By and large, the most traditional way to lengthen a limb is with the use of an external fixator, using the methods that Professor Ilizarov has beautifully described. However, with advances of modern medicine, there are certain indications where lengthening is possible with the use of an internal lengthening device.
At this time, there is only one internal lengthening nail that is FDA approved to use in the United States. It is called the Precice Nail (Nuvasive; San Diego, CA). The Precice lengthens magnetically. The powerful magnet inside the nail is attached to a series of gears, which is then attached to a lead screw, and this lead screw is attached to an inner nail. When an external magnetic device stimulates the magnet in the nail to change from north to south pole and vice versa, it stimulates the gear to move and thus the nail to lengthen. Compared to an external fixator, there are numerous benefits of lengthening with an internal lengthening nail.
Advantages of using an Internal Lengthening Nail over an External Fixator
- There are three main advantages of using an internal device over an external device
- Pain: Simply put, lengthening with a nail is universally less painful than lengthening with an external fixator. There have been numerous patients in Dr. Flanagan’s practice that have done very well with limb lengthening, and have needed nothing more than Tylenol to help with pain (once the initial pain from surgery has subsided). The most likely reason why there is less pain is because there are no pins and wires of an external fixator to deal with. Those pins and wires often become infected, and when they are infected, they are painful.
- Scarring: With an external fixator, pins and wires are being placed through the skin, through the muscle (often times), and then into bone. The holes stay open the entire time, and when the fixator is removed, the holes close on their own. The scars may be more unsightly in some people versus others.
- Range of Motion: Since there are no pins that are going through muscle, not only is the pain better, but range of motion is better preserved. This fact is critical. During lengthening, we expect your child to lose some of his motion, and if the knee, hip, or ankle becomes too stiff during lengthening, then lengthening will have to stop. As stiffening is less likely with a nail, your child will be much more likely to reach his or her lengthening goal (within reason of course).
Why not use this Nail on Every Single Child with a Limb Length Difference?
- Unfortunately, an internal lengthening nail cannot be used on every child. There are numerous contraindications to using this nail, with the most common described below
- Size of Bone: if your child’s bone is either too narrow and/or too short, the nail will not be small enough to fit, and therefore cannot be used. Typically, once your child is approximately 10 years old, lengthening nails can be considered.
- Skeletal Maturity: For lengthening the tibia bone with an internal nail, your child needs to be either fully grown or nearly fully grown. This is because the nail goes through the growth area of the top portion of the tibia bone, and this growth area may contribute approximately ½” of bone growth per year. In the femur, sometimes a nail can be placed through the top of the bone (greater trochanter) prior to your child being fully mature as long as he/she has a bone that is big enough. However, there are times when your doctor may prefer to place the nail up through the knee joint into the bottom part of the femur bone. In that case, another major growth area is penetrated. Thus, we typically wait until your child is nearly fully grown prior to lengthening with this type of nail.
- Severe Deformity: If your child has a crooked bone in addition to a limb length difference, lengthening with a nail may not be possible. However; if the deformity is “mild” and in the “correct” location, sometimes we can straighten the bone and lengthen it all with one surgery. The nails are simply not designed to maintain and hold the crooked bone straight and then lengthen at the same time. If you and your child are 100% against the idea of an external fixator, there are times in whichyour doctor can do one surgery first to straighten the bone, and then come back for another surgery to remove the hardware and then insert the nail for limb lengthening.
Obviously, all these scenarios are quite complex and unique to your child. The surgeons at COA encourage open discussion so that we can work with you and your child to come up with the best treatment plan for your child.
Here is an Example of a Patient who Underwent a Limb Lengthening Procedure with the Precice Nail