AMISTEM H FEMORAL STEMS

Additional Manufacturer Narrative

R&D ANALYSIS FROM THE IMAGES AND INFORMATION REPORTED IT IS VISIBLE THE EXPLANTED STEM COVERED WITH PATIENT BLOOD. ON THE BODY NO SINGS OF HA RESIDUALS SEEMS TO BE PRESENT, MEANING THAT METABOLIC ACTIVITY WAS TAKING PLACE AND THAT, PRESUMABLY, ADEQUATE BONE CONTACT WAS ACHIEVED AT THE TIME OF SURGERY. THE POST-OP X-RAY ANALYSIS COULD POSSIBLY PROVIDE MORE INSIGHT, SUCH AS THE EVALUATION OF POSSIBLE EARLY ROTATIONAL INSTABILITY OR INITIAL STRESS-SHIELDING. SOME SIGNS OF MINOR DAMAGE AND SCRATCHES ARE PRESENT ON THE NECK OF THE EXPLANTED STEM, WHICH IS LIKELY DUE TO THE REVISION SURGERY AND NOT RELEVANT TO THE REPORTED ISSUE. BASED ON THE ANALYSIS COMPLETED AND INFORMATION AVAILABLE, IT IS NOT POSSIBLE TO IDENTIFY A ROOT CAUSE OF THE STEM LOOSENING REPORTED. CLINICAL EVALUATION A REVISION SURGERY WAS PERFORMED APPROXIMATELY EIGHT YEARS AFTER THE PRIMARY RIGHT THA DUE TO PERSISTENT THIGH PAIN AND SUSPECTED FEMORAL STEM LOOSENING. THE AVAILABLE RADIOGRAPHS SHOW AN IMPLANT THAT APPEARS TO HAVE BEEN POSITIONED APPROPRIATELY, WITHOUT EVIDENT GROSS MALALIGNMENT OR MECHANICAL FAILURE. HOWEVER, AN EXTENSIVE AREA OF PROXIMAL BONE RAREFACTION AND REMODELING IS VISIBLE AROUND THE FEMORAL COMPONENT, COMPATIBLE WITH OSTEOLYSIS OR AN ADVERSE LOCAL HOST RESPONSE. NO POLYETHYLENE WEAR OR OTHER ACETABULAR ABNORMALITY WAS REPORTED, AND THE ACETABULAR SHELL WAS RETAINED; THEREFORE, POLYETHYLENE DEBRIS DOES NOT APPEAR TO BE THE MOST LIKELY EXPLANATION FOR THE PROXIMAL BONE REACTION. THE INCREASED METABOLIC ACTIVITY REPORTED ON BONE SCAN, TOGETHER WITH THE MINIMAL RESISTANCE DURING STEM REMOVAL AND THE ABSENCE OF VISIBLE BONE INGROWTH, SUPPORTS A LOSS OF BIOLOGICAL FIXATION. IT IS UNUSUAL FOR SUCH EXTENSIVE LOSS OF FIXATION TO BECOME EVIDENT AFTER THIS DURATION IN VIVO, PARTICULARLY WHEN IMPLANTATION APPEARS TECHNICALLY SATISFACTORY. UNFORTUNATELY, THE PATIENT`S CLINICAL AND RADIOGRAPHIC COURSE DURING THE FIRST POSTOPERATIVE YEARS IS UNKNOWN, SO IT CANNOT BE ESTABLISHED WHETHER FIXATION WAS INITIALLY SUCCESSFUL OR SYMPTOMS HAD BEEN PRESENT EARLIER. THE ROOT CAUSE REMAINS UNDETERMINED, AND THERE IS NO EVIDENCE OF DEVICE MALFUNCTION. BATCH REVIEW PERFORMED ON 14 JULY 2026 LOT 157339: (B)(4) ITEMS MANUFACTURED AND RELEASED ON 05-APR-2016. EXPIRATION DATE: 2021-MAR-23. NO ANOMALIES FOUND RELATED TO THE PROBLEM. TO DATE, ALL ITEMS OF THE SAME LOT HAVE BEEN SOLD WITH ONE SIMILAR REPORTED EVENT DURING THE PERIOD OF REVIEW. ROOT CAUSE: BASED ON THE AVAILABLE CLINICAL AND RADIOGRAPHIC INFORMATION, THE STEM LOOSENING APPEARS TO BE ASSOCIATED WITH EXTENSIVE PROXIMAL BONE RAREFACTION AND REMODELING AROUND THE FEMORAL COMPONENT, SUGGESTING A CASE-SPECIFIC BIOLOGICAL AND/OR MECHANICAL PROCESS DEVELOPED OVER TIME. NO EVIDENT IMPLANT DAMAGE OR MECHANICAL FAILURE WAS IDENTIFIED. HOWEVER, THE AVAILABLE INFORMATION IS INSUFFICIENT TO ESTABLISH A DEFINITIVE ROOT CAUSE

Description of Event or Problem

REVISION SURGERY DUE TO STEM LOOSENING APPROXIMATELY 8 YEARS AND 4 MONTHS AFTER THE PRIMARY BILATERAL HIP REPLACEMENT. THE SURGEON REVISED LINER, HEAD AND STEM. THE STEM CAME OUT WITH MINIMAL EFFORT AND SHOWED NO SIGNS OF ANY BONE GROWTH.