They didn't die from a broken foot - they died from complications from an injury. You can die if you get tetnus from a rose but it wasn't the scratch that killed you. The scratch just let the disease enter your bloodstream. People still die from pneumonia and the flu, even from seasickness. Intense pain can even bring on a heart attack that could kill someone.

Any broken bone or shock to the body can cause you to develop a blood clot and childbirth can trigger them but most people don't get them. It's little comfort to those who do but statistically, it's unlikely that you'll develop a blood clot that kills you so I wouldn't worry about it.