Total hip and knee replacement surgery is not the exclusive domain of the middle-aged and elderly. Thousands of young people, as young as mid teens, experience bone death, putting them at increased risk for early joint replacement surgery. The cause of osteonecrosis in this young population is almost always the high-dose corticosteroids used to extend their lives during treatment for leukemia and lymphoma, lupus, asthma and other diseases.
A new surgical procedure being studied at Stanford gives patients with osteonecrosis a reprieve from automatic joint replacement surgery by infusing bone-forming stem cells into decayed bone during core decompression surgery. The procedure offers a 60 to 90 percent success rate in treating Stage I and Stage II osteonecrosis, before joint collapse has occurred, according to Stuart Goodman, MD, PhD, the Robert L. and Mary Ellenburg Professor of Surgery. Goodman is studying the technique as a means of delaying the need for joint replacement surgery.
"My interest is in bone regeneration," said Goodman, a professor with tenure in the Department of Orthopaedic Surgery. "We see kids as young as 14 who need total knee replacements. With osteonecrosis, we want to regenerate bone and save a joint rather than replace it, especially in these young kids."
Core decompression has been a mainstay in the treatment of Stage I and Stage II osteonecrosis. This surgical procedure involves drilling into the area of dead bone near the joint to reduce pressure, improve blood flow and stimulate an inflammatory response that can lead to healing. However, the repair often ceases to stop the progression of bone loss and collapse. When a deteriorated joint is surrounded by dead, unresponsive cells, the inflammatory response is stifled. "It needs a kick-start," said Goodman, who has turned to cell grafting to provide that spark.
In the enhanced core decompression procedure, Goodman makes a hole in the bone, then debrides the area, cleaning out as much dead tissue as he can without compromising the stability of the joint. He then injects a concentrated pellet of bone-forming stem cells directly into the area of decay. These progenitor and mesenchymal stem cells are retrieved from the patient's iliac crest via biopsy during the initial 30 minutes of the surgery. The entire procedure takes about one and a half hours to complete.
Until recently, Goodman had no visual assurance of how many cells made it to the target, or how long they survived. But cell labeling and tracking technology being studied at Stanford is being used to keep tabs on where the cells land, tracking them in vivo.
"This is one of the first studies that allows us to directly visualize stem cells that are delivered in a patient," said Heike Daldrup-Link, MD, PhD, associate professor of radiology. "Before, we couldn't see the cells directly so it was difficult to tell how many cells ended up in the desired location."
Goodman works with colleagues in radiology, rehabilitation, rheumatology and immunology to identify high-risk patients and diagnose the condition as early as possible when the joints are still salvageable. Because the only symptom of early disease is vague pain, the trick is to identify patients early enough in the deterioration process to save the joint, he said. "I do MRIs on more people than have osteonecrosis because if it's a salvageable joint, you don't want to miss it."
Thirty thousand new cases of osteonecrosis occur in the U.S. each year. Core decompression with osteo-progenitor cells can be done in any area of osteonecrosis, but it can only be performed once, so early detection is essential.
This current therapy is part of a more broad-based basic science and clinical research collaboration that includes bioengineers, material scientists, immunologists, radiologists and cell and molecular biologists to improve the diagnosis and treatment of osteonecrosis.