Re: Need advise for a cedar hedge in TERRIBLE shape
They are Arborvitae (Thuja occidentalis) not cedars (Cedrus).
Not much you can do, and certainly no way of getting the base to fill in again, unfortunately. Arborvitae can't be cut back more than a very small amount; if they are cut back beyond the green foliage, it leaves a bare dead area (as your deer have already shown!) which won't recover. You could either leave them as a row of trees and accept the space under the crowns (or plant shade-tolerant shrubs to fill the gap), or else remove them altogether and start over. If replanting, or adding shrubs, you will have to put up fencing to keep deer out of the area altogether; soap and socks don't work well enough to protect a large hedge.