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On (b)(6) 2020 was the initial surgery (l3 / l4 / l5 plif procedure).Three (3) months after the surgery, the l5 right set screw was found to be loosening.On (b)(6) 2021 was the revision surgery to replace the set screw.During surgery, it was found that the l3 and l4 set screws were also loosening and the surgeon re-screwed the sets.
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Review of the device history records, did not identify any manufacturing or processing related irregularities.Investigation of the set screw showed, that the threads are not deformed.Which indicates, that set screw was not cross threaded.The bottom surface of the set screw was examined for wear patterns created against the construct rod, during final set screw tightening.The expectation for the bottom surface of a set screw installed in a stable construct is a symmetric hour glass pattern.None of the three (3) screws examined demonstrated, the expected hour-glass pattern.Based on these findings, the anterior wear marks on the set screws, indicate the set screw disengagement is a result of a non-distributed loading and non-normalized rod conditions at final lock down.
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