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It was reported that during a tka procedure, there was an unexpected joint laxity whilst trialing, it was planned for a 9mm poly and ended up with an 18 mm poly and still laxity medially in high flexion with an 18mm.The case proceeded as normal and without issue.Then the tibial twin peg drill holes noted to be not in bone, tibial resection increased to 11 mm to allow for burr hole placement in bone and increased planned poly to an 11 mm to account for larger tibial cut.The femoral cut made had no issues and normal resection depth noted.The tibial burr holes made with burr without issue, twin peg guide placed into burr holes and attempted to be verified with verification plate varus/valgus correct but system indicated that the slope was out by 13 degrees too much posterior slope, checkpoint verified and found to be correct.Numerous attempts made to verify the correct position of cut block.However, the navio tibial cut was abandoned and changed to manual instruments, made with extra medullary jig, attempted, tibial off cut was measured and well within specs, 9mm off lateral side and 7mm medial side.The case proceeded to trialing ps implants used, but the joint was found to be unstable.The poly increased sequentially until 18 mm stable in extension but still loose medially in high flexion.This caused a delay greater than 30 minutes.
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The navio surgical system au, pn: npfs02070, sn: (b)(6) used for treatment was not returned to the designated complaint unit for evaluation, therefore, visual and functional inspections could not be performed.A screenshot review was conducted and confirmed the reported complaint.The initial implant planning screen shows a 9 mm poly was planned and was increased to 11 mm after virtual positioning of the tibia cut guide was planned prior to bone removal.The case information screen shows the final poly size implanted was 18 mm.The case was put in casevisualizer, where it was confirmed that the checkpoints were placed and taken correctly.The drill holes of the tibia cut guides appear accurate in the screenshots, however, if the tibia cut guide was not adequately fixed to the bone, the resulting slope could be inaccurate.The tibia visualize cut screen confirms that the tibial slope was 13.5 degrees.This screen also shows that an additional 3.6 mm resection of the tibia would have been taken than planned.However, the user reverted to manual instrumentation for the remainder of the tibia cut.Therefore the final tibia cut cannot be confirmed other than what was reported.Screenshots show that the legion implant was chosen.This implant is planned to have a 9 mm resection for both the femur and tibia cuts.The final implant planning screen confirms that greater than suggested resection depths were planned for.However, the user reverted to manual instrumentation for the remainder of the tibia cut.Therefore the final tibia cut cannot be confirmed other than what was reported.The report states that the tibia cuts were 9 mm laterally and 7 mm medially.Because manual instrumentation was used for the tibia cut, the large medial gap in high flexion cannot be confirmed, despite the post-op gap assessment screenshot confirming the large medial gap in high flexion.A review of manufacturing records indicate the software met all specifications upon release into distribution.A complaint history review found similar reports, this issue will continue to be monitored.Clinical review determined that smith and nephew had not received adequate materials (operative reports) to fully evaluate the complaint, but if additional clinically relevant materials are later received, then the case may be re-opened for further evaluation.There are several factors that most likely caused a larger than planned gap that resulted in an 18 mm poly.An increase in the tibia resection for the tibia cut guide as well as resection cuts greater than the recommended 9 mm for the legion implant increases the gap.There is a possibility that in preop gap planning, the user may have artificially created a larger gap by overstressing the joint and causing too much laxity, which could lead to an over-section of the bone.Refer to the applicable implant surgical technique (legion) for guidance on recommended resection depths.Refer to the navio surgical system user¿s manual and the navio surgical technique guide for knee arthroplasty when performing and assessing the preoperative gap assessment.There may have been instability in the tibia cut guide, causing the 13 degree slope in the visualize cut screen.Secure the cut guide on the bone surface using 1/8¿ diameter non-rimmed speed pins provided in the smith & nephew implant system trays.Refer to the surgical technique guide for proper preparation of the twin peg cut guide and verification of the cut.Use the plane visualization tool to ensure that the cut guide is placed in its intended position.This helps ensure that the depth of the cuts are consistent with the plan.Because the tibia was cut with manual instrumentation, the reported large, medial gap in flexion could not be confirmed.However, a tight lateral and loose medial gap in flexion could be due to a knee sitting in a varus position.Refer to the surgical technique guide for implant manipulation to account for a loose medial compartment in flexion.To avoid inadvertent ligament release, refer to the surgical technique for proper bone removal.The navio¿ surgical system does not prohibit cutting of soft tissue, which may be in the surgical area.Always use retractors to protect ligaments and other capsular structures.Use steady movement to minimize potential for ligament damage.Otherwise, if ligament release results, laxity information may be re-collected.This situation was captured in the navio risk assessment released at the time of the complaint.Based on the investigation, no containment or corrective actions are recommended at this time.
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