On 20 july 2017 the r&d project manager checked the retrieved images of the broken item with the following comment: based on the event description as well as on the received pictures it was observed that the locking screw was broken in the smallest cross section, between the collar and the end of the threading design.It was assumed that during the final locking a wrong manoeuvre was performed: most lilkely a lateral force were exerted along the screw axes arising potential stress in the minimal cross section.However, the safety and functionality of the locking screw was successfully verified and validated through mechanical tests.Results confirmed that the design was appropriate to assure optimal mechanical strength necessary to perform the final locking procedure.A rescue instrument is available in the instrument set to remove damaged screw properly.Batch review performed on 26 july 2017.Lot 141365: (b)(4) items manufactured and released on 22 october 2014.Expiration date: 2019-06-30.No anomalies found related to the issue.To date, (b)(4) items of this lot have been sold and this is the third similar event reported on this lot.On 27 july 2017 the medical affairs commented the received x-ray as following: the cause for this adverse event is not of clinical origin, as it happened during surgery and it is clearly connected with screw insertion, not with the performance of the screw or other devices in vivo.No clinical consequence should be expected either since the only adverse effect was the 5 minute delay.During the visual inspection it was observed and confirmed that the locking screw was broken off in the smallest cross section, just at the end of the threading geometry.However, the reason that generated such a fragile fracture is still unknown.As supposed during the visual inspection, a wrong manoeuvre that arose higher stress was performed during final fixation.Additionally, it was observed that the driving interface recess was partially damaged during the removal phase with the rescue instrument.This confirms that in case of unexpected failure it is possible to totally remove the device form the patient.Visual investigation was performed on 31st of july, 2017 by r&d project manager.
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