That still left the challenge of controlling the implanted distractor. Working with Kaban’s group, the Harvard Surgical Planning Laboratory created a computerized treatment planning system, called Osteoplan, that writes a prescription—based on a three-dimensional model of a patient’s skull made from a CT scan—that specifies the exact radius of curvature and length of the device needed to correct specific jaw defects. The surgeon can use the program to determine where to cut existing bone and place the distractor.

The laboratory also modeled more than 400,000 theoretical bone corrections in the jaw and found that a set of four distraction devices, each with a unique radius of curvature, would accommodate the full range of surgical movement. “That meant a manufacturer could make a kit for the operating room with just four curved distractors,” Kaban says. The surgeon can choose which device will work for a particular patient.

The custom-made device Kaban and Troulis have begun to use in patients has all the elements of Kaban’s original vision, minus an implanted motor. A thin cable projecting out of the patient’s skin—the only visible sign of the fixator—ends in a hexangle nut that the patient turns daily, rotating a gear inside the implanted device and distracting the bone. Within three to four years, Kaban and Troulis expect to add a micromotor and battery to the device. Troulis has already tested the motorized distractor on pigs, but the wallet-size battery is too large to implant. “If we can’t make the battery small enough to implant in, say, the chest, then we’ll have a patient plug two tiny wires into an external battery at night,” Troulis says. “But the goal is to implant the battery so continuous distraction is possible.”

Distraction osteogenesis tends to work better for facial bones than those in the arms or legs. Bones heal and grow more quickly in the face, there are fewer infections, and the amount of new bone that’s needed is smaller. But the long bones of the arms and legs are straighter than facial bones, and new devices are addressing many of the problems inherent in distracting long bones.

“With the Ilizarov frames, you had to create a complicated system of connecting hardware to correct bone deformities, which are usually multidimensional,” says Mikhail Samchukov, who was deputy director of Ilizarov’s research institute in Kurgan and is now co-director of the Center for Excellence in Limb Lengthening and Reconstruction at Texas Scottish Rite Hospital for Children in Dallas. “And you had to continually reconfigure the frame.”

With one new device, the Fitbone, everything is automatic. The only electrically driven, totally buried fixator, it consists of a “nail,” or rod, containing a micromotor that a surgeon inserts into the cavity of the bone that is to be distracted and attaches it with small screws. There’s also an antenna, connected to the nail, that’s implanted beneath the skin. Three times a day, for 90 seconds, the patient places a handheld transmitter against the skin that sends a high-frequency signal, via the antenna, to a motor in the implanted distractor. The telescoping nail gradually lengthens, distracting the bone.

“The Fitbone uses the kind of induction energy that drives an electric toothbrush,” says orthopedic surgeon Peter Thaller, who does about 50 Fitbone procedures each year at the Limb Lengthening Center in Munich, Germany. Thaller works with Rainer Baumgart, an inventor of the Fitbone.