Artificial hearts, fractured valves, and other problems with medical devices.
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Equipment Failure↗
Biomedical subjects
R Kossowsky
Publications and source records attributed to R Kossowsky.
Reporting the failure of medical devices.
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Equipment Failure↗
Aneurysm clip motion during magnetic resonance imaging: in vivo experimental study with metallurgical factor analysis.
Because of various mechanical, metallurgical, and commercial constraints, aneurysm clips are manufactured from different alloys, including several stainless steel and cobalt alloys. Some of the steels contain volume fractions of the crystal phase known as martensite. Martensitic alloys have body-centered cubic structure, are prone to stress corrosion failure, and are ferromagnetic. Martensitic steel can be displaced like a compass needle when exposed to a magnetic field such as that generated during magnetic resonance imaging (MRI). The force exerted by the magnetic field is proportional to the volume fraction of the magnetic phase. We investigated the martensitic content and magnetic field-induced displacement of 12 common aneurysm clips. Four clips of each of the following types were examined: Sugita, Sundt-Kees Multi-Angle, Heifetz (two types), Vari-Angle McFadden, Yasargil (two types), Scoville, Mayfield, Vari-Angle, Pivot, and Kapp. Phase homogeneity and crystal structure were analyzed by x-ray diffraction using a Phillips x-ray diffractometer. Clip deflection in an Oxford Research Systems MRI spectrometer was measured in our in vivo rat abdominal aortic aneurysm model. Results showed that the volume fraction of the martensitic phase in the various clips correlated with the magnitude of the deflection. Among the clips examined, the Yasargil, Sugita, Heifetz Elgiloy, and Vari-Angle McFadden had a nonmartensitic composition and did not deflect in the magnetic field. The Scoville contained 5% martensite and deflected only marginally. Martensite comprised 35% of the Mayfield clip, which deflected 45 degrees, and 90% of the Heifetz, Vari-Angle, Pivot, and Sundt-Kees Multi-Angle clips, which deflected approximately 70 degrees or slipped off the aneurysm.(ABSTRACT TRUNCATED AT 250 WORDS)
Alloys↗
Mechanical and metallurgical properties of carotid artery clamps.
The mechanical and metallurgical properties of carotid artery clamps were evaluated. The pressure plate retreat propensity, metallurgical composition, surface morphology, magnetic properties, and corrosion resistance of the Crutchfield, Selverstone, Salibi, and Kindt clamps were tested. None of the clamps showed evidence of pressure plate retreat. The clamps differed significantly in their composition, surface cleanliness, magnetic properties, and corrosion resistance. The Crutchfield clamp was the only one manufactured from an ASTM-ANSI-approved implantable stainless steel (AISI 316) and the only clamp in which the surfaces were clean and free of debris. The Selverstone clamp was made principally from AISI 304 stainless steel, as was one Salibi clamp. The pressure plate on another Salibi clamp was made from a 1% chromium and 1% manganese steel. Machining and surface debris consisting principally of aluminum, silicon, and sulfur was abundant on the Selverstone and Salibi clamps. The Kindt clamp was manufactured from AISI 301 stainless steel with a silicate-aluminized outer coating. The Crutchfield and Selverstone clamps were essentially nonferromagnetic, whereas the Salibi and Kindt clamps were sensitive to magnetic flux. In the pitting potential corrosion test, the Crutchfield clamp demonstrated good corrosion resistance with a pitting potential of 310 mV and no surface corrosion or pitting by scanning electron microscopy examination. The Selverstone clamp had lower pitting potentials and showed various degrees of corrosion and surface pitting by scanning electron microscopy. The Salibi pressure plate had a very low pitting potential of -525 mV and showed severe corrosion. By metallurgical criteria, only the Crutchfield clamp is suitable for long term implantation.
Animals↗
Corrosion of aneurysm clips: evaluation and clinical implications. Part 1: Metallurgical foundations of stress corrosion failure.
