Mastoidectomy is a surgical procedure that removes an infected portion of the mastoid bone when medical treatment is not effective.

and Simple (or closed) Mastoidectomy. The operation is performed through the ear or through a cut (incision) behind the ear. The surgeon opens the mastoid bone and removes the infected air cells. The eardrum is incised to drain the middle ear.
and Radical Mastoidectomy. The procedure removes the most bone and is usually performed for extensive spread of a cholesteatoma. The eardrum and middle ear structures may be completely removed. Usually the stapes bone is spared if possible to help preserve some hearing.
and Modified Radical Mastoidectomy (MRM). In this procedure, some middle ear bones are left in place and the eardrum is rebuilt by Tympanoplasty.

Mastoidectomy being performed
Modified Radical Mastoidectomy: Modified Radical Mastoidectomy (MRM) is surgery on the middle ear to repair the ear drum and the mastoid bone, which lies behind the ear. The bony partition between the external ear and mastoid is removed to reach the mastoid. An incision is made behind the ear for this procedure.
Need for a good Meatoplasty after MRM

meatoplasty
Meatoplasty is routinely performed as an integral part of a canal wall down –Modified Radical-Mastoidectomy (MRM). It is typically performed at the end of the Mastoidectomy to assist in ventilation and to provide easy access for cleaning of the cavity postoperatively.

Lack of aeration is one of the causes of a permanent moist cavity. Hence a wide canal opening to the mastoid cavity is important.
Numerous methods for modified meatoplasty have been introduced. Within the different techniques for meatoplasty, partial removal of conchal cartilage and different types of flap designs have been described in order to get a dry and clean cavity without aesthetic deformity for the patient.
If meatoplasty is not done properly a stenotic EAC will be the end result.
Deformities of the EAC are especially more severe in children than in adults due to the thinner, more elastic and less rigid nature of their cartilage.