Sentinel event?

[pdh0224]

Dear teacher,

Dr. McGowan said that a fracture was "really a sentinel event in an older person - any fracture."

Q : What does "sentinel event" mean in the sentence? Does it mean that it often occur?


All the best,

[Alan]

Actually, I've never heard this expression, but I imagine that it means something like a 'key event', or possibly a 'warning event'.