BEUDAMED
    FDA Adverse Event Injury Summary report: N

    NIM-SPINE MAINFRAME

    MDR report key: 2190528 · Received August 4, 2011

    Report

    Report Number
    1045254-2011-00055
    Event Type
    Injury
    Date Received
    August 4, 2011
    Date of Event
    January 1, 2009
    Report Date
    January 19, 2011
    Manufacturer
    XOMED MFG JACKSONVILLE
    Product Code
    GWF
    PMA / PMN Number
    K03510
    Adverse Event
    Yes
    Product Problem
    Yes
    Report Source
    Manufacturer report
    Reporter Location
    KS
    Reporter Occupation
    PHYSICIAN

    Narratives

    Additional Manufacturer Narrative · 1

    DURING THE PROCEDURE, THE PATIENT HAD AN ESTIMATED BLOOD LOSS OF 9000ML, HER BLOOD PRESSURE FELL TO 50/30, NECESSITATING VASOPRESSOR SUPPORT WITH DOPAMINE, AND TRANSFER TO THE INTENSIVE CARE UNIT POST-OPERATIVELY. DUE TO THE SURGICAL CORRECTION OF HER SPINAL CONDITION AND HYPOTENSIVE EPISODE, THE PATIENT DEVELOPED SPINAL CORD SHOCK, ACCORDING TO THE AUTHORS. SEVERAL LETTERS WERE SUBMITTED TO THE EDITOR OF THE PUBLISHING JOURNAL [SPINE] BY PHYSICIANS AND NEUROPHYSIOLOGISTS THAT REVIEWED THE PAPER. SOME OF THESE LETTERS WERE PUBLISHED IN SPINE VOLUME 35, NUMBER 6, PP 714-723. IN THE LETTERS PUBLISHED IT WAS THE OPINION OF THE LETTER-WRITERS THAT THE SURGEONS MAY NOT HAVE FULLY UNDERSTOOD AND PROPERLY INTERPRETED THE DATA PRESENTED BY THE NIM MONITOR DURING THE COURSE OF THE SURGICAL PROCEDURE. ADDITIONAL COMMENTS AND CONCLUSIONS WERE AS FOLLOWS: THAT THE DATA INDICATED THAT THE ELECTRODES WERE REVERSED (EITHER IN HOW THEY WERE PLUGGED IN OR HOW THEY WERE LABELED ON THE SCREEN); THAT THE SET-UP OF THE MONITOR MADE THE TRACES DIFFICULT TO READ AND ANALYZE DUE TO THE MANNER IN WHICH THEY WERE DISPLAYED (OVERLAP BETWEEN THE TRACES); THAT DESPITE THE QUESTIONABLE ELECTRODE SET-UP AND THE OVERLAPPED TRACES THERE WERE STILL REAL MEP CHANGES (DROPS IN AMPLITUDES) THAT INDICATED A "TRUE-POSITIVE" AND NOT A FALSE-NEGATIVE AND SHOULD HAVE PROMPTED, AT A MINIMUM, AN INVESTIGATION OF A POTENTIAL PROBLEM; THAT THE TC-MEP DATA PROVIDED ON THE MONITOR WAS CONSISTENT WITH THE POST-OP CLINICAL RESULTS OBSERVED AFTER THE SURGERY (PARAPLEGIA) . MEDTRONIC ALSO HAD A NEUROPHYSIOLOGIST (PH.D.) ON STAFF REVIEW THE PAPER AND ANALYZE THE DATA PROVIDED. FOLLOWING ARE THE CONCLUSIONS OF THIS REVIEW: AFTER READING THE CASE REPORT, IT IS CLEAR THAT THE NIM DID NOT MALFUNCTION, AND IN FACT PERFORMED AS DESIGNED. AS MENTIONED IN THE "LETTERS TO THE EDITOR" THE LEADS WERE SWITCHED. WHILE THE AUTHORS CLAIM THAT THEY WERE CAREFUL IN PLACING THE LEADS, THEIR OWN DATA DEMONSTRATES THE ERRORS: CHANNEL 1 (LEFT UPPER LIMB): PREOP = 508UV, AFTER SCREW INSERTIONS = 27UV, AFTER CURVE CORRECTION = 40UV, POST-PROCEDURE = 27UV (95% REDUCTION) CHANNEL 2 (LEFT LOWER LIMB): PREOP = 2898UV, AFTER SCREW INSERTIONS = 698UV, AFTER CURVE CORRECTION = 1141UV, POST-PROCEDURE = 1292UV (76%-56% REDUCTION) CHANNEL 3 (RT UPPER LIMB): PREOP = 1156UV, AFTER SCREW INSERTIONS = 350UV, AFTER CURVE CORRECTION = 16UV, POST-PROCEDURE = 14UV (88% REDUCTION) CHANNEL 4 (RT LOWER LIMB): PREOP = 2288UV, AFTER SCREW INSERTIONS = 2214UV, AFTER CURVE CORRECTION = 1958UV, POST-PROCEDURE = 1991UV (14% REDUCTION). EVEN IF IT IS ASSUMED THAT THE LEAD PLACEMENT WAS CORRECT, THEIR DATA INDICATED THAT 3 OF THE LIMBS WERE BELOW 50% OF BASELINE AFTER SCREW INSERTION AND CURVE CORRECTION, AND SHOULD HAVE BEEN ADDRESSED. ALSO, THEIR EXPLANATION OF REVERSED LATENCY IS INVALID. THEY CLAIM THAT A SHORTER LATENCY FOR THE LOWER LIMBS CAN BE DUE TO MUSCLE EXCITATION FROM SUBSEQUENT STIMULI OF THE 8 PULSE TRAIN, AND THAT THEY STIMULATED AT 1 HZ. THIS IS NOT POSSIBLE BECAUSE THE TRACES ARE GATED TO THE STIMULUS. THE SCREENSHOTS SHOW TWO STIMULUS PULSE TRAINS PER TRACE SEPARATED BY ONE SECOND. IT IS ALSO CLEAR THAT THE TRACES ARE NOT OVERLAPPED TRACES. WHILE THEY DID NOT DESCRIBE THE PULSE TRAIN, IT CAN BE SEEN THAT THE WIDTH OF THE TRAINS ARE MUCH LESS THAN THE DIFFERENCE IN LATENCY (BY ALMOST HALF). THIS MEANS EVEN IF THE UPPER LIMB MOTOR POTENTIALS WERE DRIVEN BY THE 8TH PULSE, AND THE LOWER LIMB BY THE FIRST PULSE IN THE TRAIN, THE DIFFERENCE IN TIME IS NOT SUFFICIENT TO PRODUCE THE REVERSED LATENCY THEY DESCRIBE. IT MIGHT HAVE BEEN A POSSIBLE EXPLANATION IF THE TRACES WERE OVERLAPPED FROM MULTIPLE RUNS, BUT THESE ARE SINGLE TRACES. FURTHERMORE, WITH A 1HZ STIMULUS PULSE TRAIN, AND AT 60-70M/SEC CONDUCTION VELOCITY OF THE CORTICOSPINAL TRACT AXONS, A RESPONSE FROM SUBSEQUENT STIMULI WOULD HAVE BEEN OFF THE SCREEN. IT IS POSSIBLE TO SHORTEN THE LATENCY, FOR INSTANCE BY PRECONDITIONING THE NEURONS, EITHER WITH MULTIPLE STIMULATION (AS IN THE PAPER) OR VOLUNTARY CONTRACTION OF THE TARGET MUSCLES. THESE SCENARIOS ARE UNLIKELY, BECAUSE SIMILAR EFFECTS WOULD HAVE BEEN SEEN FOR THE UPPER LIMBS AS WELL AS THE LOWER LIMBS, AND THE PATIENT WAS ANESTHETIZED. SO, IT IS IMPOSSIBLE (BASED ON THEIR OWN DATA) THAT THE UPPER AND LOWER LEADS WERE NOT SWITCHED. ALTHOUGH OUR INVESTIGATION, AND SEEMINGLY ALL THAT HAVE REVIEWED THIS EVENT CONCLUDE THAT THE MEDTRONIC NIM SPINE DID NOT MALFUNCTION, WE ARE REPORTING THIS EVENT IN A MEDICAL DEVICE REPORT AS THE NIM SPINE WAS APPARENTLY A FACTOR IN THE SERIOUS INJURY THAT OCCURRED, EVEN IF THE ROOT CAUSE APPEARS TO BE A USE ERROR.

