thanks eric for blowing up the picture; dendro's peepers don't peep like they useta without his hand lens.
even so, a shred of intact cambium can grow, and even torn cambium can graft and reconnect. if braced the path for circulation would be less strained--except for the hole.
A 1/4", .5cm bolt should do. or could use 1/8" cable and wirestop fasteners. first you could spiralwrap some arbortie further out the branch and guy it back to the stem, aka a soft support system.
why did the branch break?