Considering the forces involved in many sports, it's no surprise that professional athletes sustain serious injuries to their muscles, ligaments, tendons and bones. A spate of bone fracture–related injuries seems to be dogging professional teams this year. The Houston Rockets of the National Basketball Association lost seven-time all-star Tracy McGrady to season-ending microfracture surgery in February. And on Monday, Rocket’s team physician Tom Clanton announced in the Houston Chronicle that all-star center Yao Ming's fractured foot, which he sustained in a play-off game against the Los Angeles Lakers in May, has worsened over time and may end his career. The possibility that New York Mets centerfielder Carlos Beltran might have a microfractured knee turned fans and fantasy baseball owners into nervous wrecks. Such an injury ended the career of NBA star Jamal Mashburn.
So how do these fractures develop? And why can they have such impact on athletes' careers, in some cases forcing players into early retirement? To find out, we turned to Howard Palamarchuk, a former Olympic-class race walker who is the director of sports medicine at Temple University School of Podiatric Medicine.
[An edited transcript of the interview follows.]
What is a stress fracture, and how does it develop?
It's actually a very small, microscopic fracture that occurs in the outside portion of a bone called the cortex. A bone that is constantly under stress will eventually weaken or give. The body keeps up with these stresses by generating osteoblasts, cells that make bones. At the same time there are osteoclasts—cells that take away older diseased or broken bone, or bone that is worn out.
You have a balance between osteoblastic activity and osteoclastic activity. Eventually osteoclastic activity wins out, and that is literally the breaking point.
Speculation was that Carlos Beltran might have a microfracture in his knee. What is the difference between a microfracture and a stress fracture?
That’s a good question. I almost see them being the same except maybe the location where they occur. You don't see too many stress fractures in the knees. Stress fractures are more an issue of overuse. A microfracture could be caused by trauma, like getting hit by something.
An MRI can generally give you an answer between a bone bruise [which Beltran was diagnosed with] and a microfracture without second-guessing.
Yao Ming fractured the tarsal navicular bone of his left foot. Which bone is that exactly?
If you look at the foot from the side, it is the bone that sits at the top of the arch. It is a bone you could equate to a keystone of an arch—the stone that keeps an arch from falling in on itself. It carries a lot of weight. The bone is in the mid-tarsal region, where the heel bone and forefoot meet. There is a lot of stress and force on that bone.
One possible treatment for Yao is to let the fracture heal naturally. Can all fractures heal naturally?
No—specifically, not in bones that do not have a good blood supply. Without a good blood supply you will not get the osteoblast cells. These areas are "nonunions"—they will not heal—due to the poor blood supply.
The tarsal navicular bone has poor blood supply. Yao injured the foot in May, and we are in July. They did another bone scan, and they can tell it is not healing. So now they have to ask, what will be the difference if we let it rest another six months or should we do more aggressive treatments, like a bone bridge or a bone graft, where you take a different region of bone and insert it into the gap?
How long does it take to recover from such injuries?
Under the best conditions, say you were a relatively healthy and nonsmoking young person and you had no big competition in front of you, the textbook would say eight to 12 weeks. A problem is that pros rush back to play. Sometimes they put titanium screws and plates in to take the stress, but the bones may not heal.