what about fitbone ?
External nails will be at risk for infection during the entire lengthening period which takes at least 3 months. After lengthening, LON and LATN will remove frame and put some rod inside. I know LON but no idea about LATN. Anyway, after this moment until wounds are healed, you may have a risk for infection. After wounds are healed, no infection will occur. However, traditional illizarov doesn't remove the external frame, so you will be at risk for injection until the frames are off, which takes 10-12 months.
Internal devices, including every kind as long as they are completely inserted inside, have an infection rate only during after surgery until wounds are healed which takes 7-10 days. In this case, infection rate is not depending on the type of device but depending on the doctor and hospital. Sometimes, patient's careless behaviors such as shower, water dripping to wounds, or dirty environments may cause infection too. I don't really consider some internal nails which have some sort of screws coming out of the bones. In this case, you will still have high risk of injection during the entire lengthening period, perhaps at a little less extent to external method.