22 Obliteration with a Fat Graft

Fat is rarely used as an obliteration material in middle ear surgery, whereas in translabyrinthine acoustic neuroma surgery, fat is the only material used to obliterate the huge translabyrinthine cavity and prevent cerebrospinal fluid leakage.

In extensive petromastoid surgery for carcinoma of the middle ear, fat grafting has been used since the 1940s (Penha 1951, Piquet et al. 1958), and in translabyrinthine acoustic neuroma surgery, it has been used since the early 1960s by House (House and Luetje 1979).

In middle ear surgery, van Deinse proposed a method of extended antrotomy for inspection of the tympanic cavity, whilst partly preserving the posterior ear canal wall, as well as the bridge. He suggested filling the retroauricular cavity with abdominal fat (van Deinse and van den Borg 1958, Kuhweide and van Deinse 1960). After radical mastoid surgery, Kadariu (1960) used fat for obliteration of the cavity. Ringeberg and Fornato (1962) used fat for cavity obliteration in specific cases with an intakt posterior bony ear canal wall or intact ear canal skin. In myringoplasty, fat is sometimes used to close small perforations (Vol. 1, pp. 117–18).

The author has used abdominal fat in more than 650 patients after translabyrinthine removal of acoustic neuromas (Tos and Thomsen 1991) and other skull base surgery procedures, but only very occasionally for obliteration of a cavity after a canal wall–down mastoidectomy.

The following features of fatty tissue have been found to limit its use as an ideal obliteration material: a) Fatty tissue can only be used as a “filler”, b) Because of its consistency, it cannot be used in the reconstruction of the ear canal wall in the way that musculoperiosteal flaps can. c) Fatty tissue becomes fibrotic, and gradually shrinks. We have noticed that all patients undergoing surgery for acoustic neuromas who had the cavity obliterated with fat developed extensive retraction postauricularly, and at repeat surgery carried out for other reasons, e. g., removal of residual tumor, the amount of fatty and fibrous tissue was reduced to a quarter of its original volume. The shrinkage of the fatty tissue starts soon after surgery, and postauricular retraction is visible within three months, and progresses over the first two years.

Possible Application of Fat Graft

In the author’s opinion, after canal wall–down mastoidectomy for chronic ear disease, fatty tissue should only be used as one of the “fillers” in combined-graft obliteration techniques behind a new ear canal wall, reconstructed with soft tissue.

Obliteration with fatty tissue behind an intact ear canal wall, as in acoustic neuroma surgery, can be performed in cases of chronic ear disease, but any communication between the tympanic cavity and the mastoid cavity should be tightly closed.

Intact Canal Skin

In the following situations, fatty tissue can reasonably be used to replace other grafts as a “filler” of the cavity.

1. Obliteration of a canal wall–down mastoidectomy cavity in cases with intact ear canal skin, as used by Dagget (1949) (Figs. 255–257). The attic perforation can be closed with fascia and the fat placed in the cavity, instead of blood (Fig. 257).

2. Cavities formed after endaural surgical techniques with preservation of the canal wall skin, as described by Andrew (1956), can be obliterated using fat instead of blood, and the endaural incision can be sutured, as indicated in Figures 258 and 259. Shrinkage of the fatty tissue will lead to diffuse enlargement of the ear canal and a small cavity, which is usually, however, selfcleaning.

Intact Bony Ear Canal Wall

1. Obliteration of the cavity with an intact posterior bony ear canal wall and scutumplasty. The attic is thightly separated from the tympanic cavity with cartilage, as indicated in Figures 381–385, and in this situation fatty tissue can be placed behind the muscle grafts and cartilage grafts supplementing the obliteration. Shrinkage of the fatty tissue will result in retraction of the postauricular skin.

2. Fatty tissue can also be used in partial obliteration techniques after canal wall–up mastoidectomy and scutumplasty. Fatty tissue can supplement the obliteration lateral to the reconstructed attic, instead of using bone paté and fibrin glue (Figs. 385, 386).

3. In cases with temporary displacement or temporary removal of the bony ear canal wall and subsequent obliteration of the cavity, as described by Mercke (Fig. 524), fatty tissue placed behind a Palva flap can supplement the obliteration, particularly in large cavities.

4. In the Farrior techniques, with the mastoid cavity behind an intact and displaced bony ear canal wall (Figs. 556–559), fatty tissue can be used as an additional graft placed behind the muscle (Fig. 561), or used instead of muscle. Similarly, in Olaizola’s techniques, the cavity can be obliterated behind a tight closure of the aditus, instead of being ventilated (Figs. 566, 567).

