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Multicenter Study Shows Bone Substitute Superior to Bone Graft for Bone Defects

Bone graft material is used whenever there's a need for extra bone to support a fracture site or defect in the bone. It's easily available (taken from the patient's pelvic bone) and inexpensive. And it is bone inductive (fosters bone growth) to provide structural support to the damaged area.

The downside is that the graft site can be painful for a very long time. In some cases, infection can delay recovery. Patients often report difficulty walking due to the pain. And the combination of pain and impaired walking result in loss of function.

To help patients avoid the major and minor complications of bone graft, scientists are exploring the use of bone substitutes. One of those bone substitutes (alpha-BSM) is the subject of this study. Patients with an acute fracture of the tibial plateau were the subject of this multicenter study. Twelve study sites from around the North American continent were involved.

The tibial plateau is the flat top of the upper portion of the tibia (lower leg bone). This type of fracture was once called a bumper or fender fracture. During a car accident (fender bender), force directed from the femur (thigh bone) down onto the tibial plateau, results in fracture of the plateau. Car accidents aren't the only way this type of injury occurs. Falls, industrial accidents, and getting hit by a car as a pedestrian are also possible ways to sustain a tibial plateau fracture.

Patients were randomly assigned by computer to one of two groups. The first group had an autogenous iliac bone graft. Autogenous means the patient's own bone was used. The second group received alpha-BSM, a bioabsorbable substitute.

FDA regulations required a 2:1 ratio of bone substitute to bone graft patients. This means that twice as many patients had the bone substitute compared to the bone graft group. The reason for this was because bone graft is considered more risky with a greater chance of complications.

Alpha-BSM is a calcium phosphate powder that can be reconstituted with saline (salt solution) and implanted into the bone defect. Heat is created within the material and within four hours, it is set and strong enough to resist compression. Once the fracture was repaired, the remaining hole in the bone was filled with bone graft or bone substitute.

All patients were followed at regular intervals for 12 months. Outcome measures (results) included X-rays and knee range-of-motion. X-rays were used to see if the bone had healed properly and to look for subsidence. Subsidence refers to a collapse or sinking of the articular cartilage and the first, thin layer of bone down into the bone matrix. The independent panel of orthopedic surgeons who reviewed the X-rays also looked for signs of early resorption of the graft.

They found a higher rate of subsidence in the bone graft group. In other words, collapse and resorption of the bone was more likely in the bone graft group. As many as 30 per cent of the patients in the bone graft group were affected. This was compared to only nine per cent in the bone substitute group. Most of the time, subsidence occurred early on (during the first three to six months after surgery).

In summary, alpha-BSM bone substitute is an acceptable replacement for bone graft material. In fact, it appears to be a better choice. X-rays taken a year after the fracture show the alpha-BSM material is still present in most fractures. It is stiffer, offers more support, and holds up better under load compared with autogenous bone graft. There is also less sideways shifting or subsidence of the healing bone with this type of bone substitute.


Thomas A. Russell, MD, and Ross K. leighton, MD. Comparison of Autogenous Bone Graft and Endothermic Calcium Phosphate Cement for Defect Augmentation in Tibial Plateau Fractures. In The Journal of Bone & Joint Surgery. October 2008. Vol. 90-A. No. 10. Pp. 2057-2061.

10/29/2008

*Disclaimer:* The information contained herein is compiled from a variety of sources. It may not be complete or timely. It does not cover all diseases, physical conditions, ailments or treatments. The information should NOT be used in place of visit with your healthcare provider, nor should you disregard the advice of your health care provider because of any information you read in this topic.
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