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The reported event could be confirmed.The device inspection revealed the following: the product was returned and is indeed broken in at least three parts.Two out of the three were returned, in addition to a bone remain cylinder, maybe including a piece of the screw.The returned screw is highly twisted proving that high torsional loads were applied to it.Considering that the patient was only (b)(6) at the time of the event, very hard bone and a high osseointegration between the screw and the bone can be considered the root cause of the inability to extract the device out of the patient.The implant extraction set states that ¿to avoid damaging the screw, make sure the screwdriver is in line with the screw axis and fully inserted.Never use a worn or damaged screwdriver to remove screws.It is recommended that the solid screwdriver be used for screw removal.Strong bone formation around the implant is possible in the pediatric cases using partially threaded screws.This may lead to difficult implant removal with an increased risk of screw head breakage or stripping of screw hexagonal head.¿ during the extraction, the screw was under high tension and combined with the rotational moves, this led to a torsional fracture.However, regardless of the implant size or type the torque needed to explant a screw can be higher than the torque needed to implant a screw.In some cases the torque required to remove the implant is higher than the mechanical properties of the screw.In these cases the implant breaks during explantation.Specific instruments dedicated for implant removal are offered by stryker to help explanation of screws.Stryker offers dedicated instrument sets (implant extraction set, moduli (b)(4) and modul 2 (b)(4)).By using these specific extraction sets, the removal of screws will be easier.A review of the device history for the reported lot did not indicate any abnormalities.No corrective actions are required at this time.A review of the labeling did not indicate any abnormalities.No indications of material, manufacturing or design related problems were found during the investigation.If any further information is provided, the investigation report will be updated.
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Customer reported : "these screws were placed in the patient on (b)(6) 2019 at the level of the medial malleolus.The two screws were removed on (b)(6) 2020.The first screw was extracted without any problem.However, during the extraction of the second screw, the pre-threaded axis twisted and prevented its removal.An attempt was made to extract the screw with a strong pair of pliers and then with a trephine, which allowed the pre-threaded bone core to be removed without allowing the screw to be removed in reverse.Part of the screw is left intraosseous.".
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