Reported event: an event regarding inaccurate resection involving a mako tka software was reported.The event was confirmed.Method & results: :-product evaluation and results: review of the case session files noted the following: the rio system was performing within its specifications, there is no indication of system malfunction.Probe check passed as well as rio registration, pre-surgery checks, bone registration, and bone checkpoints.Cutting accuracies of 1 to 1.5 mm is within the specifications of the mako system: "the combined translational error of the proximal tibial cut and the distal femoral cut along the anatomical z axis shall be =2.41mm from plan when resection is made within the rio working volume." the user failed to lower the robot during rio registration.To improve arm accuracy the user must lower the rio during robot registration.The accuracy of the robotic arm can be compromised by a failure to lower the rio system during rio registration."ensure the mako lift mechanism has been lowered and the mako is down on its feet.An icon will appear in the main window if the mako has not been lowered onto the feet." mako tka application user guide the user has a torque limit error in joint 5 and 6.The arm accuracy can also be compromised by rough handling of the arm and pushing through the stereotactic."to ensure accuracy, do not exert strong forces on the robotic arm, particularly as the blade initially contacts the bone.Large forces applied to the cutting system handle may result in flexing of the blade." mako tka application user guide performing the distal resection after the anterior chamfer may prevent deflection of the saw blade providing a more accurate distal resection.Performing the anterior chamfer resection before the anterior resection can also prevent saw blade deflection."to minimize blade skiving, carefully score the bone with the saw blade as you enter the cut.If the blade is deflected when it initially enters the bone, it will be difficult to ensure an accurate cut unless the saw blade is removed and entry point into the bone is corrected." mako tka application user guide.The field service engineer reported: problem reproduced? no.Trouble shooting notes: none.Work performed: mps reported deep distal cuts.Performed all accuracy tests with successful results.Performed find gravity constants as a preventative measure.Observed indentation on j2 bump stops.Replaced j2 bump stops.Performed pm including all accuracy testing with continued successful results.Placed robot back into service.Work order disposition: system investigation completed successfully as per service manual.All system checks and tests passed, system is ready for use.-clinician review: no medical records were received for review with a clinical consultant.-product history review: a review of device history records shows that rob1266 was inspected and the quality inspection procedures were completed with no reported discrepancies.-complaint history review: a review of complaints in trackwise related to p/n 219999, robot number: rob1266 shows no other similar complaints for tka software - inaccurate resection.Conclusions: the alleged failure mode was confirmed to have been caused by a number of issues.The user failed to lower the robot during rio registration.The user has a torque limit error in joint 5 and 6.This was additional noted by the field service engineer who observed indentations on the j2 bump stops.No additional investigation or specific actions are required.If additional information is received then the complaint will be reopened.
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