How can an underlaid fascia graft form the middle layer of a reconstructed tympanic membrane?

OBJECTIVE/HYPOTHESIS: Autogenous fascia is a material popularly applied as a connective tissue graft for reconstruction of the tympanic membrane. The objective was to establish how an underlaid fascia graft can form the middle layer of a reconstructed tympanic membrane.

STUDY

DESIGN

In the underlaid technique, the graft is laid on the medial surface of the tympanic remnant without removal of the mucous membrane, which is covered with entodermal epithelium. Interestingly earlier authors have regarded this fact as natural, though, if it is really so, it must be a result of an unexpected, special mechanism that apparently contradicts the general rules of transplantation.

METHODS

Experimental operations were performed on one ear of 114 adult, male guinea pigs. The posterior quadrants of the tympanic membrane were removed, and the perforation was closed with an underlaid temporal fascia graft. Examinations were made after different survival times. The temporal bones were removed immediately, and specimens were processed histologically.

RESULTS

The graft proved to be well adapted to the margin of the tympanic membrane. The epithelium of the outer surface grew both from the meatal skin and from the margin of the tympanic remnant. In connection with the regeneration of the mucous membrane of the inner surface, unexpected, special events were observed. The originally intact epithelium of the mucous membrane was annihilated, and disappeared completely. Consequently, the fibrous layer of the tympanic remnant and the graft came into direct contact and grew together. The regeneration of the mucous membrane started at the margin of the graft.

CONCLUSIONS

The histologic observations described have clarified the problem of the underlaid technique.