Unlike many of our other, more easily injured joints, the hip does its job with relatively few complaints. Designed to provide stability and strength to our lower bodies, the hips take a remarkable amount of pressure in stride, withstanding a force equal to three or four times our body weight with every step.

But hips can suffer some serious, crippling maladies -- and while most of these conditions tend to be associated with age, some affect younger people as well.

Thousands of adults between the ages of 20 and 50 suffer from a debilitating hip disorder called avascular necrosis (AVN), in which the femoral head of the hip bone (the "ball" part of the joint's ball-and-socket design) dies due to inadequate blood supply. The three most common causes of AVN are hip fractures, alcohol abuse, and long-term use of corticosteroid medications. (A severe sports injury known as a hip subluxation can also lead to the condition.) Nearly three out of four people with AVN have it in both hips.

Despite remarkable advances in joint replacement technology, even state-of-the-art hip replacements last only a few decades, due to the continual stresses placed on the joint. So, while a hip replacement is a good option for older patients whose hips have succumbed to degenerative conditions such as osteoarthritis, it's less suitable for younger people with AVN, who later must undergo the ordeal of repeated surgeries.

Thirty years ago, James Urbaniak, MD, Virginia Flowers Baker Professor of orthopaedic surgery, developed another approach to AVN: a remarkable procedure known as a free vascularized fibular graft.

To perform the graft, Urbaniak first removes the blood-starved dead bone from the hip, then inserts into the hip bone a section of the fibula -- the small bone in the lower leg whose removal does not affect walking. Once Urbaniak links this healthy implanted bone to nearby blood vessels, it rejuvenates the femoral head, or ball, of the joint, literally bringing the hip back to life.

"Until we developed this technique, virtually the only other option was to fuse the hip, making it stiff," Urbaniak says. "However, later in life, these patients developed often severe back and knee pain, because the hip was rigid."

Urbaniak has performed more than 3,500 free vascularized fibular grafts, and the results have been remarkable. "If we catch AVN early enough, the procedure can restore normal function in 90 percent of young people's hips," Urbaniak adds. "Our success rate drops to 70 percent if we catch them later, which is why we emphasize that patients should come to us as early as possible."

The wealth of data gleaned from the experiences of past patients has steadily improved Urbaniak's ability to determine whether the operation will help a patient. In fact, he considers such data so important that he has even been known to hire a private detective to track down patients to determine their outcomes.

Even with his impressive success rate, however, Urbaniak remains unsatisfied. Dr. Urbaniak recently retired from active surgery and his surgical procedure continues to be performed by a well-trained and experienced team of his colleagues, including David Ruch, MD, Marc Richard, MD, and Samuel Wellman, MD.

Urbaniak and his colleagues are currently seeking to improve the operation by treating patients with natural substances called growth factors that encourage the spread of new blood vessels to better nourish the regenerating bone. He emphasizes that prevention of AVN in the first place is the Holy Grail that guides his ongoing research efforts.

"We don't really know why alcohol, steroids, or blood coagulation disorders focus on bone death in the hip," Urbaniak says. "We have identified some factors that prevent blood from getting to the bone. If further research allows us to pinpoint the causes, we envision the development of medications or gene therapy that would one day allow us to increase blood flow to a hip to treat bone disease -- or prevent it altogether."