Case Study: Broken Coffee Mug Hand Injury

Katie Wohlust

A friend of mine, Ann, was involved in a hand injury accident at work. She suffered several lacerated tendons in her right hand. She graciously allowed me to interview her as a case study for this blog to illustrate how the Cause Mapping® method can be used to investigate a hand injury.

Ann came to work one morning as usual. She went to the kitchen to get some coffee. When she opened the kitchen cabinet door a glass mug fell out of the cabinet, bounced off the counter, and one of the sharp edges of the broken glass coffee mug cut her right hand. It all happened very quickly, so she didn’t have time to react and pull her hands away from the potential danger. The bleeding was bad, so Ann was taken to the emergency room where she learned she had two lacerated tendons in her right hand. The injury required surgery, and Ann missed several weeks of work—requiring her employer to hire a temporary employee for three weeks.

How did this happen? It turns out there are more coffee mugs in the office than there is space in the cabinet, so coffee mugs get stacked on top of one another. Additionally, the mugs are all different shapes and sizes, so they don’t stack evenly. One of the mugs, which was stacked on top of another mug, was leaning against the cabinet door so it fell as soon as the cabinet door opened. Of course, employees couldn’t see this hazard waiting to happen, and Ann happened to be the first person in the office that day getting a coffee mug. She opened the door with her left hand and was reaching for a mug with her right when the accident happened.

Here is an example of a 4-Why Cause Map™ diagram for this injury.


As you ask more Why questions, the map becomes more detailed and there are more possible solutions to reduce the risk of a similar coffee cup hand injury happening again. Click on the below image to view the PDF of the more in-depth 23-Why Cause Map analysis.

CM - Mug Hand Injury - v4 BB

Prior to this accident, stacking mugs at Ann’s workplace was deemed safe and acceptable. No one recognized the hazard, or if they did, no one brought attention to it. After this incident, the office rolled out a new policy prohibiting stacked coffee mugs. It’s a simple and inexpensive solution that will likely be effective in preventing this type of incident again.

Solutions to Prevent Hand Injuries

We recognize that it is impossible to remove all risk, but we can still strive to reduce the risk associated with tasks. This includes protecting employees’ hands to the best of our ability, being aware of the hazards and trying to control them to the best of our ability. Consider these possible solutions to hand injuries:

  • Ensure the selected glove protects from the hazard. For example, latex gloves will protect you from chemicals but not from extreme temperatures or most sharp objects. Leather gloves are good for preventing scratches but not from preventing electrical shock.
  • Take time to understand the hazards associated with a task, and then try to control or remove the hazards before starting the task. We see many organizations use a “take two,” a “job hazard/safety analysis,” or a “tailgate meeting” to identify hazards. Once employees are aware of the hazard, then they will have a better understanding of how to avoid contact with the hazard.
  • Ensure equipment and tools are in proper working order and well maintained.

If a task is routine, then the hazards associated with that task should be well documented. What is predictable is preventable.

Investigating a Hand Injury

There are four basic parts of a hand injury:

  1. The hand
  2. The hazard
  3. Contact between the hand and the hazard
  4. Severity of the contact

You can understand better how to begin a hand injury investigation by reading one of my previous blogs, How to Investigate a Hand Injury. If you ever get stuck or you need help with the problem outline or the Cause Map analysis, then we are here to help. Feel free to give us a call and one of our facilitators can coach you through the beginning of the investigation.

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