Delayed Sternal Union

I am a 42 year old male that had an emergency medain sternotomy 12/23/08 for cardiac tamponade.  I returned to work within 4 weeks and have resumed most activities.  Since the surgery I have been popping, tightness, and discomfort in my sternum.  After a couple of inconclusive xrays, had a CT done three weeks ago that showed delayed union of part of the sternum.  None of the sternum is completely healed but there is union with the exception of the top 25% or so.  The distance between the boney edges ranges from 1 to 4 mm.  My doctor said that the sternum should continue to heal itself since it is mostly bonded and advised me to continue to baby it for the next two months.  I was under the initial impression that the bones would be healed in 6-8 weeks.  We are now almost 15 weeks.  

My question is:  Is there anything that I can do to assist/speed the healing process?  I am already taking Vitamin C, D, and calcium supplements and trying not to do anything to aggravate the area.

[Cleveland Clinic]

I am not aware of any medications that can help to heal your sternum. I would avoid strenuous activity as he as suggested and see if it improves. Because if it doesn't then you may need to see the surgeon again and need to be re operated.