SDRs would be produced in a variety of diameters to suit specific applications. Typical diameters are expected to range from 0.02 to 0.1 in. (about 0.5 to 2.5 mm). An SDR could be fabricated as a matrix/fiber composite material: The fibers could be made of a biocompatible glass or polymer, and the matrix would be made of a bioabsorbable material that could be therapeutically loaded with bone-growth and infection-fighting chemicals. Optionally, the fibers could be made of a bioabsorbable material, so that in time, nothing of the SDR would remain in the healed bone. Yet another option would be to fabricate an SDR as a metal tube containing bone-growth and infection-fighting chemicals that would leach out through pores.
Once the bone segments were fixed in place by insertion of SDRs, additional structural support and immobilization would be provided by wrapping and co-curing a multilayer composite-material shell around the outer surface of the fractured bone. This shell would be made of a fabric preimpregnated with a curable, bioabsorbable matrix resin. From a purely structural perspective, it would be preferable to form the shell around the entire circumference of the bone; from a surgical perspective, it could be more practical to form the shell part way around the circumference and strengthen the bone by use additional SDRs.
The curing of the composite would create a rigid structural element integrally bonded to the bone. The combination of the SDRs and the composite shell may be sufficient to restore the bone to its original strength, or nearly so. Hence, there would be little or no need for a cast or other external immobilizing device. At the least, the amount of time the patient must wait before returning to normal activity should be less than it would be if the repair were performed by the traditional method.
This work was done by Gary L. Farley of the U. S. Army Research Laboratory for Langley Research Center. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Bio-Medical category. LAR-16354-1