Last Updated on 18 October 2007.

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Mastoid Cavity obliteraiton using Karnataka flap
(Posteriorly based perichondrial and periosteal flap with Conchal cartilage)
An Easy and Reproducible technique with very high positive results

Dr. Prahlada N.B
Karnataka ENT Hospital & Research Center
Opp. S.P Office, turuvanur Road, Kelagote,
Chitradurga - 577501,
Karnataka,
India.

Introduction

Considering patients preferences, financial limitations and cost effectiveness, the optimal treatment for cholesteatoma must be one operation, provided it achieves a dry safe ear. Canal wall down surgery with full cavity obliteration has become surgery of choice for all Chronic suppurative otitis media with cholesteatoma (8). Moreover, the altered acoustic behavior of the open cavity is known to cause partial extensive discrepancies of the resonance-caused sound-pressure augmentation in the frequencies of 3 and 4 kHz, which are important for speech perception. The average difference is reported to be more than 10 dB (SPL). Proved surgical techniques of cavity obliteration and meatoplasty can lead to a nearly normalized acoustic behavior of the outer ear in a statistic significant way (9). Swimming, diving, and free participation in all other aquatic sports are important additional benefits of cavity obliteration techniques Even fitting a canal type hearing aid may pose difficulty in large cavities. Hereby I decribe this technique of mastoid cavity obliteration using Karnataka flap.

Surgical Technique

Step 1: Endaural incisions and elevation of Modified Korner’s flap:
First endaural incision is made starting from at 12 ‘o’ clock position on the superior meatal wall, 5 mm away from the annulus, extending in the same horizontal plane over the posterior meatal wall and then to inferior meatal wall up to 6 ‘o’ clock position (Fig 1).

Second endaural vertical incision is made beginning again at the 12 ‘o’ clock position on the superior meatal wall where the first incision began. The second incision extends to the point between the root of the helix and the upper border of the tragus (Fig. 2).

No third incision is made. The incisions are deepened to the periosteum and posterior canal wall flap is raised outwards using a canal knife (Fig. 3). The inner flap (endomeatal flap) is not disturbed at this moment.

Step 2: Post-aural sulcus incision and harvesting of temporalis fascia graft:
A post-auricular sulcus incision with 1 centimeter superior extension is made (Fig. 4).

The ear is elevated forward, exposing the areolar tissue superficial to temporalis fascia, temporalis muscle and post-auricular muscles. The post-aural skin is undermined using a sharp tissue dissecting scissors. Temporalis fascia graft of 1 x 1.5 inches measurement is harvested, allowed for drying.

Step III: Conchal perichondrial incision and elevation of the post-aural perichondrial flap:
Soft tissue and Perichondrium over the conchal cartilage on back of the pinna is incised along the anti-helical line(Fig. 5).

The conchal perichondrium is elevated using a periosteal elevator. Once the medial edge of the conchal cartilage is reached, a No.15 knife or sharp tissue dissecting scissors is used to elevate the soft tissue flap over skin of the external auditory canal as a continuity to the conchal perichondrium, until the bony meatal wall is reached. Care is taken not to injure the skin of the meatal wall.

Step IV : Post-aural soft tissue and periosteal incision and elevation of posteriorly based flap:
The post-aural soft tissue and the periosteum over the mastoid cortex is incised around the bony meatal wall from 12 ‘o’ clock position to the 6 ‘o’ clock position in a semicircular fashion (Fig. 6).

The conchal perichondrial flap raised earlier is left attached to the post-aural soft tissue and periosteum and not to the skin of the external auditory canal. Care is taken not to injure the skin of the meatal wall. Next, 3/4 to to 1 inch long horizontal incision parallel to linea temporalis is made into the post-auricular soft tissue and periosteum over the mastoid cortex beginning from the 12 ‘O’ clock position of the earlier incision (Fig. 7).

Another parallel horizontal incisions is made beginning from the 6 ‘O’ clock position of the first incision (Fig. 8).

Now, a posteriorly based flap is elevated off the mastoid cortex which now includes the conchal perichondrium, post-aural soft tissue and periosteum (Fig. 9).

