This is a very tricky question since it depends on your current height and is tailored to each patient. You would probably want to maximize the amount of lengthening you can achieve but we all know that lengthening limbs beyond a certain limit becomes unsafe.
There’s a saying in our field that the first three centimeters is free, and after that you start to get complications. So generally, for ephemeral lengthening, if you ask me what is safe, my answer would almost always be intramedullary nail lengthening at a limit of about 6.5 centimeters. In some instances we can stretch that even more, if possible.
From a surgical perspective, most nails now allow 8 centimeters of lengthening, but for the majority of patients, the best risk benefit ratio is around 6.5 centimeters in the femur. When we look at the tibia or the lower leg the length increase differs since we need to accommodate multiple bones, including the fibula and the achilles tendons.
Realistically, we can lengthen the femur and tibia by 4.5 centimeters, we can probably safely gain around 11 centimeters in height. It definitely depends and needs to be tailored to each patient’s individual physiology, anatomy, and journey.
We often embark on the journey, and once we reach a certain target, we have a discussion to determine if it is safe to continue with additional limb lengthening, which is possible in certain patient’s scenarios.
