Anatomy

The tympanic membrane is a semi-transparent membranous structure that constitutes a wide part of the lateral wall of the tympanic cavity at the end of the bony external ear. The membrane is placed obliquely (45°), at a sharp angle to the inferior wall of the external auditory canal (EAC), and its lateral surface is directed downward and forward. The adult tympanic membrane extends ~ 8 to 9 mm horizontally and 9 to 10 mm vertically. The larger area of the membrane is tense (pars tensa), but superiorly there is a soft portion (pars flaccida, Shrapnell membrane). The annulus fibrosus of the tympanic membrane anchors it into the tympanic sulcus. The anulus fibrosus does not fully encircle the tympanic membrane; the ends of the fibrous ring meet in the area of the processus brevis. The extension in front is called the stria anterior and the one at the back the stria posterior, and these ligaments carry the malleus–incus complex, forming malleolar folds by encircling the striae. The lateral process of the malleus together with the posterior and anterior malleolar folds separate the pars flaccida from the pars tensa. The Shrapnell membrane serves as the lateral wall of the Prussak space.1,2

Etiology and Classification of Tympanic Membrane Perforations

Tympanic membrane perforations result mainly from infectious and traumatic etiologies. Among the infectious etiologies are acute otitis media, chronic otitis media, and tuberculous otitis media. Penetrating trauma, non-explosive and explosive blast injuries and iatrogenic causes are among the traumatic etiologic factors.

It is possible to classify the perforations according to their localizations and the area where they affect the tympanic membrane. The tympanic membrane is divided by a vertical line through the umbo, so that perforations can be classified as anterior and posterior. In addition, perforations can be categorized clinically as central when located within the limits of the anulus fibrosus, and marginal where the anulus is destroyed. Finally, the terms “total” or “subtotal” can also be used based on the perforation area that affects the tympanic membrane.3

Aim of Surgery

Although tympanic membrane reconstruction is generally considered to be an “easy” operation, it is one of the most difficult otologic surgeries to perform successfully. This is because there are two goals of the operation that must be accomplished for it to be regarded as a successful surgery. First, the perforation must be repaired successfully; and second, hearing is expected to be improved while the ear′s function and other structures are preserved. Failure to reach these goals may cause patient dissatisfaction.4

Surgical Approaches for Tympanic Membrane Reconstruction

Three different surgical approaches are being used for membrane reconstruction. These are the endaural, postauricular, and endomeatal approaches. Each approach has its advantages and disadvantages. In the endaural approach there is less bleeding and trauma compared with the postauricular approach,5 and a natural meatoplasty is obtained by leaving the inferior part of the incision unsutured. In the postauricular approach, it is easier to expose the anterior remnant of the tympanic membrane in subtotal perforations. This also applies to cases where the anterior wall is prominent. The endomeatal approach is preferred in perforations, especially those located in the posterior part of the tympanic membrane, and it provides a cosmetic advantage because there is no visible incision. As there is less tissue trauma, it is possible to maintain natural tissue integration.

F: fascia

Graft Materials

Fascia temporalis is the most frequently used grafting material in tympanoplasty, with a rate of success reaching 95%6,7 ( Fig. 2.1 ). However, this rate decreases in some patients. Lower success rates occur in chronic tubal dysfunction, adhesive process, tympanosclerosis, and recurrent perforations. In such cases, cartilage grafts are more commonly preferred.8,9 The primary reasons for preferring the cartilage graft are mechanical stability and resistance to high negative pressure changes in the middle ear.10 Subtotal perforations are also cases where fascia grafting has lower success rates; failure in these patients generally stems from graft dislocation from the anterior wall. The primary reasons for failure are:

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  Decrease in the medial support of the graft by absorbable gelatin sponges placed in the anterior mesotympanum that is displaced toward the eustachian tube over time.

  
  
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  Decreased visibility of the area in cases with a prominent anterior canal wall.

  
  
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  After the graft is placed anteriorly, it may be dislocated while the surgeon is conducting manipulation in the posterior part of the graft.

