine relationships between surface processing and local adverse tissue reactions. The findings presented here highlight the importance of surface processing on in-vivo nickel release and subsequent impact on local biological response for nitinol implants.

Non-contact infrared thermometers (NCITs) are being widely used during the COVID-19 pandemic as a temperature-measurement tool for screening and isolating patients in healthcare settings, travelers at ports of entry, and the general public. To understand the accuracy of NCITs, a clinical study was conducted with 1113 adult subjects using six different commercially available NCIT models. A total of 60 NCITs were tested with 10 units for each model. The NCIT-measured temperature was compared with the oral temperature obtained using a reference oral thermometer. The mean difference between the reference thermometer and NCIT measurement (clinical bias) was different for each NCIT model. The clinical bias ranged from just under − 0.9 °C (under-reporting) to just over 0.2 °C (over-reporting). The individual differences ranged from − 3 to + 2 °C in extreme cases, with the majority of the differences between − 2 and + 1 °C. Depending upon the NCIT model, 48% to 88% of the individual temperature measurements were outside the labeled accuracy stated by the manufacturers. The sensitivity of the NCIT models for detecting subject’s temperature above 38 °C ranged from 0 to 0.69. Overall, our results indicate that some NCIT devices may not be consistently accurate enough to determine if subject’s temperature exceeds a specific threshold of 38 °C. Model-to-model variability and individual model accuracy in the displayed temperature were found to be outside of acceptable limits. Accuracy and credibility of the NCITs should be thoroughly evaluated before using them as an effective screening tool.

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The flow and polymerization characteristics of poly(methylmethacrylate) (PMMA) bone cement can be changed by manipulating the temperature of the bone cement components or the environment that they are prepared in. To quantify the effects of the initial component temperature (T(ic)) of acrylic bone cement on the rheological and handling characteristics, ASTM F451-99a compliant methods and clinically relevant testing methods were utilized. A rheometer was designed and fabricated using the dimensions of a clinical, commercially available, cement gun and nozzle. The influence on the apparent viscosity and handling characteristics (setting time, working time, and peak exotherm temperature) for a high viscosity (HV) commercially-available acrylic bone cement, Palacos R, were determined. The values of T(ic) used were 23 degrees C (room), 6 degrees C (refrigerator), and -14 degrees C (freezer). Using the apparent viscosity of a medium viscosity (MV) bone cement as a benchmark (Simplex P at room temperature), it was found that by adjusting the T(ic) the HV cement was able to mimic the flow characteristics of the MV cement. Lowering the T(ic) lowered the apparent viscosity of the bone cement. The effects of T(ic) on the polymerization of bone cement were studied in dynamic and static conditions. The dynamic test recorded temperature and torque from stirring resistance. Setting times were also determined using the ASTM exotherm mold method. The setting times determined by the dynamic testing conditions were consistently shorter than those determined by the ASTM method. Lowering the T(ic) increased the working and setting times; however, it did not have a significant effect on the peak exotherm temperature.

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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.