If that is a really good apple, and you want to keep the variety, as davidpoland suggested, some of the branch tip extensions or upright rain sprouts could be used to graft to new rootstock. You could try whip and tongue or even cleft grafting now, although optimally would be using dormant collected scion wood.... you wouldn't be out anything but the trying and if it takes... so much ahead. Or try again in the summer to bud graft. All dependent on the ability of the tree to push some new growth.

I'd expect, if the trees been unattended for a long while, the new growth could be quite short. Hopefully you would have some pencil thick new growth, 8"-12" or more. If not, try clipping a couple of upward growing tips off now, to try to stimulate the first three or four buds down the line to extend for apical dominance.... you might get some response growth long enough to hold on to more easily, for later summer budding or next dormant season use.

Rooney suggested to look for root suckers indicating vigor yet in the roots. If the bark damage is due to critters chewing or weed whackers, and there are root suckers... you could try bridge grafting those root suckers over the damage to good bark cambium... Heroic.       Or grafting your scion wood directly on to the root suckers. Once you've assured the graft take, removal of the questionable tree remains an option

if the damage is from disease (i.e.. spongy wood behind bark lesions; anthracnose like) you might not want the bother; and..... be very discriminating about any propagation wood you select to take.

Is it that good an apple or is it time to research other varieties for taste or disease resistance, size of tree or pollination... and replace it? People get emotionally attached to a certain set of roots and fruits, but you can still pass on a tree grafted from that apple tree you sat in the rope swing from as a kid.