MARINE CORAL SUCCESFULLY USED AS BONE SUBSTITUTE People who fracture an arm or leg bone and undergo an operation to repair it often find the painful treatment for the injury is often its own worst side effect. The solution to this problem may come from the ocean by way of a Southern California company. A marine coral-based synthetic graft material promotes the natural healing process without risking the major drawbacks of previous grafting methods, such as disease transmission, biological rejection, and second surgeries to collect bone for grafting. Marine coral-based Pro Osteon, a clinically proven, cost-effective material that has changed the way many orthopaedic surgeons do bone grafts, is sterile, osteoconductive, biocompatible and easily sculpted to fill a defect in fractured bones. Developed and manufactured by Interpore Cross International, a biomaterials company in Irvine, California, Pro Osteon mimics the internal architecture of human bone. In the manufacture of Pro Osteon, marine coral, which is remarkably similar to human bone to begin with, is subjected to a proprietary chemical process resulting in coralline hydroxyapatite, the primary strength-giving mineral in bones. Although the coral content has been converted, the porous, interconnected structure of the coral remains intact, providing an ideal matrix through which new bone can grow. Currently available as a bone graft substitute in more than 40 countries, Pro Osteon is packaged as blocks of various sizes, as well as granules. It has received the CE mark in Europe, giving it broad approval for use as a bone graft substitute in any indication where a surgeon is currently using a cancellous bone graft material. While it is FDA approved for long-bone procedures in the US, Pro Osteon has also been used successfully in lumbar and cervical spine procedures internationally. Interpore currently has clinical trials underway for the use of Pro Osteon in a variety of spinal procedures as well as backfill for defects in the iliac crest1. Pro Osteon is osteoconductive, which means bone cells weave into and through the porous microstructure of the implant. The graft provides a sort of trellis to support new bone, blood cells and soft tissue as they grow to connect the fractured bone segments. In a process called resorption, certain bone cells are triggered to “eat” the implant, while other cells are triggered to build new bone tissue. Stress on the grafted bone tells the body that more bone is needed; thus, more stress induces more natural bone-building. Eventually the new bone replaces the implant. Pro Osteon Implant 500, generically called “bone void filler,” is fully approved by the Food and Drug Administration to be marketed for metaphyseal long-bone fractures, or fractures at the ends of long bones in the arms and legs. In clinical tests conducted over eight years, Pro Osteon’s healing time and resulting strength compared favorably to autograft (the use of a patient’s own bone material as void filler elsewhere in the body). In some 30,000 procedures, use of Pro Osteon has never resulted in biological rejection of the material by a patient’s immune system. Orthopaedic surgeons have found many uses for Pro Osteon. Some orthopedic surgeons have employed it to repair defects caused by fractures — an ideal procedure in cases where bone is missing or impacted and the surgeons need something to act as a mechanical buttress to support the fractured fragment from within. Surgeons may also decide to use Pro Osteon to augment bone insufficiencies caused by disease such as tumors or osteoporosis and to fill in open-section defects created by other procedures. Arthur Ting, a Palo Alto, Calif.-based orthopaedic surgeon who specializes in sports medicine, has found Pro Osteon to be the perfect solution for giving injured athletes the extra strength they need to resume their careers. In anterior crucial ligament (ACL) reconstructions of the knee, Dr. Ting will use the patella (kneecap) tendon as graft material. During the same surgical procedure, he fills that graft site with a Pro Osteon implant. Before Pro Osteon became commercially available in 1992, filling the graft site was not a procedure Dr. Ting would have performed, even though leaving the defect exposed the athlete to increased risk of injury. “Now, having Pro Osteon, it’s easy to justify filling the defect without subjecting the patient to more involved surgery,” Dr. Ting said. Until recently, the most common bone-grafting method has been autograft, in which bone is removed from the patient’s own body. Typically, bone is harvested from the iliac crest, or hip. In many cases, long after the repaired bone has healed, patients continue to experience crippling pain in the hip area. “One of the longest-lasting bad effects of surgery is removal of bone from the iliac crest,” said John Thalgott, an orthopaedic surgeon in Las Vegas. In addition to the lingering pain associated with autograft surgeries, the patient can experience increased blood loss, a longer hospital confinement and recovery period, and loss of time from work and other normal activities. The second surgery that comes with autograft procedures also increases costs to the health care system due to the longer time needed in the operating room and hospital, the extra staff to attend the surgery, and the possibility of complications such as infection or prolonged wound drainage. The difference between the procedures is therefore particularly significant to the patient. A second bone-graft method to which Pro Osteon offers a better alternative is allograft, which uses bone harvested from cadavers. This bone, which is purchased from bone banks, is sometimes rejected by a patient’s immune system. Use of cadaver bone also carries the risk of transmitting viruses that cause diseases. There is some government regulation of U.S. bone banks, and a smaller number of banks adhere to the more stringent guidelines of the American Association of Tissue Banks. Not all facilities comply with these guidelines, however, and cadaver bone is sometimes imported from other countries. “Internationally, it remains a concern, especially in the patients’ minds,” notes Dr. Thalgott. Interpore International’s coral-based technology originated in the early 1970s with a group of science professors and medical researchers who saw the potential of porous coral skeleton as bone graft material. Johnson and Johnson held the first license, but later let it lapse because of the lengthy clinical trials required for FDA approval. Interpore then acquired the license and conducted clinical trials from 1982 to 1989. The company’s first product was a synthetic dental implant product. In 1992, with FDA approval of Pro Osteon Implant 500, Interpore entered the orthopaedic market. Future development will focus on expanding domestic and international markets, and broadening the FDA-approved applications of Pro Osteon. Other promising developments incorporating Pro Osteon are underway, including a bone growth technology that combines Pro Osteon with human growth factor derived from the patient’s blood to accelerate bone growth. “In the future, we will be moving away from taking bone from the body and toward the use of synthetics,” Dr. Thalgott predicted. “Organic material such as Pro Osteon has a definite role, and that role is rapidly expanding.” ### For more information on Interpore Cross or Pro Osteon, contact the company directly at 800-722-4489.
