I remember a maple tree across the street from us that was split right down the middle from lightening. My neighbor did not want to lose the tree, so many of us neighbors gathered together what we could to help save the tree:
We got the longest bolt, washers & nut we could find, some chain, & straps & got to work.
With the straps, winch together the tree as tight as you can get it.
Drill a hole right thru the middle of the tree & install the very long bolt with a wide washer through it. Attach a washer & nut on the other side. Wrap the tree very tight with the chain just above the bolted area to keep the pressure off the bolt. Remove the strap, but leave the chain. The tree will heal around the bolt, around the chain & mend the crack.
If the crack is due to an injury, it will absorb the hardware within itself.
If the tree is split due to disease, be sure to treat the sick tree, then perform the surgery after.
That maple tree lived for 30 plus years after it was bolted & chained back together. You couldn't even tell where the chain or bolt was!