M.U.S.T. MIDLINE CORTICAL (MC) SCREW SYSTEM

Description of Event or Problem

REVISION SURGERY WAS PERFORMED 1 YEAR AND 8 MONTHS FROM PRIMARY DUE TO PERSISTENT PATIENT PAIN AND RADIOLOGICAL FINDINGS SUGGESTIVE OF NON-UNION. DURING REVISION SURGERY, THE LEFT S1 SCREW WAS FOUND BROKEN VERY DISTALLY. THE DISTAL FRAGMENT COULD NOT BE RETRIEVED AND WAS THEREFORE LEFT IN SITU. ALL SCREWS WERE REVISED TO COMPETITOR DEVICES.

Additional Manufacturer Narrative

BATCH REVIEW PERFORMED ON 12 JUNE 2026 LOT 2461374: (B)(4) ITEMS MANUFACTURED AND RELEASED ON 19-JULY-2024. EXPIRATION DATE: 2029-07-04. NO ANOMALIES FOUND RELATED TO THE PROBLEM. TO DATE, (B)(4) ITEMS OF THE SAME LOT HAVE BEEN SOLD WITH NO SIMILAR REPORTED EVENTS DURING THE PERIOD OF REVIEW. CLINICAL EVALUATION DURING REVISION SURGERY, THE LEFT S1 SCREW WAS FOUND BROKEN VERY DISTALLY. THE DISTAL FRAGMENT COULD NOT BE RETRIEVED AND WAS THEREFORE LEFT IN SITU. THE AVAILABLE IMAGES ARE OF VERY POOR QUALITY AND DO NOT ALLOW A RELIABLE ASSESSMENT OF THE RESIDUAL POSITION OF THE BROKEN FRAGMENT, ITS STABILITY, OR ANY POTENTIAL SECONDARY MIGRATION. FOR THIS REASON, ALTHOUGH THE MATERIAL IS INTENDED FOR LONG-TERM IMPLANTATION, POTENTIAL SECONDARY ISSUES RELATED TO THE RETAINED FRAGMENT CANNOT BE DEFINITIVELY EXCLUDED. REGARDING THE BREAKAGE MECHANISM, THE UNDERLYING CAUSE REMAINS UNCLEAR. POSSIBLE CONTRIBUTING FACTORS MAY INCLUDE PRE-EXISTING FATIGUE MECHANISM, OR DELAYED UNION; HOWEVER, NONE OF THESE CAN BE CONFIRMED BASED ON THE AVAILABLE DOCUMENTATION. THE FRACTURE OF THE SCREW SHOULD HARDLY BE CONSIDERED AS THE MAIN CAUSE FOR REVISION, JUDGING FROM THE SURGICAL STRATEGY UNDERTAKEN BY THE REVISION SURGEON. ANALYSIS PERFORMED BY R&D MANAGER DURING THE REVISION PROCEDURE PERFORMED FOR NON-UNION, ONE SCREW WAS FOUND TO BE FRACTURED AT THE MID-SHAFT, AS SHOWN IN THE PROVIDED IMAGE. BASED ON THE AVAILABLE INFORMATION, BONE NON-UNION MAY INDICATE INSUFFICIENT BONE GROWTH OR INADEQUATE BONE INTEGRATION. IN SUCH A CONDITION, THE FIXATION CONSTRUCT MAY HAVE BEEN EXPOSED TO REPEATED CYCLIC LOADING, WHICH COULD HAVE CONTRIBUTED TO FATIGUE-RELATED BREAKAGE. ROOT CAUSE: THE MOST PLAUSIBLE CONTRIBUTING FACTOR IS THE LACK OF SOLID OSSEOUS FUSION POSTOPERATIVELY, WHICH MAY HAVE RESULTED IN INCREASED MECHANICAL LOADING ON THE SCREWS UNDER PHYSIOLOGICAL CONDITIONS, POTENTIALLY LEADING TO FATIGUE CRACK INITIATION AND EVENTUAL BREAKAGE. WHILE THE EXACT ROOT CAUSE CANNOT BE DEFINITIVELY CONFIRMED, THE INVESTIGATION FOUND NO EVIDENCE OF MANUFACTURING DEFECTS OR SYSTEMIC ISSUES RELATED TO THE DEVICES.