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The involved screw was not received at our facility.Since we could not examine the item, it was difficult to determine the reason for the reported fault.Nevertheless, examination of the production records of the involved item indicated it was manufactured according to specification.In addition, results of mechanical tests performed on sample pedicle screws manufactured at the same period as the involved lot, were according to specification.In order to simulate the reported case, a torsion test was performed for two 5.5mm diameter carboclear pedicle screws, with results that met carbofix acceptance criteria.The test included pedicle screw insertion into a bone model (rigid polyurethane foam) using a screwdriver and torque meter (no tapping was performed prior to insertion, in order to simulate worst case scenario).
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During fixation of t6-t11 vertebrae of oncological patient in (b)(6), one of the screws at t9 was inserted in a manner that the screw tulip touched the pedicle.This caused significant resistance that led to excessive torque and breakage of the screw.The physician decided the construct is strong enough (leaving the screw in situ, with fixation of two levels above and two levels below the affected vertebrae).
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