Radiologic and mechanical properties of inactivated ossicle homografts

Objective: This study examined the effects of old and new inactivation (ste rilization) techniques on the radiologic and mechanical properties of ossic le homografts. Materials and Methods: Ninety normal incuses and malleuses r eceived either treatment with 1) 5% formaldehyde/cialit, 2) 1N NaOH, 3) 0.9 % LpH,(R) or 4) autoclaving at 134 degrees C, or no treatment. All ossicles were assessed radiologically by high-resolution computed tomography, After imaging, all ossicles underwent mechanical testing by destructive axial co mpression in a mechanical testing machine measuring force and displacement, Results: Ossicles treated with cialit, NaOH, or autoclaving showed a signi ficant decrease of ultimate force and stiffness compared with controls. LpH treatment caused no such changes in these structural properties. Material properties of yield strength, ultimate strength, and elastic modulus were a lso altered by cialit, NaOH, and autoclaving, but were much more difficult to assess because of uncertainty in parameter estimates. There was a signif icant increase in radiologic density in autoclaved ossicles, a reduction in cialit- and LpH-treated ossicles, and no change in NaOH-treated ossicles. Conclusions: All tested inactivation procedures changed the biomechanical a nd/or radiologic properties of ossicle homografts. However, the new procedu res used to inactivate infectious agents produced changes similar to the ol der treatments with formaldehyde/cialit. Human allografts are able to withs tand harsh but safe sterilization procedures, The NaOH treatment seems to b e the most suitable method for the future. The biologic (osteogenic) potent ials of ossicle homografts treated with these new preservation/inactivation methods are still unknown. Further investigations are necessary to re-eval uate the clinical use of ossicle homografts in middle ear reconstructive su rgery.