Hello Norman, yes it is common , especially after a big injury infact this can affect the rider physically but also mentally leaving traces of this event for a long time but normally this apprehension can be managed with mental coaching.
Fear and apprehension remain if you keep your mind focused in the past and in what has happened and if you know how to manage your mind.
This state of mind can become an obstacle in going back to initial level and sometimes it can also sabotage you in your improvement because it puts you in a vicious circle:
You are afraid -> You put less potential in your riding -> your actions are of lower quality -> your results are below your level -> you still are afraid etc.
To interrupt this vicious cycle it is important to get over the injury and get over the feeling of apprehension, with mental coaching this is very fast and easy to obtain.
I have personally worked with a top rider after an injury and I can tell you that she has totally recovered from it going back at an even higher level!!