There are certain techniques that can be applied to prevent the graft from moving away from the anterior edge of the tympanic membrane. One technique involves placing the graft under the anterior external ear canal skin and anulus fibrosus. However, this is a difficult technique, and there is a risk of blunting in the anterior part of the EAC. Pulling the edges of the graft through a small incision of the tympanic membrane at the site of the anulus is another method that can be applied. A further option is to apply overlay tympanoplasty. Although there is a greater chance of success in overlay tympanoplasty, it has some known complications, such as the longer recovery period, anterior blunting, graft lateralization, and epithelial pearl formation.11 Many studies suggest that the overlay technique has more disadvantages and that it is prone to more complications.12

In recent years there has been an increased tendency to use cartilage grafts in tympanoplasty. The most significant reason for this is their strength and the high graft success rate. There are various techniques for cartilage tympanoplasty, but the most frequently used are the “palisade” and “island” techniques.9 In our clinic we use an anterior cartilage reinforced tympanoplasty technique for total and anterior perforations, and an island technique for revision cases. Cartilage is used from the tragus or conchal part of the auricular cartilage. In the anterior cartilage reinforced tympanoplasty technique, after the placement of absorbable gelatin sponges in the middle ear up to the drum level, the cartilage graft is placed under the remnant of the tympanic membrane in front. The fascia graft is then placed, using an underlay technique, between the drum remnant and the cartilage. Posteriorly, the fascia lies over the bony EAC. The purpose of this technique is to minimize detachment of the fascia graft anteriorly. The placement of cartilage in the anterior hypotympanum supports the fascia graft medially. In the event that the fascia graft moves away from the anulus, epithelialization may continue over the cartilage ( Figs. 2.2 and 2.3 ). In addition, it is possible to observe the middle ear in the postoperative period, as regards cholesteatoma or effusion, because cartilage is only present on the medial part of the anterior part of the newly formed membrane.

Intraoperative Complications

Bleeding

Bleeding may occur during surgery and in the postoperative period. Maintaining a blood-free surgical field is important if one is to perform a correct and successful graft placement.

A meticulous preparation technique is very important to obtain a bloodless field. Bleeding may initially come from the incision, and preoperative injection of the incision line with 2% lidocaine and 1:100,000 epinephrine helps to reduce bleeding. It is important, particularly during the graft harvesting, to dissect the correct surgical plane between the fascia and the muscle; injury of the muscle tissue under the temporalis fascia leads to troublesome bleeding. Another location of bleeding may be the anterior superior part of the bony EAC, where the posterior tympanic artery may be damaged during the elevation of the skin flaps.2 Hypertension may also cause generalized bleeding from many locations. Introduction of new hypotensive agents such as remifentanil (Ultiva; GlaxoSmithKline, Philadelphia, PA, USA) has greatly improved surgical vision and manipulation during microsurgery by reducing bleeding. If the middle ear has had a recent infection, this may also cause bleeding from the granulation tissues. All these bleeding points should be cauterized or controlled with epinephrine-soaked gelatin sponges before proceeding, otherwise the surgeon may be faced with difficulty during graft placement.

When working on or in close proximity to the facial nerve, arterial bleeding may also occur. This should be controlled with gelatin sponges. It should also warn the surgeon of the proximity of the nerve.

Preoperative high-resolution computed tomography of the temporal bone is routinely obtained at Hacettepe University before tympanoplasty). In addition, to evaluate the middle ear or mastoid pathology, axial and coronal imaging shows if there is a high jugular bulb or an aberrant internal carotid artery.13 Although these entities are rare, they can lead to devastating consequences if the surgeon fails to recognize them. Accidental injury to a highly placed or uncovered jugular bulb can be treated by applying oxidized cellulose (Surgicel; Ethicon Company, Somerville, NJ, USA)). Ideally, the pieces of oxidized cellulose (Surgicel) should be larger than the defect, and they should cover the jugular bulb without being pushed into the lumen, to avoid pulmonary embolism.14

Damage to the Tympanomeatal Flap

Preservation of the ear canal flaps is very important for rapid and uncomplicated healing in the postoperative period; they may support graft epithelialization and avoid scar and stenosis formation in the EAC.15 They have to be handled with care and should be intact at the end of the operation. Usually it is necessary to elevate the skin from the tympanosquamous suture anterosuperiorly, up to the 6 o′clock position (right ear) inferiorly before using the bur. If the meatal skin cannot be removed sufficiently from the drilling area, the flap may also be removed and retransplanted at the end of the surgery. Enlargement of the bony canal by drilling is a routine part of the myringoplasty to obtain a better exposure of the middle ear and improve postoperative care. During this process the flaps may be damaged by the bur. It is good practice to protect the flaps with suction while the bur is being used; if the ear canal skin is properly elevated and protected, the risk of damage by the bur is very low.

Due to the enlargement of the bony EAC, the original canal skin is generally not enough to completely cover the bony surface at the end of the operation. Additional fascia can be used to cover the bone, which is placed under the skin, to improve regular wound healing and avoid unwanted scar formation in the EAC.

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