i agree with sqad
the biggest thing is going to be getting over the anaesthetic
if he can stop smoking (even at this late time) that will help. When he comes round, he needs to do deep breathing every hour (or when he remembers) plus ankle exercises (as often as he remembers). Also, he should squeeze his bum cheeks together and hold for 10 seconds and do that 10 times., 4-5 times a day
Being in as good health as possible before will help, so good nutrition and good hydration. They will probably get him out of bed the same day and give him exercises to do on the bed (straight leg raise, knee bend) and he should follow the instructions given