A comprehensive investigation was immediately initiated on receipt of the complaint.The product was not returned to manufacturer for evaluation, and a thorough investigation could not be completed as the lot number has not been identified/confirmed in this case.Since the screw remains in the patient, no physical, chemical evaluation could be performed, and the exact cause of the reported issue could not be ascertained.Looking at the position of the movable paw in one of the post-op images, it did not appear that the implant was fully locked.The space between the draw screw and the tooth assembly appeared to be larger in the immediate post-op images, indicating that the teeth were not fully engaged.However, this was difficult to confirm because the x-rays were taken in different planes and were not high-resolution images.While we cannot definitively say that this was the direct or only cause, it is possible that the inserter/expander was not fully withdrawn prior to tightening the draw screw.If the wedge was not fully removed, the teeth could have been misaligned, which may have resulted in an insufficient lock, therefore making it much easier to collapse the cage.Based on the information provided it is difficult for us to identify any other potential causes at this time.While none of the products were returned, a general review of the manufacturing and inspection records revealed no additional information.Remains in patient.
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