Method: visual inspection, device history review, complaint history review, risk assessment.Result: the customer reported event was confirmed via visual inspection.The device was returned in 2 pieces, with the tulip head disengaged from the screw shank.There was still a blocker threaded into the es2 screw blades.Deformation was found on the tulip locking ring and on the screw shank head.Manufacturing history was reviewed and no issues were identified.Conclusion: according to risk file, too much stress on the construct may cause stress concentration resulting in the failure of screw tab intra op.Root cause of the reported event could not be determined conclusively but potentially could be due to: user error, blocker not correctly aligned in tulip threads, too much torque applied (in excess of 12nm), counter torque tube not used, cantilever force applied during final tightening, rod seated poorly in tulip.
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