Hi- the degree of defoliation suggests that the trees have been declining for some time. If the cause is not a major root issue or canker disease it might be possible to remove the dead and declining wood to see if new shoots can be trained as new scaffold branches. This will take a good deal of work and require you to begin a spray program to protect the trees from the diseases that likely contributed to their decline.
https://extension.umd.edu/hgic/topics/apples

VA Tech home fruit management guide (see section 3 beginning on page 87):
https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/456/456-018/ENTO-336.pdf
Another option is to remove the trees.
Jon