The screw was returned in 2 pieces with the tulip disengaged from the shank.The screw was returned in the unlocked state, but anodization loss shows that the screw was fully locked at one time.There is deformation on the bottom of the tulip and on the shank head where the head disengaged from the shank.This deformation is in a single direction.Device history records were reviewed for this lot, no relevant manufacturing issues were identified.Complaint history records were reviewed for this catalog number, no adverse trends were identified.Patient activity was described as sitting and the patient did not fall.Screw holes and final tightening was reportedly done per the surgical technique.Patient was described as neuromuscular and had good/normal bone.Partial x rays were provided showing the screw with a disengaged tulip in the patient.The construct is heavily fixated with 5 screws in the upper thoracic with 2 rods running parallel down the spine.There is no further fixation shown on the x ray.It is likely the construct is fixated further down the spine.From the ifu: "potential adverse events associated with spinal fusion procedures include, but are not limited to pseudoarthrosis; loosening, bending, cracking or fracture of components, or loss of fixation in the bone with possible neurologic damage, usually attributable to pseudoarthrosis, insufficient bone stock, excessive activity or lifting, or one or more of the factors listed in contraindications, or warnings and precautions; infections possibly requiring removal of devices; palpable components, painful bursa, and/or pressure necrosis; and allergies, and other reactions to device materials which, although infrequent, should be considered, tested for (if applicable), and ruled out preoperatively.Internal fixation devices are load sharing devices which maintain alignment until healing occurs.If healing is delayed or does not occur the implant could eventually break, bend or loosen.Loads produced by load bearing and activity levels will impact the longevity of the implant.Metallic implants can loosen, fracture, corrode, migrate, cause pain, or stress shield bone even after a bone has healed.If an implant remains implanted after complete healing, it can actually increase the risk of refracture in an active individual.The surgeon should weigh the risks versus benefits when deciding whether to remove the implant.Implant removal should be followed by adequate postoperative management to avoid refracture." based on the information provided, the likely cause is multifactorial.The construct design where it is heavily fixated at the top and bottom of the spine with no additional fixation in-between could cause a moment arm that would apply excess stress on the construct, causing the screw tulip to disengage.Additionally, the screw was implanted for a period of 2 years, subject to these repeated stresses and strains over time, which combined with the construct design, may have lead to it disengaging.
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