Device history records and complaint history were reviewed for the corresponding lot number and no relevant issues or similar complaints were identified.Visual inspection of returned device reveals there is one deformation mark on the bottom of the blocker.The single deformation mark indicates that the rod was not horizontally placed into the head of the associated screw tulip.Deformation from rod is much more shallow than expected for 8nm of torque indicating the blocker was under tightened.Chattering marks are also observed on bottom of blocker.Chattering marks result from repetitive movement over the rod during blocker back out and indicate that the blocker was not sufficiently tightened on a properly placed rod.It cannot be confirmed which returned screw is associated with this blocker, however, there are multiple screws with deformation marks at high angles on the tulip and shank head.This evidence further supports that the rod was not properly positioned in the screw tulip head(s).Device ifu and sgt were reviewed: 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.To final tighten; use the anti-torque key and the torque wrench: place the anti-torque key over the screw head.Place the torque wrench through the anti-torque key until it is guided into the blocker.Line up the two arrows to achieve the final tightening torque of 8nm.The torque wrench indicates the optimal torque force that must be applied to the implant for final tightening.Note: do not exceed 8nm during final tightening.The anti-torque key must be used for final tightening.The anti-torque key performs two key functions: allows the torque wrench to align with the tightening axis.Helps to maximize the torque needed to lock the implant assembly improper selection, placement, positioning and fixation of these devices may result in unusual stress conditions reducing the service life of the implant.Contouring or bending of rods or plates is recommended only if necessary according to the surgical technique of each system.Rods or plates should only be contoured with the proper contouring instruments.Incorrectly contoured rods/plates, or rods/plates which have been repeatedly or excessively contoured must not be implanted.The most likely cause of the reported event was determined to be improper placement of the rod in the tulip head during final tightening.The blocker was also most likely over-tightened, as indicated by the deep rod indentation mark.There is evidence from the other blockers used in the construct that they were also misaligned in the tulip heads and/or over- or under-torqued, which would add additional stress to each individual blocker.
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