If you are catching 1 or 2 'hump-back' bass like that a year (and you're sure it's not the same fish), then I would think you've somehow ended up with some kind of bass breeding that amplifies that spine condition.
If you like LMB, then adding in some new LMB to add to the gene pool is generally a good idea. Now, if you had some kind of very unique and awesome situation going on in your pond, adding new LMB may not be the right move.
