Revision surgery was conducted on (b)(6) 2020.The left l4 set screw was loose causing the rod to move back and forth.The patient could hear audible squeaking with slight flexion and extension.Set screw, rod, and screw were removed and replaced.The invictus spinal fixation system was implanted on (b)(6) 2020.
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There were two set screws returned for evaluation.Both are of the same product part number but contain separate identifying lot numbers.It is unknown which belongs to the backed out screw.15100; set screw, lot# sm122537, manufactured 2/29/2020.15100; set screw, lot# 8301101s5, manufactured 7/11/2019.An evaluation of the returned implants found.Set screw 1.Continuous wear on outer circumference of set screw indicates that the rod had contact under force for greater than 360 deg (this is indicative that the set screw was used to reduce a rod).There is symmetric wear mark which indicates that the set screw did have normal contact to the mating rod at full lock down.Note that one side of the wear mark is less pronounced, this indicates that the set screw had more contact on one side than the other.Based on these wear marks, it is inferred that the set screw was used to reduce a non-normal rod causing the wear mark on the outer circumference, but able to have a normalized lock down at final tightening.Set screw 2.Continuous wear on outer circumference of set screw indicates that the rod had contact under force for greater than 360 deg (this is indicative that the set screw was used to reduce a rod).Note that the continuous wear mark ends in a non-symmetric condition; this indicates that the set screw was not normal to the rod at final lockdown.There is a second wear mark located counter-clockwise to the final lockdown position.This wear mark is a result of rod motion relative to the set screw and the counter-clockwise position is in a "loosened" conditioned compared to final lockdown.Based on these wear marks, it is inferred that the set screw did not have a normalized lock down at final tightening, resulting in set screw loosening and rod motion.
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