A comprehensive investigation was immediately initiated on receipt of the complaint.The product was not returned to manufacturer for evaluation, and a thorough investigation could not be completed as the lot number has not been identified in this case.Since the screw was retained by the hospital, no physical, chemical evaluation could be performed, and the root cause of the reported issue could not be ascertained.During revision it was noticed the right l4 screw had pulled out slightly with a fracture at the base of the transverse process.The left l4 screw appeared to have a loose set screw condition.The order of events (screw pull out or set screw loosening) can not be determined.Either event could contribute to the other due to load transfers.
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