The mayfield modified skull clamp (a1059) was returned for evaluation: device history record (dhr): the dhr was reviewed and shows no abnormalities related to the reported failure.Failure analysis - evaluation of the returned unit was unable to duplicate slippage.However, the lock has both rotational and lateral movement and a residue buildup is present.It was noted that the index knob and the lock will need new components added to replace worn internal parts.The unit will need to be machined to have heli-coils added to large starburst thread along with general cleaning and maintenance.To resolve the wear issues, the roundhead screw, adjustment screw, label, washers, screw, nut, teflon o-ring, ball bearings, wave springs and helicoils will be replaced.Preventative maintenance (pm) will be performed since this is the first servicing of the unit.The unit was sent to quality engineering for further investigation due to reported injury; further investigation by quality engineering confirms the findings of the service & repair evaluation: the index knob for the lock was loose and had little resistance to turn to the locked position.Root cause - evaluation found no device deficiencies that would have contributed to the reported complaint as slippage could not be duplicated.The unit has slight movement in the lock and the index knob is loose, but when the clamp is properly positioned and put under pressure, it will not move in the locked position.Probable root cause is improper or suboptimal placement of the skull clamp on the patient.No further investigation is required based on the acceptability of risk and no adverse trends were identified.This will be monitored and trended going forward.At present, we consider this complaint to be closed.
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