See under "Game notes" at the bottom of this article:
Pittsburgh Pirates vs. San Francisco Giants - Recap - August 10, 2011 - ESPN
Hopefully, this one is less serious than his past surgeries. However, with his history, anything that will keep him out until next Spring Training MUST reduce the probability that Hart will ever become a useful pitcher for the Pirates.
I had high hopes for the Gorzelanny-Grabow trade when it was made. However, with Ascanio pitching very poorly at triple-A and Hart on the DL seemingly forever, it appears that Josh Harrison is the only remaining hope.