It's definitely a risk. It's not exactly common, but the risk is much higher in people who do both tibia and femur very fast together.
Doing both segments is much less dangerous if you do them separately, like a year in between. The risks of this safer way is much much less, and there's less suffering at the moment. Solomon does cross lengthening which results in a very quick lengthening that is much more dangerous than a normal procedure. By the time you're done with the first external fixators, you're already onto the second. Your body has no time to heal, and you can imagine how rough that would be. And if you lengthen fast like Solomon does you can certainly damage your nerve.
