Initially in the report it was reported that the awareness date was january 08, 2019.Today, after control it was noticed that the correct awareness date is december 21, 2018.For this reason the mdr is reported with delay.Details of the tibial baseplate involved in the case are not available batch review performed on 07 february 2019: lot 151224: (b)(4) items manufactured and released on 08 october 2015.Expiration date: 2020-09-22.No anomalies found related to the problem.To date, (b)(4) items of the same lot have been already sold without any similar reported event.Preliminary investigation performed by r&d product manager: revision surgery of a gmk hinge tibial insert after 1 year from implantation due to tibia dislocation.Preliminary investigation based on the pictures of the explanted components.Articular surface of the tibia insert looks damaged with scratches and dents, most likely caused during the procedure to explant the component.Central cone of the insert has been resected to facilitate removal of the insert from the joint.Tibia insert locking screw is not damaged.This suggests that after dislocation, tibial insert was found still fixed on the tibia baseplate and central post of the femur dislocated from the tibia insert.Causes for dislocation still remain unknown.
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Visual inspection performed by r&d knee manager: revision surgery of a gmk hinge implant for tibia luxation after 1 years from primary surgery.It was then reported by the surgeon that the inlay locking screw was found broken.From visual inspection, both the inlay locking screw and the hinge post locking screw have been found intact and not broken as reported; they can even be screwed respectively on the baseplate and on the post.The central cone of the tibia insert has been cut during revision surgery in the attempt to remove the insert from the baseplate.Some particles / debris can be seen in the threaded hole of the hinge post.From visual inspection, we can suppose that the event was most likely caused by unscrewing of one of the 2 screws.The unscrewing was probably related to the hinge post screw; we can infact suppose that the poly was not dislocated since its cone has been cut to be removed from the baseplate and so the inlay screw was in site.It is not clear if the debris/particles that we found in the hinge post threaded hole was the cause of bad-fixation of the post to the femoral component or if the debris had come inside the hole only after the screw was loosened and the femur was dislocated.Self unscrewing of the hinge post secure screw was most likely caused by insufficient tightening torque during fixation ( the usage of the torque limiting screwdriver has not been confirmed ) or presence of debris in the hole screw that didn't guarantee proper fixation.
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