[Management of open and closed cavities in otology].
Surgery of chronic otitis follows a few basic principles, some of which are long-standing but still topical. In the majority of cases, opening of the cavities of the middle ear uses one of the following two techniques: the open technique (radical mastoidectomy), or the closed technique (transmastoid approach or canal up technique). Whatever the technique used, a readjustment of the cavity is often indispensable to avoid any recurrence of the pathology (cholesteatoma) or the appearance of a new pathology (chronic otorrhea) and facilitates a functional step if required. Open techniques must therefore always follow the rule of the ratio V/S (where V = the volume of circulating air coming from outside, and S = the surface area of the skin of the cavity). This ratio is specific to each individual. The readjustment must enable either an increase of V (meatoconchaplasty) or a decrease of S (reconstruction of the posterior auditory canal, obliteration of the cavity), or a combination of the two. Closed techniques must also be adjusted to avoid any retraction towards the posterior or upper cavities. Depending on the clinical background and on the aggressivity of the pathology, the posterior tympanotomy can be closed, and the attic and aditus cavities of the middle ear separated by a bony fragment leaving the protympanum open upwards to enable normal ventilation towards the attic, the aditus and the antrum, or much more rarely, these cavities can be completely closed.