I agree 1000% with blackbeltgirl...your husband has LOTS of options! In his current doctor's opinion, there is nothing left to do but remove the kneecap. But another surgeon, especially one whose practice is limited to TKR's and revisions, may well have a vastly different approach.
Kneecaps are critical to proper patellar mechanics...and a TKR prosthesis relies on proper mechanics so as not to wear out prematurely. I would never let anyone remove my kneecap unless it A) had a tumor or b) smashed into a gazillion pieces or c) had a non-union even with an external fixator and internal fixation attempts. It's pretty common to have to resort to an external fixator if internal screws, wires, and plates don't get the job done. This is long, tedious for the surgeon (who has to adjust the fixator at least weekly, if not more often), and a pain for the patient...but it may preserve the patellar mechanics. I'm not a doctor, and I'm sure your husband has a unique situation...but I have one of those, too, in that I have a very rare and seldom treated problem. The first SEVEN top OS's I saw in my city of 3 million people told me there was simply nothing to be done to help me. My eigth surgeon consult got me walking again--without a limp. It pays to get multiple opinions, and to make sure the opinions are from the right kind of doctor. A specialist in the problem your husband has--a TKR with complication of patellar fracture.
PS there is a TKR section down at the bottom of the main bulletin board--you may find more info there. Best of luck to you and your husband...things will get better once you have a plan of attack that everyone is comfortable with. That may well be a patellectomy (removal of the patella), but you should explore all other options first.