The most traditional way to lengthen a limb is with an external fixator. However, there are certain cases where lengthening is possible with an internal device.
An internal fixator uses a magnetic nail to lengthen the limb. A powerful magnet inside the nail is attached to a series of gears that can extend the nail. When an external magnetic device stimulates the magnet in the nail, it activates the gears that lengthen the nail. Compared to an external fixator, there are numerous benefits to using an internal lengthening nail, such as:
- Pain: Lengthening with an internal nail is less painful than lengthening with an external fixator. This is because there are no pins and wires. Pins and wires often become infected, which can cause pain.
- Scarring: With an external fixator, pins and wires are placed through the skin, sometimes through the muscle, and into bone. The holes for the pins and wires stay open the entire time, and when the fixator is removed, scars can form over the holes.
- Range of motion: Since there are no pins that are going through muscle, not only is there less pain, but the child has better range of motion. A nail is also less likely to cause stiffness, meaning your child will be much more likely to reach his or her lengthening goal.
There are some reasons that we may decide internal lengthening nails are not right for your child. These reasons include:
- Size of bone: If your child’s bone is too narrow or too short, the nail cannot be used because it is not be small enough to fit. Typically, internal nails can be used once your child is approximately 10 years old.
- 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 plate of the top portion of the tibia bone. In the femur, a nail can sometimes be placed through the top of the bone prior to your child being fully grown as long as he or she has a bone that is big enough. However, there are times when your doctor may prefer to place the nail through the knee joint and into the bottom of the femur bone. In that case, another major growth area is affected. We typically wait until your child is nearly fully grown before using internal lengthening nails.
- Severe deformity: If your child has a crooked bone in addition to a difference in limb length, lengthening with an internal nail may not be possible. The nails are not designed to hold the crooked bone straight and lengthen at the same time. However, if the deformity is mild and in the correct location, sometimes the bone can be straightened and lengthened with one surgery.
Each child’s needs are unique. Our team works closely with your family to create an individualized treatment plan for your child.