It was reported that patient underwent tlif and plif surgery at l3-s1 (l3/4: tlif, l4/5: plif, l5/s: tlif).During the surgery, both sides l5 set screw was stripped and it could not be tightened during final tightening.The surgeon checked it in the out of surgical field and it was found that the thread of set screw was damaged.Burrs left in the surgical field and they were removed.A surgeon decided to break the tab first and then perform final tightening because excessive force was loaded to the connect part of screw head and the tab due to the alignment was bad.The surgeon broke the tab as he said and he performed final tightening with a counter.The surgeon considered twist might be occurred at transition of a screw head and a tab in the cases which reverse direction of the force is applied to a screw and a tab or bad alignment.The set screw could not be withstood the force.The surgical time was extended for 31-60 min.The set screws were overloaded when right and left set screws at l5 were temporary tightened.Both screws were rounded off at the time of final tightening so they were replaced for few times.The burrs were disposed at the hospital.
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