Here's the latest. According to Adam Wogan, the Mets Director of Minor League Operations, the team is very pleased with Havens' progress. He's currently rebuilding his strength and participating in limited baseball drills. Specifically, he is fielding ground balls and throwing, but is not yet swinging a bat. The Mets hope that he will begin swinging next week, but that is dependent on his continued progress in the next few days.
The use of this procedure, which shaved down one of Havens' ribs that was creating irritation, for a professional baseball player is essentially unprecedented. While professional athletes in other sports and amateur athletes have had success with similar procedures, I can't find any evidence of a professional baseball player using this technique.