Roxanne Yamaguchi Moster
(310) 206-1960
[email protected]
Best Candidates are Young, Active Patients
UCLA DEVELOPS NEW TECHNIQUE TO REGROW BONE IN HIPBONE-DEFECT PATIENTS
A UCLA orthopedic surgeon has developed a new technique to treat bone death in human hips that early results suggest may prevent the need for a total hip replacement. Called osteoregeneration, the procedure implants a capsule filled with bone-morphogenetic protein (BMP) that induces the body to grow new bone. Only UCLA offers BMP and the attendant procedure.
"Hip osteonecrosis literally means 'bone death,'" explained Dr. Jay Lieberman, assistant professor of orthopedic surgery and originator of the technique. "It occurs when the blood supply feeding the head of the femur bone dies." The femoral head, the knobby end of the thighbone, fits into the hip socket.
"Early intervention is important," Lieberman added, "If a significant amount of bone dies, the femoral head eventually collapses under the weight of the hip joint."
Surgeons see some 20,000 new cases of hip osteonecrosis each year. Scientists have not yet determined why the blood supply gets cut off, but have identified a number of risk factors, including trauma to the hip, steroid drug use and chronic alcohol abuse. Roughly 25 percent of cases cannot be traced to any known risk factor.
Lieberman modified an existing technique called core decompression, in which the surgeon drills a hole into the femoral head removing the dead bone inside. In the new procedure, the surgeon inserts a BMP implant -- a capsule of osteoinductive material stimulating the body's ability to grow new bone -- into the resulting cavity. An allograft, or implant of purified human bone impregnated with BMP, follows providing structural support to the bone during post-surgical healing. Lieberman believes the combination of BMP and transplanted bone induces the formation of new bone to replace the decayed bone.
"In the 12 cases we've done since 1991, the procedure has obtained good to excellent pain relief for our patients," said Lieberman. "People who had difficulty walking across the room are now hiking, golfing and returning to fully active lives." Best candidates for the procedure are active people in good general health, under age 60 possessing limited femoral head bone loss, he observed.
Scientists still do not understand how BMP works. "We don't know how BMP induces new bone to grow," Lieberman acknowledged. "But on the basis of experiments on laboratory animals, we know that it does."
Previously, orthopedic surgeons relied on one of four methods, all of which present limitations.
1. In core decompression, the surgeon drills a hole in the femoral head to relieve pressure, restore blood flow and encourage new bone growth. This method is only effective in the earliest stages of osteonecrosis and may weaken the femur if the cavity is made too large.
2. In osteotomy, the femoral head is rotated so the body's weight is supported by a healthy portion of the bone. It is most effective in patients with minimal bone damage to the femoral head.
3. In a vascularized fibula graft, living bone from the patient's lower leg is transplanted to the femoral head cavity with its blood supply intact. The blood vessels are then reconnected to the hip area to encourage new bone growth. Results of this procedure are promising, but the operation is long, costly and complex. Patients often prefer less invasive alternatives that don't affect their healthy lower leg.
4. The most complex, expensive option is a total hip replacement, in which a metal hip joint completely replaces the extracted femoral head and socket. It is not encouraged for young, active patients. The artificial hip has a limited lifespan and typically needs replacement more than once.
Dr. Marshall Urist, a founding faculty member and professor of orthopedic surgery at the UCLA Bone Research Laboratory, discovered BMP in 1965. In a landmark paper, Urist determined that BMP occurs naturally in small quantities in the bone matrix, where it induces bone growth and can be extracted to create bone when implanted in non-bony sites of the body.
"Bone is the only tissue in the body that regenerates completely and flawlessly," said Urist. "BMP imitates the bone development process that appears very early in embryonic life. The quantity of bone BMP produces in adults is proportional to the mass of implanted protein."
Testing of BMP in clinical trials to repair bone defects and to help fractures heal better and faster is ongoing. BMP is also used for spinal fusions and knee ligament grafts as well as in the oral-maxillofacial area to repair craniofacial bone defects, repair periodontal defects and augment jawbone mass for the placement of dental implants.
-UCLA-
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