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New Ceramic Graft Substitute Not Recommended

Scientists are studying new materials to replace bone graft for use in spinal fusion surgery. In this study, Chitra-HABg, a glass ceramic composite was used on one side of the spine. Natural bone graft harvested from the patient's own pelvic bone. This is called an autologous bone graft. The harvested bone was placed on the other side of the spine.

Patients were followed for a full year. But it quickly became apparent that the ceramic graft substitute was being absorbed by the body without bone to replace it. Fusion failed on the ceramic side of the spine. As a result, the study was ended early.

Biodegradable, bioactive ceramic substitutes such as Chitra-HABg combine the best mechanical and biologic properties of various ceramics available. But it can't be used alone as a bone graft substitute.

Researchers will continue to explore ways to avoid using autologous bone grafts. The complications at the donor site are often the biggest problem patients have after spinal fusion.

Bone substitutes must be porous in weight and structure like the surrounding bone. New bone grows into the interconnecting pores in the bone. A microlock forms between new and old bone. Autologous bone takes three months to a year to form a solid fusion. Bone graft substitutes or graft extenders must provide equally rapid growth of new bone.

Glass ceramic seems like a good choice for a bone substitute material. It is strong and provides a chemical surface that allows for new bone cells to stick. But it appears that new bone doesn't go deep enough into the ceramic. It may be a problem with in-growth but it could be that the ceramic is too thick.

Other factors in the failure of fusion to occur with Chitra-HABg include poor local bone growth, too large of a soft tissue gap to fill in, and too small of a bone surface area for fusion to occur within. Despite more than three years of clinical trials, the makers of this ceramic bone substitute are back to the drawing board.

References: Narayana K. Acharya DNB (Ortho), et al. Hydroxyapatite-Bioactive Glass Ceramic Composite as Stand-Alone Graft Substitute for Posterolateral Fusion of Lumbar Spine: A Prospective, Matched, and Controlled Study. In Journal of Spinal Disorders & Techniques. April 2008. Vol. 21. No. 2. Pp. 106-111.

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