Visual inspection: the blocker was returned and showed chattering on the bottom of the blocker, caused by contact with the rod as the blocker migrated out of the screw tulip.This is the most likely blocker to have migrated out.The initial indentations are lighter than what is expected for 12nm of torque, indicating this blocker may have been undertightened.Device and complaint history records were reviewed, and no relevant manufacturing issues or similar complaints were identified.Per surgical technique: once the correction procedures have been carried out and the spine is fixed in a satisfactory position, the final tightening of the blockers is performed.Use the anti-torque key and the torque wrench.The anti-torque key and torque wrench come in two sizes; standard and short.Place the anti-torque key around the screw head.Place the torque wrench through the anti-torque key until it is guided into the blocker.The torque wrench indicates the optimal torque force that must be applied to the implant for final tightening.The surgical technique outlines the steps for final tightening.The blockers must be final tightened to 12nm.Due to the indentations on the blocker, it is likely the blocker was not fully tightened to 12nm.Other possible root causes that could have contributed to the event include patient fall, excessive post op activity, poor fixation construct, and/or poor bone quality.
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