Well, the obvious thought (without any other evidence) is that he was contra-indicated for artificial disc replacement.

Why, we don't know. We may find out in time. Here's a bit more:

http://www.espn.com/golf/story/_/id/...alleviate-pain

If Tiger wood receive ADR on L5S1 from his surgeon, does it mean ADR most likely will cause problem on this level so we need to fuse it. This make me worry whether i will be heading ADR or fusion, as my surgeon ask me to decide as i am qualify for both. Oh my god, what should i do...

From the article that Rich quoted:

"...bottom lower-back disk had severely narrowed because of previous herniations and surgeries. Conservative therapy, which included rehabilitation, medications and limiting activities, failed as a permanent solution..."

Sounds like Woods had long-term problems that he'd attempted to resolve with conservative care and microdisectomies. If you look over this board, those do work for some people but, for those they don't, they tend to set you up with more severe damage at the affected level. From that, I'd believe Rich's comment that Tiger Woods likely wasn't a candidate for ADR.

With the amount of torque he puts on this back with his swing, I'm going to guess he probably had some facet issues.