Hi, I came on here hoping for a bit of advice myself but your situation is similar to what I've just been through.
Earlier this year I broke my Tibia. I've also torn my ACL, Medial Collateral ligaments and broke up a fair bit of the Meniscus tissue in my knee at the same time and I'm still waiting on surgery for the ligament damage.
I don't know the exact position of your injury or what state your at.
If you've had a rod inserted then you'll need to wait until the wounds are fully healed but I found that the swimming pool became my best friend.
I concentrated on doing the front crawl every second day as it put no real stress on my leg or joints and the majority of work is done by the upper body.
Don't underestimate it as a means of building or maintaining cardiovascular fitness and your shoulders and triceps will certainly display the benefits.
It can get repetitive though and a great deal of care has to be taken getting in and out of the pool.