I'd combine a slow return to the bike with a targeted rehabilitation program that promotes bone density (walking at first, then some light jogging and jump rope) and strengthens the muscles and connective tissue all throughout the affected leg.

Your bones have likely lost a lot of density due to the lack of weight-bearing demanded of them for the past few months, and my strong suspicion is that riding a bike (especially fixed gear) applies the kind of chronic stress that is enough to endanger the integrity of compromised bones without being enough to really promote strengthening. Plus, if you crash, compromised bone density plus a lack of muscle for cushioning puts you at a higher risk of injury.