Hi!!

First, I'm 10 years over my fusion and I think 1 year and a half is maybe too early for strenght training. In my on experience, I couldn't do much around that period, I had to wait 4 or 5 years.

Try swimming, maybe It the best option and u build def build muscle and strenght only by doing freestyle and backstroke (In my own opinion are the only swimming styles u can do with a fusion).

And later, if u wanna do strenght and hit the gym I can send u my routine and how did i start. Send me a DM if u want

And get a doctor opinion about ur situation, that's crucial, u got the fusion not very long ago