CHECK AND RECHECK Surgeons should repeatedly reassess accuracy while using navigational systems, says the FDA.
Frameless stereotaxic navigation systems, which are often used in orthopedic, ENT and neurosurgical procedures, are vulnerable to accuracy errors that have led to deaths, serious injuries, and inaccurate, aborted or prolonged medical procedures, says a new Safety Communication from the FDA.
The benefits of such systems outweigh the risks, says the FDA, and no single system appears to be more dangerous than any other, it adds. But surgeons, it says, should repeatedly assess accuracy while using the systems by positioning instrument tips on identifiable anatomical landmarks and comparing actual tip location to what's displayed by the system.
Myriad factors can lead to errors, says the agency, including software anomalies, hardware damage or defects, human factors (for example, errors related to system setup or surgical techniques), anatomical complexity, poor registration and tracking, and inadequate or incomplete imaging.
Additionally, says the agency, users should
- monitor recommended software updates;
- inspect systems, including components and accessory devices, before using them; and
- be aware of technological principles and limitations, including (with electromagnetic-based systems) potential interference from metallic objects or other emitters that can impact navigational accuracy, and (with optical-based systems) line-of-sight issues and interference from infrared light sources.
Not all surgical instruments are appropriate for stereotaxic navigation, the agency adds. For example, systems may not be able to predict the location of asymmetrical or flexible instruments.
And accuracy, it says, decreases when surgeons navigate to targets farther away from the tracked structure, in part because anatomy can shift during procedures.
Stereotaxic navigation uses computed tomography or magnetic resonance imaging scans to generate a "map" surgeons use to guide their instruments. Some systems use a frame that's fixed to the patient with screws or pins to orient the device, but the more common frameless systems do not. They rely upon various technologies to track the location of the patient and navigated instruments in 3D space relative to registered patient imagery. Although the FDA's warning focuses on frameless systems, many of its recommendations apply to framed navigation systems, too, says the FDA.