Reconstructed Ear Canal Wall

1. In techniques involving reconstruction of the ear canal wall in order to ventilate the cavity, it is sometimes desirable to obliterate such a cavity, or at least its lateral part, and leave only the medial part ventilated. In such situations (Fig. 814), a plug of fatty tissue placed behind the Palva flap can be used.

2. In ear canal wall reconstructions using fascia and an endaural approach (Figs. 822, 823), a piece of fat can support the fascia laterally. Because of the difficulty of raising a large musculoperiosteal flap in an endaural approach, a fat graft could be used more often, e. g., in reconstructing the ear canal in an endaural approach using tragal cartilage (Figs. 825, 826). In this situation, a plug of fat obliterating the lateral part of the cavity, whilst still preserving the advantage of ventilation of the antrum and attic, is an option.

3. In reconstruction of the ear canal wall using autogenous tragal cartilage (Fig. 831), allogenous septal cartilage (Fig. 833), or knee cartilage (Figs. 834, 835), the most lateral part of the cavity can be obliterated, either with muscle or a plug of fat.

4. Most methods of obliteration with muscle, as described in Chapter 18, can be supplemented by the use of a piece of fatty tissue in the most posterior part of a large cavity tucked behind the muscle tissue and the reconstructed ear canal wall. In obliteration techniques using a superiorly-based bipartite muscle flap (Figs. 891, 892), or other superiorly based flaps (Figs. 878, 899) that are too short to completely obliterate the mastoid tip, a piece of fatty tissue can be used to fill this part of the cavity.

Palva flap obliteration is particularly suited to additional obliteration by fatty tissue, or other material (Figs. 927, 931–939, 941). The fatty tissue can act as a “filler,” instead of Gelfoam, which has often been used to fill the cavity behind the Palva flap (Fig. 931).

With an obliteration using inferiorly-based a muscle flap, a particularly large mastoid tip can be obliterated with fatty tissue placed under the muscle. The same method can be used in the Naumann obliteration method behind an intact canal wall (Fig. 965).

5. In obliteration of a canal wall–down mastoidectomy cavity using cartilage, additional tissue is sometimes needed. Fatty tissue could be placed behind a Palva flap and tragal cartilage, as shown in Figures 979, 980, and 985.

In obliteration using hard tissue, the use of fatty tissue, with its tendency to shrink, is less appropriate. A canal wall reconstructed using hard tissue cannot retract, and may create irregularities within the cavity, with deep and dangerous retraction pockets. In obliteration techniques using bone paté behind cartilage and a Palva flap as described by Honda (Fig. 1009), the lateral part of the cavity can be additionally obliterated using a plug of fat.

Fatty tissue can be used instead of muscle behind a cartilage plate in partial obliteration of the cavity (Chapter 14), either involving the sinodural angle, the mastoid tip, or of some perilabyrinthine air cells (Figs. 729, 730).

Adipose tissue can be used as additional filling material, mainly in the posterior or lateral parts of the cavity, in cases when insufficient muscle is available. However, for the relatively small amount of fatty tissue that is required, the surgeon may feel that it is not worthwhile to make an abdominal incision to harvest the fatty tissue. Usually, autogenous tissue is available around the mastoid process, and this can be used as free grafts, e. g., subcutaneous tissue, muscle, periosteum, bone pieces and bone paté, as well as cartilage. It is therefore understandable that fat is used only sporadically. The tendency for fatty tissue to shrink by about one-third during the first three months is also a great disadvantage. In the author’s opinion, therefore, a fat graft, when used in the obliteration of a canal wall–down mastoidectomy cavity, should only be applied behind a reconstructed ear canal wall of soft tissue using a meatoplasty, so that the large cavity that results from shrinkage can be surveyed and cleaned.

Risk of AIDS

In several countries, regulations do not permit the use of any allogenous tissue unless it has been sterilized by boiling or in an autoclave. Even though storage of allogenous cartilage, dura, or ear drum in Cialit, formaldehyde, or alcohol will kill the HIV virus, the use of the allogenous cartilage, dura and ear drum has become impossible in these countries.

Allogenous cartilage, as used in scutumplasty (Figs. 360–364) or in ear canal reconstruction, as described in Chapter 17 (Figs. 332–335), can be replaced by autogenous tragal or conchal cartilage. Allogenous dura in ear canal wall reconstruction (Figs. 840–841) can be replaced by fascia lata.

In obliteration with allogenous cartilage, as described in Chapter 19, however, the amount of available autogenous cartilage is inadequate to replace the allogenous cartilage (Figs. 973, 975, 981–990). In this situation, fatty tissue can serve as a filler in a large cavity. Of course, other autogenous materials can also be used, such as muscles, subcutaneous tissue, bone paté and bone chips, or hydroxyapatite granules.