Avascular necrosis (AVN), also called osteonecrosis, aseptic necrosis, or ischemic bone necrosis, is a condition that occurs when there is loss of blood to the bone. Because bone is living tissue that requires blood, an interruption to the blood supply causes bone to die. If not stopped, this process eventually causes the bone to collapse.
Avascular necrosis most commonly occurs in the upper leg. Other common sites are the upper arm, knees, shoulder, and ankles.
"Mechanically, it works fine -- it's just the pain is starting to be
unbearable," Landis recently told the Atlanta
That pain is the result of osteonecrosis -- also known as avascular necrosis
(AVN). It's the same condition that disrupted the career of baseball and
football star Bo Jackson.
What Is Osteonecrosis?
Osteonecrosis develops when blood vessels that feed bones are injured,
destroyed, or blocked. This causes a lack of blood circulation to the bone,
which can lead to bone death. In Landis' case, the damage reportedly occurred
in conjunction with a hip fracture he suffered in 2003.
"When you are young and strong it takes a powerful force to cause a hip
to break. And because of that, often key blood vessels in the area can be
injured as well," says James Urbaniak, MD, professor of orthopaedics at
Duke University Medical Center in North Carolina.
While doctors say some patients may generate new blood vessels to resupply
the area naturally, when that doesn't happen, bone can quickly begin to break
"Without adequate circulation, the bone simply begins to crumble and
die," says Michael Bronson, MD, chief of joint replacement surgery at the
Mount Sinai School of Medicine in New York City.
Moving Painfully With Osteonecrosis
In Landis' case, problems were complicated further since the area normally
fed by the injured vessels was the femoral head, or tip of the thigh bone,
which sits directly inside the hip socket.
"So now, instead of having a smooth, spherical shape to the end of that
bone, allowing it to move freely inside the socket, it begins to crumble, and
becomes irregularly shaped," says Bronson.
As a result, he says movement becomes like "trying to put a square peg
in a round hole."
Urbaniak tells WebMD that over time the socket also can become damaged so
that nearly every movement of the leg causes bone to rub against bone. This not
only results in significant pain, but in Landis' case, a muscular imbalance
that also caused one leg to become shorter.
In most instances, doctors say a secondary arthritis usually develops as well, further
increasing pain, and facilitating the need for hip
"Some people come to replacement surgery as the result of pain from the
necrosis alone, others have it when arthritis secondary to the crumbled bone
sets in," says Bronson.
In the surgery that Landis reportedly plans to have this fall, doctors will
likely replace the end of the crumbling thigh bone with a smooth, artificial
tip. They will then remove the old, worn socket and replace that with a
mechanical new one.
"The end result will be a smooth moving new joint that is
pain-free," says Bronson.
Because the new "parts" are man-made, they don't require the blood
supply that bone needs to remain healthy. So even if the blood deficiency to
the area remains, the joint is no longer affected.