The reported event could be confirmed.By doing the visual inspection, the returned locking screw was inspected under a microscope.The thread below the screw head which is intended to lock the screw in the plate, shows plastic deformation which could explain the loss of the angular locking ability.The damage pattern shows that a high force was applied during the locking attempts.The t10 recess has clearly visible deformations in clockwise and counterclockwise direction, which indicates that the screw was exposed to high forces during insertion and/or extraction.A review of the device history for the reported lot did not indicate any abnormalities.No deviation from the specifications was noted.No indications of material, manufacturing or design related problems were found during the investigation.A review of the labeling did not indicate any abnormalities.Based on investigation, the root cause was attributed to a user related issue.The failure was caused by over tightening of the locking screw in the final position, which did lead to a deformation of the locking thread.If any further substantial information is provided, the investigation report will be updated.
|