NEW TECHNIQUE REVEALS METHOD FOR BETTER BONE GRAFTS
22 February 2005 - Georgia Institute of Technology

Tissue engineers can choose from a wide range of living cells, biomaterials and proteins to repair a bone defect. But finding the optimum combination requires improved methods for tracking the healing process.

Georgia Tech researchers used the new technique to help develop bone graft substitutes that combine the availability and structural integrity of bone allografts, or bone grafts taken from a human donor, with the better healing properties of bone autografts, or bone grafts taken from the patient.

Unlike a traditional x-ray that only shows the presence of bone in two dimensions, the new micro-CT technique provides high-resolution 3-D images of vascularization and mineralization during bone repair. This approach allows tissue engineers to optimize the design of implants.

The findings of the project, headed by Dr. Robert Guldberg, a research director at the Georgia Tech/Emory Center for the Engineering of Living Tissues and an associate professor in Georgia Tech's School of Mechanical Engineering, were presented Feb. 20 at the annual meeting of the American Association for the Advancement of Science.

"We're applying 3-D imaging techniques to quantify vascularization and mineralization in order to evaluate which of these tissue engineering approaches is going to be able to best and most quickly restore bone function," Guldberg said. "We've always known that vascularization is very important to bone repair, but we've never really had a good method to measure the process."

Guldberg's team has used micro-CT imaging to study fracture healing and repair of large bone defects that can result from the removal of bone tumors or crushing injuries. Large bone defects are typically repaired with allografts because large structural pieces are available from human donors.

But allografts are processed to avoid transmitting any diseases from the donor to the patient, leaving the bone sterile but dead. Allografts therefore lack living cells that could help the implants better integrate with existing bone. Consequently, they don't heal as well as autografts and can re-break in up to 30 percent of patients within a year. Live autograft bone integrates much better, but large amounts of bone are needed to repair a site. They are often too large to remove elsewhere in the patient's body and cause substantial additional pain.

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