Several intracranial failures of aneurysm clips have been documented recently. Consistently, the mechanism of failure has been stress corrosion. These failures could have been anticipated if certain metallurgical properties of the clips had been known. In this paper, we review the metallurgical basis of stress corrosion failure and offer serial metallurgical tests as screening procedures to determine a clip's propensity towards failure. The importance of determining a clip's fracture toughness, a key indicator of stress corrosion resistance, is emphasized.
Corrosion↗
Corrosion of aneurysm clips: evaluation and clinical implications. Part II: Individual performance.
The intracranial fracture of aneurysm clips due to stress corrosion failure is an increasingly common long term postoperative complication. To study the susceptibility of different clips to this process, we evaluated seven aneurysm clips (Mayfield, Yasargil, Vari-Angle McFadden, Scoville, Heifetz, and Pivot) in vitro. Microstructures, hardness, chemical composition, and susceptibility to stress corrosion failure were all measured by standard metallurgical techniques. Certain clips such as Heifetz, Pivot, and Vari-Angle showed a much greater propensity to stress corrosion failure than the others. As a result of our tests, we recommend that only the clips that show high stress corrosion resistance in in vitro testing should be considered for long term in vivo implantation.
Corrosion↗
Intracranial clips: an examination of the devices used for aneurysm surgery.
A properly functioning aneurysm clip is of paramount importance in the surgical ablation of intracranial aneurysms. An appropriate match between the closing force needed to ablate an aneurysm and the force exerted by the aneurysm clip must be achieved. In this study, the opening and closing forces exerted by several commonly used aneurysm clips were tested. There was a strong correlation between the classification of the clips, according to the Dujovny system, and their mechanical behavior. Minimal variability among different lots of the same clip type and minimal hysteresis were generally exhibited by the alpha mobile fulcrum class clips, such as the Yasargil, Vari-Angle McFadden, Scoville, and Mayfield clips. Significant exceptions included several types of Mayfield and Drake clips. In contrast, pivot class clips generally showed twice as much lot variability among different lots, as well as a significant amount of hysteresis. Clips of this class include the Vari-Angle, Heifetz, and Pivot clips. Because significant variations in clip force exist and because several other factors can compound these differences, it is suggested that aneurysm clips be individually tested for their closing forces before they are used in an operation.
Humans↗
Mechanical and metallurgical properties of vascular clips designed for temporary use.
Six commonly used surgical clips (Kleinert-Kutz, Pivot, Vari-Angle, Yasargil, Biemer, and Acland) that have been designated by their manufacturer as being suitable for temporary occlusion were studied in terms of their mechanical and metallurgical properties. Opening and closing forces were determined for all of the clips. Significant variations in clip force with respect to blade gap were found in all of the pivot-type clips. Metallurgical testing showed that all six clips exhibited properties that contraindicate long-term implantation.
Corrosion↗
Failure of a Heifetz aneurysm clip.
A 16-year-old girl died from an acute subarachnoid hemorrhage following the fracture of a blade of a Heifetz aneurysm clip. The clip was manufactured from 17-7PH steel, which on metallurgical testing was found to be highly sensitive to intergranular corrosion. The fracture mechanism was stress corrosion, brought on by the combination of a stress load, an electrolytic environment, and a susceptible steel.
Adolescent↗
Metallurgical evaluation of the compatibility of surgical clips with their appliers.
Five aneurysm clips and their respective appliers (Heifetz, Vari-Angle, McFadden, Scoville, and Yasargil) were tested for the production of small metal shards that could provoke a foreign body reaction or increase the risk of a stress-corrosion failure. Pivot and Vari-Angle-McFadden clips produced numerous large shards, the Scoville clip produced a few fine shards, and the Yasargil and Heifetz clips produced none. Metal shard production due to cold metal transfer is attributed to the abrasive mechanical interaction between clips and appliers made from metals with different degrees of hardness.
Aneurysm↗
Heifetz clip failure. A metallurgical study.
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Aged↗