In the context of LL, there are 2 causes of nerve injury.
1) Procedural error: Cheap surgeons who have inadequate training and equipment, often cannot judge their incision well. There are cases where surgeons accidently severe or damage muscles and nerves. This type of nerve injury is very difficult to recover from and often lead to some permanent deformity. However, this risk can be almost completely mitigated by choosing a reputable surgeon, not cheap ones from India and Turkey.
2) Lengthening too quickly: Some individuals can have rapid bone formation. This results in pre-consolidation, which often leads to the surgeon advising faster than acceptable lengthening schedule. I've seen anywhere between 1.2mm-2mm a day. This results in extreme nerve pain and can result in nerve damage. Luckily for most people, our bones don't consolidate faster than 0.25mm a day. However, while lengthening too fast can lead to nerve damage, we can usually recover from this.