Hi vincent, I understand your concern, I've had 6 spinal fracture and surgeries and I know the requirements for bmd and surgery.  Has anyone mention kyphoplasty or vertebroplasty instead of a fusion?  Fusions surgeries are very invasive unless you are looking at the minimally invasive type.  Both of the surgeries above involve injecting surgical cement into the fracture and it's usually done as an out-patient procedure.

I would ask about these two possibilities, if you haven't already.  Here's a video on both of these procedures so you can see what I'm referring to.  Once the procedure is done the patient usually goes home the same day unless there is some complication.  There are some risks, as there are with any procedure, of the cement leaking out of the fracture and into other areas, this is the biggest concern.  Also, using cement can make the vertebra above and below the surgical site more vulnerable and prone to problems so make sure to find all this out.  That said, a fusion has many concerns as well and takes much longer to heal.  Kyphoplasty from Spine Universe (video)

Vertebroplasty explanation from Spine Universe

Both of these procedures have to be completed on fairly "new" fractures so they may not work for you, but check with your Dr. on it.  I don't know what else to suggest if they want you bmd to be higher before considering spinal fusion surgery, which is good advice.  The fusion may not do well if you bmd is too low.

I hope that helps since I've been through this many times.