Twenty years ago my husband, Mark, broke his left ankle and was in a cast and on crutches for nearly two months. Last year he broke the other ankle. But this time, after surgery, his doctor surprised us by instructing Mark to walk on it two weeks later.
It turns out the standard advice to stay off a broken leg bone for at least six weeks is based less on scientific evidence and more on cultural caution—physicians like to play it safe. But now studies show that complications are no more likely with early weight-bearing than with a long delay. Except in a few complex cases, walking around earlier helps broken bones heal, and it improves quality of life: for example, people can return to work and other activities faster.
If you are fully immobilized, “you come out of the cast with a sort of hairy, withered leg that takes forever to overcome,” says orthopedic trauma surgeon Alex Trompeter of St. George’s University of London. “The science tells us that the rate at which you lose muscle mass is far faster than the rate at which you gain it.” You’re slow to build bone, too. Consider astronauts. After six months in zero gravity at the International Space Station, they lose 10 percent of their bone density, and to ward off that loss they do exercises in space that are equivalent to bearing weight.
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In the 19th century German surgeon and anatomist Julius Wolff recognized that healthy bones adapt and change in response to the load placed on them. That is why everyone—but especially women, who are more susceptible than men to osteoporosis—should lift weights as they age. It increases bone density.
Those who walked early on femurs that had broken just above the knee had no higher rate of complications than those who stayed off the leg for six weeks.
When you fracture a bone anywhere in the body, physicians first worry about stability. How much will the bone fragments move if you put weight on them? If the answer is too much, surgery is usually indicated—first a “reduction” to realign the pieces of bone and then “fixation” to hold them in place with screws, plates or rods.
That procedure sets up a bone, which is living tissue, to heal naturally by making new bone and resorbing damaged cells. In the gap caused by a fracture, a healing tissue called callus forms first, which then turns into bone. The right amount of load or movement (here’s where Wolff’s discovery applies) is critical to this process. Too little results in no callus; too much prevents the bone from knitting back together. “It’s all about the strain environment,” says orthopedic surgeon Chris Bretherton of Queen Mary’s Hospital in London.
Surgical implants hold the alignment until that process is complete. “It’s a little bit of a race postoperatively between the bone healing and the fixation breaking,” says orthopedic trauma surgeon Marilyn Heng of the University of Miami Miller School of Medicine. In that contest, she roots for the new bone. “Once the body heals and forms bone across the fracture site, the hardware we put in becomes extraneous. The crux of our decisions for weight-bearing status is we want to win that race.”
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