During an extreme lumbar interbody fusion on the l4-5 while using electromyography (emg) on a surgical dilator, the system notified the surgeon that the dilator was in close proximity to a nerve in every direction tested, which the surgeon believed to be incorrect.No patient harm was reported as a result of the reported event.
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An on-site company representative was permitted to troubleshoot the system during the case and was able to confirm the reported event.The device has been used by the site since the reported event with the on-site company representative reporting they have seen no further emg monitoring issues.No device was returned for evaluation.Based on the information obtained the root cause of the reported event is unable to be determined, but may be the result of signal interference between the stimulation and recording electrodes on the patient as a result of patient anatomy and electrode placement.Labeling review: "warnings, cautions, and precautions.While the pulse system is designed to assist in the electromyographic location of spinal nerves in proximity to the surgical site, it is not intended to take the place of thorough knowledge of spinal anatomy and appropriate surgical technique, nor should the information provided by the system be construed as definitive indicators of nerve location.Such factors as the distance from the nerve, the position and placement of electrodes, individual muscle and/or nerve responses, the proximity and strength of sources of electrical interference, and other patient and environmental factors, may influence the operation.If, in the judgment of the clinician, this resistance is sufficient to preclude proper placement of instruments, the procedure should be suspended." ".To optimize accuracy of emg recording, the emg common electrode should be located between the site of stimulation and the recording electrodes." ".While a positive emg detection by the pulse system can be associated with a high level of certainty that a nerve is in close proximity to the dilator tip, the absence of such an emg detection cannot be construed as a certain indication that no nerves are close to the dilator tip.Do not advance dilator probes until all available data have been considered." ".Do not advance the dilator faster than the rate of update of detection data." ".Movement of the patient during stimulation can cause excessive electrical ¿noise¿ and/or false emg (noise) artifacts.".
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