Most scientists are very concerned about the final outcome of any study. As you've probably seen from the news, lawsuits costing millions of dollars can occur when a new drug or device isn't researched fully.
Before new ideas are ever tried out on humans, the researchers use cadavers and animals. Once the product is shown to be safe, then it can be used on humans. Usually, a small number of people are involved in the first studies. If proven safe and effective, the same study is conducted using a larger number of people.
Fusion cages for the spine were approved by the FDA in 1999. From 1991 to 1993 studies were done on humans using this device. A recent study reported the 10-year results of the FDA clinical trial. They found a high rate of success in the experimental group.
Long-term results are of vital importance to science. It's likely the people in charge of your study have a long-range plan for follow-up. Be sure and ask what is this plan and how often and for how long will you be contacted.