Video: How limb lengthening surgery works

A limb length discrepancy is, quite simply, a difference in size between the length of an individual's arms or legs, and can occur in the upper and lower portions of each. The difference in length can range from a fraction of an inch to several inches.

Many of us have slight difference between the lengths of our arms or legs, but often the discrepancy is so slight that it presents no problems. The greater the difference, however, the more likely it will cause pain or interfere with activities.

Limb length discrepancies can be present at birth or can happen as the result of trauma. For instance, if a broken bone is in a crooked position as it heals, it might stay that way, resulting in that limb becoming shorter than the other arm or leg.

Although it is not a limb, the two sides of the pelvic bone can also be uneven—typically due to an underlying skeletal condition present at birth. When this happens, the spine has to adjust to the difference, which can lead to back and hip pain or arthritis, as well as other gait or walking problems, explains David Frumberg, MD, a Yale Medicine orthopaedic surgeon. "Much like a building, if the structure is uneven, the rest of the building has to accommodate that."

Fortunately, limb lengthening surgery can treat the discrepancy, though it is a process that takes months. The first step, Dr. Frumberg explains, is an initial surgery in which the bone is cut in such a way that it can be slowly lengthened. This may be done with an external device that connects to the bone through the skin or a motorized rod that goes inside the bone. This technology uses an external device with a control that gradually extends the length of the bone, typically 0.75 to 1 millimeter per day.

Throughout the day, very slowly, the device lengthens the limb until a point called "consolidation" is reached, Dr. Frumberg explains. "At this phase, the body has achieved its desired length and made new—or regenerated—bone. We then have to ensure that when the rod is removed, which typically occurs 10 to 12 months after the initial surgery, the structure will be able to support itself."

At Yale, specially trained surgeons rely on sophisticated 3D technology to achieve ideal results. "The technology is making all of this much easier and safer for patients," Dr. Frumberg says.