T.O.,
Add to both replies that it also takes varying lengths of time to be evaluated, depending on the transplant center -- in most cases a minimum of 3 months, with the average time even longer in many centers. So, it is possible with your center that the work-up / evaluation may itself take up much of that wait time.
Moreover, the minimum wait time after surgery may vary with whether the bone graft to be inserted comes from you or from a deceased donor -- and if it comes from you, do you also need to receive a blood transfusion. Both those factors are related to blood-borne infections (HIV, hepatitis B & C & D, etc.) I am guessing that the bone comes from you & that you will not need a transfusion. The center probably wants potential donors to have a minimum wait time just to fully recover from any surgery.
Bill