The most vexing problem of the operative treatment of otosclerosis is the fact that in many instances the operative fistula still heals with bony closure in spite of all improvements of the surgical technic. In attempts to solve the problem animals have been widely used, but it seems doubtful that a complete answer will ever be furnished by animal experiments alone. Otosclerosis is a disease which occurs exclusively in man and has never been observed in animals. This seems to indicate that there are basic differences between the human capsule and that of animals.Under these circumstances the study and the analysis of the changes which take place during the healing of human fistulas have gained particular importance.Fistula in the osseous wall of a semicircular canal either follows disease of the middle ear or is the result of operative trauma.The lateral semicircular canal, being more accessible from the middle ear and the antrum, is also more exposed to disease and traumatism than the others.Most frequently fistula follows chronic otitis media with cholesteatoma, sometimes chronic otitis without cholesteatoma or subacute otitis media due to Pneumococcus type HI, rarely acute otitis media and occasionaly tympanomastoidectomy. Cases of tuberculosis of the middle ear will not be discussed.Operative injury occurs most frequently in cases in which during tympanomastoidectomy the bone in the upper part of the facial ridge is taken down too far.In the overwhelming majority of instances a fistula which is not followed by a severe labyrinthine complication heals with bony closure of the defect. Occasionally, however, the defect in the osseous wall is filled with connective tissue only, and the fistular test remains positive for an indefinite period. This is an unwelcome event in the course of suppuration of the middle ear or after operation. The condition has been discussed in the literature frequently.
