A T score less than -1.0 indicates osteopenia; a T score less than -2.5 indicates osteoporosis. The scores are a way of comparing your bone density to the average bone density of a 20-something woman (at the peak of bone density). The scores are subject to several variables, including whether you are short, which machine was used and your exact position during the scan, whether you have scoliosis (and probably whether you have osteophytes).
You can get more info here:
Bone Health for Life - DEXA
According to your scores, the osteopenia is showing in your hip and not your spine. Also, if I remember correctly, the cut-off at least for the ADR trials, was -2.0. Ultimately, it will be your surgeon's decision, of course.
Again, because of the medication you are on, I would ask about some treatment for bone density--a woman I know who is being treated for breast cancer just received some IV med for bone density. I'm not sure if IV biophosphanates are the way to go because they've been more associated with jaw necropsy, so you need to really discuss this with your doctor.
Sorry to make this more complicated for you!