A construct spanning l2-pelvis was being implanted during a lumbar posterior fusion.An everest polyaxial screw was being implanted into the left iliac when it fractured.Subsequently, another screw was implanted into the same site and fractured during insertion.The bone was properly prepared with an undersized tap, a 7.5mm tap for an 8.5mm screw.The bone quality of the patient appeared normal.The implants were not inserted at difficult angles, and no excessive forces or complex maneuvers were utilized during insertion.The screwdriver was firmly attached to the screws as described in the surgical technique.No damage to surrounding bone or tissue was reported.During the same surgery, a screw was implanted into level l5.After insertion, the surgeon determined the screw was too long and decided to replace it with a different sized screw.During removal of the l5 screw, it fractured.The screw could not be removed from the patient, resulting in level l5 being skipped in the construct.A visual inspection was performed and the following was revealed: three everest polyaxial screw tulip heads were returned along with the two fractured shafts that were removed from the patient.Unknown removal tools were left attached to the screw shafts.The removal tools appear to have sustained damage in the same position on each device, indicating similar forces required to remove the fractured screw shafts from the patient's bone.One shaft was observed to have tissue lodged between the threads and removal tool, with the fracture surface appearing relatively even.The other shaft had metal shears lodged in the removal tool, possibly from screw thread deformation acquired during removal, with an uneven and rigid fracture surface.The tulips were inspected to find similar fracture patterns on their surfaces as well.The base of the tulip was observed to be damaged, with a significant amount of material deformation assumed to be acquired during the removal process.This type of deformation suggests an improper removal tool was utilized to grasp the external base of the screw in order to back it out of the bone.Device history records were reviewed for this lot, and no relevant manufacturing issues were identified with all units meeting stryker specifications.A complaint history record review was performed for this lot and catalog number and no previous complaints were identified.The everest deformity surgical technique guide states: "the screw may be removed with the driver and t-handle.Engage the driver tip with the inner hexalobe of the implant and turn in a counter-clockwise direction to remove the screw." the approved removal tool for the everest spinal system is the height adjustment driver (catalog# 5101-90107).If this tool is not used for the removal of everest screws, the screw may experience uneven forces resulting in fracture."the size and shape of bones and soft tissue place limitations on the size and strength of the implants and proper selection will reduce the risk of neurological injury during implantation as well as metal fatigue leading to bending or breakage of the device." the reported screw fracture during insertion could have potential causes such as insufficient tapping to the required depth, excessive torsional and/or axial forces utilized during insertion, or patient factors such as hard bone density.However, a root cause for the reported issue could not be conclusively determined.
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