Patients can now lengthen their legs using a remote control. “It’s a new way,” says Shawn Gilbert, MD, a pediatric orthopedic surgeon with UAB practicing at Children’s of Alabama. “Everything is inside, and nothing is sticking out anymore.”
Leg lengthening is a fairly straightforward process. Surgeons make a cut in the bone and gradually stretch it apart. The tissue around the bone will stretch, and the nerves and skin accommodate and grow as well. The gap in the bone will gradually fill in with new bone.
Until recently, the surgeon connected both sides of the cut or broken bone to something on the outside that would gradually stretch the leg—an external fixator. A series of screws would be fixed into the bone above and below the cut or break. They would stick out of the skin and attach to something that would consistently pull on the bone at increasing lengths.
In the 1950s, Gavriil Ilizarov, a Russian orthopedic surgeon, created a device where the screws attached to metal rings that encircled the leg. Rods attached between the rings could be manipulated to pull on the bone in increments. Ilizarov had even worked out the best rate of lengthening to steadily stimulate tissue growth with the least discomfort. Orthopedic surgeons have been using the Ilizarov method in America since 1987.
“It’s a difficult procedure to go through, because the device sticking out of the skin frequently gets infections around the pins and often limits motion at the joints,” Gilbert says. Considering the device can stay on six months or more, depending on the length desired, it could lead to permanent joint stiffness.
But all that is changing. Precice Nail, released in the U.S. at the end of last year, is all internalized and very accurate. UAB became the first medical center in Alabama to use the new device. It utilizes a complex internal gear system that is controlled by permanent magnets.
An inter-locking rod —called a nail when put in a bone—is inserted into the medullary cavity of the tibia or femur. Secured at each end with internal screws, the rod encapsulates a magnet that controls the gear box to extend the rod and create tension on the bone. “It’s like an internal clutch on a rod inside a rod,” Gilbert says.
To activate the rod, the patient uses a remote control. The large device has two handlebars connected to two magnets resembling spools of wire. Preprogrammed, the patient holds the device over their leg, and it generates a large enough magnetic field to turn the nail inside the bone. “The remote looks like two little barrels with a handle that you hold up against the leg,” Gilbert says. “The magnets on the remote spin in one direction causing the gear inside the rod to spin and lengthen or shorten it.”
The patient activates the remote three times a day. “It’s done in small doses, so it doesn’t hurt,” Gilbert says, explaining that the extension runs about a millimeter a day. “We program it for them. They just have to sit there with it spinning each time. We then check once a week with x-rays that it’s lengthening the proper amount.”
It can also move backward, shortening the rod. “That doesn’t happen, really, but it does let you slow it if you’re not seeing bone forming in the gap. Previous nail systems didn’t have the ability to reverse.”
Prior nails designed for lengthening were purely mechanical and difficult to control. “They did not have a magnetic control. That’s the major innovation,” Gilbert says.
The only mechanical lengthening rod system used in the U.S. was the ISKD that worked on a ratcheting mechanism. The patient had to make very tiny movements to activate the ratchet. The patient couldn’t tell if he had activated it enough or not, so it could lengthen too fast which would lead to pain or difficult healing. Or it could move the nail too little and the bone would heal before it was done lengthening,” Gilbert says. “Complete control is so important.”
The Precice intramedullary nail also comes in a small enough diameter to fit more patients, especially children. “It was hard to get rods small enough yet strong enough to support the weight of the bone. These are 8 to 10mm wide,” Gilbert says.
Gilbert has done three procedures at UAB so far since December. “It is incredibly easier for the patients. It makes my job easier too, because there are far fewer complications.” Using the external fixator, Gilbert says almost everyone would get at least one infection and be on antibiotics regularly. “Some were worse and required surgery to clean out the infection. With the new way, there are zero infections.”