Biomedical Engineering Reference
In-Depth Information
for protection of hospital staff involved in patient care and should be fol-
lowed with more rigorous procedures, as previously noted, before others,
such as lay persons, lawyers, students, and so on, may come in contact
with retrieved devices
Patient protection
and informed
consent
The study of the devices and the corresponding clinical information,
beyond the immediate needs of diagnosis and treatment, will require
informed consent from the patients. It should be routine practice to ask
patients on admission to donate their devices and tissue for research and
educational uses outside the DRA program. For implantable devices,
since the devices are normally retrieved during the course of revision
surgery, the collection process will pose no additional risks than those
associated with the revision surgery itself. As part of the informed con-
sent process, the patient should be asked to agree to share anonymized
clinical data, records, and radiographs with researchers. In accordance
with patient protection policies, based on law,* patient identifiers are
safeguarded by all research investigators and not made publicly avail-
able. The retrieval facilities should also have controlled access.
Tools for characterizing retrieved implants and tissue
Nondestructive
documentation
and retrieval
evaluations
An initial triage step is recommended to determine what level of non-
destructive and destructive evaluations, if any, is performed. However,
prior to any destructive testing, every implant will be photodocumented
for its macroscopic appearance, using digital photography and optical
microscopy. Additional imaging tools such as micro-computed tomog-
raphy or scanning electron microscopy (SEM) can also be used to
visualize the presence of different damage modes such as burnishing,
abrasion, pitting, surface deformation, delamination, scratching, embed-
ded debris, and cracks.
Destructive testing
After nondestructive testing has been completed, various forms of
destructive tests can be performed, depending on the type of materials
comprising the explant. These tests may include protocols for detailed
failure, microstructural and chemical analyses, and the determination of
physical and mechanical properties.
For metallic devices, the specimens can be etched to allow micro-
scopic examination of inclusion content, grain size, grain boundary
constituents, microporosity, and corrosion. Fractographic analysis from
SEM imaging can be used to identify the presence of fatigue striations,
evidence of ductile overload, and defects associated with crack initia-
tion. If the device has a metallic coating, any missing sections of coating
should be examined microscopically. Coating thickness and void content
may be also determined. Energy dispersive x-ray is also a useful tool for
*
Health Insurance Portability and Accountability Act of 1996; U.S. Department of
Health and Human Services Privacy Rule; 45 Code of Federal Regulations (CFR) Part
160 and Part 164, Subparts A and E.
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