Your physician would have to be the one to answer this. Rib expansion is one of many different individual strategies that join together in an additive way to assist with breath support.
It may be that your doc gives you the OK to expand your ribs to the extent that you are able. On the other hand the doc may have reasons to advise you to avoid rib expansion.
If your doctor says to avoid rib expansion, then by all means follow the doctor's advice. It won't be the end of the world. It will just mean that that one particular tool will not be available to you, and your breath support may be compromised in that one way.
The doc may say do it, it's fine, but because of the condition, your benefits from rib expansion may be compromised.
It could be that doing rib expansion to the extent possible might be beneficial to you. I'm no doctor, but you should seek the advice of a good one and follow that advice. Whatever they say, you can still follow all of the KTVA practices that ARE approved for you by your doctor, and end up still being a much more accomplished singer than you otherwise would have ever been.
The idea behind rib expansion is to take the gravitational load off of the lungs to the extent possible, in order to assist with the ability to retain air in the lungs for as long as possible. In many cases, the ribcage is held up in such a manner as if to be a puppet on a string, suspended from the sternum. The intercostal muscles help to keep the individual ribs spread apart, expanding the ribcage all the more. With this action going on, there is minimum force upon the lungs to expel air, except for the force exerted by the rising diaphragm.
This helps to allow us to very slowly, and in a very controlled way, let very little air come out as we sing.
You may find that you will be able to develop an ability to meter your air out slowly, despite the different design of your individual ribcage. You may have to get very good at some of the other methods, such as pressing downwards on your innards to oppose the rise of the diaphragm, and that will still allow you to get better and better at regulating and supporting your singing breath.
All my best to you, friend!