This event is being reported as part of a retrospective review of servicing events.During servicing of the nvm5 unit, it was found the unit failed simulated stimulation testing; specifically, the unit was not providing appropriate responses to returned stimulation values.The stimulation board was found faulty and the patient module was replaced to address the issue.The cause of the issue can therefore be attributed to the stimulation board.Service history review: review of the service records for the three previous service events for this device identified no similar service events in which the system was found to fail simulated stimulation testing or had the stimulation board replaced.Labeling review: "precaution.While the nvm5 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.The nvm5 system is to be used only as an adjunct to medical judgment and appropriate surgical practices.Dilator insertion and advancement should be conducted only after careful analysis of radiographic images of the operative target area.While a positive emg detection by the nvm5 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.".
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