The patient had previous surgeries on unknown dates (plif l5-s1 and after a while removal of the pedicular screws).Plif cages were removed and an alif cage inserted.Indication for alif was pseudarthrosis.The surgeon used the drill to prepare the screwholes.An hammer was used because of the severe sclerotic bone.He didn't use a tap.Additional information received on 10 january 2017 and includes: the surgeon rarely uses an antitorque.He finds it dangerous because he is afraid the screwdriver slips of and damaged the soft tissue.On the fluoroscopy nothing was visible.At post-op x-ray, it is visible that there is a small gap between cage and the endplate of s1.The surgeon stated that he broke off 2 screws, and he also mentioned that he used the drill and the tab.Batch review performed on 06 february 2017.Lot 1620157: (b)(4) items manufactured and released on 02 august 2016.Expiration date: 2021-07-19.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.On 08 february 2017 the (b)(4) performed a visual inspection and commented as follows: the head of the screw checked was broken just at the end of the center hole ø1.5mm length 3.6mm.The torque to failure of the alif screw is 7.4nm without plate and bigger than 10nm into the plate.An additional test, on the lot 1620157 and similar lots, was performed in order to ensure that there is not a specific decrease of the performance of the screw itself.The results confirm that there are no modification of the screw performance.In addition, according the surgical technique, to perform the final tightening it's necessary to use the torque limiter that can apply a torque of 5.5nm +/- 10% that is enough to guarantee a stable construct.In the complaint updating, it was reported that the surgeon has skipped the usage of torque limiter and it applied the final tightening torque with free hand.The breakage of the screw happened when the screw was in contact with the plate, as reported in the complaint and shown in the x-ray pictures.In that condition the resistance of the screw head is bigger than 10nm.Due to these reasons, the route cause of the breakage should be the application of a tightening torque higher than 10nm.
|