    Description of Event or Problem · 1

    [CLINICAL ARTICLE CITATION] PER THE ABOVE ARTICLE: PATIENT IN (B)(4) UNDERWENT SURGERY FOR CORRECTION OF SEVERE KYPHOSIS AND FUSION OF THE SPINE USING PEDICLE SCREW INSTRUMENTATION. MONITORING OF TRANSCRANIAL MOTOR-EVOKED POTENTIAL (TC-MEP) USING MEDTRONIC NIM-SPINE WAS PERFORMED THROUGHOUT THE PROCEDURE AS AN ADJUNCT TO MONITOR SPINAL CORD FUNCTION. ALTHOUGH "MEP MONITORING WAS PRESERVED" AND "MEP AMPLITUDE REMAINED WITHIN NORMAL LIMITS" THROUGHOUT THE PROCEDURE ACCORDING TO THE AUTHORS, INDICATING NO SIGNS OF SPINAL CORD INJURY, THE PATIENT AWOKE WITH TRANSIENT PARALYSIS OF HER LEGS. WHEN THE PARAPLEGIA WAS DISCOVERED, THE PATIENT WAS IMMEDIATELY RETURNED TO THE OR, AND ALL SPINAL IMPLANTS WERE RELEASED DUE TO THE OVERSTRETCHING OF THE PATIENT'S SPINAL CORD. WHILE SENSATION AND SOME FUNCTION WAS RECOVERED OVER THE NEXT SEVERAL WEEKS, IT IS UNCLEAR FROM THE ARTICLE AS TO THE EXTENT OF FUNCTIONAL RECOVERY.

    Devices

    Seq Brand Generic Product Code Manufacturer Model Lot UDI-DI
    1 NIM-SPINE MAINFRAME STIMULATOR, ELECTRICAL, EVOKED RESPONSE GWF XOMED MFG JACKSONVILLE UNK

    Patients

    Seq Age Sex Outcome Treatment
    1 00015 YR Congenital Anomaly| R| S