Stem cells studied as minimally invasive treatment for avascular necrosis of the femoral head

Avascular necrosis (AVN) of the femoral head is a devastating joint disease that is newly diagnosed in 20,000 Americans each year at an average age of 38. The disease is characterized by decreased blood flow to the femoral head, which can lead to collapse of the femoral head and subsequent degenerative changes. Collapse of the femoral head is typically accompanied by severe pain, and the disease course rarely regresses.

Risk factors for AVN

Although the pathophysiology of AVN is not yet well-understood, it is thought to be a multifactorial disease, with patients reporting a history of exposure to one or more risk factors, including trauma to the hip, alcohol abuse, corticosteroid use, hemoglobinopathies, pregnancy, coagulopathies, organ transplant, chemotherapy, caisson disease, HIV and autoimmune conditions.

Some assert that the disease results from a clotting disorder or genetic abnormality that leads to vascular compromise, while others hypothesize that increased intramedullary pressure in the femoral head leads to decreased blood flow and cell death via a mechanism similar to compartment syndrome following a traumatic injury.

A new approach to treatment

Options to halt the progression of AVN include core decompression, osteotomy and medical treatments. Results associated with these options have been disappointing, with up to 40 percent of patients progressing to total hip arthroplasty.

Mayo Clinic researchers recently began studying the use of concentrated autologous bone marrow and platelet-rich plasma (PRP) as adjuvants to minimally invasive decompression to treat patients with early-stage AVN. After surgeons decompress the femoral head, adult mesenchymal stem cells obtained from the iliac crest and platelet-rich plasma are injected into the area of osteonecrosis.

After this procedure, patients are discharged from the hospital using crutches to assist with ambulation as tolerated for approximately two weeks. In patients who undergo bilateral procedures, crutches are recommended until hip pain subsides.

A Mayo Clinic team recently performed a retrospective analysis of 60 patients who were treated using minimally invasive hip decompression augmented by injections of bone marrow concentrate and platelet-rich plasma. Of the 73 hips receiving this treatment, 16 hips (22 percent) progressed to further stages of osteonecrosis, ultimately requiring total hip replacement. Patients were followed for an average of 17 months. Twenty-five patients underwent unilateral decompression and 24 underwent bilateral decompression. Significant pain relief was reported in 86 percent of patients (n = 60), while the rest of patients reported little or no pain relief. There were no significant complications in any patient.

"We found that this treatment resulted in significant pain relief and halted the progression of disease in a reasonable amount of patients," explains Rafael J. Sierra, M.D., an orthopedic surgeon at Mayo Clinic's campus in Rochester, Minnesota, and principal investigator of the Mayo study.

In conclusion, the combination of hip decompression and injection of mesenchymal stem cells into the necrotic lesion provides satisfactory results in patients with early-stage AVN and can lead to complete resolution of the necrotic lesion in select cases. The procedure is simple, with a low complication rate, and the patients are allowed to bear weight as tolerated, allowing them an early return to function and activities of daily living.

Mayo Clinic physicians and researchers are continuing to refine this procedure. In the future, this approach may give clinicians an effective way to regenerate diseased hip tissue, delaying or eliminating the need for hip replacement in people with osteonecrosis of the hip.