If your ttree is truly girdled...and this is the worst possible time for that to happen due to sap being ready to rise for spring...all the painting in the world will not help. Once the continuity of the cambium is broken there is no way for the nutrients to feed the tree. ONE very old hope is to do several bridge grafts using thin bridges of healthy stemwood with each end having a fairly long & flat tapers on both sides coming to a V ..about 1 1/2 inches. Several of these should be used vertically to circle the trunk at fairly close intervals..say 1/2 inch apart. Place the tapers well above and below the wounds in incision strips that will be the same width as the stem wood. The stem wood should be about 1/4 inch wide or even a bit thinner to be totally flexible. Place them just under the bark so that they are assured of cambial contact with both the trunk and bark cambium. Then use duct tape to hold them firmly in place around the trunk. You will end up with several vertcal stems forming parallel bridges. Then paint everything with an asphalt would dressing that you can find in most Lowes or garden centers. Even if you have already painted the wounds, you can still do this. Your tree must have the ability for the sap to reach the top before spring...as in ASAP.

A quarter inch of intact bark will likely keep your tree alive. But I would think it is pretty hard to tell visually at this point.

Bridge grafting will work but isn't needed if there is any continuous live bark.

You need to avoid a repeat of this next year. It was probably not deer. Much more likely rabbits or voles. Protect that lower trunk next winter.

The Grafter's Handbook has details of how to save a girdled tree. You take several small branches and graft them into the cambium above and below the girdle. I inherited an almost girdled very old tree and the only living part was above the only continuous bark. The rest simply died.

What you are looking for is information on "Bridge grafting". I don't know how difficult it is to do. I failed miserably last year with everything but chip bud grafting, but at this point you don't have a lot to loose by trying.

The Grafter's Handbook by R.J. Garner. ISBN# 9781844030392.

Here is a link that might be useful: The Grafter's Handbook

Kevin,
I would not count on that strip keeping the top alive. Great if it does. Just in case grab scion wood off the tree and save it for spring and graft it where you can.(other trees) If your tree lives on that little strip the dead side will become dried out and brittle which means that a wind storm will snap it off so to prevent that from happening tie that tree to several good stakes to prevent any movement for several years or until new wood has strengthened the damaged area. Do this even if you do the bridge grafting.
Bberry

Thanks to everyone for all the GREAT advice and willingness to help with my apple tree.
What I ended up doing was following the advice of my Amish friend (David Schlabach) of Schlabach nursery. He advised me to paint the girdled bark with a light latex paint.
The little bit of connective cambium bark not only kept the tree alive, but it soon swelled. It still has a way to go before it swells enough to enclose the damaged area. Im hoping by summer of 2011 or at least 2012 it will be completely covered.

The tree did so well in 2010 I attempted three more grafts (2 Fuji and 1 Baldwin) and all 3 took and flourished! It really did well last season and it is now a 9-in-1 tree.

Before this winter, I gave the trunk two more coats of latex paint to protect from the deer and the elements. Just a few days ago, I checked out the tree and discovered new deer damage, but it is minimal. They nibbled a few branches but most importantly they did not touch any of the painted areas.

This spring, im hoping to try and graft Jonagold and Winter Banana on the tree. Jonagold is one of my girlfriend Lisa's favorite apples. I have read it is possible to graft a pear onto an apple tree using Winter Banana as an interstem. I guess I will see in 2012 or 2013.

I will give another follow up (and pics) in the spring of 2011.

Thanks again to everyone!

2014 update-

My girdled apple tree is alive and well!!!

Please read on-

In the spring of 2012, I attempted to graft a Pear scion onto my apple tree using Winter Banana Apple as an inter stem.
(All of he grafting i do is "Whip and Tongue" grafts wrapped in grafting tape. I then coat the wrapped union with grafting wax)

The parent branch was a Winesap Apple branch with a grafted Winter Banana Apple scion from a few years before.
(I actually have two of these paired branches.)
I then attempted to graft two "Kieffer" Pear scions onto my two Winter Banana Apple inter stems. The "Kieffer" Pear scions started to grow, but died a few weeks later.

This spring (2014) I attempted to graft this Apple / Pear union again using the same Winter Banana Apple inter stems. I had just enough branch on my Winter Banana branches to try this experiment one more time. This time around, I used "Sunrise Pear" scionwood.
The grafting was a screaming success! (I had enough "Sunrise Pear" scionwood to graft two branches onto my apple tree, and two more onto an ornamental pear. All four pear grafts were a success!)

I have no idea why this experiment failed in 2012 and was a success in 2014. I do not know if it had to do with the pear variety used, or if it had to do with environmental circumstances. I will re-post in 2015 with an update.

There are a few different treads on this subject so I will be re-posting on those threats also.

Below are pictures taken on 07/27/2014.

Picture #2