Answer: Based on your description I am not certain what has happened to your boxwoods. They sound to be very stressed, so it is possible they are dead. You can check this by looking at the branches and twigs. Live wood is supple and has green just inside the bark. Dead wood is off color brown or gray and is brittle and snaps in your hand. You would begin at the tips and work your way along each branch, pruning off any dead wood until you reach live wood. Then, you could prune additionally to restore a somewhat symmetrical look.
As to why they defoliage each winter, it is possible there is an underlying pest or disease problem or that the location is not suitable for boxwoods. I would suggest you consult with your local county extension and see if they can diagnose the cause for you and based on knowing that, determine how to proceed.
On the other hand, if you are very dissatisfied with the shrubs, you could certainly replace them. I would suggest you not replace them with boxwoods, however, in case there is a problem that would affect the new plants as well. I'm sorry I can't be more specific for you long distance.
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