Vibration characteristics of grafts for the tympanic membrane

Perforation of the tympanic membrane occurs frequently as a result of infection, external trauma, and high-level impulsive sound pressure, such as that associated with an explosion. Many different surgical techniques can be used to repair the tympanic membrane and ossicles. Clinical operations such as tympanoplasty are undertaken to repair the damaged tympanic membrane and ossicles, thus improving hearing and reducing the chance of infection. The membrane is repaired or replaced with the use of graft materials, either from the patient's body or from artificial sources. The selection of graft material is very important because, as much as possible, it must exhibit the same dynamic behavior as the natural membrane. To compare various allograft materials, investigators developed a model of the ear on which different graft materials can be replaced. Three different membrane materials - irradiated allograft dura (Tutoplast Dura; IOP Inc., Costa Mesa, Calif), irradiated allograft fascia lata (Tutoplast Fascia Lata; IOP Inc.), and irradiated allograft fascia temporalis (Tutoplast Fascia Temporalis; IOP Inc.) - were used. Vibration responses of these membrane materials produced by defined sound signals with different frequencies were recorded by a small strain gauge; the spectra of sound for various corresponding input signals were recorded, and the results were compared with those of the sample graft material. Tutoplast Fascia Lata accomplished the best dynamic performance in vitro. Additional clinical and experimental data are needed, however, to determine which of these materials provides the best audiological and clinical performance.