Lessons Learned: Microtome Injury
The injured worker was setting up the vibratome (a vibrating blade microtome). They donned neoprene gloves and removed the knife holder from the plastic tray it was stored in on the workbench. The blade was observed to be in the knife holder. The injured worker started to attach the knife holder to the cutting head. To do so the injured worker held the knife holder with the right hand began to turn the knife holder clamping screw with the left hand. The injured worker expressed they are unsure what happened next but the thumb came in contact with the blade. When the injury occurred, the injured worker released their grip on the knife head and it fell from the cutting head, meaning it had not yet been fully secured to the cutting head. The injured worker received medical treatment.
What went right?
1. The lab had assigned oversight of the preventative maintenance of the microtome to a responsible party.
2. The lab had assigned responsibility for training operators on the use of the microtome and had conducted informal hands-on training for all operators including the injured worker. While this informal training does not meet UC Davis guidelines or Cal/OSHA requirements it is still an effort on the part of the lab to reduce risk to the operator.
3. The injured worker followed the manufacturer's guidelines by placed the buffer tray in the designated location prior to attempting to attach the knife holder. This is important because when attaching the knife holder to the cutting head, there is potential lateral movement of the knife holder and blade as the knife holder clamping screw is tightened. It takes several turns for the threads of the clamping screw to attach to the cutting head. While the knife holder can move laterally when the clamping screw is being tightened, the buffer tray blocks the lower portion of knife holder where the blade is located from moving past the buffer tray walls. This prevents the blade from swing upwards, reducing the likelihood contact with the operator but not fully preventing it.
4. EH&S was notified of the accident through the on-call process and the Employer's First Report was completed.
What should have been done differently?
A job hazard analyses for the tasks associated with this piece of equipment should have been completed. If that had been done prior to the accident the injured worker would have had standard operating procedures to follow that would have reduced the likelihood of contact with the blade. This would have included using tools like a magnet to manipulate the blade when it is not in the knife holder and requiring the use of cut resistant gloves while handling the knife holder containing the blade.
How to prevent this in the future?
Control Measure 1: Job hazard analysis (JHA) and updated formalized standard operating procedures (SOPs):
Each step of an individual task (set-up, operation, disassembly) associated with the microtome will be documented and hazards associated with those steps will be identified to ensure the most effective controls or combination of controls for each hazard are implemented. The operator’s manual will be reviewed and used as a reference when completing the JHA. Based on the findings of the job hazard analyses, new standard operating procedures that include the identified safety measures will be created and documented.
Control Measure 2: Formalized, documented training on new standard operating procedures (SOPS):
Formal training will be created based on the new standard operating procedures that include safety measures. It is a best practice to demonstrate the SOPs, walk the operators through the SOPs, then have the operator perform the SOPs for observation and coaching. Training for each operator will be documented and records of trainings retained.
Control Measure 3: Safety equipment selection to create distance between the operator’s hands and the blade:
The purchase and use of a magnet with a handle is being examined. This allows the operator to remove the blade from the knife holder and dispose of it without having to contact the blade with their hands. If possible, the magnet should be used to place the blade into the knife holder and then if needed the operator could fine tune the blade placement manually while wearing cut resistant gloves. This is meant to limit the operator’s contact frequency and duration with the blade.
Control Measure 4: Personal protective equipment selection, cut resistant gloves:
Cut resistant gloves made of Kevlar or composite Kevlar yarn/fabric will utilized for any tasks involving handling of the blade or knife holder while the blade is installed.