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An evaluation of the returned polyaxial screwdriver found that the distal tip had fractured and became separated from the instrument.Inspection under magnification revealed circular fracture lines indicative of a torsional overload.The detached portion which remains implanted within the polyaxial screw, entrapped beneath both the rod and set screw is approximately 4.38mm wide and 2.8mm in length.The section is manufactured from 465ss and is certified to atsm a564 standards.A previous investigation conducted for this type of occurrence determined that this is likely the result of implantation in hard dense bone, which required an increased torsional load that exceeded the design limits of the instrument.
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