Clinical Trials outside U.S.: Avascular Necrosis

AVASCULAR NECROSIS (AVN), or osteonecrosis, is a painful condition in which bone tissue dies as a result of ischémie injury and is unable to regenerate itself. The head of the femur is affected in 90 percent of patients and is caused most commonly by traumatic hip injury but can also result from alcoholism, excess steroid use, vasculitides or coagulop—athies, Caisson disease, iatrogenic injury during hip surgery, radiation exposure, and sickle cell disease. In children, AVN of the femoral head can result from Legg—Calvé-Perthes disease, slipped capital femoral epiphysis (SCFE), and congenital hip dys—plasia. Other sites of avascular necrosis include the humérus of the upper arm, femoral condyles of the knee, scaphoid and lunate bones of the wrist, calca—neus and navicular bones of the foot, and the jaw.

AVN mostly occurs in adults age 25 to 50 and in younger children, and it is more common in males than females (ratio 8:1). Up to 20,000 new patients are diagnosed with AVN each year in the United States, and thousands more go unrecognized worldwide. The femoral head eventually collapses if left untreated, leading to joint instability and arthritis that require total hip replacement. At present, there are no drugs for the definitive prevention or treatment of osteonecrosis, and current therapies have limited efficacy. The development of effective treatments has been problematic [Page 111]because three distinct tissues are involved in AVN: bone, bone marrow, and blood vessels.

However, researchers worldwide have recendy started to explore stem cell therapy as a therapeutic approach to regenerating all of these tissue types. Histostem, a Korean company, was the first to treat AVN of the femoral head and various other disorders using umbilical cord stem cells, and this group has branched out to India and other nations for further research. Orthopaedic researchers in Taiwan have recently used mesenchymal stem cells in bone marrow to restore damaged blood vessels in AVN. Aastrom, an American company, has also started a clinical trial in Spain to determine whether its patented bone tissue repair cells can treat AVN.

The trials presented here are a testament to the potential for stem cell therapy to treat previously incurable diseases such as avascular necrosis. New directions in the treatment of AVN will continue to evolve; however, it is important to continually evaluate and retain proper ethical standards for stem cell research.