Step V: Harvesting Conchal cartilage:
The exposed crescent shaped conchal cartilage is incised along the skin incision line with a down word extension to involve the cartilage of the floor and partially anterior wall of the external auditory canal, i.e., tragal cartilage. Cartilage is elevated off the perichondrium and skin using periosteal elevator or sharp dissecting scissors and care is taken not injure the skin which is usually very thin (Fig. 11 & 12).

Step VI : Isolation of the Retraction pocket or freshening the margins of the tympanic membrane:
(A) If there is a retraction pocket, the tympanic membrane and the meatal wall skin, 2-3 mm away and around the retraction pocket is incised and retraction pocket island is created (Fig. 11).

(B) If there is a perforation, the margins of the perforation are trimmed and freshened.
(C) If complete pars tensa is retracted and plastered over the promontary, the drum is incised all around immediately medial to the annulus.

Step VII: Endomeatal incision and elevation of endomeatal flaps:
Now two oblique endomeatal incisons are made over the remaining skin of the external auditory canal. First incision, starting from the 12 ‘o’ clock position to 2 ‘o’clock position, 3 mm away from the annulus. Second, starting from the 6 ‘o’ clock postion to 4 ‘o’ clock position, 3 mm away from the annulus (Fig. 12).

The meatal flaps are elvated and fibrous annulus is detached from the inferior, posterior and superior meatal walls. The elevated flap is cut lateral to medial at 11 ‘o’ clock position in cases of retracton pocket or at 9 ‘o’ clock position in other cases (Fig. 13). Now, the two limbs of endomeatal flaps are retracted anteriorly and preserved to avoid injury from further instrumentation in the middle ear.

Step VIII: Mastoidectomy:
Modiefied radical mastoidectomy is doneand complete disease is cleared and Ossiculoplasty is done, if it is planned as a single step procedure. Once this is being done, the mastoid cavity is ready for obliteration(Fig.14).

Step IX: Obliteration of the attic and mastoid cavity:
A properly shaped and cut conchal cartilage is used to obliterated the attic pit above the tympanic segment of the facial canal and covered with temporalis facia graft completely (Fig. 13). The cartilage should not be bare and exposed. Remaining conchal and tragal cartilage is used to obliterate the tip area, sino-dural angle and remaining cavity, under the cover of the temporalis fascia (Fig. 14). The posteriorly based post auricular flaps is turned into the mastoid cavity, placed below the temporalis fascia, such as that, the flap will be covering the cartilage pieces used to obliterate the cavity (Fig. 15). As such this flap consists of post-aural soft tissue and periosteum over the mastoid cortex, they sort of fall in or cave in into the mastoid, which is now devoid of cortex, the chances of flap retraction is less.

Now, Care is taken to drape the temporalis fascia completely over the cavity filled with cartilage pieces and post-aural flaps. This avoids raw area, the chances of cartilage exposure and extrusion .

Next, the superior endomeatal skin flap is reposited in such a way that, the upper flap lies in the attic region covering the cartilage piece and the temporalis fascia (Fig. 16). The inferior endomeatal skin flaps reposited over the part of the facial ridge close to it, covering the temporalis fascia graft (Fig. 17). These flaps are very important and they stabilize the temporalis fascia graft, nourish the fascia the help in early epithelialization.

Step X: Meatoplasty:
Now, the modified Korner’s skin flap of posterior meatal wall is fixed with catgut sutures to the temporal muscle superiorly and to the soft tissues over the mastoid tip area, to ensure that the flap is over the facial ridge, covering the temporalis fascia and post-auricular flaps (Fig. 18) .When this is done, one should be able to pass index finger though the entrance of the meatus. Care is taken to not to pull out the post-auricular flap inadvertently.

Through these steps of surgery, the cavity is obliterated with autologous cartilage pieces which were harvested from the vicinity, and covered by three fibrous tissue layers, i.e., periosteum and conchal perichondrium which get rich blood supply from the branches of the occipital artery and the temporalis fascia whose nutritional needs are minimal, and helps in the reconstruction of the middle ear space as well as hearing mechanism. These are further reinforced by the endomeatal skin flaps and the Korner’s flap which would help in epithelialization (Fig. 19).

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prahladnb@gmail.com

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Thulasi Charitable Medical Foundation (R) , Chitradurga - 577501, Karnataka, India