Cycling may work for you.. if leaning over the handle bars bothers your back .. there are different bike options. Some stationary bikes definitely come in a more seated upright position. Agree with esquinchi.. pool exercises may work.
There is inline skating which would be less jarring than running.. but it comes with falling risk so may not be palatable to you.
Diet is far far more important than exercise in keeping off or losing weight so maybe while you are in recovery phase you could focus a bit on exercise, but more on learning about and incorporating good nutrition .. Fuhrman, Esselstyn and Mcdougall are good sources and all have books out and websites.
Sounds like that was quite a nasty fall.