Wednesday, November 26, 2014
Memorial Sloan Kettering has taken the lead in applying a limb-lengthening technique in people with bone cancer to restore long gaps in bone after removal of a tumor.
When people with bone cancer in an arm or leg undergo surgery, doctors typically offer one of two options: replace the tumor with either a piece of metal or a section of cadaver bone.
But while these materials can often help keep the limb useable, they are far from ideal and often get infected, wear out, or pose other complications as the body’s immune system adjusts to the unfamiliar tissue.
A solution that orthopaedic surgeon Daniel Prince now offers at Memorial Sloan Kettering requires a small — but literal — leap of faith.
“With this relatively novel approach to limb lengthening, we take advantage of the fact that bone is one of the few organ systems in the body that is able to heal itself by regenerating bone that’s just as strong and healthy as normal bone,” he explains. “We give people back their own bone by tricking it into thinking there’s a fracture, so it makes new bone to jump across and seal the gap.”
How It Works
The technique was originally developed about 50 years ago and has been widely used for restoring limbs in infants with congenital growth problems and correcting improperly healed bone fractures in adults.
But it has only recently been tested in oncology, and mostly for repairing small bone defects in people who don’t need chemotherapy.
MSK is now able to treat people with longer bone defects and patients who may also need chemotherapy. The method is ideally suited to restoring the limb after tumor removal. “Currently, this isn’t done regularly in the United States for people with cancer,” says Dr. Prince, who practiced the technique in Florida for several years before bringing it back to MSK, where he had done his fellowship training.Back to top
The Four-Month Surgery
Dr. Prince describes the technique as “four-month restorative surgery” because the actual changes occur after the procedure, while the patient is recuperating, rather than in the operating room.
During the operation to remove the cancer, surgeons cleanly cut the bone and install a device — in most cases on the outside of the limb — that holds the bone very still. In the months following the surgery, the patient or caretaker makes very small adjustments each day to this external device based on a schedule that Dr. Prince provides.
“Every day, depending on how much we need, we increase that gap and so we keep tricking the bone into thinking, ‘Oh, there’s a fracture I need to heal.’ The bone cells jump across the gap, and then we move it again,” he explains. “Then it jumps across again — and we move it again. When we move it at a millimeter a day, the effect can be dramatic.”
Over the past 12 years, Dr. Prince and others using the technique in people with cancer have helped nearly 40 people worldwide lengthen a limb following surgery to remove a tumor.
He says the external device can initially cause pain because it’s attached to the bone through the skin, but after a few days the daily adjustments are painless because they are so minimal. And with the external fixator in place, patients are usually active after three weeks or so — even going to the gym, swimming, and going back to work — while the bone is doing its lengthening work.
Visits to the doctor’s office are needed every couple of weeks. “It’s a very intensive process. A lot of things can come up that we want to address right away, such as adjustment or replacement of the pins,” Dr. Prince says.
The ideal candidates for the procedure are children, he says, because they make bone so quickly. But it is not just for children; limb-lengthening for adults with cancer is also increasing. “As long as you’re alive, you have this ability — this innate ability — to heal broken bones,” he says.
“Our goal at MSK is not just to treat patients for their cancer, but to move beyond even that — we want you to have the best function and quality of life possible after your cancer is cured so you can get back to a full, healthy life.”Back to top