One solution may not be appropriate in all cases and it may need to be modified depending on the type and extent of the break. A backstrap is good if the crack does not go all the way through into the nut slot or headstock veneer. It the headstock veneer is compromised, a backstrap may not be enough. A break through a Gibson truss rod nut recess may be best repaired with splines. Some breaks go directly across the grain which may need multiple techniques, like the Epi I mentioned in a previous thread.

The last time I used splines I used short and small carbon fiber bars instead of the normal wood splines.

I just cut them from long bars that I use for neck reinforcement. I like 1/4" high by 0.093" wide bars from Dragon Plate.